USRE36559E - Method and apparatus for encoding audio signals divided into a plurality of frequency bands - Google Patents

Method and apparatus for encoding audio signals divided into a plurality of frequency bands Download PDF

Info

Publication number
USRE36559E
USRE36559E US08/245,451 US24545194A USRE36559E US RE36559 E USRE36559 E US RE36559E US 24545194 A US24545194 A US 24545194A US RE36559 E USRE36559 E US RE36559E
Authority
US
United States
Prior art keywords
iadd
iaddend
frequency
digital signal
frequency bands
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US08/245,451
Inventor
Yoshihito Fujiwara
Tomoko Umezawa
Masayuki Nishiguchi
Makoto Akune
Naoto Iwahashi
Kenzo Akagiri
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sony Corp
Original Assignee
Sony Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP1249835A external-priority patent/JP2906477B2/en
Priority claimed from JP1278207A external-priority patent/JP2906483B2/en
Application filed by Sony Corp filed Critical Sony Corp
Priority to US08/245,451 priority Critical patent/USRE36559E/en
Application granted granted Critical
Publication of USRE36559E publication Critical patent/USRE36559E/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03MCODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M7/00Conversion of a code where information is represented by a given sequence or number of digits to a code where the same, similar or subset of information is represented by a different sequence or number of digits
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/66Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission
    • H04B1/667Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission using a division in frequency subbands
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/66Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission
    • H04B1/665Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission using psychoacoustic properties of the ear, e.g. masking effect

Definitions

  • This invention relates to a digital signal encoding apparatus for encoding input digital signals.
  • .Iadd.audio .Iaddend.signals on the time axis are divided into signals .[.of.]. .Iadd.in .Iaddend.a plurality of frequency bands for encoding, .[.a.]. so-called adaptive transformation coding (ATC).Iadd., .Iaddend.in which .[.voice.]. audio signals on the time axis are transformed into signals on the frequency axis by orthogonal .[.transformation and the.]. .Iadd.transformation. Then the .Iaddend.resulting signals are divided into signals .[.of.]. .Iadd.in .Iaddend.a plurality of frequency bands for .[.adaptive.].
  • ATC adaptive transformation coding
  • APC-AB adaptive bit allocation
  • .Iaddend. which is a combination of the above mentioned SBC and .[.APC.]. .Iadd.ATC.Iaddend., and in which the .[.voice.]. .Iadd.audio .Iaddend.signals on the time axis are divided into signals .[.of.]. .Iadd.in .Iaddend.a plurality frequency bands and the signals .[.of.]. .Iadd.in .Iaddend.the respective bands are converted into base band or low range signals, after which multiple order linear predictive analyses are performed .[.for.]. .Iadd.to carry out ep predictive coding.
  • the signals from the filters are then supplied to quantizers 134 1 to 134 n , respectively, to undergo down-sampling at a suitable sampling frequency. It is noted that a higher sampling frequency should be used for a broader frequency band.
  • the signals .[.in which the data have been compressed.].
  • .Iadd.resulting from compression .Iaddend.by requantization in this manner are outputted at terminal 138 by way of a multiplexer 136.
  • the output signals are then transmitted over a transmission channel to a terminal 148 of a decoder 140 and thence to dequantizers 144 1 to 144 n via demultiplexer 149 for decoding.
  • the decoded signals are converted by frequency converters 142 1 to 142 n into signals .[.of.]. .Iadd.in .Iaddend.the frequency bands on the time axis and .[.adds.]. .Iadd.are added .Iaddend.at a summing junction 146 so as to be outputted at a terminal 150 as the decoded .[.voice.]. .Iadd.audio .Iaddend.signals.
  • the conventional practice for acquiring the bit allocation information has been to transmit the energy value information of each frequency band as side information in addition to the signals of the respective bands.
  • the energy values of signals of the respective bands are computed at energy detection means 133 1 to 133 n , from the signals divided into the frequency bands by the frequency division filters 131 1 to 131 n of the encoder .[.130 and,.]. .Iadd.130.
  • the optimum numbers of bit allocation and the steps of quantization at the time of quantization of the signals of the respective bands are found .[.at a allocation-step.]. .Iadd.by the bit allocation .Iaddend.computing unit 135.
  • the results obtained .[.at.]. .Iadd.by .Iaddend.the computing unit 135 are used for requantizing the signals of the respective bands at quantizers 134 1 to 134 n .
  • the output signals that is the auxiliary or side information from the allocation-step computing unit 135, are transmitted to .[.an allocation-step.]. .Iadd.a bit allocation .Iaddend.computing unit 145 of the decoder 140, and the data from the unit 145 are transmitted to dequantizers 144 1 to 144 n where .[.an inverse operation of.]. .Iadd.an operation inverse to .Iaddend.that performed at the quantizers 134 1 to 134 n is performed to perform signal decoding.
  • frequency division and coding noise shaping or the like may be taken into account in keeping with human auditory characteristics, and more information may be allocated to those frequency bands in which the .[.voice.]. .Iadd.audio .Iaddend.energies are concentrated or which contribute more to subjective .[.voice.]. .Iadd.audio .Iaddend.quality, such as clarity.
  • Signal quantization and dequantization for the respective frequency bands are performed with the allocated number of bits for reducing the extent of obstruction of hearing by the quantization .[.noises.]. .Iadd.noise .Iaddend.to reduce the number of bits on the whole.
  • the above mentioned frequency division and coding results in generation of quantization noises only in the frequency band concerned without affecting the remaining bands.
  • the energy values of the signals of the respective bands may advantageously be employed as the quantization step widths or normalization factors of the respective frequency band signals.
  • the frequency band division is usually performed in such a manner that, in order to suit to the frequency analysis capability of the human auditory sense, a narrower bandwidth and a broader bandwidth are selected for the low frequency range and the high frequency range, respectively.
  • the size of the analytic block for each frequency range that is the number of samples or data will differ from one frequency range to another because of the difference in the band widths of the frequency .[.bands, with the result.]. .Iadd.bands.
  • the result of this is .Iaddend.that the efficiency of the analytic processing and hence the encoding efficiency are lowered.
  • .Iadd.domain i.e., the time for which an audio signal has a constant amplitude, .Iaddend.is thought to be longer and shorter for the low and high frequency signals, respectively, so that an efficient encoding consistent with the constant amplitude .[.period.]. .Iadd.domain .Iaddend.cannot be performed.
  • a digital signal encoding apparatus in which the input digital .[.signals are.]. .Iadd.signal is .Iaddend.divided into a plurality of frequency bands .[.which are so set that the bands with.]. higher frequencies will have broader bandwidths, and in which encoded signals are synthesized and outputted for each of .[.said.]. .Iadd.the .Iaddend.frequency ranges, wherein the improvement resides in that properties of the frequency components of the frequency bands are detected .Iadd.to provide a detection output .Iaddend.and encoding is controlled as a function of the detection output, and in that the detection time duration is selected to be longer for lower frequencies.
  • the definition of anlyses along the time axis is changed as a function of the bandwidths of the respective frequency bands to realize an optimum time interval for analyses for each frequency band.
  • FIG. 1 is a block diagram showing an example of the conventional frequency division and encoding.
  • FIG. 2 is a block diagram showing a first embodiment of the present invention.
  • FIG. 3 is a diagrammatic view showing the operation of the embodiment of FIG. 2.
  • FIG. 4 is a block diagram for illustrating a modified quantization system.
  • FIG. 5 is a block diagram showing a second embodiment of the present invention.
  • FIG. 6 is a diagrammatic view for illustrating the operation of the second embodiment shown in FIG. 5.
  • FIG. 7 is a block diagram showing the filter bank of FIG. 5 in detail.
  • FIG. 8 is a block diagram showing a decoder corresponding to the embodiment of FIG. 5.
  • FIGS. 9 and 10 are charts for illustrating the operation of the embodiment shown in FIG. 5.
  • FIG. 11 is a block diagram showing a third embodiment of the present invention.
  • FIG. 12 is a chart for illustrating the operation of the embodiment of FIG. 11.
  • FIG. 2 shows diagrammatically the construction of a digital signal encoding apparatus according to a first embodiment of the present invention, wherein the frequency range is divided into four bands, as shown in FIG. 3.
  • FIG. 2 .[.voice signals,.]. .Iadd.an audio signal .Iaddend.for example, .[.are supplied as.]. .Iadd.is supplied as an .Iaddend.input digital .[.signals.]. .Iadd.signal .Iaddend.to an input terminal 1 of the digital signal encoding apparatus. .[.These voice signals are.]. .Iadd.This audio signal is .Iaddend.first supplied to band-pass filters (BPFs) 11 to 14. These BPF filters divide the frequency range of the .[.voice signals.].
  • BPFs band-pass filters
  • Low-pass filters are built in the BPFs 11 to 14 so that the signals are shifted .[.towards the low frequency sides.]. .Iadd.downwards in frequency .Iaddend.by amounts corresponding to the .[.central.]. .Iadd.center .Iaddend.frequencies of the pass bands of the BPFs 11 to 14.
  • the signals of the respective frequency bands are quantized by quantizers 41 to 44.
  • the frequency characteristics of the frequency components .[.of.]. .Iadd.in .Iaddend.the respective bands are detected by spectrum analysis circuits 21 to 24, respectively; and quantization is controlled as a function of the detected output. That is, with the present encoding apparatus, the numbers of allocated bits at the time of quantization are determined on the basis of the results of the signal spectral analyses for the respective frequency bands, and quantization .[.at.]. .Iadd.by .Iaddend.the quantizers 41 to 44 is performed on the basis of the so determined numbers of bit allocation.
  • the signals of the respective frequency bands from the BPFs 11 to 14 are transmitted to spectrum analysis circuits 21 to 24, respectively, where spectral analyses for the .[.refractive.]. .Iadd.respective .Iaddend.frequency bands are performed.
  • the results of the analyses are transmitted to bit allocation .[.numbers.]. .Iadd.number .Iaddend.decision circuits 31 to 34 which allocate the number of the bits at the time of quantization, so that the bit allocation numbers are determined .[.at.]. .Iadd.by .Iaddend.the circuits 31 to 34 on the basis of the results of the analyses. Quantization .[.at.].
  • the temporal analytic accuracy that is, the analytic accuracy along the time axis
  • the durations of the spectral analyses are selected to be shorter and longer for the high and low frequency ranges, respectively.
  • the period of the analyses which is the detection time interval or the time width as a unit of the analyses along the time axis, is selected to be the longer, the lower the frequency.
  • Selection of the detection time intervals for .Iadd.the .Iaddend.spectral analyses as a function of the frequencies may be made on the basis of each of the clock signals obtained .[.upon.]. .Iadd.by .Iaddend.dividing the clock frequency of the clock .[.signals.]. .Iadd.signal .Iaddend.contained in the .[.voice signals..]. .Iadd.audio signal. .Iaddend.
  • the so separated clock .[.signals CK are.]. .Iadd.signal CK is .Iaddend.sequentially transmitted through 1/2 frequency dividers 3, 4 and 5 to produce frequency-divided clock .[.signals.]. .Iadd.signal .Iaddend.(1/2) CK, divided to one half the original clock frequency CK, frequency-divided clock .[.signals.].
  • .Iadd.signal .Iaddend.(1/4) CK divided to one-fourth the original clock frequency CK and frequency-divided clock .[.signals.]. .Iadd.signal .Iaddend.(1/8) CK, divided to one-eighth the original clock frequency CK.
  • CK is .Iaddend.transmitted to a spectrum analysis circuit 24 and a bit allocation number decision circuit 34, the frequency-divided clock .[.signals.]. .Iadd.signal .Iaddend.(1/2) CK .[.are.].
  • the detection time duration of the spectral analyses that is, the unit time width for the analyses, .[.becomes.]. .Iadd.is a .Iaddend.maximum at the spectrum analysis circuit 21, .[.while it becomes.]. .Iadd.is .Iaddend.progressively shorter at the spectrum analysis circuits 22 and 23, .[.becoming.]. .Iadd.and is .Iaddend.shortest at the spectrum analysis circuit 24.
  • the relative magnitude of the division ratio is preferably selected in the above described manner. Such relative magnitude is in keeping with the direction in which the block size of the spectral analyses, that is the width of the analytic block along the time axis, may be made the same, so that the efficiency is not lowered.
  • bit allocation numbers for quantization are determined in the above embodiment by the spectral analyses, the bit allocation numbers for quantization may also be determined using .Iadd.the .Iaddend.floating coefficients .[.for.]. .Iadd.of .Iaddend.a so-called block floating operation.
  • FIG. 4 shows a portion of the digital signal encoding apparatus of the present embodiment responsible for only one frequency band.
  • the maximum value detection circuit 51 is fed with the frequency-divided clock signals shown in FIG. 2 and the precision of definition along the time axis of the floating coefficient or the analysis time interval of the floating coefficient is determined on the basis of these frequency-divided clock signals. That is, in the present embodiment, the precision of definition along the time axis is selected to be higher and lower for the high and low frequencies, respectively, for realizing more efficient quantization.
  • the floating coefficients, for which the time intervals for analyses have been determined in this manner, are transmitted to a normalization circuit 52.
  • the aforementioned block .[.data are.]. .Iadd.of samples is .Iaddend.also supplied to the normalization circuit 52, so that the block .[.data are.]. .Iadd.of samples is .Iaddend.processed in the normalization circuit 52 by block floating on the basis of the above mentioned floating coefficients, and the blocks thus processed by block floating are quantized subsequently.
  • the block floating also is preferably performed in the constant-amplitude .[.signal domain,.]. .Iadd.domain of the signal, .Iaddend.the time interval of the floating coefficient for the constant-amplitude .[.signal.]. domain is selected to be longer for the low frequency range where the constant-amplitude domain is longer for realizing efficient block floating.
  • encoding is controlled in accordance with the detection output of the characteristics of the components of the frequency bands, while the detection time interval is selected to be longer for the lower frequencies, with the result that the detection efficiency is not lowered and hence efficient encoding suited to the nature of the input digital signals may be achieved.
  • FIG. 5 shows diagrammatically a typical construction of a high efficiency encoding apparatus for digital data according to the second embodiment.
  • the high efficiency encoding apparatus for .[.digital data.]. .Iadd.a digital signal .Iaddend.according to the present embodiment is constituted by a filter bank 104, made up of mirror filters, such as quadrature mirror filters, as the frequency division filters, orthogonal transform circuits 105 1 to 105 5 for performing an orthogonal transform, that is a transform of the .[.time axis into.]. .Iadd.the digital signal on the time axis to .Iaddend.the frequency axis, such as fast Fourier transform, and a bit allocation number decision circuit 106 for determining the bit numbers allocated to the respective frequency bands.
  • a filter bank 104 made up of mirror filters, such as quadrature mirror filters, as the frequency division filters, orthogonal transform circuits 105 1 to 105 5 for performing an orthogonal transform, that is a transform of the .[.time axis into.]. .Iadd.the digital signal on the time axis to .Iaddend.the frequency
  • .Iadd.input digital signal is .Iaddend.divided into a plurality n of, herein five, frequency bands .[.so that the bandwidths become.]. .Iadd.that have bandwidths that are .Iaddend.broader .[.for.]. .Iadd.towards .Iaddend.higher frequencies.
  • the input digital .[.data are.].
  • .Iadd.signal is .Iaddend.divided roughly into five channels, that is a channel CH1 with the frequency band of 0 to 1 kHz, a channel CH2 with the frequency band of 1 to 2 kHz, a channel CH3 with the frequency band of 2 to 4 kHz, a channel CH4 with the frequency band of 4 to 8 kHz and a channel CH5 with the frequency band of 8 to 16 kHz, as shown in FIG. 6.
  • Such frequency division in which the bandwidth .[.becomes broader for.]. .Iadd.is broader towards .Iaddend.higher frequencies is a frequency division technique taking human auditory characteristics into account, .[.similarly.].
  • the critical band which takes the human auditory characteristics into account, means the band occupied by a narrow band noise masking a pure tone or sound, wherein the noise has the same amplitude as and .[.encompassing the level or.]. .Iadd.encompasses the .Iaddend.pitch of the pure tone or sound, wherein, the higher the frequency, the broader becomes the bandwidth of the critical band. For each of these five channels, blocks each consisting of a plurality of .[.samples,.].
  • .Iadd.samples of the input digital signal, .Iaddend.that is a unit time block, are formed by the orthogonal transform circuits 105 1 to 105 5 and orthogonal transform, such as a fast Fourier transform, is performed .[.for.]. .Iadd.on .Iaddend.each unit time block of each channel to produce coefficient data .[.by.]. .Iadd.as a result of .Iaddend.the orthogonal transform, such as the FFT coefficient data for FFT.
  • the coefficient data of the respective channels are transmitted to the bit allocation number decision circuit 106, where the bit allocation number data for the respective channels are .[.formed.]. .Iadd.determined .Iaddend.and the coefficient data for the respective channels are quantized.
  • the encoder output is outputted at an output terminal 102, while the bit allocation number data are outputted at an output terminal 103.
  • the number of samples in the unit time block .[.becomes smaller for.]. .Iadd.is smaller in .Iaddend.the low frequency channels of narrower .[.bandwidths, while becoming larger for.]. .Iadd.bandwidths than in .Iaddend.the high frequency channels or broader bandwidths. In other words, the frequency resolution becomes lower and higher for the low and high frequency regions, respectively.
  • the coefficient data .[.by.].
  • .Iadd.resulting from .Iaddend.the orthogonal transformation may be obtained .[.at.]. .Iadd.in .Iaddend.each channel over the full frequency range at an equal interval on the frequency axis, so that the same .[.high.]. frequency resolution may be realized at both .[.the high and low frequency sides.]. .Iadd.high and low frequencies.Iaddend..
  • the unit time block .[.in.]. .Iadd.on .Iaddend.which the orthogonal transform is performed is composed of the same number of .[.sample data for.]. .Iadd.samples in .Iaddend.each band or channel.
  • the unit time block has different block lengths from one channel to another, in such a manner that the low .[.range has.]. .Iadd.frequency channels have .Iaddend.a longer block length and the high .[.range has.]. .Iadd.frequency channels have .Iaddend.a shorter block length. That is, .[.the power of.]. .Iadd.a high .Iaddend.frequency resolution is maintained at .[.a higher value for the lower frequency range while it is set.]. .Iadd.lower frequencies while the frequency resolution is reduced .Iaddend.so as not to be higher than is necessary .[.for the higher frequency range.]. .Iadd.at higher frequencies .Iaddend.and the .[.power of.]. temporal resolution is set to be high .[.for the higher frequency range.]. .Iadd.at higher frequencies.Iaddend....
  • the blocks with the same number of samples are subjected to .[.orthogonal transform for.]. .Iadd.the orthogonal transform in .Iaddend.channels CH1 to CH5, so that the same number of coefficient data, such as 6-point (pt) coefficient data may be obtained in the respective channels.
  • the channel block length is 32 ms for channel CH1, 32 ms for channel CH2, 16 ms for channel CH3, 1 ms for channel CH4 and 4 ms for channel CH5. If the fast Fourier transform is performed .[.by way of.].
  • the amount of processing is 64 log 2 64 for channels CH1 and CH2, 64 log 2 64 ⁇ 2 for channel CH3, 64 log 2 64 ⁇ 4 for channel CH4 and 64 log 2 64 ⁇ 8 for channel CH5, in the example of FIG. 6.
  • a high .[.power of.]. frequency resolution may be obtained at .[.the low frequency range.]. .Iadd.lower frequencies .Iaddend.which is critical for the human auditory sense, while the requirement for .[.a.]. .Iadd.the .Iaddend.higher temporal resolution necessary .[.with.]. .Iadd.for .Iaddend.transient signals rich in high frequency components as shown in FIG. 9 may also be satisfied.
  • the filter bank, the orthogonal transform circuits .[.or.]. .Iadd.and .Iaddend.the like may be those used conventionally so that the construction may be simplified and reduced in costs and the delay time in each circuit of the apparatus may be diminished.
  • FIG. 7 shows the .[.concrete.]. .Iadd.practical .Iaddend.construction of the filter bank 104.
  • QMF .Iadd.filter .Iaddend.141 where the 0 to 16 kHz input digital data are divided into 0 to 8 kHz output data and 8 to 16 kHz output data, of which the 8 to 16 kHz output data are supplied to a low range conversion circuit 145 5 .
  • the 8 to 16 kHz data undergo down-sampling in the low range conversion circuit 145 5 to generate 0 to 8 kHz data, which are outputted at output terminal 149 5 .
  • the 0 to 8 kHz output from QMF 141 is transmitted to a filter QMF 142, where it is similarly divided into a 4 to 9 kHz output transmitted to a low range conversion circuit 145 4 and a 0 to 4 kHz output transmitted to a QMF 143.
  • the 0 to 4 kHz .[.data.]. .Iadd.signal.Iaddend., converted into .[.the base band data, are.]. .Iadd.a base band signal is .Iaddend.obtained at the low range conversion circuit 145 4 so as to be outputted at output terminal 149 4 .
  • a 0 to 2 kHz output and a 2 to 4 kHz output are produced at .[.filter.].
  • QMF .Iadd.filter .Iaddend.143, while a 0 to 1 kHz output and a 1 to 2 kHz output are produced at .[.filter.].
  • QMF .Iadd.filter .Iaddend.144 so as to be converted into low range signals in low range conversion circuits 145 3 to 145 1 before being outputted at output terminals 149 3 to 149 1 .
  • These outputs are transmitted via channels CH1 to CH5 to the orthogonal transform circuits 105 1 to .[.105 5 , meanwhile, the.]. .Iadd.105 5 .
  • the .Iaddend.low frequency conversion circuit 145 1 may be omitted if so desired.
  • FIG. 8 shows the construction of a decoder.
  • the above mentioned encoder output is supplied to an input terminal 122, while the above mentioned bit allocation number information is supplied to an input terminal 123.
  • These restored coefficient data are transmitted to inverse orthogonal conversion circuits 125 1 to 125 5 where an .[.inverse.].
  • the allowable signal noise level is .[.set.]. .Iadd.calculated .Iaddend.and the masking effect is taken into consideration at this time so that the allowable noise level will be higher for the higher band frequency for the same energy value for determining the allocation bit number for each band.
  • the masking effect means both the masking effect for signals on the time axis and that for signals on the frequency axis. That is, .[.by such.]. .Iadd.according to the .Iaddend.masking effect, any noise .[.in the masked signals, if any, may.].
  • the orthogonal transform block consists of the same number of .[.sample data for.]. .Iadd.samples in .Iaddend.each band, so that .[.a high power of.]. .Iadd.the high .Iaddend.frequency resolution required for the lower .[.frequency range.]. .Iadd.frequencies .Iaddend.may be realized, while the requirement for a high .[.power of.]. temporal resolution for transient signals rich in high frequency components may also be satisfied.
  • the construction for implementing the encoder of the present embodiment may be simple and inexpensive since the components may be those used conventionally.
  • FIG. 11 showing, as a typical example of high efficiency encoding, a high efficiency encoder in which the above mentioned adaptive transform coding is applied.
  • the input digital .[.data are.]. .Iadd.signal is .Iaddend.transmitted via input terminal 201 to a block forming circuit 211 where .[.they are.]. .Iadd.it is .Iaddend.formed into blocks .[.at.]. .Iadd.of .Iaddend.a predetermined time .[.interval.]. .Iadd.duration .Iaddend.before being transmitted to a fast Fourier transform (FFT) circuit 212.
  • FFT fast Fourier transform
  • the FFT coefficient data expressed by the phase angle of 1023 points and the amplitude point of 1025 points (or the imaginary number part of 1023 points and the real number part of 1025 points), may be found. These FFT coefficient data are transmitted to critical band separation circuits 213 1 to 213 25 where they are divided into, for example 25 critical bands so as to be formed into blocks.
  • an approximately equal number of .[.samples of the.]. .Iadd.coefficient .Iaddend.data .[.of.]. .Iadd.in .Iaddend.the respective bands are collected and arranged into a block form. That is, the numbers of .Iadd.coefficient .Iaddend.data in the blocks are approximately equal. For example, .[.sample.]. .Iadd.N coefficient data .Iaddend.(FFT coefficient data) are collected along the frequency axis into one block. Referring to the signal path downstream of the critical band separation circuit 213 1 , .[.samples.].
  • .Iadd.N coefficient data .Iaddend.(one block) are outputted from the critical band separating circuit 213 1 .
  • This block is transmitted to the normalization circuit 214 1 , while also being transmitted to a floating coefficient computing circuit 217 1 .
  • the floating coefficient is computed and transmitted to the normalization circuit 214 1 , where the floating operation for the block is performed with the use of the floating coefficient for normalization.
  • the output of the normalization circuit 214 1 is transmitted to the quantization circuit 251 1 for quantizing the normalized block.
  • the quantization is performed on the basis of the bit number information from a bit allocation number decision circuit 219 determining the number of the bits allocated to the respective critical bands.
  • the output from the quantizer 215 1 is supplied to a synthesizer 216.
  • the floating coefficient is quantized in a floating coefficient quantization (FC quantization) circuit 218 1 , with a predetermined number of bits c for each block as a unit, before being transmitted to the .[.synthesizer.]. .Iadd.multiplexer .Iaddend.216.
  • FC quantization floating coefficient quantization
  • the quantization outputs from the block and the quantization output of the floating coefficient are .[.synthesized in the synthesizer.]. .Iadd.multiplexed in the multiplexer .Iaddend.216 so as to be outputted at an output terminal 202.
  • the FC quantization circuit is adapted to perform quantization with .[.or.]. .Iadd.a .Iaddend.number of bits which is .[.the lesser.]. .Iadd.less .Iaddend.the higher the frequency of the floating coefficient. That is, with the present high efficiency encoding apparatus, .Iadd.k .Iaddend.blocks each consisting of .Iadd.N .Iaddend.consecutive .[.samples.].
  • the output of the critical band separating circuit 213 25 is transmitted to .Iadd.k .Iaddend.sub-band forming circuits 221 25 ,1 to 221 25 ,k from which the blocks are consisting of .Iadd.N .Iaddend.consecutive .[.samples.]. .Iadd.coefficient data .Iaddend.are generated.
  • FC quantization circuits 218 25 ,1 to 218 25 ,k the floating coefficients .[.have been quantized on the block-by-block basis.]. .Iadd.are quantized block-by-block .Iaddend.with the number of bits r .[.lesser.]. .Iadd.which is less .Iaddend.than the predetermined number of bits c .[.at.]. .Iadd.used by .Iaddend.the FC quantization circuit 218, (c>r). .[.Meanwhile, the.].
  • a predetermined number of bits .[.r lesser.]. .Iadd.r which is less .Iaddend.than the predetermined number of bits c .[.for the lower range.]. .Iadd.used in the lower frequency .Iaddend.bands, such as band B 1 , B 2 , . . . among the critical bands B1 to B25, .[.are.]. .Iadd.is .Iaddend.provided to .[.k sub-bands sb 25 ,1 1 to sb 25 ,1 k in a higher range.].
  • bits may for example be 6 for the bands B1 and B2 and 4 for band B25, that is, four bits .Iadd.for .Iaddend.each of the sub-bands .[.sb 25, 1 to sb 25 1 k, as shown in brackets.]. .Iadd.sb 25 ,1 to sb 25 ,k, as shown in parentheses .Iaddend.in the drawing.
  • 6 bits, 5 bits and 4 bits may be provided to bands B1 to B5, B6 to B15 and bands B16 to B25, respectively.
  • the number of .[.the.]. bits may be adjusted .[.with the data.]. .Iadd.taking the signal .Iaddend.dispersion in the block .[.taken.]. into consideration. In this case, the numbers of allocation bits for the floating coefficients are decreased for the blocks with larger dispersion.
  • the predetermined number of bits are provided to the .[.sub-bands of the high frequency range.]. .Iadd.higher-frequency sub-bands .Iaddend.at the time of quantization of the floating .[.coefficients, it does not occur that.]. .Iadd.coefficients .Iaddend.the numbers of the bits of the floating coefficients per .[.sample.]. .Iadd.one of the coefficient data .Iaddend.in the .[.frequency band in the high frequency range be.]. .Iadd.higher frequency bands is not .Iaddend.decreased drastically as compared to the numbers of the bits for the .[.low frequency range,.].

Abstract

This invention relates to a digital signal encoding apparatus in which the .[.width of the range in.]. .Iadd.digital signal is divided into frequency components in plural frequency bands and the bandwidth of the frequency bands is .Iaddend.selected to be wider for .[.the.]. higher .[.frequency range.]. .Iadd.frequencies .Iaddend.of the digital .[.signals divided into a plurality of regions.]. .Iadd.signal .Iaddend.and in which the encoded signals are synthesized for the respective .[.ranges.]. .Iadd.frequency bands .Iaddend.wherein encoding is controlled as a function of the output detecting the characteristics of the .Iadd.frequency .Iaddend.components .[.of.]. .Iadd.in .Iaddend.the .[.divided.]. frequency .Iadd.bands .Iaddend.and the detection time interval is selected to be longer for the lower frequency .Iadd.bands .Iaddend.to enable more efficient encoding to be performed as a function of the properties of input digital signals.

Description

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a digital signal encoding apparatus for encoding input digital signals.
2. Prior Art
As a technique of high efficiency encoding of .Iadd.an .Iaddend.input .[.signals.]. .Iadd.signal.Iaddend., there are known .[.encoding.]. techniques .Iadd.of encoding .Iaddend.by so-called bit allocation, according to which input signals are divided into plural channels on the time or frequency axis and certain numbers of bits are adaptively allocated to the respective channels (bit allocation). Among the above mentioned .[.encoding.]. techniques .Iadd.of encoding .Iaddend.by bit allocation are so-called sub-band coding (SBC) in which .[.voice.]. .Iadd.audio .Iaddend.signals on the time axis are divided into signals .[.of.]. .Iadd.in .Iaddend.a plurality of frequency bands for encoding, .[.a.]. so-called adaptive transformation coding (ATC).Iadd., .Iaddend.in which .[.voice.]. audio signals on the time axis are transformed into signals on the frequency axis by orthogonal .[.transformation and the.]. .Iadd.transformation. Then the .Iaddend.resulting signals are divided into signals .[.of.]. .Iadd.in .Iaddend.a plurality of frequency bands for .[.adaptive.]. .Iadd.adaptively .Iaddend.coding .[.for.]. each frequency .[.band and a.]. .Iadd.band. Also known is .Iaddend.so-called adaptive bit allocation (APC-AB).Iadd., .Iaddend.which is a combination of the above mentioned SBC and .[.APC.]. .Iadd.ATC.Iaddend., and in which the .[.voice.]. .Iadd.audio .Iaddend.signals on the time axis are divided into signals .[.of.]. .Iadd.in .Iaddend.a plurality frequency bands and the signals .[.of.]. .Iadd.in .Iaddend.the respective bands are converted into base band or low range signals, after which multiple order linear predictive analyses are performed .[.for.]. .Iadd.to carry out ep predictive coding.
.[.The sub-band.]. .Iadd.Sub-band .Iaddend.coding, for example, .[.is.]. .Iadd.may be .Iaddend.performed by .[.a.]. .Iadd.the .Iaddend.circuit shown in FIG. 1. In this figure, digital g .[.voice.]. .Iadd.audio .Iaddend.signals, supplied to an input terminal 110 of an encoder 130, are fed to frequency division filters 1311 to 131n, which may for example be mirror filters, such as quadrature mirror filters (QMFs), so as to be limited in the frequency range and be shifted .[.to lower frequency sides..]. .Iadd.downwards in frequency. .Iaddend.That is, in these frequency division filters 1311 to 131n the input digital .[.voice.]. .Iadd.audio .Iaddend.signals are divided into separate frequency bands by band-pass filters or BPFs and subsequently passed through low-pass filters so as to be shifted to the lower frequency sides by amounts corresponding to the center frequencies of the pass bands of the LPFs. The signals from the filters are then supplied to quantizers 1341 to 134n, respectively, to undergo down-sampling at a suitable sampling frequency. It is noted that a higher sampling frequency should be used for a broader frequency band. The signals .[.in which the data have been compressed.]. .Iadd.resulting from compression .Iaddend.by requantization in this manner are outputted at terminal 138 by way of a multiplexer 136. The output signals are then transmitted over a transmission channel to a terminal 148 of a decoder 140 and thence to dequantizers 1441 to 144n via demultiplexer 149 for decoding. The decoded signals are converted by frequency converters 1421 to 142n into signals .[.of.]. .Iadd.in .Iaddend.the frequency bands on the time axis and .[.adds.]. .Iadd.are added .Iaddend.at a summing junction 146 so as to be outputted at a terminal 150 as the decoded .[.voice.]. .Iadd.audio .Iaddend.signals.
In signal .[.data.]. compression by the encoder 130, .[.quantization bits are adaptively allocated.]. .Iadd.quality is improved by adaptively allocating quantization bits .Iaddend.to the respective frequency bands .[.for minimizing.]. .Iadd.to minimize .Iaddend.the effects of .[.noises.]. .Iadd.noise .Iaddend.produced .[.on data compression of voice signals to improve the quality..]. .Iadd.as a result of compressing the audio signal. .Iaddend.The decoder 140 also acquires the bit allocation information by some means or other in performing the decoding.
The conventional practice for acquiring the bit allocation information has been to transmit the energy value information of each frequency band as side information in addition to the signals of the respective bands. In this case, the energy values of signals of the respective bands are computed at energy detection means 1331 to 133n, from the signals divided into the frequency bands by the frequency division filters 1311 to 131n of the encoder .[.130 and,.]. .Iadd.130. Then, .Iaddend.based on the computed values, the optimum numbers of bit allocation and the steps of quantization at the time of quantization of the signals of the respective bands are found .[.at a allocation-step.]. .Iadd.by the bit allocation .Iaddend.computing unit 135. The results obtained .[.at.]. .Iadd.by .Iaddend.the computing unit 135 are used for requantizing the signals of the respective bands at quantizers 1341 to 134n. The output signals, that is the auxiliary or side information from the allocation-step computing unit 135, are transmitted to .[.an allocation-step.]. .Iadd.a bit allocation .Iaddend.computing unit 145 of the decoder 140, and the data from the unit 145 are transmitted to dequantizers 1441 to 144n where .[.an inverse operation of.]. .Iadd.an operation inverse to .Iaddend.that performed at the quantizers 1341 to 134n is performed to perform signal decoding.
With the above described frequency division and coding, noise shaping or the like may be taken into account in keeping with human auditory characteristics, and more information may be allocated to those frequency bands in which the .[.voice.]. .Iadd.audio .Iaddend.energies are concentrated or which contribute more to subjective .[.voice.]. .Iadd.audio .Iaddend.quality, such as clarity. Signal quantization and dequantization for the respective frequency bands are performed with the allocated number of bits for reducing the extent of obstruction of hearing by the quantization .[.noises.]. .Iadd.noise .Iaddend.to reduce the number of bits on the whole. The above mentioned frequency division and coding results in generation of quantization noises only in the frequency band concerned without affecting the remaining bands. Meanwhile, when the energy value information is transmitted as the auxiliary data, as described above, the energy values of the signals of the respective bands may advantageously be employed as the quantization step widths or normalization factors of the respective frequency band signals.
Should the frequency division and coding be applied to musical or voice signals, the frequency band division is usually performed in such a manner that, in order to suit to the frequency analysis capability of the human auditory sense, a narrower bandwidth and a broader bandwidth are selected for the low frequency range and the high frequency range, respectively.
However, with such a frequency band division, suited to the frequency analysis capability of the human auditory sense, if the definition of temporal analyses for the respective frequency bands, that is the time width as the unit of analyses along the time axis, should be the same, the size of the analytic block for each frequency range, that is the number of samples or data will differ from one frequency range to another because of the difference in the band widths of the frequency .[.bands, with the result.]. .Iadd.bands. The result of this is .Iaddend.that the efficiency of the analytic processing and hence the encoding efficiency are lowered. On the other hand, the constant amplitude .[.period.]. .Iadd.domain, i.e., the time for which an audio signal has a constant amplitude, .Iaddend.is thought to be longer and shorter for the low and high frequency signals, respectively, so that an efficient encoding consistent with the constant amplitude .[.period.]. .Iadd.domain .Iaddend.cannot be performed.
OBJECT AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a digital signal encoding apparatus in which, in encoding .[.voice.]. .Iadd.audio .Iaddend.signals divided into a plurality of frequency bands to suit the frequency analysis capability of the human auditory sense, a more efficient encoding consistent with the properties of the .[.voice.]. .Iadd.audio .Iaddend.signals may be achieved.
It is another object of the present invention to provide a digital signal encoding apparatus in which a higher power of frequency resolution is realized .[.for a low frequency range.]. .Iadd.at lower frequencies .Iaddend.and a higher power of temporal resolution is achieved .[.for higher frequency range.]. .Iadd.at higher frequencies .Iaddend.where .Iadd.the .Iaddend.duration the constant amplitude .[.state.]. .Iadd.domain .Iaddend.is shorter.
According to the present invention, there is provided a digital signal encoding apparatus in which the input digital .[.signals are.]. .Iadd.signal is .Iaddend.divided into a plurality of frequency bands .[.which are so set that the bands with.]. higher frequencies will have broader bandwidths, and in which encoded signals are synthesized and outputted for each of .[.said.]. .Iadd.the .Iaddend.frequency ranges, wherein the improvement resides in that properties of the frequency components of the frequency bands are detected .Iadd.to provide a detection output .Iaddend.and encoding is controlled as a function of the detection output, and in that the detection time duration is selected to be longer for lower frequencies.
Thus, according to the present invention, the definition of anlyses along the time axis is changed as a function of the bandwidths of the respective frequency bands to realize an optimum time interval for analyses for each frequency band.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing an example of the conventional frequency division and encoding.
FIG. 2 is a block diagram showing a first embodiment of the present invention.
FIG. 3 is a diagrammatic view showing the operation of the embodiment of FIG. 2.
FIG. 4 is a block diagram for illustrating a modified quantization system.
FIG. 5 is a block diagram showing a second embodiment of the present invention.
FIG. 6 is a diagrammatic view for illustrating the operation of the second embodiment shown in FIG. 5.
FIG. 7 is a block diagram showing the filter bank of FIG. 5 in detail.
FIG. 8 is a block diagram showing a decoder corresponding to the embodiment of FIG. 5.
FIGS. 9 and 10 are charts for illustrating the operation of the embodiment shown in FIG. 5.
FIG. 11 is a block diagram showing a third embodiment of the present invention.
FIG. 12 is a chart for illustrating the operation of the embodiment of FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
By referring to the drawings, certain preferred embodiments of the present invention will be explained in detail.
FIG. 2 shows diagrammatically the construction of a digital signal encoding apparatus according to a first embodiment of the present invention, wherein the frequency range is divided into four bands, as shown in FIG. 3.
In FIG. 2, .[.voice signals,.]. .Iadd.an audio signal .Iaddend.for example, .[.are supplied as.]. .Iadd.is supplied as an .Iaddend.input digital .[.signals.]. .Iadd.signal .Iaddend.to an input terminal 1 of the digital signal encoding apparatus. .[.These voice signals are.]. .Iadd.This audio signal is .Iaddend.first supplied to band-pass filters (BPFs) 11 to 14. These BPF filters divide the frequency range of the .[.voice signals.]. .Iadd.audio signal .Iaddend.into a plurality of frequency bands so that the bandwidth will become broader for the higher frequency bands so as to suit the frequency discriminating capability of the human auditory sense. Low-pass filters are built in the BPFs 11 to 14 so that the signals are shifted .[.towards the low frequency sides.]. .Iadd.downwards in frequency .Iaddend.by amounts corresponding to the .[.central.]. .Iadd.center .Iaddend.frequencies of the pass bands of the BPFs 11 to 14.
The .[.voice signals,.]. .Iadd.audio signal, .Iaddend.thus divided into plural frequency bands and shifted .[.to the lower frequency sides.]. .Iadd.downwards in frequency .Iaddend.by the BPFs 11 to 14, .[.are.]. .Iadd.is .Iaddend.divided into frequency bands B1, B2, B3 and B4 by the BPFs 11, 12, 13 and 14, as shown in FIG. 3. These frequency bands B1 to B4 are selected so that the bandwidths will be the broader, the higher the frequencies, as mentioned previously.
The signals of the respective frequency bands are quantized by quantizers 41 to 44. During such quantization, the frequency characteristics of the frequency components .[.of.]. .Iadd.in .Iaddend.the respective bands are detected by spectrum analysis circuits 21 to 24, respectively; and quantization is controlled as a function of the detected output. That is, with the present encoding apparatus, the numbers of allocated bits at the time of quantization are determined on the basis of the results of the signal spectral analyses for the respective frequency bands, and quantization .[.at.]. .Iadd.by .Iaddend.the quantizers 41 to 44 is performed on the basis of the so determined numbers of bit allocation.
Thus the signals of the respective frequency bands from the BPFs 11 to 14 are transmitted to spectrum analysis circuits 21 to 24, respectively, where spectral analyses for the .[.refractive.]. .Iadd.respective .Iaddend.frequency bands are performed. The results of the analyses are transmitted to bit allocation .[.numbers.]. .Iadd.number .Iaddend.decision circuits 31 to 34 which allocate the number of the bits at the time of quantization, so that the bit allocation numbers are determined .[.at.]. .Iadd.by .Iaddend.the circuits 31 to 34 on the basis of the results of the analyses. Quantization .[.at.]. .Iadd.by .Iaddend.the quantizers 41 to 44 .[.are.]. .Iadd.is .Iaddend.performed on the basis of the so determined bit allocation numbers. .[.Quantization.]. .Iadd.The quantized .Iaddend.outputs of the quantizers 41 to 44 are synthesized by a multiplexer 6 so as to be outputted at an output terminal 7 of the digital signal encoding apparatus of the present embodiment.
It is noted that, in quantizing the .[.voice signals.]. .Iadd.audio signal .Iaddend.previously divided into plural frequency bands to suit the frequency analysis capability of the human auditory sense, since the bandwidths of the respective frequency bands differ from one frequency band to another, the block sizes of the spectral analyses, that is the widths along the time axis of the analytic blocks, will differ from one frequency band to another for the same assumed precision in definition of the analyses along time axis of the frequency .[.bands, with the result that.]. .Iadd.bands. As a result, .Iaddend.the efficiency of spectral analyses, and hence the quantization efficiency, .[.are.]. .Iadd.is .Iaddend.lowered. Since it is thought in general that the constant amplitude domain of .[.the low frequency range signal.]. .Iadd.lower frequency signals .Iaddend.is longer and that of .[.the high frequency range signal.]. .Iadd.higher frequency signals .Iaddend.is shorter, an efficient coding taking .[.such.]. .Iadd.into account this .Iaddend.difference in the length of the constant amplitude domain cannot be realized.
With this in view, the temporal analytic accuracy, that is, the analytic accuracy along the time axis, is selected to be higher and lower for the high and low frequency range, respectively, for realizing a more efficient quantization. In other words, the durations of the spectral analyses are selected to be shorter and longer for the high and low frequency ranges, respectively.
That is, .[.for.]. .Iadd.in the .Iaddend.spectral analyses .Iadd.performed .Iaddend.by the spectral analysis circuits 21 to 24, the period of the analyses, which is the detection time interval or the time width as a unit of the analyses along the time axis, is selected to be the longer, the lower the frequency. Selection of the detection time intervals for .Iadd.the .Iaddend.spectral analyses as a function of the frequencies may be made on the basis of each of the clock signals obtained .[.upon.]. .Iadd.by .Iaddend.dividing the clock frequency of the clock .[.signals.]. .Iadd.signal .Iaddend.contained in the .[.voice signals..]. .Iadd.audio signal. .Iaddend.
Thus, in the present embodiment, the clock signal .[.components in the voice signals.]. .Iadd.in the audio signal .Iaddend.supplied to the input terminal 1 .[.are.]. .Iadd.is .Iaddend.separated in a clock circuit 2. The so separated clock .[.signals CK are.]. .Iadd.signal CK is .Iaddend.sequentially transmitted through 1/2 frequency dividers 3, 4 and 5 to produce frequency-divided clock .[.signals.]. .Iadd.signal .Iaddend.(1/2) CK, divided to one half the original clock frequency CK, frequency-divided clock .[.signals.]. .Iadd.signal .Iaddend.(1/4) CK, divided to one-fourth the original clock frequency CK and frequency-divided clock .[.signals.]. .Iadd.signal .Iaddend.(1/8) CK, divided to one-eighth the original clock frequency CK. Of the so-produced clock signals.Iadd., .Iaddend.the clock .[.signals CK are.]. .Iadd.signal CK is .Iaddend.transmitted to a spectrum analysis circuit 24 and a bit allocation number decision circuit 34, the frequency-divided clock .[.signals.]. .Iadd.signal .Iaddend.(1/2) CK .[.are.]. .Iadd.is .Iaddend.transmitted to a spectrum analysis circuit 23 and a bit allocation number decision circuit 33, the frequency-divided clock .[.signals (1/4) CK are.]. .Iadd.signal (1/4) CK is .Iaddend.transmitted to a spectrum analysis circuit 22 and a bit allocation number decision circuit 32 and the frequency-divided clock .[.signals (1/8) CK are.]. .Iadd.signal (1/8) CK is .Iaddend.transmitted to a spectrum analysis circuit 21 and a bit allocation number decision circuit 31.
.[.Hence.]. .Iadd.Consequently.Iaddend., the detection time duration of the spectral analyses, that is, the unit time width for the analyses, .[.becomes.]. .Iadd.is a .Iaddend.maximum at the spectrum analysis circuit 21, .[.while it becomes.]. .Iadd.is .Iaddend.progressively shorter at the spectrum analysis circuits 22 and 23, .[.becoming.]. .Iadd.and is .Iaddend.shortest at the spectrum analysis circuit 24.
By changing the detection time intervals for spectral analyses in this manner, it becomes possible to .[.realize.]. .Iadd.perform .Iaddend.efficient spectral analyses and hence efficient quantization at the time of quantizing the .[.voice signals.]. .Iadd.audio signal .Iaddend.divided into a plurality of frequency bands to suit the frequency analysis capability of the human auditory sense. With the detection time interval thus changed, the spectrum for each frequency band may be thought to be constant in each block of the band, so that the values of the spectrum analyses for the long-time block may be used in the lower frequency range in substitution for the short-time spectral waveform.
.[.Meanwhile, the.]. .Iadd.The .Iaddend.division ratio of the frequency range need not necessarily be inversely .[.proportionate.]. .Iadd.proportional .Iaddend.to the time durations for spectrum analyses, that is the time durations bearing the ratios of 8:4:2:1 to the .[.frequency.]. .Iadd.period .Iaddend.of the clock signals CK. However, the relative magnitude of the division ratio is preferably selected in the above described manner. Such relative magnitude is in keeping with the direction in which the block size of the spectral analyses, that is the width of the analytic block along the time axis, may be made the same, so that the efficiency is not lowered.
Although the bit allocation numbers for quantization are determined in the above embodiment by the spectral analyses, the bit allocation numbers for quantization may also be determined using .Iadd.the .Iaddend.floating coefficients .[.for.]. .Iadd.of .Iaddend.a so-called block floating operation.
FIG. 4 shows a portion of the digital signal encoding apparatus of the present embodiment responsible for only one frequency band.
In this figure, .[.voice signals.]. .Iadd.the audio signal .Iaddend.at an input terminal 1 .[.are.]. .Iadd.is .Iaddend.passed through a band-pass filter (BPF) 50 where .[.the signals of.]. .Iadd.components of the audio signal in .Iaddend.a predetermined frequency band are .[.taken out.]. .Iadd.extracted .Iaddend.as a block which is then transmitted to a maximum value detection circuit 51 adapted for detecting the maximum value .[.data.]. .Iadd.of the samples .Iaddend.in the block. In this maximum value detection circuit 51, the maximum value .[.data.]. .Iadd.sample .Iaddend.in the block is detected, and the floating coefficient for the block floating operation is found on the basis of the maximum value .[.data.]. .Iadd.sample.Iaddend..
In detecting the floating coefficient, if the same degree of accuracy is used for .Iadd.the .Iaddend.temporal analyses of the respective frequency bands, the efficiency of detection of the floating coefficients and hence the quantization efficiency tends to be lowered, while it is not possible to perform efficient encoding in accordance with the constant-amplitude domains.
Thus the maximum value detection circuit 51 is fed with the frequency-divided clock signals shown in FIG. 2 and the precision of definition along the time axis of the floating coefficient or the analysis time interval of the floating coefficient is determined on the basis of these frequency-divided clock signals. That is, in the present embodiment, the precision of definition along the time axis is selected to be higher and lower for the high and low frequencies, respectively, for realizing more efficient quantization.
The floating coefficients, for which the time intervals for analyses have been determined in this manner, are transmitted to a normalization circuit 52. The aforementioned block .[.data are.]. .Iadd.of samples is .Iaddend.also supplied to the normalization circuit 52, so that the block .[.data are.]. .Iadd.of samples is .Iaddend.processed in the normalization circuit 52 by block floating on the basis of the above mentioned floating coefficients, and the blocks thus processed by block floating are quantized subsequently.
Since the block floating also is preferably performed in the constant-amplitude .[.signal domain,.]. .Iadd.domain of the signal, .Iaddend.the time interval of the floating coefficient for the constant-amplitude .[.signal.]. domain is selected to be longer for the low frequency range where the constant-amplitude domain is longer for realizing efficient block floating.
That is, in the above described first embodiment of the digital signal encoding apparatus of the present invention, encoding is controlled in accordance with the detection output of the characteristics of the components of the frequency bands, while the detection time interval is selected to be longer for the lower frequencies, with the result that the detection efficiency is not lowered and hence efficient encoding suited to the nature of the input digital signals may be achieved.
A second embodiment of the present invention will be hereinafter explained by referring to FIG. 5, et seq.
FIG. 5 shows diagrammatically a typical construction of a high efficiency encoding apparatus for digital data according to the second embodiment.
Referring to FIG. 5, the high efficiency encoding apparatus for .[.digital data.]. .Iadd.a digital signal .Iaddend.according to the present embodiment is constituted by a filter bank 104, made up of mirror filters, such as quadrature mirror filters, as the frequency division filters, orthogonal transform circuits 1051 to 1055 for performing an orthogonal transform, that is a transform of the .[.time axis into.]. .Iadd.the digital signal on the time axis to .Iaddend.the frequency axis, such as fast Fourier transform, and a bit allocation number decision circuit 106 for determining the bit numbers allocated to the respective frequency bands.
To the input terminal 101 .[.are supplied.]. .Iadd.is supplied a .Iaddend.0 to 16 kHz input digital .[.data.]. .Iadd.signal .Iaddend.obtained upon sampling .[.audio signals.]. .Iadd.an audio signal .Iaddend.with a sampling frequency fs=32 kHz. .[.These input data are.]. .Iadd.The input digital signal is .Iaddend.transmitted to the filter bank 104, by means of which the .[.input data are.]. .Iadd.input digital signal is .Iaddend.divided into a plurality n of, herein five, frequency bands .[.so that the bandwidths become.]. .Iadd.that have bandwidths that are .Iaddend.broader .[.for.]. .Iadd.towards .Iaddend.higher frequencies. Thus the input digital .[.data are.]. .Iadd.signal is .Iaddend.divided roughly into five channels, that is a channel CH1 with the frequency band of 0 to 1 kHz, a channel CH2 with the frequency band of 1 to 2 kHz, a channel CH3 with the frequency band of 2 to 4 kHz, a channel CH4 with the frequency band of 4 to 8 kHz and a channel CH5 with the frequency band of 8 to 16 kHz, as shown in FIG. 6. Such frequency division in which the bandwidth .[.becomes broader for.]. .Iadd.is broader towards .Iaddend.higher frequencies is a frequency division technique taking human auditory characteristics into account, .[.similarly.]. .Iadd.similar .Iaddend.to the so-called critical band. The critical band, which takes the human auditory characteristics into account, means the band occupied by a narrow band noise masking a pure tone or sound, wherein the noise has the same amplitude as and .[.encompassing the level or.]. .Iadd.encompasses the .Iaddend.pitch of the pure tone or sound, wherein, the higher the frequency, the broader becomes the bandwidth of the critical band. For each of these five channels, blocks each consisting of a plurality of .[.samples,.]. .Iadd.samples of the input digital signal, .Iaddend.that is a unit time block, are formed by the orthogonal transform circuits 1051 to 1055 and orthogonal transform, such as a fast Fourier transform, is performed .[.for.]. .Iadd.on .Iaddend.each unit time block of each channel to produce coefficient data .[.by.]. .Iadd.as a result of .Iaddend.the orthogonal transform, such as the FFT coefficient data for FFT. The coefficient data of the respective channels are transmitted to the bit allocation number decision circuit 106, where the bit allocation number data for the respective channels are .[.formed.]. .Iadd.determined .Iaddend.and the coefficient data for the respective channels are quantized. The encoder output is outputted at an output terminal 102, while the bit allocation number data are outputted at an output terminal 103.
In this manner, by constituting the unit time blocks from channel .[.data.]. .Iadd.signals .Iaddend.having broader bandwidths for higher frequencies, the number of samples in the unit time block .[.becomes smaller for.]. .Iadd.is smaller in .Iaddend.the low frequency channels of narrower .[.bandwidths, while becoming larger for.]. .Iadd.bandwidths than in .Iaddend.the high frequency channels or broader bandwidths. In other words, the frequency resolution becomes lower and higher for the low and high frequency regions, respectively. By performing orthogonal transformation of each of the time blocks of the respective channels, the coefficient data .[.by.]. .Iadd.resulting from .Iaddend.the orthogonal transformation may be obtained .[.at.]. .Iadd.in .Iaddend.each channel over the full frequency range at an equal interval on the frequency axis, so that the same .[.high.]. frequency resolution may be realized at both .[.the high and low frequency sides.]. .Iadd.high and low frequencies.Iaddend..
If the human auditory characteristics are considered, .[.while.]. the frequency resolution .[.power.]. needs to be high .[. in the low frequency range, it.]. .Iadd.at lower frequencies, but .Iaddend.need not be so high .[.in the high frequency range.]. .Iadd.at higher frequencies.Iaddend.. For this reason, with the present embodiments, the unit time block .[.in.]. .Iadd.on .Iaddend.which the orthogonal transform is performed is composed of the same number of .[.sample data for.]. .Iadd.samples in .Iaddend.each band or channel. In other words, the unit time block has different block lengths from one channel to another, in such a manner that the low .[.range has.]. .Iadd.frequency channels have .Iaddend.a longer block length and the high .[.range has.]. .Iadd.frequency channels have .Iaddend.a shorter block length. That is, .[.the power of.]. .Iadd.a high .Iaddend.frequency resolution is maintained at .[.a higher value for the lower frequency range while it is set.]. .Iadd.lower frequencies while the frequency resolution is reduced .Iaddend.so as not to be higher than is necessary .[.for the higher frequency range.]. .Iadd.at higher frequencies .Iaddend.and the .[.power of.]. temporal resolution is set to be high .[.for the higher frequency range.]. .Iadd.at higher frequencies.Iaddend..
It is noted that, with the present embodiment, the blocks with the same number of samples are subjected to .[.orthogonal transform for.]. .Iadd.the orthogonal transform in .Iaddend.channels CH1 to CH5, so that the same number of coefficient data, such as 6-point (pt) coefficient data may be obtained in the respective channels. In this case, the channel block length is 32 ms for channel CH1, 32 ms for channel CH2, 16 ms for channel CH3, 1 ms for channel CH4 and 4 ms for channel CH5. If the fast Fourier transform is performed .[.by way of.]. .Iadd.as .Iaddend.the aforementioned orthogonal transform, the amount of processing is 64 log2 64 for channels CH1 and CH2, 64 log2 64×2 for channel CH3, 64 log2 64×4 for channel CH4 and 64 log2 64×8 for channel CH5, in the example of FIG. 6. In case of the fast Fourier transform for the full frequency range, the amount of processing is 1024 log2 1024=1024×10 for the sampling frequency fs=32 kHz and the coefficient data is 1024 pt for the block length equal to 32 ms.
With the above described construction of the present embodiment, a high .[.power of.]. frequency resolution may be obtained at .[.the low frequency range.]. .Iadd.lower frequencies .Iaddend.which is critical for the human auditory sense, while the requirement for .[.a.]. .Iadd.the .Iaddend.higher temporal resolution necessary .[.with.]. .Iadd.for .Iaddend.transient signals rich in high frequency components as shown in FIG. 9 may also be satisfied. The filter bank, the orthogonal transform circuits .[.or.]. .Iadd.and .Iaddend.the like may be those used conventionally so that the construction may be simplified and reduced in costs and the delay time in each circuit of the apparatus may be diminished.
FIG. 7 shows the .[.concrete.]. .Iadd.practical .Iaddend.construction of the filter bank 104. In this figure, the 0 to 16 kHz input digital .[.data.]. .Iadd.signal .Iaddend.with the sampling frequency fs=32 kHz is supplied to an input terminal 140 of the filter bank 104. .[.These.]. .Iadd.This .Iaddend.input digital .[.data are.]. .Iadd.signal is .Iaddend.first supplied to a .[.filter.]. QMF .Iadd.filter .Iaddend.141 where the 0 to 16 kHz input digital data are divided into 0 to 8 kHz output data and 8 to 16 kHz output data, of which the 8 to 16 kHz output data are supplied to a low range conversion circuit 1455. The 8 to 16 kHz data undergo down-sampling in the low range conversion circuit 1455 to generate 0 to 8 kHz data, which are outputted at output terminal 1495. The 0 to 8 kHz output from QMF 141 is transmitted to a filter QMF 142, where it is similarly divided into a 4 to 9 kHz output transmitted to a low range conversion circuit 1454 and a 0 to 4 kHz output transmitted to a QMF 143. The 0 to 4 kHz .[.data.]. .Iadd.signal.Iaddend., converted into .[.the base band data, are.]. .Iadd.a base band signal is .Iaddend.obtained at the low range conversion circuit 1454 so as to be outputted at output terminal 1494. Similarly, a 0 to 2 kHz output and a 2 to 4 kHz output are produced at .[.filter.]. QMF .Iadd.filter .Iaddend.143, while a 0 to 1 kHz output and a 1 to 2 kHz output are produced at .[.filter.]. QMF .Iadd.filter .Iaddend.144, so as to be converted into low range signals in low range conversion circuits 1453 to 1451 before being outputted at output terminals 1493 to 1491. These outputs are transmitted via channels CH1 to CH5 to the orthogonal transform circuits 1051 to .[.1055, meanwhile, the.]. .Iadd.1055. The .Iaddend.low frequency conversion circuit 1451 may be omitted if so desired.
FIG. 8 shows the construction of a decoder. In this figure, the above mentioned encoder output is supplied to an input terminal 122, while the above mentioned bit allocation number information is supplied to an input terminal 123. These .[.data.]. .Iadd.signals .Iaddend.are supplied to a channel information generator 126 where the .[.data of.]. .Iadd.signal from .Iaddend.the encoder output .[.are restored into.]. .Iadd.is dequantized to restore the .Iaddend.coefficient data of the respective channels on the basis of the bit allocation number information. These restored coefficient data are transmitted to inverse orthogonal conversion circuits 1251 to 1255 where an .[.inverse.]. operation .Iadd.inverse .Iaddend.to that in the orthogonal conversion circuits 1051 to 1055 is performed .[.to produce data in which.]. .Iadd.in which the coefficient data on .Iaddend.the frequency axis is converted into .Iadd.samples of a signal on .Iaddend.the time axis. The .[.data of.]. .Iadd.samples .Iaddend.the respective channels on the time axis are decoded by a synthesis filter 124 before being outputted as the decoder output .Iadd.signal .Iaddend.at output terminal 121.
In .[.forming.]. .Iadd.determining .Iaddend.the bit allocation information for each channel in the bit allocation number decision circuit 106 of FIG. 5, the allowable signal noise level is .[.set.]. .Iadd.calculated .Iaddend.and the masking effect is taken into consideration at this time so that the allowable noise level will be higher for the higher band frequency for the same energy value for determining the allocation bit number for each band. The masking effect means both the masking effect for signals on the time axis and that for signals on the frequency axis. That is, .[.by such.]. .Iadd.according to the .Iaddend.masking effect, any noise .[.in the masked signals, if any, may.]. .Iadd.that is masked by a signal will .Iaddend.not be heard. Hence, in .[.the.]. actual audio signals, any .[.noises in the masked.]. .Iadd.noise masked by .Iaddend.signals on the frequency axis .[.are allowable noises.]. .Iadd.is allowable noise.Iaddend., so that, during quantization of the .[.audio.]. .Iadd.coefficient .Iaddend.data, it becomes possible to diminish the number of the allocated bits corresponding to the allowable noise level.
In the above described second embodiment of the high efficiency encoder for .[.digital data,.]. .Iadd.an input digital signal, .Iaddend.the input digital .[.data are.]. .Iadd.signal is .Iaddend.divided into a plurality of bands .[.so that the bandwidth will become broader for the higher frequency range,.]. .Iadd.that have bandwidths that are broader towards higher frequencies, .Iaddend.blocks each consisting of a plurality of samples are formed for each band and orthogonal transform is performed for each of the blocks so as to produce the coefficient data to realize encoding with a higher frequency resolution .[.power.].. The orthogonal transform block consists of the same number of .[.sample data for.]. .Iadd.samples in .Iaddend.each band, so that .[.a high power of.]. .Iadd.the high .Iaddend.frequency resolution required for the lower .[.frequency range.]. .Iadd.frequencies .Iaddend.may be realized, while the requirement for a high .[.power of.]. temporal resolution for transient signals rich in high frequency components may also be satisfied.
In this manner a highly efficient encoding consistent with the human auditory characteristics may be achieved. The construction for implementing the encoder of the present embodiment may be simple and inexpensive since the components may be those used conventionally.
A third embodiment of the present invention will be hereinafter explained by referring to FIG. 11 showing, as a typical example of high efficiency encoding, a high efficiency encoder in which the above mentioned adaptive transform coding is applied.
In FIG. 11, the input digital .[.data are.]. .Iadd.signal is .Iaddend.transmitted via input terminal 201 to a block forming circuit 211 where .[.they are.]. .Iadd.it is .Iaddend.formed into blocks .[.at.]. .Iadd.of .Iaddend.a predetermined time .[.interval.]. .Iadd.duration .Iaddend.before being transmitted to a fast Fourier transform (FFT) circuit 212. In this FFT circuit 212, the .[.data in the form of unit time blocks.]. .Iadd.unit time blocks of the input digital signal .Iaddend.are converted into .Iadd.coefficient .Iaddend.data on the frequency axis. Assuming that the FFT operation for 2048 samples is to be performed, the FFT coefficient data expressed by the phase angle of 1023 points and the amplitude point of 1025 points (or the imaginary number part of 1023 points and the real number part of 1025 points), may be found. These FFT coefficient data are transmitted to critical band separation circuits 2131 to 21325 where they are divided into, for example 25 critical bands so as to be formed into blocks.
Since the band or block width .Iadd.of the critical bands .Iaddend.becomes progressively broader .[.for the higher frequency range,.]. .Iadd.towards higher frequencies, .Iaddend.the number of .[.samples in one block becomes larger for the higher frequency range than for the lower frequency range.]. .Iadd.coefficient data in each band is larger at higher frequencies than at lower frequencies.Iaddend.. In such case, the efficiency of block floating .[.for the higher frequency range,.]. .Iadd.applied to the higher-frequency bands, .Iaddend.which will be explained subsequently, .[.becomes lower..]. .Iadd.is reduced. .Iaddend.
Thus, with the present embodiment, an approximately equal number of .[.samples of the.]. .Iadd.coefficient .Iaddend.data .[.of.]. .Iadd.in .Iaddend.the respective bands are collected and arranged into a block form. That is, the numbers of .Iadd.coefficient .Iaddend.data in the blocks are approximately equal. For example, .[.sample.]. .Iadd.N coefficient data .Iaddend.(FFT coefficient data) are collected along the frequency axis into one block. Referring to the signal path downstream of the critical band separation circuit 2131, .[.samples.]. .Iadd.N coefficient data .Iaddend.(one block) are outputted from the critical band separating circuit 2131. This block is transmitted to the normalization circuit 2141, while also being transmitted to a floating coefficient computing circuit 2171. In the computing circuit 2171, the floating coefficient is computed and transmitted to the normalization circuit 2141, where the floating operation for the block is performed with the use of the floating coefficient for normalization. The output of the normalization circuit 2141 is transmitted to the quantization circuit 2511 for quantizing the normalized block. The quantization is performed on the basis of the bit number information from a bit allocation number decision circuit 219 determining the number of the bits allocated to the respective critical bands. The output from the quantizer 2151 is supplied to a synthesizer 216. The floating coefficient is quantized in a floating coefficient quantization (FC quantization) circuit 2181, with a predetermined number of bits c for each block as a unit, before being transmitted to the .[.synthesizer.]. .Iadd.multiplexer .Iaddend.216. The quantization outputs from the block and the quantization output of the floating coefficient are .[.synthesized in the synthesizer.]. .Iadd.multiplexed in the multiplexer .Iaddend.216 so as to be outputted at an output terminal 202.
It is noted that, for maintaining .Iadd.the efficiency of .Iaddend.the block floating operation at .[.the higher frequency range.]. .Iadd.higher frequencies .Iaddend.and achieving effective bit allocation which takes human auditory characteristics into account, the FC quantization circuit is adapted to perform quantization with .[.or.]. .Iadd.a .Iaddend.number of bits which is .[.the lesser.]. .Iadd.less .Iaddend.the higher the frequency of the floating coefficient. That is, with the present high efficiency encoding apparatus, .Iadd.k .Iaddend.blocks each consisting of .Iadd.N .Iaddend.consecutive .[.samples.]. .Iadd.coefficient data .Iaddend.are generated from each band .[.for the high frequency range having.]. .Iadd.at higher frequencies where the bands have .Iaddend.a broader band width and .[.a large number of samples,.]. .Iadd.include a larger number of coefficient data, .Iaddend.wherein k denotes a natural number which differs from one band to another. Taking .[.an.]. .Iadd.the .Iaddend.output of the critical band separating circuit 21325 of the high frequency range as an example, the output of the critical band separating circuit 21325 is transmitted to .Iadd.k .Iaddend.sub-band forming circuits 22125,1 to 22125,k from which the blocks are consisting of .Iadd.N .Iaddend.consecutive .[.samples.]. .Iadd.coefficient data .Iaddend.are generated. These blocks are processed by the normalization circuits 21425,1 to 21425,k, floating coefficient computing circuits 21725,1 to 21725,k, quantization circuits 21525,1 to 21525,k and by the FC quantization circuits 21825,1 to 21825,k, similar to those downstream of the critical band separating circuits 21425,1 to 21425,k before being transmitted to the synthesize 216.
.[.At this time, in.]. .Iadd.In .Iaddend.the FC quantization circuits 21825,1 to 21825,k, the floating coefficients .[.have been quantized on the block-by-block basis.]. .Iadd.are quantized block-by-block .Iaddend.with the number of bits r .[.lesser.]. .Iadd.which is less .Iaddend.than the predetermined number of bits c .[.at.]. .Iadd.used by .Iaddend.the FC quantization circuit 218, (c>r). .[.Meanwhile, the.]. .Iadd.The .Iaddend.numbers of .[.samples N of.]. .Iadd.coefficient data N in .Iaddend.the respective .[.bands.]. .Iadd.blocks .Iaddend.are provided so as to be uniform to some extent.
As shown for example in FIG. 12, a predetermined number of bits .[.r lesser.]. .Iadd.r, which is less .Iaddend.than the predetermined number of bits c .[.for the lower range.]. .Iadd.used in the lower frequency .Iaddend.bands, such as band B1, B2, . . . among the critical bands B1 to B25, .[.are.]. .Iadd.is .Iaddend.provided to .[.k sub-bands sb25,1 1 to sb25,1 k in a higher range.]. .Iadd.each of the k sub-bands sb25,1 to sb25,k in a higher frequency .Iaddend.band such as band B25, and quantization is performed with the number of bits r. The predetermined numbers of .[.the.]. bits may for example be 6 for the bands B1 and B2 and 4 for band B25, that is, four bits .Iadd.for .Iaddend.each of the sub-bands .[. sb 25, 1 to sb 251 k, as shown in brackets.]. .Iadd.sb25,1 to sb25,k, as shown in parentheses .Iaddend.in the drawing. Although not shown, 6 bits, 5 bits and 4 bits may be provided to bands B1 to B5, B6 to B15 and bands B16 to B25, respectively. In determining the numbers of floating coefficient quantization bits, the number of .[.the.]. bits may be adjusted .[.with the data.]. .Iadd.taking the signal .Iaddend.dispersion in the block .[.taken.]. into consideration. In this case, the numbers of allocation bits for the floating coefficients are decreased for the blocks with larger dispersion.
With the above described third embodiment, since the predetermined number of bits are provided to the .[.sub-bands of the high frequency range.]. .Iadd.higher-frequency sub-bands .Iaddend.at the time of quantization of the floating .[.coefficients, it does not occur that.]. .Iadd.coefficients .Iaddend.the numbers of the bits of the floating coefficients per .[.sample.]. .Iadd.one of the coefficient data .Iaddend.in the .[.frequency band in the high frequency range be.]. .Iadd.higher frequency bands is not .Iaddend.decreased drastically as compared to the numbers of the bits for the .[.low frequency range,.]. .Iadd.lower frequency bands, .Iaddend.even in cases wherein the band or block width is enlarged .[.for the high frequency range,.]. .Iadd.at higher frequencies, .Iaddend.such as in the above mentioned critical bands, so that it becomes possible to prevent the .[.effect.]. .Iadd.efficiency .Iaddend.of the block floating .[.in the high frequency range.]. .Iadd.at higher frequencies .Iaddend.from being lowered. On the other hand, the floating coefficients .[.of the higher frequency range.]. .Iadd.at higher frequencies .Iaddend.are quantized with .[.the smaller number of the bits,.]. .Iadd.a smaller number of bits .Iaddend.so that bits may be used more efficiently at .[.the high frequency region where the larger number of the bits in.]. .Iadd.higher frequencies where a larger number of bits is .Iaddend.not required .[.in view.]. .Iadd.as a result .Iaddend.of the human auditory characteristics.

Claims (18)

What is claimed is:
1. A digital signal encoding method of the type in which .Iadd.an .Iaddend.input digital .[.signals are.]. .Iadd.signal is .Iaddend.divided into .Iadd.frequency components in .Iaddend.a plurality of frequency bands which are so set that the .Iadd.frequency .Iaddend.bands with higher frequencies will have broader bandwidths, and in which encoded signals are synthesized and outputted for each of the frequency bands, wherein the improvement resides in the steps of:
detecting by spectral analyses properties of the frequency components of the frequency bands, .[.with the period of.]. the spectral analyses.[.,.]. .Iadd.having a .Iaddend..[.which is the.]. detection time interval .[.or the time width as a unit of the analyses along the time axis, being.]. selected to be longer for lower frequencies, and generating a corresponding detection output signal; and
controlling the synthesizing and encoding as a function of the detection output signal.
2. The digital signal encoding method according to claim 1.Iadd., .Iaddend.wherein the input digital .[.signals have.]. .Iadd.signal has .Iaddend.a given sampling rate determined by a .Iadd.sampling rate .Iaddend.clock signal.Iadd., .Iaddend.and.Iadd., .Iaddend.in the step of detecting the properties of the frequency components.Iadd., .Iaddend..[.the frequency of.]. clock signals used in the spectral .[.analysis.]. .Iadd.analyses .Iaddend.are derived from the sampling rate clock signal and .[.are.]. .Iadd.have frequencies .Iaddend.selected to be lower for lower frequency bands.
3. A high efficiency digital .[.data.]. .Iadd.signal .Iaddend.encoding method.Iadd., .Iaddend.comprising the steps of:
dividing .Iadd.an .Iaddend.input digital .[.data.]. .Iadd.signal .Iaddend.into a plurality of bands .[.so that the.]. .Iadd.having progressive broader .Iaddend.bandwidths thereof .[.will become progressively broader.]. for higher frequency bands;
forming a plurality of blocks, each consisting of a plurality of samples of the divided input digital .[.data,.]. .Iadd.signal, .Iaddend.for each band; and
performing .Iadd.an .Iaddend.orthogonal transformation of each block of the bands to generate coefficient data.
4. The method according to claim 3.Iadd., .Iaddend.wherein the block in which the orthogonal transformation is performed is composed of the same .[.numbers of.]. .Iadd.number .Iaddend.the sample.Iadd.s .Iaddend..[.data for.]. .Iadd.of the divided input signal in .Iaddend.the respective bands.
5. A high efficiency encoding method of the type in which .Iadd.an .Iaddend.input digital .[.data are.]. signal is converted into data on .[.the.]. .Iadd.a .Iaddend.frequency axis to produce data divided according to predetermined frequency bands, the data of the respective .Iadd.frequency .Iaddend.bands are formed into blocks by selecting .[.the.]. band-widths .Iadd.of the blocks .Iaddend.to be broader .[.for the high frequency ranges.]. .Iadd.at higher frequencies .Iaddend.to compute .[.the.]. floating coefficients for the respective blocks, a floating operation .[.for.]. .Iadd.on .Iaddend.the respective blocks is performed .[.with.]. .Iadd.using .Iaddend.the floating coefficients, and the floating coefficients are quantized, wherein the improvement resides in that:
in the step of forming the data .[.of.]. .Iadd.in .Iaddend.the respective .Iadd.frequency .Iaddend.bands into blocks, the number of the data in each block .[.are.]. .Iadd.is .Iaddend.selected to be approximately equal; and
in the step of quantizing the floating coefficients, the floating coefficients .[.for the high frequency ranges.]. are quantized in such a manner that .[.the numbers of.]. .Iadd.progressively fewer .Iaddend.bits are .[.progressively smaller for.]. .Iadd.allocated to .Iaddend.the floating coefficients of .[.the higher frequency ranges..]. .Iadd.the frequency bands at higher frequencies. .Iaddend.
6. A digital signal encoding apparatus of the type including means for dividing .Iadd.an .Iaddend.input digital .[.signals.]. .Iadd.signal .Iaddend.into .Iadd.frequency components in .Iaddend.a plurality of frequency bands which are so set that the .Iadd.frequency .Iaddend.bands with higher frequencies will have broader bandwidths.Iadd., .Iaddend.and means for synthesizing and outputting encoded signals for each of the frequency bands, wherein the improvement comprises:
means for detecting by spectral analyses properties of the frequency components of the frequency bands, .[.with the period of.]. the spectral analyses.[., which is the.]. .Iadd.having a .Iaddend.detection time interval .[.or the time width as a unit of the analyses along the time axis, being.]. selected to be longer for lower frequencies, and generating a corresponding detection output signal; and
means for controlling the synthesizing and encoding as a function of the detection output signal.
7. The digital signal encoding apparatus according to claim 6.Iadd., .Iaddend.wherein the input digital signals have a given sampling rate determined by a .Iadd.sampling rate .Iaddend.clock signal.Iadd., .Iaddend.and the means for detecting includes means for deriving.Iadd., .Iaddend..[.clock signals.]. from the sampling rate clock signal .[.and the frequency of these.]. .Iadd.clock signals for use in the spectral analyses, the .Iaddend.clock signals .[.used in the spectral analysis are.]. .Iadd.having frequencies .Iaddend.selected to be lower for lower frequency bands.
8. A high efficiency digital .[.data.]. .Iadd.signal .Iaddend.encoding apparatus.Iadd., .Iaddend.comprising:
means for dividing .Iadd.an .Iaddend.input digital .[.data.]. .Iadd.signal .Iaddend.into a plurality of bands .[.so that the.]. .Iadd.having progressive broader .Iaddend.bandwidths .[.thereof will become progressively broader.]. for higher frequency bands;
means for forming a plurality of blocks, each consisting of a plurality of samples of the divided input digital .[.data,.]. .Iadd.signal, .Iaddend.for each band; and
means for performing .Iadd.an .Iaddend.orthogonal transformation of each block of the bands to generate coefficient data.
9. The apparatus according to claim 8.Iadd., .Iaddend.wherein the block in which the orthogonal transformation is performed is composed of the same .[.numbers.]. .Iadd.number .Iaddend.of the .[.sample data for.]. .Iadd.samples of the divided input digital signal in .Iaddend.the respective bands.
10. A high efficiency encoding apparatus of the type which includes means for converting .Iadd.an .Iaddend.input digital .[.data.]. .Iadd.signal .Iaddend.into data on .[.the.]. .Iadd.a .Iaddend.frequency axis to produce data divided according to predetermined frequency bands, means for forming the data .[.of.]. .Iadd.in .Iaddend.the respective .Iadd.frequency .Iaddend.bands into blocks by selecting .[.the.]. bandwidths .Iadd.of the blocks .Iaddend.to be broader .[.for the high frequency ranges.]. .Iadd.at higher frequencies .Iaddend.to compute .[.the.]. floating coefficients for the respective blocks, means for performing a floating operation .[.for.]. .Iadd.on .Iaddend.the respective blocks .[.with.]. .Iadd.using .Iaddend.the floating coefficients, and means for quantizing the floating coefficients, wherein the improvement .[.comprises:.]. .Iadd.resides in that: .Iaddend.
.[.that.]. the means for forming the data .[.of.]. .Iadd.in .Iaddend.the respective bands into blocks selects the number of the data in each block to be approximately equal; and
the means for quantizing the floating coefficients quantizes the floating coefficients .[.for the high frequency ranges.]. in such a manner that .[.the numbers of.]. .Iadd.progressively fewer .Iaddend.bits are .[.progressively smaller for.]. .Iadd.allocated to .Iaddend.the floating coefficients of the .[.higher frequency ranges..]. .Iadd.frequency bands at higher frequencies. .Iaddend.
11. A digital signal encoding method of the type in which .Iadd.an .Iaddend.input digital .[.signals are.]. .Iadd.signal is .Iaddend.divided into .Iadd.frequency components in .Iaddend.a plurality of frequency bands which are so set that the frequency bands with higher frequencies will have broader bandwidths, and in which encoded signals are synthesized and outputted for each of the frequency bands, wherein the improvement resides in the steps of:
detecting properties of the frequency components .[.of.]. .Iadd.in .Iaddend.the frequency bands, .[.with the time duration of.]. this detection of the properties of the frequency components .[.being.]. .Iadd.having a time duration .Iaddend.selected to be longer for lower frequencies, and generating a corresponding detection output signal, wherein the step of detecting the properties of the frequency components includes a spectrum analysis step.Iadd., .Iaddend.and wherein .[.the frequency of.]. clock signals used in the spectral analysis step .[.is.]. .Iadd.have frequencies .Iaddend.selected to be lower for .Iadd.the .Iaddend.clock signals for .[.lower.]. .Iadd.the .Iaddend.frequency bands .Iadd.with lower frequencies.Iaddend.; and
controlling the synthesizing and encoding as a function of the detection output signal.
12. A digital signal encoding apparatus of the type including means for dividing .Iadd.an .Iaddend.input digital .[.signals.]. .Iadd.signal .Iaddend.into .Iadd.frequency components .Iaddend.a plurality of frequency bands which are so set that the .Iadd.frequency .Iaddend.bands with higher frequencies will have broader bandwidths.Iadd., .Iaddend.and means for synthesizing and outputting encoded signals for each of the frequency bands, wherein the improvement comprises:
means for detecting properties of the frequency components .[.of.]. .Iadd.in .Iaddend.the frequency bands, .[.with the time duration of.]. this detection of the frequency components .[.being.]. .Iadd.having a time duration .Iaddend.selected to be longer for lower frequencies, and generating a corresponding detection output signal, wherein the means for detecting the properties of the frequency components includes a spectrum analysis means.Iadd., .Iaddend.and wherein .[.the frequency of.]. clock signals used in the spectral analysis means .[.is.]. .Iadd.have frequencies .Iaddend.selected to be lower for the clock signals for .[.lower.]. .Iadd.the .Iaddend.frequency bands .Iadd.with lower frequencies.Iaddend.; and
means for controlling the synthesizing and encoding as a function of the detection output signal. .Iadd.
13. A digital signal encoding method for encoding an input digital signal, the method comprising the steps of:
dividing the input digital signal into frequency components in a plurality of frequency bands;
synthesizing and outputting encoded signals for each of the frequency bands;
detecting by spectral analyses properties of the frequency components in the frequency bands, and generating a corresponding detection output signal; and
controlling the synthesizing of the encoded signals as a function of the detection output signal. .Iaddend..Iadd.
14. The digital signal encoding method according to claim 13, wherein:
in the step of dividing the input digital signal into a plurality of frequency bands, the input digital signal is divided into frequency bands having broader bandwidths at higher frequencies; and
in the step of detecting properties of the frequency components, the spectral analyses have a detection time selected according to the bandwidth of the respective frequency band. .Iaddend..Iadd.15. The digital signal encoding method according to claim 14, wherein:
the input digital signal has a given sampling rate determined by a sampling-rate clock signal; and
the step of detecting properties of the frequency components includes the step of deriving, from the sampling-rate clock signal, clock signals for use in the spectral analyses. .Iaddend..Iadd.16. The digital signal encoding method according to claim 15, wherein, in the step of deriving clock signals for use in the spectral analyses, the clock signals have frequencies selected according to the bandwidth of the respective frequency band. .Iaddend..Iadd.17. The digital signal encoding method according to claim 15, wherein, in the step of detecting by spectral analyses, the spectral analyses have a detection time selected according to the bandwidth of the respective frequency band. .Iaddend..Iadd.18. The digital signal encoding method according to claim 13, wherein, in the step of dividing the input digital signals into a plurality of frequency bands, the input digital signal is divided into least two frequency bands having equal bandwidths. .Iaddend..Iadd.19. A digital signal encoding method for encoding an input digital signal, the method comprising the steps of:
dividing the input digital signal into a plurality of frequency bands;
forming a plurality of blocks, each consisting of a plurality of samples of the divided input digital signal, for each frequency band; and
performing an orthogonal transformation of each block of the frequency bands to generate coefficient data. .Iaddend..Iadd.20. The digital signal encoding method according to claim 19, wherein the method additionally comprises the ste p of dividing the coefficient data into predetermined frequency blocks having broader bandwidths at higher frequencies.
.Iaddend..Iadd.21. The digital signal encoding method according to claim 19, wherein, the step of forming a plurality of blocks forms, in one of the frequency bands, blocks consisting of samples equal in number to the samples in the blocks in at least one other of the frequency bands. .Iaddend..Iadd.22. The digital signal encoding method according to claim 19, wherein, in the step of dividing the input digital signal into a plurality of frequency bands, frequency bands with higher frequencies have broader bandwidths. .Iaddend..Iadd.23. The digital signal encoding method according to claim 19, wherein, in the step of dividing the input digital signal into a plurality of frequency bands, at least two of the frequency bands have equal bandwidths. .Iaddend..Iadd.24. A digital signal encoding method for an input digital signal, the method comprising the steps of:
converting the input digital signal into coefficient data on a frequency axis;
dividing the coefficient data into predetermined frequency bands;
forming the coefficient data in the respective frequency bands into blocks of approximately equal numbers of coefficient data;
computing a floating coefficient for the each of the blocks;
performing a floating operation on each of the blocks using the respective floating coefficient; and
quantizing the floating coefficients in a manner that allocates progressively fewer quantizing bits to the floating coefficients of the frequency bands at higher frequencies. .Iaddend..Iadd.25. The digital signal encoding method according to claim 24, wherein the step for dividing the coefficient data into predetermined frequency bands divides the coefficient data into predetermined frequency bands having broader bandwidths at hither frequencies. .Iaddend..Iadd.26. The digital signal encoding method according to claim 24, wherein, in the step of forming the coefficient data into blocks, more than one block is formed in a frequency band at a higher frequency. .Iaddend..Iadd.27. A digital signal encoding an apparatus, comprising:
frequency dividing means for dividing an input digital signal into frequency components in a plurality of frequency bands;
means for synthesizing and outputting encoded signals for each of the frequency bands;
means for detecting by spectral analyses properties of the frequency components in the frequency bands, and for generating a corresponding detection output signal; and
means for controlling the means for synthesizing and outputting encoded
signals as a function of the detection output signal. .Iaddend..Iadd.28. The digital signal encoding apparatus according to claim 27, wherein:
the frequency dividing means divides the digital input signal into frequency bands having broader bandwidths at higher frequencies; and
the means for detecting detects by spectral analyses having a detection time selected according to the bandwidth of the respective frequency band. .Iadd.29. The digital signal encoding apparatus according to claim 27, wherein:
the input digital signal has a given sampling rate determined by a sampling-rate clock signal; and
the means for detecting includes means for deriving, from the sampling-rate clock signal, clock signals for use in the spectral analyses. .Iaddend..Iadd.30. The digital signal encoding apparatus according to claim 29, wherein the means for deriving clock signals for use in the spectral analyses includes means for selecting frequencies for the clock signals according to the bandwidth of the respective frequency band. .Iaddend..Iadd.31. The digital signal encoding apparatus according to claim 29, wherein the means for detecting detects by spectral analyses having a detection time selected according to the bandwidth of the respective frequency band. .Iaddend..Iadd.32. The digital signal encoding apparatus according to claim 27, wherein the frequency dividing means divides the input digital signal into frequency bands in such a manner that two of the frequency bands have equal bandwidths. .Iaddend..Iadd.33. A digital signal encoding apparatus, comprising:
means for dividing an input digital signal into a plurality of frequency bands;
means for forming a plurality of blocks, each consisting of a plurality of samples of the divided input digital signal, in each frequency band; and
means for performing an orthogonal transformation of each block in each of the frequency bands to generate coefficient data. .Iaddend..Iadd.34. The digital signal encoding apparatus according to claim 33, wherein the means for forming a plurality of blocks forms, in one of the frequency bands, blocks consisting of samples equal in number to the samples in the blocks in at least one other of the frequency bands. .Iaddend..Iadd.35. The digital signal encoding apparatus according to claim 33, wherein the means for dividing the input digital signal into a plurality of frequency bands divides the input digital signal into frequency bands having broader
bandwidths at higher frequencies. .Iaddend..Iadd.36. The digital signal encoding apparatus according to claim 33, wherein the means for dividing the input digital signal into a plurality of frequency bands divides the input digital signal into frequency bands, at least two of the frequency bands having equal bandwidths. .Iaddend..Iadd.37. A digital signal encoding apparatus, comprising:
means for converting an input digital signal into coefficient data on a frequency axis;
means for dividing the coefficient data into predetermined frequency bands;
means for forming the coefficient data in the respective bands into blocks, the numbers of coefficient data in the blocks being selected to be approximately equal;
means for computing a floating coefficient for each of the blocks;
means for performing a floating operation on each of the blocks using the respective floating coefficient, and
means for quantizing the floating coefficients in a manner that allocates progressively fewer quantizing bits to the floating coefficients of frequency bands at the higher frequencies. .Iaddend..Iadd.38. The digital signal encoding apparatus according to claim 37, wherein the means for dividing the coefficient data into predetermined frequency bands divides the coefficient data into predetermined frequency bands having broader bandwidths at higher frequencies. .Iaddend..Iadd.39. The digital signal encoding apparatus according to claim 37, wherein the means for forming the coefficient data into blocks forms more than one block in a frequency band at a higher frequency. .Iaddend..Iadd.40. A digital signal encoding apparatus for encoding an input digital signal, the apparatus comprising:
means for orthogonally transforming the input digital signal to provide data on a frequency axis; and
means for dividing the data into frequency bands having broader bandwidths at higher frequencies. .Iaddend..Iadd.41. The digital signal encoding apparatus according to claim 40, wherein the means for dividing divides the data into frequency bands corresponding to critical bands. .Iaddend..Iadd.42. The digital signal encoding apparatus according to claim 40, additionally comprising:
block forming means for forming the data in the frequency bands into blocks of approximately equal numbers of data, and
means for applying block floating to each block of data.
.Iaddend..Iadd. The digital signal encoding ap paratus of claim 42, wherein the block forming means includes means for dividing the data in a frequency band into plural blocks, each block corresponding to a sub band obtained by dividing the frequency band in frequency. .Iaddend..Iadd.44. A digital signal encoding method for encoding an input digital signal, the method comprising the steps of:
orthogonally transforming the input digital signal to provide data on a frequency axis; and
dividing the data into frequency bands having broader bandwidths at higher frequencies. .Iaddend..Iadd.45. The digital signal encoding method according to claim 44, wherein the step of dividing the data into frequency bands divides the data into frequency bands corresponding to critical bands. .Iaddend..Iadd.46. The digital signal encoding method according to claim 44, additionally comprising the steps of:
forming the data in the frequency bands into blocks of approximately equal numbers of data, and
applying block floating to each block of data. .Iaddend..Iadd.47. The digital signal encoding method according to claim 46, wherein the step of forming the data into blocks includes the step of dividing the data in a high frequency band into plural blocks, each block corresponding to a sub band obtained by dividing the high frequency band in frequency. .Iaddend.
US08/245,451 1989-09-26 1994-05-18 Method and apparatus for encoding audio signals divided into a plurality of frequency bands Expired - Lifetime USRE36559E (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US08/245,451 USRE36559E (en) 1989-09-26 1994-05-18 Method and apparatus for encoding audio signals divided into a plurality of frequency bands

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP1-249835 1989-09-26
JP1249835A JP2906477B2 (en) 1989-09-26 1989-09-26 Digital signal encoding method
JP1278207A JP2906483B2 (en) 1989-10-25 1989-10-25 High-efficiency encoding method for digital audio data and decoding apparatus for digital audio data
JP1-278207 1989-10-25
US07/586,494 US5115240A (en) 1989-09-26 1990-09-21 Method and apparatus for encoding voice signals divided into a plurality of frequency bands
US08/245,451 USRE36559E (en) 1989-09-26 1994-05-18 Method and apparatus for encoding audio signals divided into a plurality of frequency bands

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US07/586,494 Reissue US5115240A (en) 1989-09-26 1990-09-21 Method and apparatus for encoding voice signals divided into a plurality of frequency bands

Publications (1)

Publication Number Publication Date
USRE36559E true USRE36559E (en) 2000-02-08

Family

ID=26539517

Family Applications (2)

Application Number Title Priority Date Filing Date
US07/586,494 Ceased US5115240A (en) 1989-09-26 1990-09-21 Method and apparatus for encoding voice signals divided into a plurality of frequency bands
US08/245,451 Expired - Lifetime USRE36559E (en) 1989-09-26 1994-05-18 Method and apparatus for encoding audio signals divided into a plurality of frequency bands

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US07/586,494 Ceased US5115240A (en) 1989-09-26 1990-09-21 Method and apparatus for encoding voice signals divided into a plurality of frequency bands

Country Status (4)

Country Link
US (2) US5115240A (en)
EP (1) EP0420745B1 (en)
KR (1) KR100242864B1 (en)
DE (1) DE69023604T2 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090235710A1 (en) * 2008-03-22 2009-09-24 Fette Gmbh Adjustable knurling tool

Families Citing this family (79)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5230038A (en) * 1989-01-27 1993-07-20 Fielder Louis D Low bit rate transform coder, decoder, and encoder/decoder for high-quality audio
US5752225A (en) * 1989-01-27 1998-05-12 Dolby Laboratories Licensing Corporation Method and apparatus for split-band encoding and split-band decoding of audio information using adaptive bit allocation to adjacent subbands
US5222189A (en) * 1989-01-27 1993-06-22 Dolby Laboratories Licensing Corporation Low time-delay transform coder, decoder, and encoder/decoder for high-quality audio
US5502789A (en) * 1990-03-07 1996-03-26 Sony Corporation Apparatus for encoding digital data with reduction of perceptible noise
CN1062963C (en) * 1990-04-12 2001-03-07 多尔拜实验特许公司 Adaptive-block-lenght, adaptive-transform, and adaptive-window transform coder, decoder, and encoder/decoder for high-quality audio
US5388181A (en) * 1990-05-29 1995-02-07 Anderson; David J. Digital audio compression system
US5365553A (en) * 1990-11-30 1994-11-15 U.S. Philips Corporation Transmitter, encoding system and method employing use of a bit need determiner for subband coding a digital signal
JP3158458B2 (en) * 1991-01-31 2001-04-23 日本電気株式会社 Coding method of hierarchically expressed signal
ZA921988B (en) * 1991-03-29 1993-02-24 Sony Corp High efficiency digital data encoding and decoding apparatus
JP3134338B2 (en) * 1991-03-30 2001-02-13 ソニー株式会社 Digital audio signal encoding method
JP3134337B2 (en) * 1991-03-30 2001-02-13 ソニー株式会社 Digital signal encoding method
GB2257606B (en) * 1991-06-28 1995-01-18 Sony Corp Recording and/or reproducing apparatuses and signal processing methods for compressed data
DE4124493C1 (en) * 1991-07-24 1993-02-11 Institut Fuer Rundfunktechnik Gmbh, 8000 Muenchen, De
EP0525809B1 (en) * 1991-08-02 2001-12-05 Sony Corporation Digital encoder with dynamic quantization bit allocation
GB2258372B (en) * 1991-08-02 1995-05-31 Sony Corp Apparatus for and methods of recording and/or reproducing digital data
JP3178026B2 (en) * 1991-08-23 2001-06-18 ソニー株式会社 Digital signal encoding device and decoding device
EP0535889B1 (en) * 1991-09-30 1998-11-11 Sony Corporation Method and apparatus for audio data compression
JP3141450B2 (en) * 1991-09-30 2001-03-05 ソニー株式会社 Audio signal processing method
JP3134455B2 (en) * 1992-01-29 2001-02-13 ソニー株式会社 High efficiency coding apparatus and method
US5765127A (en) * 1992-03-18 1998-06-09 Sony Corp High efficiency encoding method
JP3104400B2 (en) * 1992-04-27 2000-10-30 ソニー株式会社 Audio signal encoding apparatus and method
US5304994A (en) * 1992-06-09 1994-04-19 Hewlett Packard Company Minimal delay leading one detector with result bias control
JP3153933B2 (en) * 1992-06-16 2001-04-09 ソニー株式会社 Data encoding device and method and data decoding device and method
JP3233234B2 (en) * 1992-09-07 2001-11-26 ソニー株式会社 Disk recording device
JP3508146B2 (en) * 1992-09-11 2004-03-22 ソニー株式会社 Digital signal encoding / decoding device, digital signal encoding device, and digital signal decoding device
JP3127600B2 (en) * 1992-09-11 2001-01-29 ソニー株式会社 Digital signal decoding apparatus and method
JP3343962B2 (en) * 1992-11-11 2002-11-11 ソニー株式会社 High efficiency coding method and apparatus
JP3185413B2 (en) * 1992-11-25 2001-07-09 ソニー株式会社 Orthogonal transform operation and inverse orthogonal transform operation method and apparatus, digital signal encoding and / or decoding apparatus
JPH06202285A (en) * 1992-12-28 1994-07-22 Sony Corp Projection film
JP3123286B2 (en) * 1993-02-18 2001-01-09 ソニー株式会社 Digital signal processing device or method, and recording medium
JP3186292B2 (en) * 1993-02-02 2001-07-11 ソニー株式会社 High efficiency coding method and apparatus
US5392044A (en) * 1993-03-08 1995-02-21 Motorola, Inc. Method and apparatus for digitizing a wide frequency bandwidth signal
JP3123290B2 (en) * 1993-03-09 2001-01-09 ソニー株式会社 Compressed data recording device and method, compressed data reproducing method, recording medium
TW232116B (en) * 1993-04-14 1994-10-11 Sony Corp Method or device and recording media for signal conversion
JP3173218B2 (en) * 1993-05-10 2001-06-04 ソニー株式会社 Compressed data recording method and apparatus, compressed data reproducing method, and recording medium
US5717821A (en) * 1993-05-31 1998-02-10 Sony Corporation Method, apparatus and recording medium for coding of separated tone and noise characteristic spectral components of an acoustic sibnal
DE69431223T2 (en) * 1993-06-29 2006-03-02 Sony Corp. Apparatus and method for sound transmission
PL174314B1 (en) * 1993-06-30 1998-07-31 Sony Corp Method of and apparatus for decoding digital signals
TW272341B (en) * 1993-07-16 1996-03-11 Sony Co Ltd
TW327223B (en) * 1993-09-28 1998-02-21 Sony Co Ltd Methods and apparatus for encoding an input signal broken into frequency components, methods and apparatus for decoding such encoded signal
US5737720A (en) * 1993-10-26 1998-04-07 Sony Corporation Low bit rate multichannel audio coding methods and apparatus using non-linear adaptive bit allocation
JP3318931B2 (en) * 1993-11-04 2002-08-26 ソニー株式会社 Signal encoding device, signal decoding device, and signal encoding method
CN1111959C (en) * 1993-11-09 2003-06-18 索尼公司 Quantization apparatus, quantization method, high efficiency encoder, high efficiency encoding method, decoder, high efficiency encoder and recording media
US5608713A (en) * 1994-02-09 1997-03-04 Sony Corporation Bit allocation of digital audio signal blocks by non-linear processing
DE4405659C1 (en) * 1994-02-22 1995-04-06 Fraunhofer Ges Forschung Method for the cascaded coding and decoding of audio data
JP3186412B2 (en) * 1994-04-01 2001-07-11 ソニー株式会社 Information encoding method, information decoding method, and information transmission method
JP3277682B2 (en) * 1994-04-22 2002-04-22 ソニー株式会社 Information encoding method and apparatus, information decoding method and apparatus, and information recording medium and information transmission method
TW295747B (en) * 1994-06-13 1997-01-11 Sony Co Ltd
JP3250376B2 (en) * 1994-06-13 2002-01-28 ソニー株式会社 Information encoding method and apparatus, and information decoding method and apparatus
JP3277705B2 (en) 1994-07-27 2002-04-22 ソニー株式会社 Information encoding apparatus and method, and information decoding apparatus and method
JP3341474B2 (en) * 1994-07-28 2002-11-05 ソニー株式会社 Information encoding method and decoding method, information encoding device and decoding device, and information recording medium
US5893065A (en) * 1994-08-05 1999-04-06 Nippon Steel Corporation Apparatus for compressing audio data
JP3536996B2 (en) * 1994-09-13 2004-06-14 ソニー株式会社 Parameter conversion method and speech synthesis method
US5926791A (en) * 1995-10-26 1999-07-20 Sony Corporation Recursively splitting the low-frequency band with successively fewer filter taps in methods and apparatuses for sub-band encoding, decoding, and encoding and decoding
US5956674A (en) * 1995-12-01 1999-09-21 Digital Theater Systems, Inc. Multi-channel predictive subband audio coder using psychoacoustic adaptive bit allocation in frequency, time and over the multiple channels
US5822370A (en) * 1996-04-16 1998-10-13 Aura Systems, Inc. Compression/decompression for preservation of high fidelity speech quality at low bandwidth
US5848391A (en) * 1996-07-11 1998-12-08 Fraunhofer-Gesellschaft Zur Forderung Der Angewandten Forschung E.V. Method subband of coding and decoding audio signals using variable length windows
JP3318825B2 (en) * 1996-08-20 2002-08-26 ソニー株式会社 Digital signal encoding method, digital signal encoding device, digital signal recording method, digital signal recording device, recording medium, digital signal transmission method, and digital signal transmission device
JPH1084284A (en) * 1996-09-06 1998-03-31 Sony Corp Signal reproducing method and device
JP4121578B2 (en) * 1996-10-18 2008-07-23 ソニー株式会社 Speech analysis method, speech coding method and apparatus
JP3496411B2 (en) * 1996-10-30 2004-02-09 ソニー株式会社 Information encoding method and decoding device
FI114248B (en) * 1997-03-14 2004-09-15 Nokia Corp Method and apparatus for audio coding and audio decoding
US6476735B2 (en) * 2000-12-02 2002-11-05 Daniel David Lang Method of encoding bits using a plurality of frequencies
GB0108080D0 (en) * 2001-03-30 2001-05-23 Univ Bath Audio compression
JP2003110429A (en) * 2001-09-28 2003-04-11 Sony Corp Coding method and device, decoding method and device, transmission method and device, and storage medium
US7240001B2 (en) * 2001-12-14 2007-07-03 Microsoft Corporation Quality improvement techniques in an audio encoder
US6934677B2 (en) * 2001-12-14 2005-08-23 Microsoft Corporation Quantization matrices based on critical band pattern information for digital audio wherein quantization bands differ from critical bands
JP4676140B2 (en) 2002-09-04 2011-04-27 マイクロソフト コーポレーション Audio quantization and inverse quantization
US7502743B2 (en) 2002-09-04 2009-03-10 Microsoft Corporation Multi-channel audio encoding and decoding with multi-channel transform selection
JP4657570B2 (en) * 2002-11-13 2011-03-23 ソニー株式会社 Music information encoding apparatus and method, music information decoding apparatus and method, program, and recording medium
US7460990B2 (en) * 2004-01-23 2008-12-02 Microsoft Corporation Efficient coding of digital media spectral data using wide-sense perceptual similarity
US9319028B2 (en) 2005-02-23 2016-04-19 Vios Medical Singapore Pte. Ltd. Signal decomposition, analysis and reconstruction using high-resolution filter banks and component tracking
US7702502B2 (en) 2005-02-23 2010-04-20 Digital Intelligence, L.L.C. Apparatus for signal decomposition, analysis and reconstruction
US7885819B2 (en) * 2007-06-29 2011-02-08 Microsoft Corporation Bitstream syntax for multi-process audio decoding
US8249883B2 (en) * 2007-10-26 2012-08-21 Microsoft Corporation Channel extension coding for multi-channel source
US8666753B2 (en) 2011-12-12 2014-03-04 Motorola Mobility Llc Apparatus and method for audio encoding
US11602311B2 (en) 2019-01-29 2023-03-14 Murata Vios, Inc. Pulse oximetry system
CN110111800B (en) * 2019-04-04 2021-05-07 深圳信息职业技术学院 Frequency band division method and device of electronic cochlea and electronic cochlea equipment
US11095999B1 (en) * 2020-03-19 2021-08-17 Lisnr Channel-based control of audio transmissions

Citations (50)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3349183A (en) * 1963-10-29 1967-10-24 Melpar Inc Speech compression system transmitting only coefficients of polynomial representations of phonemes
US4184049A (en) * 1978-08-25 1980-01-15 Bell Telephone Laboratories, Incorporated Transform speech signal coding with pitch controlled adaptive quantizing
US4285014A (en) * 1979-03-20 1981-08-18 Olympus Optical Co., Ltd. Channel division recording/reproducing apparatus
US4516241A (en) * 1983-07-11 1985-05-07 At&T Bell Laboratories Bit compression coding with embedded signaling
US4535472A (en) * 1982-11-05 1985-08-13 At&T Bell Laboratories Adaptive bit allocator
US4569058A (en) * 1983-04-21 1986-02-04 Siemens Aktiengesellschaft Transmission system
US4573187A (en) * 1981-07-24 1986-02-25 Asulab S.A. Speech-controlled electronic apparatus
US4622598A (en) * 1982-12-06 1986-11-11 Sony Corporation Method of recording odd and even words of one channel PCM signals in plural tracks
US4625286A (en) * 1982-05-03 1986-11-25 Texas Instruments Incorporated Time encoding of LPC roots
US4697212A (en) * 1983-06-18 1987-09-29 Sony Corporation Method and apparatus for recording a digital information signal
US4706265A (en) * 1984-10-30 1987-11-10 Nec Corporation Code converting system and method for band compression of digital signals
US4748579A (en) * 1985-08-14 1988-05-31 Gte Laboratories Incorporated Method and circuit for performing discrete transforms
US4851906A (en) * 1986-11-04 1989-07-25 Nec Corporation Data compression using orthogonal transform and vector quantization
US4873589A (en) * 1986-12-19 1989-10-10 Sony Corporation Data recorder and method
US4882754A (en) * 1987-08-25 1989-11-21 Digideck, Inc. Data compression system and method with buffer control
US4885790A (en) * 1985-03-18 1989-12-05 Massachusetts Institute Of Technology Processing of acoustic waveforms
EP0349325A2 (en) * 1988-06-30 1990-01-03 Sony Corporation Digital signal transmission apparatus
US4896362A (en) * 1987-04-27 1990-01-23 U.S. Philips Corporation System for subband coding of a digital audio signal
US4903301A (en) * 1987-02-27 1990-02-20 Hitachi, Ltd. Method and system for transmitting variable rate speech signal
US4912763A (en) * 1986-10-30 1990-03-27 International Business Machines Corporation Process for multirate encoding signals and device for implementing said process
US4932062A (en) * 1989-05-15 1990-06-05 Dialogic Corporation Method and apparatus for frequency analysis of telephone signals
WO1990009064A1 (en) * 1989-01-27 1990-08-09 Dolby Laboratories Licensing Corporation Low time-delay transform coder, decoder, and encoder/decoder for high-quality audio
US4949383A (en) * 1984-08-24 1990-08-14 Bristish Telecommunications Public Limited Company Frequency domain speech coding
EP0411730A2 (en) * 1989-08-03 1991-02-06 MANNESMANN Aktiengesellschaft Drive system for an exterior sleeve by a multiple-step gearing
EP0423050A1 (en) * 1989-10-13 1991-04-17 France Telecom Compression apparatus for transformed digital audio signal with adaptive quantization based on psycho-acoustic criterium
US5016107A (en) * 1989-05-09 1991-05-14 Eastman Kodak Company Electronic still camera utilizing image compression and digital storage
US5040217A (en) * 1989-10-18 1991-08-13 At&T Bell Laboratories Perceptual coding of audio signals
EP0446031A2 (en) * 1990-03-07 1991-09-11 Sony Corporation Apparatus for encoding digital signals
WO1991016769A1 (en) * 1990-04-12 1991-10-31 Dolby Laboratories Licensing Corporation Adaptive-block-length, adaptive-transform, and adaptive-window transform coder, decoder, and encoder/decoder for high-quality audio
EP0458645A2 (en) * 1990-05-25 1991-11-27 Sony Corporation Subband digital signal encoding apparatus
EP0463473A2 (en) * 1990-06-12 1992-01-02 Nec Corporation Fast calculation apparatus for carrying out a forward and an inverse transform
EP0466190A2 (en) * 1990-07-13 1992-01-15 Sony Corporation Quantizing error reducer for audio signal
EP0473367A1 (en) * 1990-08-24 1992-03-04 Sony Corporation Digital signal encoders
US5150387A (en) * 1989-12-21 1992-09-22 Kabushiki Kaisha Toshiba Variable rate encoding and communicating apparatus
EP0506394A2 (en) * 1991-03-29 1992-09-30 Sony Corporation Coding apparatus for digital signals
WO1992017884A1 (en) * 1991-03-29 1992-10-15 Sony Corporation High efficiency digital data encoding and decoding apparatus
US5159611A (en) * 1988-09-26 1992-10-27 Fujitsu Limited Variable rate coder
US5222189A (en) * 1989-01-27 1993-06-22 Dolby Laboratories Licensing Corporation Low time-delay transform coder, decoder, and encoder/decoder for high-quality audio
US5243588A (en) * 1990-08-24 1993-09-07 Sony Corporation Method and apparatus for reading digital data bursts comprising data clusters and cluster linking sectors
US5264846A (en) * 1991-03-30 1993-11-23 Yoshiaki Oikawa Coding apparatus for digital signal
US5268685A (en) * 1991-03-30 1993-12-07 Sony Corp Apparatus with transient-dependent bit allocation for compressing a digital signal
US5294925A (en) * 1991-08-23 1994-03-15 Sony Corporation Data compressing and expanding apparatus with time domain and frequency domain block floating
US5311561A (en) * 1991-03-29 1994-05-10 Sony Corporation Method and apparatus for compressing a digital input signal with block floating applied to blocks corresponding to fractions of a critical band or to multiple critical bands
US5381143A (en) * 1992-09-11 1995-01-10 Sony Corporation Digital signal coding/decoding apparatus, digital signal coding apparatus, and digital signal decoding apparatus
US5384891A (en) * 1988-09-28 1995-01-24 Hitachi, Ltd. Vector quantizing apparatus and speech analysis-synthesis system using the apparatus
US5388209A (en) * 1991-08-02 1995-02-07 Sony Corporation Apparatus for high-speed recording compressed digital data with increased compression
US5388093A (en) * 1991-09-27 1995-02-07 Sony Corporation Disc recording and/or reproducing apparatus for recording continuous compressed data in plural data regions and disc therefor
US5406428A (en) * 1991-09-03 1995-04-11 Sony Corporation Apparatus and method for recording compressed data with recording integrity check after recording
US5461378A (en) * 1992-09-11 1995-10-24 Sony Corporation Digital signal decoding apparatus
US5471558A (en) * 1991-09-30 1995-11-28 Sony Corporation Data compression method and apparatus in which quantizing bits are allocated to a block in a present frame in response to the block in a past frame

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4455649A (en) * 1982-01-15 1984-06-19 International Business Machines Corporation Method and apparatus for efficient statistical multiplexing of voice and data signals

Patent Citations (53)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3349183A (en) * 1963-10-29 1967-10-24 Melpar Inc Speech compression system transmitting only coefficients of polynomial representations of phonemes
US4184049A (en) * 1978-08-25 1980-01-15 Bell Telephone Laboratories, Incorporated Transform speech signal coding with pitch controlled adaptive quantizing
US4285014A (en) * 1979-03-20 1981-08-18 Olympus Optical Co., Ltd. Channel division recording/reproducing apparatus
US4573187A (en) * 1981-07-24 1986-02-25 Asulab S.A. Speech-controlled electronic apparatus
US4625286A (en) * 1982-05-03 1986-11-25 Texas Instruments Incorporated Time encoding of LPC roots
US4535472A (en) * 1982-11-05 1985-08-13 At&T Bell Laboratories Adaptive bit allocator
US4622598A (en) * 1982-12-06 1986-11-11 Sony Corporation Method of recording odd and even words of one channel PCM signals in plural tracks
US4569058A (en) * 1983-04-21 1986-02-04 Siemens Aktiengesellschaft Transmission system
US4697212A (en) * 1983-06-18 1987-09-29 Sony Corporation Method and apparatus for recording a digital information signal
US4516241A (en) * 1983-07-11 1985-05-07 At&T Bell Laboratories Bit compression coding with embedded signaling
US4949383A (en) * 1984-08-24 1990-08-14 Bristish Telecommunications Public Limited Company Frequency domain speech coding
US4706265A (en) * 1984-10-30 1987-11-10 Nec Corporation Code converting system and method for band compression of digital signals
US4885790A (en) * 1985-03-18 1989-12-05 Massachusetts Institute Of Technology Processing of acoustic waveforms
US4748579A (en) * 1985-08-14 1988-05-31 Gte Laboratories Incorporated Method and circuit for performing discrete transforms
US4912763A (en) * 1986-10-30 1990-03-27 International Business Machines Corporation Process for multirate encoding signals and device for implementing said process
US4851906A (en) * 1986-11-04 1989-07-25 Nec Corporation Data compression using orthogonal transform and vector quantization
US4873589A (en) * 1986-12-19 1989-10-10 Sony Corporation Data recorder and method
US4903301A (en) * 1987-02-27 1990-02-20 Hitachi, Ltd. Method and system for transmitting variable rate speech signal
US4896362A (en) * 1987-04-27 1990-01-23 U.S. Philips Corporation System for subband coding of a digital audio signal
US4882754A (en) * 1987-08-25 1989-11-21 Digideck, Inc. Data compression system and method with buffer control
EP0349325A2 (en) * 1988-06-30 1990-01-03 Sony Corporation Digital signal transmission apparatus
US5159611A (en) * 1988-09-26 1992-10-27 Fujitsu Limited Variable rate coder
US5384891A (en) * 1988-09-28 1995-01-24 Hitachi, Ltd. Vector quantizing apparatus and speech analysis-synthesis system using the apparatus
WO1990009064A1 (en) * 1989-01-27 1990-08-09 Dolby Laboratories Licensing Corporation Low time-delay transform coder, decoder, and encoder/decoder for high-quality audio
US5222189A (en) * 1989-01-27 1993-06-22 Dolby Laboratories Licensing Corporation Low time-delay transform coder, decoder, and encoder/decoder for high-quality audio
US5016107A (en) * 1989-05-09 1991-05-14 Eastman Kodak Company Electronic still camera utilizing image compression and digital storage
US4932062A (en) * 1989-05-15 1990-06-05 Dialogic Corporation Method and apparatus for frequency analysis of telephone signals
EP0411730A2 (en) * 1989-08-03 1991-02-06 MANNESMANN Aktiengesellschaft Drive system for an exterior sleeve by a multiple-step gearing
EP0423050A1 (en) * 1989-10-13 1991-04-17 France Telecom Compression apparatus for transformed digital audio signal with adaptive quantization based on psycho-acoustic criterium
US5040217A (en) * 1989-10-18 1991-08-13 At&T Bell Laboratories Perceptual coding of audio signals
US5150387A (en) * 1989-12-21 1992-09-22 Kabushiki Kaisha Toshiba Variable rate encoding and communicating apparatus
EP0446031A2 (en) * 1990-03-07 1991-09-11 Sony Corporation Apparatus for encoding digital signals
WO1991016769A1 (en) * 1990-04-12 1991-10-31 Dolby Laboratories Licensing Corporation Adaptive-block-length, adaptive-transform, and adaptive-window transform coder, decoder, and encoder/decoder for high-quality audio
EP0458645A2 (en) * 1990-05-25 1991-11-27 Sony Corporation Subband digital signal encoding apparatus
US5241603A (en) * 1990-05-25 1993-08-31 Sony Corporation Digital signal encoding apparatus
EP0463473A2 (en) * 1990-06-12 1992-01-02 Nec Corporation Fast calculation apparatus for carrying out a forward and an inverse transform
US5218561A (en) * 1990-06-12 1993-06-08 Nec Corporation Fast calculation apparatus for carrying out a forward and an inverse transform
EP0466190A2 (en) * 1990-07-13 1992-01-15 Sony Corporation Quantizing error reducer for audio signal
US5204677A (en) * 1990-07-13 1993-04-20 Sony Corporation Quantizing error reducer for audio signal
US5243588A (en) * 1990-08-24 1993-09-07 Sony Corporation Method and apparatus for reading digital data bursts comprising data clusters and cluster linking sectors
EP0473367A1 (en) * 1990-08-24 1992-03-04 Sony Corporation Digital signal encoders
WO1992017884A1 (en) * 1991-03-29 1992-10-15 Sony Corporation High efficiency digital data encoding and decoding apparatus
US5311561A (en) * 1991-03-29 1994-05-10 Sony Corporation Method and apparatus for compressing a digital input signal with block floating applied to blocks corresponding to fractions of a critical band or to multiple critical bands
EP0506394A2 (en) * 1991-03-29 1992-09-30 Sony Corporation Coding apparatus for digital signals
US5264846A (en) * 1991-03-30 1993-11-23 Yoshiaki Oikawa Coding apparatus for digital signal
US5268685A (en) * 1991-03-30 1993-12-07 Sony Corp Apparatus with transient-dependent bit allocation for compressing a digital signal
US5388209A (en) * 1991-08-02 1995-02-07 Sony Corporation Apparatus for high-speed recording compressed digital data with increased compression
US5294925A (en) * 1991-08-23 1994-03-15 Sony Corporation Data compressing and expanding apparatus with time domain and frequency domain block floating
US5406428A (en) * 1991-09-03 1995-04-11 Sony Corporation Apparatus and method for recording compressed data with recording integrity check after recording
US5388093A (en) * 1991-09-27 1995-02-07 Sony Corporation Disc recording and/or reproducing apparatus for recording continuous compressed data in plural data regions and disc therefor
US5471558A (en) * 1991-09-30 1995-11-28 Sony Corporation Data compression method and apparatus in which quantizing bits are allocated to a block in a present frame in response to the block in a past frame
US5381143A (en) * 1992-09-11 1995-01-10 Sony Corporation Digital signal coding/decoding apparatus, digital signal coding apparatus, and digital signal decoding apparatus
US5461378A (en) * 1992-09-11 1995-10-24 Sony Corporation Digital signal decoding apparatus

Non-Patent Citations (16)

* Cited by examiner, † Cited by third party
Title
"An Application Specific DSP Chip Set for 100 MHZ Data Rates", Surendar Magar, Shannon Shen, Garry Luikuo, Mike Fleming and Raul Aguilar, Honeywell, Signal Processing Technologies, Colorado Springs, CO 80906, ICASSP 88, vol. IV, 1988 International Conference on Acoustics, Speech and Signal Processing, Apr. 11-14, 1988, pp. 1989-1992.
"An Application-Specific FFT Processor", 8029 Electrical Engineering, 60 (1988) Jun. No. 738, Woolwich, London, Great Britian, pp. 99-100 and 104-106.
"Application of Quadratue Mirror Filters to Split Band Coding Schemes", D. Esteban and C. Galan, IBM Laboratory, 1977 IEEE International Conference on Acoustics, Speech & Signal Processing, pp. 191-195.
"Perceptual Transform Coding of Wideband Stereo Signals", James D. Johnson, AT&T Bell Laboratories, Murray Hill, New Jersey, 07974, 1989 IEEE, pp. 1993-1994 and 1996.
"Polyphase Quadrature Filters-A New Subband Coding Technique", Joseph A. Rothweiler, RCA Goverment Communications Systems, ICASSP 83, Boston, vol. 3 of 3, pp. 1280-1283 (no date given).
"Signal Compression: Technology Targets and Research Directions", Nikil Jayant, 8272 IEEE Journal on Selected Areas in Communications, 10 (1992), Jun., No. 5, New York, U.S., pp. 796-810.
"Subband/Transform Coding Using Filter Bank Designs Based on Time Domain Aliasing Cancellation", J.P. Princen, A.W. Johnson and A.B. Bradley, University of Surrey, Guildford, Surrey, Royal Melborne Institute of Technology, Melborne, 3001, Australia, pp. 2161-2164 (no date given).
"The Critical Band Coder-Digital Encoding of Speech Signals Based on the Perceptual Requirements of the Auditory System", Michael A. Kasner, M.I.T. Lincoln Laboratory, 1980 IEEE, pp. 327-331.
An Application Specific DSP Chip Set for 100 MHZ Data Rates , Surendar Magar, Shannon Shen, Garry Luikuo, Mike Fleming and Raul Aguilar, Honeywell, Signal Processing Technologies, Colorado Springs, CO 80906, ICASSP 88, vol. IV, 1988 International Conference on Acoustics, Speech and Signal Processing, Apr. 11 14, 1988, pp. 1989 1992. *
An Application Specific FFT Processor , 8029 Electrical Engineering, 60 (1988) Jun. No. 738, Woolwich, London, Great Britian, pp. 99 100 and 104 106. *
Application of Quadratue Mirror Filters to Split Band Coding Schemes , D. Esteban and C. Galan, IBM Laboratory, 1977 IEEE International Conference on Acoustics, Speech & Signal Processing, pp. 191 195. *
Perceptual Transform Coding of Wideband Stereo Signals , James D. Johnson, AT&T Bell Laboratories, Murray Hill, New Jersey, 07974, 1989 IEEE, pp. 1993 1994 and 1996. *
Polyphase Quadrature Filters A New Subband Coding Technique , Joseph A. Rothweiler, RCA Goverment Communications Systems, ICASSP 83, Boston, vol. 3 of 3, pp. 1280 1283 (no date given). *
Signal Compression: Technology Targets and Research Directions , Nikil Jayant, 8272 IEEE Journal on Selected Areas in Communications, 10 (1992), Jun., No. 5, New York, U.S., pp. 796 810. *
Subband/Transform Coding Using Filter Bank Designs Based on Time Domain Aliasing Cancellation , J.P. Princen, A.W. Johnson and A.B. Bradley, University of Surrey, Guildford, Surrey, Royal Melborne Institute of Technology, Melborne, 3001, Australia, pp. 2161 2164 (no date given). *
The Critical Band Coder Digital Encoding of Speech Signals Based on the Perceptual Requirements of the Auditory System , Michael A. Kasner, M.I.T. Lincoln Laboratory, 1980 IEEE, pp. 327 331. *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090235710A1 (en) * 2008-03-22 2009-09-24 Fette Gmbh Adjustable knurling tool
US8250893B2 (en) * 2008-03-22 2012-08-28 Fette Gmbh Adjustable knurling tool

Also Published As

Publication number Publication date
DE69023604T2 (en) 1996-04-18
US5115240A (en) 1992-05-19
DE69023604D1 (en) 1995-12-21
KR100242864B1 (en) 2000-02-01
EP0420745A3 (en) 1992-08-19
EP0420745B1 (en) 1995-11-15
EP0420745A2 (en) 1991-04-03
KR910007293A (en) 1991-04-30

Similar Documents

Publication Publication Date Title
USRE36559E (en) Method and apparatus for encoding audio signals divided into a plurality of frequency bands
US5414795A (en) High efficiency digital data encoding and decoding apparatus
US4972484A (en) Method of transmitting or storing masked sub-band coded audio signals
US5260980A (en) Digital signal encoder
KR100295217B1 (en) High efficiency encoding and/or decoding device
AU640780B2 (en) Digital signal encoding apparatus
US5664056A (en) Digital encoder with dynamic quantization bit allocation
Crochiere On the Design of Sub‐band Coders for Low‐Bit‐Rate Speech Communication
US5680130A (en) Information encoding method and apparatus, information decoding method and apparatus, information transmission method, and information recording medium
KR100419546B1 (en) Signal encoding method and apparatus, Signal decoding method and apparatus, and signal transmission method
US5581654A (en) Method and apparatus for information encoding and decoding
JPS6161305B2 (en)
EP0772925B1 (en) Non-linearly quantizing an information signal
US5781586A (en) Method and apparatus for encoding the information, method and apparatus for decoding the information and information recording medium
JP3519859B2 (en) Encoder and decoder
EP0398973B1 (en) Method and apparatus for electrical signal coding
JPH08307281A (en) Nonlinear quantization method and nonlinear inverse quantization method
EP0709981B1 (en) Subband coding with pitchband predictive coding in each subband
JP2587591B2 (en) Audio / musical sound band division encoding / decoding device
KR0134350B1 (en) Coding and decoding system quantization bit
EP1176743B1 (en) Methods for non-linearly quantizing and dequantizing an information signal
JP2906477B2 (en) Digital signal encoding method
JPH0744500B2 (en) Encoding / decoding method and device suitable for variable rate transmission
JPS59214346A (en) Subband encoding method and its encoding decoder
JPH05308289A (en) Audio signal band split coder

Legal Events

Date Code Title Description
FPAY Fee payment

Year of fee payment: 12