WO2007138617A1

WO2007138617A1 - Video camera for desktop videocommunication

Info

Publication number: WO2007138617A1
Application number: PCT/IT2006/000395
Authority: WO
Inventors: Andrea Santilli
Original assignee: Asdsp S.R.L.
Priority date: 2006-05-25
Filing date: 2006-05-25
Publication date: 2007-12-06

Abstract

An integrated digital video camera is described, to be used for desktop videoconferencing, including a digital camera which captures video image data, a microphone array, a digital audio interface for capturing microphone signals, a digital audio interface and a high speed digital interface.

Description

VIDEO CAMERA FOR DESKTOP VIDEOCOMMUNICATION Field of the invention

This invention refers to an integrated digital video camera, to be used for desktop videoconferencing. Background of the invention

Desktop videoconferencing is becoming more and more popular, mainly due to the availability of Internet connections exhibiting both low costs and high speed and video-communication solutions based on free software: presently most the Internet Messaging ■ Service providers have added a voice chat and video chat functionalities and hence a large customer base is getting accustomed to PC based videoconferencing (software videophone) .

Despite the video quality is mainly limited by the connection speed and hence is expected to quickly improve in the near future, the audio quality is still poor and strongly limited by the audio capturing devices which are presently available. In particular, hand-free communication is often made possible only by wearing a headsets with built in microphone (placed very close to the user's mouth) : using the PC loudspeakers and a fixed microphone (either tabletop or built in the webcam) would require the use of an acoustic echo canceller (AEC) to have a full-duplex communication. In order to have a conventional acoustic echo canceller properly working, an accurate control of the audio latency is required: this is very difficult or impossible with the typical consumer level, Windows compatible audio I/O interfaces; professional level audio cards have always low and consistent latency (usually support ASIO 2 drivers) and so are suitable for AEC applications.

Several microphone array products are already available on the market but they are usually designed for speech recognition (speech-to-text) applications and so no special care is taken to make it possible for such devices to be used as input source of an echo canceller based, hand-free system: furthermore they should be placed in the same place where a webcam is usually placed: the top border of a PC monitor. So integrating a microphone array into a digital video camera (webcam) make it possible for this two peripherals to share the same location and the same digital connection while further benefits can be achieved by integrating a constant latency audio I/O interface (ASIO 2) in order to make AEC integration viable.

EP 1 377 041 discloses a web cam which is composed by 5 or more cameras, positioned along radii around a table, supported by a plastic rod and carrying array microphones on a basis thereof. This contruction is comparatively expensive and hindering. Summary of the invention

All of the above problems are brilliantly solved by this invention, which refers to an integrated digital video camera, to be used for desktop videoconferencing, characterised in that it includes a digital camera lens which captures video image data, a microphone array, a digital audio input interface for capturing microphone signals, digital audio output interface to send the received signals to loudspeakers and a high speed digital interface to send both audio and video data to the host system. Brief description of the drawings Fig. 1 shows a structure of webcam and microphones according to a preferred embodiment of the invention;

Fig. 2 shows a structure of webcam and microphones according to an alternative embodiment; and

Fig. 3 shows a structure of webcam and microphones according to another alternative embodiment of the invention. Best way to carry out the invention

As already stated, this invention refers to an integrated digital video camera, to be used for desktop video conferencing. According to a preferred embodiment, the overall device to be employed for PC based desktop videoconferencing comprises a video camera lens and an audio capturing device. As a video camera lens, a conventional webcam can be used. Preferably, in order to get a high-quality grade of the overall solution, it is desirable to choose the best state-of-the-art optical and CCD sensors, in order to provide true VGA resolution at 30 fps . For this kind of digital cameras a high-speed USB 2 link is a sufficient even though a IEEE 1394 (FireWire) interface is to be preferred for the ASIO 2 audio I/O support, which is preferably employed. In conventional devices, the audio system is separated from the video camera lens, since they are usually independent and work on different kind of circuit. According to the present invention, video camera and microphones form a unit, directly connected to the host system (for instance a personal computer) . This arrangement allows large space sparings and to optimise the system configuration.

As shown in Fig. 1, according to a preferred embodiment, a broadside linear array microphones (for instance, four elements 1 to 4) can be easily designed so as to exhibit a size smaller than the width of most PC monitors including desktop LCD screens and laptop lid displays. With the typical microphone spacing (4-6 cm) it is pretty easy to place the camera lens 5 between the central two microphones 2 and 3.

As shown in Fig. 2, an alternative embodiment uses a single end-fire array (microphones 1 and 2 are shown in Fig.2) could be positioned either on the bottom or on the top of the camera lens 5.

As shown in Fig. 3, another alternative embodiment includes a double end-fire array, where each end-fire array is placed on each side of the central camera lens. In such an arrangement, the two end-fire outputs are mixed together.

In the above embodiments, many existing beamforming algorithms, able to steer a single beam to the front direction can achieve a significant signal-to-noise ratio improvement compared to a single microphone solution. Because of its low sensitivity to calibration errors, a weighed delay and sum beamformer is chosen here. By using cardioid microphones instead of the omnidirectional capsules used in most of the commercial microphone arrays, a significant back rejection is achieved with no extra complexity: anyway, special care must be taken while designing the plastic case as cardioid microphones require large openings .

According to the second and the third embodiments , shown in Figs. 2 and 3 respectively, it is possible to attain a higher directivity (the so called "superdirectivity" ) with respect to the prior art devices, and his adaptive generalisation allows to drive a null of the directional response toward the strongest interfering noise sources and hence to achieve a significant background noise rejection, without affecting the speech coming from the front direction.

Beside the proposed array geometries and the related beamforming algorithms many other combinations of array geometries and beamforming algorithms can be used, and the above embodiments are by no means intended to limit the scope of the present invention, which is mainly directed to a combined microphone array to be used as voice capture device for hand free communication, combined with a digital camera lens in order to achieve an audio/video peripheral of reasonably small size, so that it can be installed on the top of a video screen, as it can be argued from the annexed claims.

Claims

1) An integrated digital video camera, to be used for desktop videoconferencing, characterised in that it includes a digital camera lens (5) which captures video image data, a microphone array (1 to 4) , a digital audio input interface for capturing microphone signals, a digital audio output interface to send the receeived signals to the loudspeakers and a high speed digital interface to send both audio and video data to the host system.

2) A video camera as claimed in claim 1) , characterised in that true VGA resolution at 30 fps is provided.

3) A video camera as claimed in claim 1) or 2) , characterised in that it employs an ASIO 2 audio I/O support.

4) A video camera as claimed in claim 3) , characterised in that a high-speed USB 2 link or a IEEE 1394 (FireWire) interface is provided for the ASIO 2 audio I/O support.

5) A video camera as claimed in any previous claim, characterised in that a broadside linear array microphones (1 to 4) are designed so as to exhibit a size smaller than the width of most PC monitors including desktop LCD screens and laptop lid displays .

6) A video camera as claimed in claim 5) , characterised in that microphones are spaced by 4-6 cm from each other.

7) A video camera as in claim 6) , characterised in that the camera lens (5) is positioned between the two central microphones (2 and 3) .

8} A video camera as claimed in any claim 1) to 4) , characterised in that a single end-fire microphone array is provided .

9) A video camera as claimed in claim 8) , characterised in that the end-fire array is positioned either on the bottom or on the top of the camera lens (5) .

10) A video camera as claimed in any claim 1) to 4) , characterised in that a double end-fire arrays is provided.

11) A video camera as claimed in claim 10) , characterised in that the end-fire arrays are positioned apart from the video camera lens (5) .

12) A video camera as claimed in claim 10) or 11) , characterised in that the two end fire output are mixed together. 13) A video camera as claimed in any previous claim, characterised in that one beamforming algorithm, able to steer a single beam to the front direction, is employed, in order to attain a significant signal-to-noise ratio (RSD) improvement.

14) A video camera as set forth in any previous claim, characterised in that a weighed delay and sum beamformer is chosen.

15) A video camera as claimed in any previous claim, characterised in that a cardioid microphones is used.