JPH09130263A - Data communication equipment, encoding device and decoding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arbitrarily set a compressibility without limiting the compressibility of data by the transmission rate of a communication channel. SOLUTION: This equipment is provided with the encoding device A with a compression means 7 for compressing the data of pictures and sound and a first recording and reproducing means 9 for recording the data for which the compressed data are multiplexed and reproducing the recorded data by the transmission rate of the communication channel and the decoding device B provided with a second recording and reproducing means 10 for recording the data inputted from the communication channel through a channel interface C by the transmission rate of the communication channel and reproducing the recorded data by the rate required by an expansion means 14 and the expansion means 14 for expanding and restoring the reproducing data of the second recording and reproducing means 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication device and the like in a communication system in which data is compressed on the transmitting side, the compressed data is sent via a communication line, and the compressed data is expanded on the receiving side.

[0002]

2. Description of the Related Art In a videophone and a video conference, 1
December 992 International Telegraph and Telephone Advisory Committee (CCITT,
The current H. ITU-T) was established. An image compression device compatible with the H.261 recommendation and also 1 in CCITT
G.M. was established in April 1988. It is common to use an audio compression device according to the recommendation of 722 or the like. In addition, these video telephones and video conference data communication devices generally have a conventional configuration as shown in FIG.

In FIG. 8, the data communication apparatus includes an encoding apparatus 50, a decoding apparatus 60 and a line interface 70.
Consisting of The imaging device 51 of the encoding device 50 outputs the image data obtained by photoelectric conversion by a predetermined system such as the NTSC system or the PAL system, and this output is the A / D converter 52.
After being converted into a digital signal by, it is supplied to the image compression unit 53. The image data is compressed here through processing such as sampling and information source coding, and an error correction code and the like are added if necessary.

The image compression unit 53 will be described with reference to FIG. As shown in FIG. 9, the image compression unit 53 outputs an input terminal 82 from a signal source (not shown) based on the control signal supplied from the control unit (not shown) via the input terminal 80 and the control of the encoding controller 81. The image data supplied via the above is encoded by the information source encoder 83, this data is multiplexed by the video signal multiplexer encoder 84, and is temporarily stored in the transmission buffer 85. After that, the transmission encoder 86 performs an encoding process, and outputs it via an output terminal 87.

The operation of the encoding controller 81 will be described with reference to FIG. In a general communication device for transmitting images and audio, image data and audio data generated within a unit frame of a time frame (within a fixed time), for example, within 10 milliseconds are multiplexed as shown in (h) of FIG. To transmit.

At this time, the information amount of the data within the time frame needs to be constant every time. Therefore, the encoding controller 81 increases the compression rate of the image and suppresses the generated information amount when the input image moves rapidly and the generated information amount tends to increase as in the example of frame 2 in FIG. The source encoder 83 is controlled in the direction. On the contrary, when the input image does not move much and the amount of information generated is small as in the case of the frame 1 in FIG. 13, the compression rate of the image is reduced and the information source encoder 83 is set to increase the amount of information generated. Control. Furthermore, when the input image does not move at all, the amount of information generated may not reach the predetermined value even if the compression rate is reduced to the limit. In such a case, the video signal multiplex encoder 84 is controlled to generate meaningless data A called stuffing bit, and the stuffing data is output to the transmission buffer 85 to prevent underflow. To do.

Returning to FIG. 8, the output of the audio data from the sound collector 54 is supplied to the A / D converter 55, converted into digital data here, and then supplied to the audio compression unit 56, where it is compressed. To be done. These compressed audio data and image data are multiplexed by the multiplexer 57, supplied to the line interface 70, sent out to the communication line (not shown) from the input / output terminal 71, and transmitted to the other party via this communication line. To be done.

The voice compression unit 56 will be described with reference to FIG. In FIG. 10, the voice compression unit 56 uses the CCI.
TT G.M. This is a configuration example when it is realized according to the H.722 recommendation. An audio signal input from an information source (not shown) via the input terminal 88 is supplied to the transmission quadrature mirror filter 89, where it is separated into a high frequency component and a low frequency component. Thereafter, the high frequency components are supplied to the high frequency ADPCM encoder 90, and the low frequency components are supplied to the low frequency ADPCM encoder 91, and are separately encoded. The encoded high band data and low band data are supplied to a multiplexer 92, where they are multiplexed and output via an output terminal 93.

Returning to FIG. 8 again, the input / output terminal 7 from the other party
Data input via 1 is the line interface 7
It is led to the separation circuit 61 via 0, and the sound, the image,
Separately processed for each data such as control. After that, the image data is supplied to the image expansion unit 62, and the audio data is supplied to the audio expansion unit 65. The image data is decompressed by the image decompression unit 62,
The data is converted into analog data by the D / A converter 63 and guided to the display device 64. On the other hand, the output of the voice expansion unit 65 is D /
The speaker 67 is converted into an analog signal by the A converter 66.
Supplied to

The image expanding section 62 will be described with reference to FIG. In FIG. 11, the transmission decoder 96 decodes the image data supplied from the signal source (not shown) through the input terminal 95 under the control of the control signal supplied from the controller (not shown) through the input terminal 94. After processing
This data is temporarily stored in the reception buffer 97. Thereafter, the video signal multiplex decoder 98 performs a decoding process, the information source decoder 99 restores the original image data, and the resultant image data is output via the output terminal 100.

The voice expanding unit 65 will be described with reference to FIG. In FIG. 12, the audio decompression unit 65 is a G. 7
22 is an example when it is realized according to Recommendation. The audio data supplied from a signal source (not shown) through the input terminal 101 is separated into a high frequency component and a low frequency component by a separator 102, the high frequency component is a high frequency ADPCM decoder 103, and the low frequency component is a low frequency component. Each is supplied to the ADPCM decoder 104. High band ADPCM decoder 103 and low band ADPCM decoder 10
Each audio data decoded in 4 is an orthogonal mirror filter 1
No. 05 is combined and output through the output terminal 106.

[0012]

By the way, the above-mentioned conventional image communication apparatus has the following inconveniences.

(1) Since the transmission rate of the communication line and the output rate of the multiplexing unit must be equal, the image quality and sound quality are limited by the transmission rate of the communication line, and the compression rate can be set arbitrarily. I couldn't.

(2) When an image with a lot of movement is input,
In a general image compression unit, since the compression is performed by utilizing the temporal correlation between images, the amount of generated information increases. If this increased amount is transmitted as it is, it will cause an overflow of the communication line. Therefore, generally, a means for suppressing the amount of information generated by increasing the compression rate is used in order to reduce the image quality. That is, the image quality changes depending on the content (degree of movement) of the input image.

(3) For an input image with no movement, the amount of information output from the image compression section is extremely small. In such a case, meaningless data generally called stuffing is transmitted to prevent underflow of the line. This reduces the utilization efficiency of the communication line.

Therefore, according to the present invention, the compression rate of data is not limited by the transmission rate of the communication line, and the compression rate can be set arbitrarily, and transmission can always be performed with an appropriate amount of information and stuffing. An object is to provide a data communication device that does not need to transmit data.

[0017]

The structure of the present invention for achieving the above object comprises a compression means for compressing data,
A first recording / reproducing means for recording the output data from the compressing means and reproducing the recorded data at the transmission rate of the communication line, and transmitting the reproduced data of the first recording / reproducing means to the communication circuit. An encoding device, a second recording / reproducing means for recording data from the communication circuit at the transmission rate and reproducing the recorded data, and an expansion processing means for expanding the reproduction data of the second recording / reproducing means. And a decoding device having.

Therefore, the reproduction rate at the time of reproduction by the first recording / reproducing means and the recording rate at the time of recording by the second recording / reproducing means must match the transmission rate of the communication line, but the first recording / reproducing means. May be recorded at a rate according to the output of the compression means, and the reproduction of the second recording / reproduction means may be performed by reading at the rate required by the expansion means.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. One embodiment is shown in FIGS. 1 to 8, and this data communication device is applied as an information terminal device for delivering image / sound information of a video conference, a video telephone, or the like.

FIG. 1 shows a schematic circuit block diagram of a data communication device. In FIG. 1, a data communication device includes a coding device A that compresses and multiplexes images and audio, a decoding device B that separates multiplexed data and decodes audio data and image data, and a coding device. outputs the output data from the a to the output terminal t ₁ from the communication line (not shown), and outputs the input data inputted from the output terminal t ₁ via the communication line to the decoding apparatus B line And an interface C.

The encoding device A is constructed as follows. That is, the imaging position 1 outputs the image data obtained by photoelectric conversion to the A / D converter 2 by a predetermined method such as the NTSC method or the PAL method. The A / D converter 2 digitizes the image data and outputs it to the image compression unit 3. The image compression unit 3 compresses the digitized image data through sampling, information source coding, and the like, and adds an error correction code or the like if necessary. The detailed configuration of the image compression unit 3 will be described below.

The voice data output from the sound collector 4 is A /
After being supplied to the D converter 5 and digitized here,
It is output to the voice compression unit 6. The audio compression unit 6 compresses audio data, and its detailed configuration will be described below. The audio compression section 6 and the image compression section 3 constitute a compression means 7.

The multiplexer 8 is supplied with the image data from the image compressor 3 and the audio data from the audio compressor 6, and the multiplexer 8 time-division multiplexes the image data and the audio data. This multiplexed data is output to the first recording / reproducing device 9. The first recording / reproducing apparatus 9 records the multiplexed data on the recording medium according to the output rate of the multiplexer 8 and reproduces the recorded multiplexed data at the transmission rate of the communication line. The detailed structure of the first recording / reproducing apparatus 9 will be described below.
The multiplexed data reproduced by the recording / reproducing device 9 is output to the communication line via the line interface C.

The decoding device B is constructed as follows. That is, the multiplexed data from the line interface C is guided to the second recording / reproducing apparatus 10, the second recording / reproducing apparatus 10 records the multiplexed data on the recording medium at the transmission rate of the communication line, and the recorded multiplexed data is recorded. The data is reproduced at the rate required by the expansion means 14 described below. The detailed configuration of the second recording / reproducing apparatus 10 will be described below. The multiplexed data reproduced by the second recording / reproducing apparatus 10 is separated by the separation circuit 11.
Supplied to The demultiplexing circuit 11 demultiplexes the multiplexed data into image data, audio data, control data, and the like, and outputs the image data to the image decompression unit 12 and the audio data to the audio decompression unit 13.

The image decompression unit 12 and the audio decompression unit 13 constitute a decompression means 14. The image decompression unit 12 decompresses the image data, and the detailed configuration will be described below. The voice decompression unit 13 decompresses the voice data, and the detailed configuration will be described below. The image data expanded by the image expansion unit 12 is D / A converter 15
Is converted into analog, and the analog image data is supplied to the display device 16. The image data decompressed by the audio decompression unit 13 is converted into analog by the D / A converter 17,
This analog audio data is supplied to the speaker 18.

FIG. 2 shows a circuit block diagram of the image compression section 3. In FIG. 2, a control signal from a control unit (not shown) is supplied to the input terminal t ₂ , and the image compression unit 3 is controlled based on this control signal and the control of the encoding controller 3a.
Each circuit of is controlled. Image data from the A / D converter 2 is supplied to the input terminal t ₃ , and this image data is output to the information source encoder 3b. The information source encoder 3b encodes the image data based on the compression rate control signal of the encoding controller 3a. The encoding controller 3a does not change the compression rate largely so as to keep the information amount of the data in the time frame constant as in the conventional case, but changes the compression rate small so as to maintain an almost constant image quality (FIG. 7). (See (e)). That is, as shown in (d), (e), and (f) of FIG. 7, control is performed so that the amount of information is increased in a portion having a large amount of movement and conversely, the amount of information is reduced in a portion having a small amount of movement.

The image data encoded by the information source encoder 3b is supplied to the video signal multiplex encoder 3c, and the video signal multiplex encoder 3c multiplexes the image data and outputs it to the transmission buffer 3d. To do. The transmission buffer 3d temporarily stores the image data and outputs it to the transmission encoder 3e. The data occupancy information of the transmission buffer 3d is output to the encoding controller 3a, and the encoding controller 3a slightly changes the compression rate by looking at the data occupancy information. The output of the transmission buffer 3d is supplied to the transmission encoder 3e, and the transmission encoder 3e performs encoding processing and outputs it to the output terminal t ₄ .

FIG. 3 shows a circuit block diagram of the audio compression unit 7. In FIG. 3, this voice compression unit 7 is CC
ITT G. This is an example in the case of being realized according to the H.722 recommendation. The audio data from the A / D converter 5 is supplied to the input terminal t ₅ , and this audio data is supplied to the transmission quadrature mirror filter 7a, where it is separated into a high frequency component and a low frequency component. The high-frequency component is supplied to the high-frequency ADPCM encoder 7b, and the low-frequency component is supplied to the low-frequency ADPCM encoder 7c, and are separately encoded. The encoded high band data and low band data are supplied to the multiplexer 7d, where they are multiplexed and output terminal t
It is output from ₆ .

FIG. 4 shows a circuit block diagram of the image expansion unit 12. In FIG. 4, a control signal from a controller (not shown) is supplied to the input terminal t ₇ , and each circuit is controlled based on this control signal. The image data from the separator 11 is supplied to the input terminal t ₈ , and this image data is output to the transmission decoder 12a. The transmission decoder 12 decodes the image data and once receives this data, the reception buffer 1
Store in 2b. The image data output from the reception buffer 12b is decoded by the video signal multiplex decoder 12c, restored to the original image data by the information source decoder 12d, and output from the output terminal t ₉ .

FIG. 5 shows a circuit block diagram of the audio decompression unit 13. In FIG. 5, the voice expansion unit 13 is a G.
This is an example in the case of being realized according to the H.722 recommendation. The audio data from the separator 11 (see FIG. 1) is supplied to the input terminal t ₁₀ , and this audio data is output to the separator 13a.
The separator 13a separates the high frequency component and the low frequency component of the audio data, and the high frequency component is supplied to the high frequency ADPCM decoder 13b.
The low frequency components are supplied to the low frequency ADPCM decoder 13c. High band ADPCM decoder 13b and low band ADPC
The audio element data decoded by the M decoder 13c are combined by the orthogonal mirror filter 13d to be audio data, and this audio data is output from the output terminal t ₁₁ .

FIG. 6 shows a circuit block diagram of the first recording / reproducing means 9 or the second recording / reproducing means 10. The first recording / reproducing means 9 and the second recording / reproducing means 10 have the same circuit block configuration. Have In FIG. 6, the first recording / reproducing means 9 (second recording / reproducing means 10) includes a control circuit 9a (10
a), a memory 9b (10b) as a recording medium, and a counter 9c (10c). Control circuit 9a
A control signal from an external control unit (not shown) is supplied to (10a) via the input terminal t ₁₂ , and the control circuit 9a (10
In (a), a write mode signal is output to the memory 9b (10b) when writing and a read mode signal is output when reading. The memory 9b (10b) is, for example, a first-in first-out memory,
Image data is supplied to a (10a) through an input terminal t ₁₃ . Further, the control circuit 9a (10a) outputs a clock synchronized with the input rate of the input image data to the counter 9c (10c) at the time of writing, and a clock synchronized with the desired rate at the counter 9c (10c) at the time of reading.
output to c). The counter 9c (10c) counts the clock to increase or decrease the address data,
This address data is output to the memory 9b (10b). That is, the memory 9b (10b) stores the image data according to this address data at the time of writing, and reads the image data stored according to this address data at the time of reading.

In the above configuration, in the encoding device A, the audio data is almost constant regardless of the content of the input audio in the general audio compression such as G722 described above, and the audio data from the audio compression unit 6 is constant per time frame. The amount of data is output. Further, since the image compression unit 3 compresses the image data at a substantially constant compression rate, the amount of information after compression is not constant. That is, the amount of information is large in a part having a lot of movement, and conversely, the amount of information is small in a part having little movement, resulting in a large difference in the amount of data per time frame. The audio data and the image data thus generated are multiplexed by the multiplexer 8 and stored in the first recording / reproducing means 9 at the output rate of the multiplexer 8. Then, the multiplexed data stored in the first recording / reproducing means 9 is read out and output at the transmission rate of the communication line. Therefore, the image compression unit 3 and the audio compression unit 6
Can be set to a free coating rate without being restricted by the transmission rate of the communication line. Therefore, by setting the capacity of the first recording / reproducing means 9 to be sufficiently large, high-quality images and sounds can be sent over a line with a low transmission rate over time. For example, MPEG2 (Transmission rate: 6M
bps data to telephone line (transmission rate: 28.8K)
bps or less).

Further, as described above, the amount of information is large in a portion where the motion is large during image compression, and even if the amount of information to be transmitted is reduced in a scene where there is no motion, the amount of data input to the transmission buffer 3d is relatively large. Therefore, it is not necessary to add stuffing data, and efficient transmission is possible.

In the decoding device B, the multiplexed data sent from the other side via the communication line is used by the second recording / reproducing device 10.
The recorded multiplexed data is once recorded on the basis of the time information contained in the data, and the read rate is controlled so that, for example, the time frame signal and the audio signal have a constant rate. Then, the second recording / reproducing apparatus 10
The image data and the audio data of the proper rate are reproduced from.

In the above embodiment, the recording medium of the first and second recording / reproducing means 9 and 10 is composed of the memories 9b and 10b, but it is composed of a recording medium which is detachable from the main body of the apparatus. Is also good. That is, if a non-volatile recording medium such as a magnetic disk is used, the data recorded by another device can be used, and the application range is expanded.

In the above-mentioned embodiment, since the data in which the sound and the image are multiplexed is temporarily recorded in the first recording / reproducing means 9, the past data is accumulated as long as the capacity of the first recording / reproducing means 9 allows. It becomes possible. Therefore, if this function is used for the monitoring device, it is possible to construct a system for reproducing and transmitting the past data recorded in the first recording / reproducing means 9 when the calling signal from the outside is received.

In the above embodiment, the data communication device is configured for bidirectional communication. However, only the coding device A or the decoding device B may be configured for unidirectional communication. .

Incidentally, it goes without saying that various configurations can be adopted without departing from the gist of the present invention, for example, by replacing part or all of the encoding device A and the decoding device B with software processing of a computer.

[0039]

As described above, according to the present invention, the compression means for compressing data, the output data from the compression means, and the recorded data are reproduced at the transmission rate of the communication line. An encoding device which has one recording / reproducing means and sends the reproduced data of the first recording / reproducing means to the communication circuit, records the data from the communication circuit at the transmission rate, and reproduces the recorded data. Since the decoding device having the second recording / reproducing means and the decompressing means for decompressing the reproduced data of the second recording / reproducing means is provided, the quality of the image to be transmitted, that is, the compression ratio of the image or the sound is determined by the communication line. It is possible to set a wide range without being limited by the transmission rate of. In addition, by increasing the amount of information to be transmitted in a portion having a lot of movement, it becomes possible to transmit a moving image with good image quality regardless of the degree of movement. Conversely, when there is no motion, the amount of information to be sent can be reduced, and it is not necessary to send meaningless data such as stuffing bits, so that the line can be effectively used.
Furthermore, when this communication device is used for monitoring purposes, it becomes possible to transmit video and audio in the past in the range of the capacity of the recording / reproducing means.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a data communication device (embodiment).

FIG. 2 is a circuit block diagram of an image compression unit (embodiment).

FIG. 3 is a circuit block diagram of a voice compression unit (embodiment).

FIG. 4 is a circuit block diagram of an image decompression unit (embodiment).

FIG. 5 is a circuit block diagram of a voice decompression unit (embodiment).

FIG. 6 is a circuit block diagram of recording / reproducing means (embodiment).

FIG. 7 is an explanatory diagram of data processing (embodiment).

FIG. 8 is a circuit block diagram of a data communication device (conventional example).

FIG. 9 is a circuit block diagram of an image compression unit (conventional example).

FIG. 10 is a circuit block diagram of a voice compression unit (conventional example).

FIG. 11 is a circuit block diagram of an image decompression unit (conventional example).

FIG. 12 is a circuit block diagram of a voice decompression unit (conventional example).

FIG. 13 is an explanatory diagram of data processing (conventional example).

[Explanation of symbols]

 A ... Encoding device B ... Decoding device 7 ... Compressing means 9 ... First recording / reproducing means 10 ... Second recording / reproducing means 14 ... Decompression means

Claims (4)

[Claims] 1. A compression means for compressing data, and a first recording / reproducing means for recording output data from the compression means and reproducing the recorded data at a transmission rate of a communication line. 1 an encoding device for transmitting the reproduction data of the recording / reproducing means to the communication circuit, and recording the data from the communication circuit at the transmission rate,
A data communication device comprising: a second recording / reproducing device for reproducing the recorded data; and a decoding device having a decompressing device for expanding the reproduced data of the second recording / reproducing device. 2. A compression means for compressing data, and a first recording / reproducing means for recording output data from the compression means and reproducing the recorded data at a transmission rate of a communication line. (1) An encoding device for transmitting the reproduction data of the recording / reproducing means to the communication line. 3. A second recording / reproducing means for recording the data from the communication line at the transmission rate and reproducing the recorded data, and an expanding means for expanding the reproduced data of the second recording / reproducing means. A decoding device having. 4. The recording medium of both the first recording / reproducing device and the second recording / reproducing device, or either one of them, is a recording medium detachable from the apparatus main body. The data communication device according to claim 1.