WO2001024523A1

WO2001024523A1 - Mobile radio terminal

Info

Publication number: WO2001024523A1
Application number: PCT/JP2000/006501
Authority: WO
Inventors: Mitsuru Yanagisawa
Original assignee: Kabushiki Kaisha Toshiba
Priority date: 1999-09-30
Filing date: 2000-09-22
Publication date: 2001-04-05
Also published as: EP1142331A1; JP2001103565A

Abstract

According to the present invention, a main control section (2) monitors a reception field strength and an error ratio of received data, and when it is determined from the monitoring result that a communication environment is deteriorated, an image processing section (10) performs a process of thinning the number of frames of image data picked up by a camera (11) in response to an instruction from the main control section (2), thereby reducing the amount of image data to be transmitted to a communication destination per unit time via a radio section (1).

Description

D E S C R I P T I O N

MOBILE RADIO TERMINAL

Technical Field

The present invention relates to a mobile radio terminal capable of transmitting moving pictures, such as a portable telephone terminal having, for example, a video phone capability. Background Art

As well known, conventional portable telephone terminals reduce consumed power by cutting off power supply to unnecessary circuits in accordance with a communication mode, thus elongating the operation time, such as a communication time or a standby time, ensured by a battery which has a limited amount of power.

Recently, however, there are demands of making portable telephone terminals more compact and the operation time longer. Accordingly, there are demands of compact batteries and reducing consumed power.

Disclosure of Invention It is an object of the present invention to provide a mobile radio terminal capable of reducing consumed power at the time of operation. To achieve this object, a mobile radio terminal according to this invention acquires predetermined information, reduces the number of frames of image data by thinning a plurality of frames constituting the image data by frames whose quantity accords to that acquired information, and then transmits the image data. As a result, the mobile radio terminal with the above-described structure changes the number of frames of image data to be transmitted per unit time in accordance with the acquired information, making it possible to save transmission power and reduce consumed power at the time of operation.

Further, according to this invention, the number of frames of the image data is reduced by thinning a plurality of frames constituting image data by frames whose quantity accords to the degradation level of the communication environment, and the image data is then transmitted.

Therefore, this invention can provide a mobile radio terminal which changes the number of frames of image data to be transmitted per unit time in accordance with the communication environment, thus making it possible to save transmission power and reduce consumed power at the time of operation.

Further, according to this invention, the number of frames of the image data is reduced by thinning a plurality of frames constituting image data by frames whose quantity accords to the degradation level of the communication environment, and the image data is then transmitted at a communication rate according to that number.

Therefore, this invention can provide a mobile radio terminal which changes the communication rate in accordance with the communication environment, thus making it possible to suppress unsuccessful fast communication, save power needed for image processing and transmission power and reduce consumed power at the time of operation. Furthermore, according to this invention, the number of frames of image data is subjected to a thinning process so that the number becomes an accepted frame number instructed by a user and image data is then radio-transmitted to a communication destination. Therefore, this invention can provide a mobile radio terminal which can transmit an image with frames whose quantity is instructed by a user, so that it is possible to suppress transmission of image data having multiple frames that the user does not need, and save power needed for image processing and transmission power .

Further, according to this invention, when an instruction on the communication rate from a user is accepted, image data is subjected to a thinning process and is transmitted at the communication rate that has been specified by the user.

Therefore, this invention can provide a mobile radio terminal which can transmit an image at a communication rate specified by a user, thus making it possible to suppress fast communication which is not desired by the user, save power needed for image processing and transmission power and reduce consumed power at the time of operation.

Furthermore, according to this invention, radio-transmission of image data to a communication destination is stopped when a voice of the user has not been input for a predetermined time or longer.

This invention can therefore provide a mobile radio terminal which does not unnecessarily perform image processing and transmission of image data, thus making it possible to suppress unsuccessful fast communication, save power needed for image processing and transmission power and reduce consumed power at the time of operation.

Brief Description of Drawings FIG. 1 is a circuit block diagram illustrating the structure of a mobile radio terminal according to this invention.

FIG. 2 is a flowchart for explaining the operation of an mobile radio terminal according to a first embodiment in a video communication mode. FIG. 3 is a flowchart for explaining the operation of an mobile radio terminal according to a second embodiment in a video communication mode. FIG. 4 is a flowchart for explaining the operation of an mobile radio terminal according to a third embodiment in a video communication mode.

FIG. 5 is a flowchart for explaining the operation of an mobile radio terminal according to a fourth embodiment in a video communication mode.

FIG. 6 is a flowchart for explaining the operation of an mobile radio terminal according to a fifth embodiment in a video communication mode. FIG. 7 is a flowchart for explaining the operation of an mobile radio terminal according to a sixth embodiment in a video communication mode.

Best Mode for Carrying Out the Invention Preferred embodiments of the present invention will be described below with reference to the accompanying drawings .

FIG. 1 illustrates the structure of a mobile radio terminal according to the first embodiment of this invention. "1" is a radio section which has an antenna and performs transmission and reception of radio waves of a predetermined frequency band with an unillustrated base station, and communication protocol control is executed by a main control section 2 to be discussed later. The main control section 2 has, for example, a microcomputer, performs general control of the individual sections of this mobile radio terminal to thereby accomplish video and voice communication with a communication destination.

"3" is a speech control section which forms a speech path to a communication destination by demodulating a signal received by the radio section 1 over the communication channel that is established under the communication protocol control of the main control section 2 and modulating a signal to be transmitted via the radio section 1. "4" is a speaker which outputs outside a speech signal obtained from a communication destination over the speech path formed by the communication control section 3. "5" is a microphone which gathers voices of a user and converts them into an electric signal, and sends the converted speech signal as a transmission speech to the speech path formed by the speech control section 3. The speaker 4 and the microphone 5 constitute a handset to make communication with the destination. "6" is a display section, such as a liquid crystal display, which displays various kinds of information under the control of an image processing section 10 to be discussed later. "7" is an operation input section 7 which comprises numerical keys for inputting a telephone number or the like, function keys to activate various kinds of functions, etc., and a user's request or instruction input through this section is notified to the main control section 2.

"8" is a data storage section which stores data of preset additional numbers and a phonebook, redial data, absent reception data, etc., and the main control section 2 performs an update process on the data.

The data storage section 8 also stores a frame- number determination table in which a transmitted-image frame number is associated with each of the field strength of a received signal and the error ratio of the received signal. This table is a data table set in such a manner that the lower the field strength of the received signal is and the higher the error ratio of the received signal is, the smaller the number of frames of a transmitted image becomes. "9" is an external input section which serves as an interface for receiving data from an external unit and receives input data based on the control of the main control section 2. The input data is input to the main control section 2. "10" is the image processing section which has functions of performing display control of the display section 6 and coding/decoding image data, under the control of the main control section 2. The image processing section 10 digitizes a video signal picked up by a camera 11 and then encodes the signal by a predetermined encoding scheme, thus generating encoded image data, and sends the encoded image data to the main control section 2.

The image processing section 10 decodes encoded image data given from the main control section 2 and performs analog conversion on the data, thus generating an image signal, and displays it on the display section 6.

Referring now to FIG. 2, the operation of the mobile radio terminal with the above-described structure will be described below. FIG. 2 is a flowchart for explaining that operation, which is executed by the main control section 2.

First, in step 2a, when a user operates the operation input section 7 to start a speech, the flow proceeds to step 2b where the main control section 2 detects the reception field strength of radio waves received at the radio section 1 from a base station and the error ratio o the received data, and then the flow proceeds to step 2c.

In step 2c, the main control section 2 determines if the reception field strength and error ratio detected in step 2b are lower than reference values respectively set for them. hen it is determined that at least either one of them is lower, the flow goes to step 2d, and when it is determined that both are not lower, the flow proceeds to step 2g.

In step 2d, the main control section 2 refers to the frame-number determination table stored in the data storage section 8 to acquire transmitted-image frame numbers corresponding to the reception field strength and error ratio, selects a smaller one of the acquired two transmitted-image frame numbers as a transmitted- image frame number and the flow then proceeds to step 2e.

In step 2e, in response to an instruction from the main control section 2, the image processing section 10 performs a frame thinning process of thinning image data picked up by the camera 1 in the units of frames in such a way that the number of frames of an image to be transmitted a communication destination per unit time becomes the transmitted-image frame number selected in the step 2e, and the flow proceeds to step 2f.

In step 2f, in response to an instruction from the main control section 2, the radio section 1 intermittently transmits the image data that has undergone the thinning process in the step 2e, in accordance with the number of frames of that image data, i.e., the transmitted-image frame number selected in the step 2e, and the flow proceeds to step 2i.

In step 2g, to execute normal video communication, the image processing section 10 performs a frame process on image data, picked up by the camera 1, in response to an instruction from the main control section 2, in such a way that the number of frames of an image to be transmitted the communication destination per unit time becomes a normal number and the transmitted-image frame number in a continuous transmission mode, and the flow proceeds to step 2i. In step 2h, in response to an instruction from the main control section 2, the radio section 1 performs continuous transmission of the image data that has undergone the frame process in the step 2g, in accordance with the number of frames of that image data, i.e., the number of frames of a transmitted image in continuous transmission mode, and the flow proceeds to step 2i.

In step 2i, it is monitored whether the user has made a communication termination request or a link to the communication destination has been disconnected.

When it is at least one of the cases, communication is terminated, and when neither of them is met, the flow proceeds to step 2b to keep communication.

As described above, the mobile radio terminal with the above-described structure monitors the reception field strength and the error ratio of received data and thins the number of frames of image data to be transmitted per unit time before transmission when it is determined from the monitoring result that the communication environment is deteriorated.

That is, in the circumstance where image data with a desired number of frames cannot be sent due to deterioration of the communication environment even if continuous image data is transmitted using many frames per unit time, the number of frames of image data to be transmitted per unit time is thinned to reduce the number of frames, then the image data is transmitted. Therefore, the mobile radio terminal with the above-described structure can vary the number of frames of image data to be transmitted per unit time in accordance with the communication environment, thus making it possible to save transmission power and reduce consumed power at the time of operation.

Note that this invention is not limited to the above-described embodiment.

For example, although the main control section 2 changes the number of frames of image data to be transmitted per unit time in accordance with the communication environment in the above-described first embodiment, the main control section 2 may change the communication rate of image data in accordance with the communication environment instead.

In this case, it is assumed that the data storage section 8 has communication rate data additionally recorded in association with each transmitted-image frame number in the aforementioned frame-number determination table. The communication rate data set here is set in such a way that the communication rate becomes lower as the communication environment deteriorates.

The following will describe the operation of a mobile radio terminal so constructed as to have such main control section 2, as the second embodiment, in video communication mode. FIG. 3 is a flowchart for explaining that operation.

First, in step 3a, when a user operates the operation input section 7 to start a speech, the flow proceeds to step 3b where the main control section 2 detects the reception field strength of radio waves received at the radio section 1 from a base station and the error ratio o the received data, and then the flow proceeds to step 3c.

In step 3c, the main control section 2 determines if the reception field strength and error ratio detected in step 3b are lower than reference values respectively set for them. When it is determined that at least either one of them is lower, the flow goes to step 3d, and when it is determined that both are not lower, the flow proceeds to step 3j.

In step 3d, the main control section 2 refers to the frame-number determination table stored in the data storage section 8 to acquire transmitted-image frame numbers corresponding to the reception field strength and error ratio, selects a smaller one of the acquired two transmitted-image frame numbers as a transmitted- image frame number and the flow then proceeds to step 3e .

In step 3e, the main control section 2 acquires communication rate data corresponding to the transmitted-image frame number selected in the step 3d by referring the frame-number determination table stored in the data storage section 8, and the flow proceeds to step 3f. The communication rate obtained here is lower than the one in normal mode where normal communication is possible. In step 3f, the main control section 2 executes communication protocol control in the radio section 1, and the flow proceeds to step 3g. In step 3g, the main control section 2 controls the radio section 1 to perform transmission and reception of signals associated with the setting of the communication rate acquired in step 3e with respect to the base station, and the flow proceeds to step 3h.

In step 3h, the main control section 2 sets the individual sections so as to ensure communication at the communication rate acquired in step 3e, and the flow goes to step 3i.

In step 3i, in response to an instruction from the main control section 2, the image processing section 10 performs image processing on the image data picked up by the camera 11 in accordance with the communication rate set in step 3h, and the flow goes to step 3k.

In step 3j, to execute normal video communication at the normal communication rate, the image processing section 10 performs image processing according to the normal communication rate in response to an instruction from the main control section 2, and the flow proceeds to step 3k.

In step 3k, the image data hat has been processed in the image processing section 10 is transmitted to the communication destination from the radio section 1 via the base station at the set communication rate, and the flow proceeds to step 31. When the flow proceeds there from step 3i, intermittent transmission takes place, and when the flow proceeds there from step 3j, continuous transmission takes place.

In step 31, it is monitored whether the user has made a communication termination request or a link to the communication destination has been disconnected. When it is at least one of the cases, communication is terminated, and when neither of them is met, the flow proceeds to step 3b to maintain communication. As described above, the mobile radio terminal with the above-described structure monitors the reception field strength and the error ratio of received data and decreases the image processing speed of the image processing section 10 and transmits the image data at a reduced communication rate when it is determined from the monitoring result that the communication environment is deteriorated. That is, in the circumstance where image data with a desired number of frames cannot be sent per unit time due to deterioration of the communication environment even if continuous image data is transmitted in fast communication, the image processing speed of the image processing section 10 is reduced.

As the mobile radio terminal with the above- described structure can vary the communication rate in accordance with the communication environment, therefore, it is possible to lower the image processing speed of the image processing section 10 to suppress unsuccessful fast communication, thereby saving transmission power and reducing consumed power at the time of operation. Note that this invention is not limited to the above-described embodiment.

For example, when it is determined that there is no voice input from the user, the main control section 2 may temporarily stops transmitting image data. The following will describe the operation of a mobile radio terminal so constructed as to have such main control section 2, as the third embodiment, in video communication mode. FIG. 4 is a flowchart for explaining that operation. First, in step 4a, when a user operates the operation input section 7 to start a speech, the flow proceeds to step 4b where the main control section 2 executes communication protocol control in the radio section 1, and the flow then proceeds to step 4c.

In step 4c, the main control section 2 controls the radio section 1 to perform transmission and reception of signals associated with a transition process to a mode of stopping image transmission when no voice is detected, and the flow proceeds to step 4d.

In step 4d, the main control section 2 sets the individual sections to the mode of stopping image transmission when no voice is detected, and the flow goes to step 4e.

In step 4e, the main control section 2 monitors the voice level input to the speech control section 3, and the flow goes to step 4f. In step 4f, the main control section 2 determines if there is a voice from the result of the monitoring in step 4e. When it is determined here that there is a voice input, and the flow proceeds to step 4g. When it is determined that no voice has been input for a predetermined time or longer, it is considered as no voice detection and the flow proceeds to step 4h. in step 4g, the main control section 2 controls the image processing section 10 and the radio section 1 and initiates video communication. Here, in response to an instruction from the main control section 2, the image processing section 10 performs image processing on the image data picked up by the camera 11 first, and then the radio section 1 transmits the image data obtained in this process to the communication destination via the base station. When video communication is started, the flow proceeds to step 4i. in step 4h, when video communication is being carried out at present, image processing by the image processing section 10 is temporarily interrupted to stop transmit image data in response to an instruction from the main control section 2, and the flow proceeds to step 4i.

In step 4i, it is monitored whether the user has made a communication termination request or a link to the communication destination has been disconnected. When it is at least one of the cases, communication is terminated, and when neither of them is met, the flow proceeds to step 4b to maintain communication.

As described above, the mobile radio terminal with the above-described structure monitors the level of the voice input from a user, and interrupts image processing and does not transmits image data when it is determined from the monitoring result that there is no voice input.

That is, in the case where transmission of image data is unnecessary due to breaking of conversation, image processing and transmission of image data are temporarily interrupted.

As the mobile radio terminal with the above-described structure does not unnecessarily perform image processing and transmission of image data, therefore, it is possible to save transmission power needed for image processing and reduce consumed power at the time of operation.

Further, this invention is not limited to the above-described embodiment.

For example, the main control section 2 may vary the number of frames of image data to be transmitted per unit time in accordance with update speed information received from a user.

In this case, it is assumed that the data storage section 8 has transmitted-image frame numbers recorded in association with the update speed information received from the user as the frame-number determination table. The transmitted-image frame number set here is set in such a way as to take a larger value as the update speed indicated by the update speed information becomes greater. The following will describe the operation of a mobile radio terminal so constructed as to have such main control section 2, as the fourth embodiment, in video communication mode. FIG. 5 is a flowchart for explaining that operation. First, in step 5a, when a user operates the operation input section 7 to start a speech, the flow proceeds to step 5b where the main control section 2 accepts the update speed for image data to be transmitted as update speed data from a user via the operation input section 7, and then the flow proceeds to step 5c. In step 5c, the main control section 2 refers to the frame-number determination table stored in the data storage section 8 to acquire a transmitted-image frame number corresponding to the update speed data accepted in step 5b, and the flow then proceeds to step 5d. In step 5d, in response to an instruction from the main control section 2, the image processing section 10 performs a frame thinning process of thinning image data picked up by the camera 1 in the units of frames in such a way that the number of frames of an image to be transmitted a communication destination per unit time becomes the transmitted-image frame number obtained in the step 5c, and the flow proceeds to step 5e.

In step 5e, in response to an instruction from the main control section 2, the radio section 1 intermittently transmits the image data that has undergone the thinning process in the step 5d, in accordance with the number of frames of that image data, i.e., the transmitted-image frame number acquired in the step 5c, and the flow proceeds to step 5f.

Note that when the update speed designated by the user in step 5b is the normal update speed, the normal transmission frame number is obtained in step 5c, and "0" frame is thinned from the image data picked up by the camera 11 or no thinning is performed in the subsequent step 5d. Then, normal communication is carried out in step 5e after which the flow proceeds to step 5f. in step 5f, it is monitored whether the user has made a communication termination request or a link to the communication destination has been disconnected. When it is at least one of the cases, communication is terminated, and when neither of them is met, the flow goes to step 5b to keep communication.

As described above, the mobile radio terminal with the above-described structure accepts the image update speed that is desired by a user, and performs a thinning process of thinning the image data picked up by the camera 11 in the units of frames to reduce frames to be transmitted before executing transmission. When a user does not want the normal update speed as an update speed for image data to be transmitted, therefore, the mobile radio terminal with the above- described structure thins the number of frames of image data to be transmitted per unit time in accordance with the user ' s demand to thereby reduce the update speed and performs transmission, so that it is possible to save transmission power according to the user's intention and reduce consumed power at the time of operation.

Note that this invention is not limited to the above-described embodiment.

For example, although the main control section 2 varies the number of frames of image data to be transmitted per unit time in accordance with update speed information received from a user in the above- described fourth embodiment, the main control section 2 may change the communication rate for image data in accordance with the update speed information received from the user instead.

In this case, it is assumed that the data storage section 8 has transmitted-image frame numbers and respective communication rate data recorded in association with the update speed information received from the user as the frame-number determination table. The communication rate data set here is set in such a way as that the communication rate becomes lower as the number of frames of a transmitted image becomes smaller.

The following will describe the operation of a mobile radio terminal so constructed as to have such main control section 2, as the fifth embodiment, in video communication mode. FIG. 6 is a flowchart for explaining that operation.

First, in step 6a, when a user operates the operation input section 7 to start a speech, the flow proceeds to step 6b where the main control section 2 accepts the update speed for image data to be transmitted as update speed data from a user via the operation input section 7, and then the flow proceeds to step 6c.

In step 6c, the main control section 2 refers to the frame-number determination table stored in the data storage section 8 to acquire a transmitted-image frame number corresponding to the update speed data accepted in step 6b, and the flow then proceeds to step 6d.

In step 6d, the main control section 2 acquires communication rate data corresponding to the transmitted-image frame number obtained in the step 6c by referring the frame-number determination table stored in the data storage section 8, and the flow proceeds to step 6e.

In step 6e, the main control section 2 executes communication protocol control in the radio section 1, and the flow proceeds to step 6f. In step 6f, the main control section 2 controls the radio section 1 to perform transmission and reception of signals associated with the setting of the communication rate acquired in step 6d with respect to the base station, and the flow proceeds to step 6g. In step 6g, the main control section 2 sets the individual sections so as to ensure communication at the communication rate acquired in step 6d, and the flow goes to step 6h.

In step 6h, in response to an instruction from the main control section 2, the image processing section 10 performs image processing on the image data picked up by the camera 11 in accordance with the communication rate set in step 6g, and the flow goes to step 6i.

In step 6i, in response to an instruction from the main control section 2, the radio section 1 intermittently transmits the image data that has undergone the thinning process in the step 6h, in accordance with the number of frames of that image data, i.e., the transmitted-image frame number acquired in the step 6c, and the flow proceeds to step 6j.

Note that when the update speed designated by the user in step 6b is the normal update speed, the normal transmission frame number is obtained in step 6c, and the normal communication rate is acquired in the subsequent step 6d. Further, "0" frame is thinned from the image data picked up by the camera 11 or no thinning is performed. Then, normal continuous communication is carried out in step 6i, and then the flow proceeds to step 6j.

In step 6j, it is monitored whether the user has made a communication termination request or a link to the communication destination has been disconnected.

When it is at least one of the cases, communication is terminated, and when neither of them is met, the flow goes to step 6b to keep communication.

As described above, the mobile radio terminal with the above-described structure accepts the image update speed that is desired by a user, and transmits image data at the communication rate corresponding to that image update speed.

That is, when a user does not want the normal update speed as an update speed for image data to be transmitted, the image processing speed of the image processing section 10 is reduced in accordance with the user's demand to thereby reduce the communication rate and transmits image data.

Therefore, the mobile radio terminal with the above-described structure can reduce the image processing of the image processing section 10 according to the user's intention, so that it is possible to save transmission power and reduce consumed power at the time of operation.

This invention is not limited to the above- described embodiment.

For example, the main control section 2 may change the transmission mode for image data in accordance with a user's demand.

In this case, it is assumed that the data storage section 8 has transmitted-image frame numbers recorded in association with the update speed information received from the user as the frame-number determination table. The transmitted-image frame number set here is set in such a way as to take a larger value as the update speed indicated by the update speed information becomes greater. The following will describe the operation of a mobile radio terminal so constructed as to have such main control section 2, as the sixth embodiment, in video communication mode. FIG. 7 is a flowchart for explaining that operation. First, in step 7a, when a user operates the operation input section 7 to start a speech, the flow proceeds to step 7b where the main control section 2 monitors if there is a user's request of changing the image transmission mode via the operation input section 7.

When there is the request, the flow proceeds to step 7d and when the request is not made, the flow proceeds to step 7c.

In step 7c, the main control section 2 instructs the image processing section 10 to perform the normal image processing on image data picked up by the camera 11, and the flow then proceeds to step 7j.

In step 7d, the main control section 2 determines the user's request detected in step 7b. When it is determined here that the user has requested a non-display mode of making no image display on the communication destination side as the image transmission mode, the flow proceeds to step 7e.

When it is determined here that the user has requested a still-picture display mode of displaying a still picture on the communication destination side as the image transmission mode, the flow proceeds to step 7f.

When it is determined here that the user has requested a moving-picture display mode of displaying a moving picture on the communication destination side as the image transmission mode, the flow proceeds to step 7g.

In step 7e, the main control section 2 instructs the image processing section 10 to stop image processing and stops transmitting image data to the communication destination, and the flow proceeds to step 7j.

In step 7f, the main control section 2 instructs the image processing section 10 to perform image processing only on an image for one frame, instructs the image processing section 10 to stop image processing after the processed image for one frame is transmitted, and stops transmitting image data to the communication destination, and the flow proceeds to step 7j. In step 7g, the main control section 2 accepts the update speed for image data to be transmitted as update speed data from the user via the operation input section 7, and then the flow proceeds to step 7h.

In step 7h, the main control section 2 refers to the frame-number determination table stored in the data storage section 8 to acquire a transmitted-image frame number corresponding to the update speed data accepted in step 7g, and the flow then proceeds to step 7i.

In step 7i, in response to an instruction from the main control section 2, the image processing section 10 performs a frame thinning process of thinning image data picked up by the camera 1 in the units of frames in such a way that the number of frames of an image to be transmitted a communication destination per unit time becomes the transmitted-image frame number obtained in the step 7h. Further, in response to an instruction from the main control section 2, the radio section 1 intermittently transmits the image data that has undergone the thinning process in accordance with that frame number or the transmitted-image frame number acquired in the step 7h, and the flow proceeds to step 7j.

Note that when the update speed designated by the user in step 7g is the normal update speed, the normal transmission frame number is obtained in step 7h, and "0" frame is thinned from the image data picked up by the camera 11 or normal communication is carried out without performing thinning in the subsequent step 7i. Then, the flow proceeds to step 7j. In step 7j, it is monitored whether the user has made a communication termination request or a link to the communication destination has been disconnected. When it is at least one of the cases, communication is terminated, and when neither of them is met, the flow goes to step 7b to keep communication.

As described above, the mobile radio terminal with the above-described structure transmits image data in an image transmission mode according to a user's request. That is, image data is not transmitted unnecessarily against the user's intention.

As the mobile radio terminal with the above- described structure controls the image processing of the image processing section 10 according to a user's intention, therefore, it is possible to prevent unnecessary image processing and transmission process, thereby saving transmission power and reducing consumed power at the time of operation.

Note that this invention is not limited to the above-described embodiment.

For example, according to the first and second embodiments, when either one of the detected reception field strength and error ratio is degraded as compared with the respective reference value, the number of frames of an image to be transmitted to the communication destination per unit time and the communication rate are varied (see the descriptions on step 2c in FIG. 2 and step 3c in FIG. 3). By way of contrast, when the detected reception field strength and error ratio are both degraded as compared with the respective reference values, the number of frames of an image to be transmitted to the communication destination per unit time and the communication rate may be varied. Needless to say, the present invention can be embodied in many other modifications without departing from the spirit or scope of the invention.

Claims

C L A I M S

1. A mobile radio terminal capable of transmitting image data containing a plurality of frames comprising: image processing means for reducing the number of frames of said image data by thinning said plurality of frames constituting said image data; and transmission means for radio-transmitting image data whose number of frames have been reduced by said image processing means.

2. The mobile radio terminal according to claim 1, further comprising communication environment detection means for detecting a degradation level of a communication environment based on a radio signal sent from a communication destination; wherein said image processing means reduces the number of frames of said image data by thinning said plurality of frames constituting said image data according to said degradation level of said communication environment detected by said communication environment detection means.

3. The mobile radio terminal according to claim 2, wherein said transmission means radio- transmits image data whose number of frames have been reduced by said image processing means to said communication destination at a communication rate according to a number of frames constituting that image data .

4. The mobile radio terminal according to claim 2, wherein said degradation level of said communication environment detected by said communication environment detection means is a level of reduction of a reception field strength.

5. The mobile radio terminal according to claim 2, wherein said degradation level of said communication environment detected by said communication environment detection means is an error ratio of data received from said communication destination.

6. The mobile radio terminal according to claim 1, further comprising frame number acquisition means for acquiring information of the number of frames of said image data from a user; wherein said image processing means reduces the number of frames of said image data by thinning said plurality of frames constituting said image data in such a way that the number of frames becomes said number of frames acquired from said user by said frame number acquisition means.

7. The mobile radio terminal according to claim 6, wherein said transmission means radio- transmits image data whose number of frames have been reduced by said image processing means to said communication destination at a communication rate according to a number of frames constituting that image data.

8. The mobile radio terminal according to claim 6, wherein said transmission means does not transmit said image data when the number of frames of image data whose frames have been reduced by said image processing means is 0, transmits said image data as a still picture when said number of frames is 1, and transmits said image data as a frame-by-frame image when said number of frames is plural.

9. A method of transmitting image data containing a plurality of frames between mobile radio terminals, comprising the steps of: reducing a number of frames of image data according to a frame number indicated by a user or according to communication environment; and radio-transmitting the image data whose number of frames has been reduced.

10. A mobile radio terminal capable of transmitting image data containing a plurality of frames and voices of a user comprising: voice detection means for detecting whether or not there is a voice input from said user; and means for stopping radio-transmission of said image data to a communication destination when a voice of said user has not been input for a predetermined time or longer based on a result of detection by said voice detection means.