JPH08195947A - Video telephone device, data transmitting method and video telephone system - Google Patents

Abstract

PURPOSE: To accurately and speedily transmit image data without interrupting voice even by using a communication line low in a transmission rate and prone to generate transmission errors. CONSTITUTION: In the video telephone device on a transmission side, the video supplied from a camera part 1 is made into a packet in a CPU part 7 after the video is compressed in a video processing part 3 and the video is transmitted to a called party by a modem part 8 via a public line. In the video telephone device on a reception side, a reception is continued even if a transfer error is found when the occurrence frequency of the transfer error is within a prescribed value and the image data packet received lastly is aborted. When the frequency of the transfer error is increased in more than the prescribed value, a re-transmission request is given to the transmission side and the image data with the transfer error is received again only when the transfer error is generated. When the reception of the image data of a frame is completed, the image data is displayed on an external display device via a video circuit 2 after the image data is expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a videophone device, and more particularly to a compact and lightweight videophone device for transmitting intermittent still images in color, a data transmission method and a videophone system.

[0002]

2. Description of the Related Art Conventionally, the idea of a videophone for making a phone call while looking at the face of the other party has been relatively old, and a videoconference system for business use that already uses an IDSN telephone line and an analog public line have been used. There were already black-and-white images and those that were not capable of simultaneous voice and image communication. However, it has not been realized as a consumer videophone capable of simultaneous color image voice image communication using an analog public line. There was the following background as the reason. The videophone has to send information having a relatively large amount of data, such as voice and image, to the other party within a fixed time, and there are two approaches to realize this. One is a method of increasing the data communication rate per unit time, and the other is a method of compressing a redundant portion of data to reduce the amount of data to be transmitted per unit time.

However, the former method of increasing the communication speed is
The short cut is to use the ISDN telephone line, which is a high-speed digital communication line, but ISDN has not become common enough to be used as a communication means for consumer equipment. Although many methods have been proposed for the latter compression / decompression algorithm, the amount of data is such that the sound quality and image quality reproducibility of a videophone is sufficient and that communication is possible via an analog public line. There is no compression technology, and the hardware and microprocessor to handle a large amount of compression and decompression are expensive. However, in recent years, with the increase of communication speed of data modem using analog public line, high integration of hardware, increase of microprocessor speed, and development of data compression technology, to realize videophone as a consumer device, The elemental technologies are ready.

Under such a technical background, a video telephone apparatus capable of simultaneous voice and image communication is being realized by utilizing a communication line such as an analog public line which has a low transmission rate and is susceptible to a transmission error. is there. However, when high-speed communication is performed using a general analog public line, a transfer error occurs in image data when the line state is poor.
Therefore, in the conventional videophone device, the line condition is bad,
When a transfer error occurs in the image data, one of the image data in which the error occurred is not used and is not displayed, or the image data in which the transfer error occurs is sent back again. .

[0005]

However, when a transfer error occurs, a transfer error is always generated in a conventional videophone device which does not use and displays one image data in which an error has occurred. If the number is large, there is a problem that the image data is frequently ignored and the update speed of the image of the other party becomes slow. Further, when a transfer error occurs, a conventional videophone device that always sends back image data in which a transfer error has occurred must send and receive information for determining whether or not a transfer error has occurred. However, there is a problem in that the transfer time becomes longer by the time required to send and receive the information. Further, if the transmission and reception of image data is emphasized too much, there is a problem that sound is interrupted.

Therefore, the present invention is a videophone capable of transmitting image data accurately and at high speed without interruption of voice even if a communication line such as an analog public line which has a low transmission rate and is prone to transmission errors is used. An object of the present invention is to provide a device, a data transmission method, and a videophone system.

[0007]

In order to achieve the above object, in the video telephone according to the invention of claim 1, a transfer error occurs depending on the frequency of occurrence of the transfer error in the transfer of the image data via the communication line. It is characterized by further comprising communication control means for deciding whether or not to retransmit the image data.

According to the second aspect of the present invention, the video telephone apparatus receives at least the image capturing means for capturing the user's own image and the other party image from the other party's device connected via the communication line. , Transmitting the self-portrait captured by the image capturing means to the device of the other party, and resending the image data in which the transfer error occurs in accordance with the frequency of occurrence of the transfer error in the image data transfer via the communication line. Communication control means for instructing the device of the other party, and a self-portrait captured by the image capturing means,
Display control means for displaying a partner image received from the communication control means from the partner device on a display device.

In a preferred mode, the communication control means, when the occurrence frequency of a transfer error in data transfer via a communication line is equal to or less than a predetermined value, as described in claim 3, the other party When the occurrence frequency of the transfer error is higher than a predetermined value, the device of the other party is instructed to retransmit the image data. May be.
Further, for example, as described in claim 4, in the situation where the frequency of occurrence of the transfer error is equal to or less than a predetermined value, the communication control means, even if a transfer error occurs, image data with the device of the other party. It is also possible to continue the transmission and reception of and to discard the series of finally received image data.

When the communication control means receives all the image data groups to be received, for example, as described in claim 5, the communication control means issues a reception completion instruction notifying that all the image data have been received, to the other party. A reception control means for transmitting to the device, and a transmission control means for transmitting the next image data group to the device of the other party only when receiving a reception completion instruction from the device of the other party may be provided. Good. Also,
For example, the communication control means may transmit the total number of bytes of data to be transmitted to the device of the other party immediately before transmitting the image data. The image data may be, for example, as described in claim 7.
Data for one screen transmitted in packet units,
It may be possible to determine whether or not the transfer error occurs in the transfer for one screen.

Further, in the data transmission method according to the present invention, whether or not to retransmit the data having the transfer error is determined according to the frequency of the transfer error, and the frequency of the transfer error is predetermined. When it exceeds the value, it is characterized in that the data in which the transfer error occurs is transmitted and received again.
Further, as a preferred mode, as described in claim 9, for example, in the situation where the frequency of occurrence of the transfer error is equal to or lower than a predetermined value, even if a transfer error occurs, transmission / reception of data to / from the partner device is continued. However, the finally received series of data may be discarded. Further, the data may be image data transmitted in packet units, for example, as described in claim 10.

Further, the communication control means immediately transmits the image data when receiving the connection response transmitted by the called side in response to the connection request transmitted to the other party at the time of line connection. It may be started. Further, for example, the communication control means may transmit the connection request again if the connection response cannot be received for a predetermined time after transmitting the connection request.

Further, in the video telephone according to the present invention, at least the image capturing means for capturing the user's own image and the other party image from the other party's device connected via the communication line are received. , The self-portrait captured by the image capturing means is transmitted to the device of the other party, and the image data that is constantly transmitted and received is a simple image with low resolution, and the occurrence frequency of transfer error in data transfer via the communication line is predetermined. If the value is less than or equal to the value, the other device is not instructed to retransmit the image data. On the other hand, if the frequency of occurrence of the transfer error is more than a predetermined value, the other device is notified. The communication control means for instructing re-sending of the image data, the self-portrait captured by the image capture means, and the device of the other party received by the communication control means. Characterized by comprising the opponent image display control means for displaying on a display device.

In a preferred mode, the communication control means sets the image data to be transmitted / received to a high-resolution fine image only when instructed by the user, and a transfer error occurs. In such a case, the other device may be instructed to retransmit the image data without fail. In a preferred aspect, the communication control means determines that the frequency of occurrence of transfer error is higher than a predetermined value when no normal packet can be received within a predetermined time as described in claim 15, for example. You may do it. In a preferred aspect, the communication control means, for example, as described in claim 16, when no normal packet is received over M times in N seconds and L (L <M) seconds or more, It may be determined that the frequency of occurrence of transfer errors is higher than a predetermined value.

In a preferred aspect, the communication control means, when the time from the start of transmission of image data for one screen to the end of transmission exceeds a predetermined time, for example, as described in claim 17, at that time point. The transmission of the image data may be interrupted, and the transmission of the image data of the next screen may be started. In a preferred aspect, the communication control means may transmit a resend request to the transmitting side at the time when it is determined that a transfer error has occurred in the image data, as in the eighteenth aspect. Further, in a preferred aspect, the communication control means transmits the resend request to the transmitting side at a time point when it determines that a transfer error occurs in the image data, for example, as described in claim 19, and the image data is transmitted for a predetermined time. If not received, the retransmission request may be transmitted again to the transmitting side.

Further, as a preferred mode, the communication control means may transmit a resend request to the transmission side when the image data is not received for a predetermined time, as described in claim 20, for example. Further, as a preferable mode, for example, as described in claim 21, it is determined whether or not to start the retransmission of the simple image according to the occurrence frequency of the CRC error, and when there is no normal received packet, A line state monitoring means for cutting off the videophone operation and returning to the analog phone operation by only normal voice transmission may be provided. Further, as a preferred mode, for example, a predetermined command is set, and the operation of the other side is controlled by exchanging the command between the transmitting side and the receiving side. You may

According to the video telephone system of the twenty-third aspect of the invention, in the video telephone system for transmitting voice data and image data via a communication line, the transmission data is
It consists of a voice packet containing encoded voice data, an image packet containing encoded image data, a command packet containing control data, and a resend request command packet for sending out transmission data again when an error occurs, and these Voice packets every predetermined time,
The feature is that the retransmission request packet, the command packet, and the image packet are transmitted in this order. Further, in the video telephone system according to the invention as set forth in claim 24, in the video telephone system for transmitting audio data and image data via a communication line, the transmission data is encoded as an audio packet including encoded audio data. Image packet containing image data, a command packet containing control data, and a resend request command packet for sending out transmission data again when an error occurs. Voice packet, command packet, and resend command packet are 1 packet at every predetermined time. Each of the image packets is transmitted in a predetermined amount within the predetermined time range.

Further, as a preferable mode, for example, as described in claim 25, a packet having no data among the respective packets may not be transmitted. Further, the voice packet may have a variable length, and the image packet may have a fixed length. Further, the command packet is, for example, 27
As described, it may be of variable length and the retransmission command packet may be of fixed length. Further, the transmission of the transmission data may be a process of writing in the transmission buffer of the modem section as described in claim 28.

According to the 29th aspect of the present invention, in the videophone system in which a videophone device on the transmitting side and a videophone device on the receiving side are connected to each other to transmit voice data and image data, at the time of connection, The voice data is not transmitted for the first predetermined time after the exchange of the connection request and the response. Also,
In the videophone system according to the invention of claim 30, in the videophone system in which a videophone device on the transmitting side and a videophone device on the receiving side are connected to transmit voice data and image data, a response from the receiving side is transmitted. The first mode, in which the side does not monitor and wait, and the sender monitors and waits for a response from the receiver, and when the receiver cannot receive data normally, it sends a resend request requesting data transmission again. The transmitting side has a second mode of transmitting the data again when the retransmission request is received.

In the videophone system according to the thirty-first aspect of the invention, a simple image is used in the videophone system in which the videophone device on the transmitting side and the videophone device on the receiving side are connected to transmit voice data and image data. There is a transmission mode and a fine image transmission mode. In the simple image transmission mode, the transmission side performs communication control processing in which the transmission side does not monitor and waits for a response from the reception side. In the fine image transmission mode, the response from the reception side is transmitted. Communication control in which the sending side monitors and waits, and when the receiving side cannot receive the data normally, it sends a resend request requesting the sending of data again, and the sending side sends the data again when the resending request is received. It is characterized by performing processing. As a preferred aspect, in the simple image transmission mode, as described in claim 32, for example, the transmission side monitors and waits for a response from the reception side due to an increase in the frequency of occurrence of transmission errors, and the reception side normally transmits data. Alternatively, a retransmission request for requesting the transmission of data may be transmitted again when the packet is not received, and the transmission side may switch to the communication control process for transmitting the data again when the retransmission request is received.

[0021]

According to the present invention, the communication control means determines whether or not to resend the image data in which the transfer error has occurred, in accordance with the frequency of occurrence of the transfer error in the transfer of the image data via the communication line. When the error occurrence frequency exceeds the predetermined value, the image data in which the transfer error has occurred is transmitted and received again. Therefore, even if a communication line such as an analog public line that has a low transmission rate and is prone to a transmission error is used, it is possible to transmit image data accurately and at high speed without interruption of voice.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. A. Configuration of Example A-1. Block Configuration of Videophone Device FIG. 1 is a block diagram showing the configuration of a videophone device according to an embodiment of the present invention. In the figure, the present video telephone device includes a camera unit 1, a video circuit unit 2, a video processing unit 3, a video display unit 4, an NCU unit 5, an audio processing unit 6, a CPU unit 7, a modem unit 8, a key / LED 9, and Remote control 10
And so on. The camera unit 1 captures the image of the user of the present videophone device and supplies it to the video circuit unit 2. As shown in FIG. 2, the camera unit 1 includes a lens 11, a CCD (Charge Coupled Device) 12, and a CC.
D driver 13, A / D / D / A converter 14, and D
It is composed of SP15. The lens 11 is an optical lens made of glass or plastic. CCD1
2 generates an electric signal based on the intensity of the light imaged by the lens 11, and the CCD driver 1 generates the electric signal.
It outputs by the drive signal from 3. CCD driver 13
Is an A / D / D / A converter 14 that amplifies the electric signal.
Supply to The A / D / D / A converter 14 is composed of an analog LSI having a filter or the like, converts the electric signal into a digital signal and supplies the digital signal to the DSP 15, and the digital signal subjected to color processing by the DSP 15. Is converted into an analog signal and supplied as a video signal to the video circuit unit 2 shown in FIG. The DSP 15 is for the above-mentioned color processing, and after performing the color processing on the digital signal, supplies it again to the A / D / D / A converter 14.

The video circuit section 2 is a discrete circuit such as a sync separation filter and the like. The video signal supplied from the camera section 1 and the video signal supplied from the external input terminal IN described above are supplied to the remote controller 10 which will be described later. The video processing section 3 is switched based on an instruction from
Supply to In addition, the video circuit unit 2 includes a video processing unit 3
The video signal (analog signal) supplied from the device is sent to the image output terminal OUT.

Next, the video processing section 3 is, as shown in FIG. 3, an A / D / D / A converter 31 and an image input control circuit 3.
2, RAM 33, and image compression / expansion circuit 34. The A / D / D / A converter 31 includes a PLL circuit, a filter circuit, and the like, and the synchronization signal, the luminance signal, the
And color signals are respectively converted into digital signals (hereinafter referred to as image data) and supplied to the image input control circuit 32, while output image data supplied from a video display unit 4 described later is converted into analog signals, The video signal is supplied to the video circuit unit 2 as a video signal.

The image input control circuit 32 includes A / D and D / A
When data is exchanged between the converter 31, the RAM 33, and the image compression / expansion circuit 34, writing to the RAM 33,
Controls reading. That is, the image input control circuit 3
2 temporarily stores the image data supplied from the A / D / D / A converter 31 in the RAM 33, and also stores the image data in the RAM based on an instruction from the CPU unit 7 described later.
The image data temporarily stored in 33 is sequentially read and supplied to the image compression / expansion circuit 34. When the image data is compressed or expanded, the image data temporarily stored in the RAM 33 is sequentially read out and the image compression / expansion circuit 34 is read.
Image data that is supplied to, or compressed or decompressed
The data is stored in a predetermined area of the AM 33.

Next, the image compression / expansion circuit 34 uses a predetermined encoding method, that is, an encoding method according to the type of image to be handled (still image in this case), for example, JPEG.
(JointPhotographic Coding Experts Group) algorithm, DCT (Discrete Cosin) for each 8 × 8 pixel block
Transform: Discrete Cosine Transform), quantization, Huffman coding, etc., and then the compressed image data is stored in the RAM via the image input control circuit 32.
Sequentially write to 33. In addition, the image compression / expansion circuit 34
Has a function of decoding and decompressing compressed / encoded image data, and compression / decompression stored in the RAM 33.
The encoded image data is converted into the image input control circuit 32.
After being sequentially read out via the, the decoding, the dequantization, or the expansion processing, the expanded image data is sequentially written into the RAM 33 again via the image input control circuit 32. As described above, the image data supplied from the video circuit 2, the compressed image data, and the decompressed image data are stored in the RAM 33 in respective predetermined areas under the control of the image input control circuit 32. It is like this.

As shown in FIG. 4, the video display unit 4 includes a display control circuit 41, a RAM 42, and an OSDC (On Scr).
een Disply controler) 43. The display control circuit 41 changes the input image data or the decompressed image data, which is position-stored in the RAM 33 of the video processing unit 3 described above, according to an instruction from the CPU unit 7 described later.
The image data is sequentially transferred to M42, and the output image data is generated by performing interpolation and thinning processing on these image data according to the display specifications, and temporarily stored in the RAM 42. In addition, the display control circuit 41 receives an instruction from the CPU unit 7 to cause the OSDC
The character stored in the character ROM built in 43 is read and combined with the output image data temporarily stored in the RAM 42, and the A / D.
It is supplied to the D / A converter 31.

The NCU section 5 is a control circuit for switching between a telephone line and a telephone, a circuit for simultaneously outputting a voice output signal to both the modem section interface and the telephone, a voice input signal from the telephone and an external voice input. Is a discrete circuit including a circuit for synthesizing the microphone input signal with the input signal. That is, the NCU unit 5 synthesizes the voice input signal from the telephone, the external voice input, and the microphone input signal, and supplies them to the voice processing unit 6 described later. Further, the NCU unit 5 sends the output audio signal supplied from the audio processing unit 6 to a telephone and an audio output terminal described later.

Next, the voice processing section 6 is composed of a CODEC 61, a RAM 62, and a voice compression / expansion circuit 63, as shown in FIG. The CODEC 61 includes a filter, an A / D converter, and a D / A converter, and an audio signal (analog signal) from the NCU unit 5
Are digitally converted and sequentially stored temporarily in the RAM 62.
Further, the CODEC 61 converts the decoded and expanded audio data into an analog signal as described later,
It is supplied to the NCU unit 5. The voice compression / decompression circuit 63 is R
Digital audio data temporarily stored in the AM 62, for example, based on the CELP (Code-Excited Linear Prediction) algorithm, for input data of a fixed time,
A compression / encoding process is executed by a predetermined encoding method by means for analyzing, waveform combining by analyzed parameters, error calculating means for input waveform and combined waveform, etc., and the compressed audio data is temporarily stored in RAM 62. .
Further, the audio compression / expansion circuit 63, for the compressed / encoded compressed audio data stored in the RAM 62,
Decryption and decompression processing are executed and supplied to the CODEC 61.

Next, the CPU section 7, as shown in FIG.
CPU 71, RAM 72, and GA (Gate Array) 7
3 and controls each part of the present videophone device. The CPU 71 sends out various control signals for controlling each part of the video telephone device to each part via a bus and executes a communication control program according to the type of the communication line to be connected. The CPU 71 is the camera unit 1
Alternatively, after the video signal supplied from the external input terminal IN is digitized, compressed and encoded, the image data temporarily stored in the RAM 33 of the video processing unit 3 described above, the telephone or the external voice input, the microphone input After the audio signal from is digitized and compressed / encoded, it is multiplexed with the audio compression data temporarily stored in the RAM 62 of the audio processing unit 6 described above, and is transmitted as image / audio compression data via the bus. It is supplied to the modem unit 8 described later. Also,
The CPU 71 controls the modem unit 8 which will be described later for the image / sound data multiplexed and transmitted from the other party's videophone device.
When demodulated by, the demodulated image / audio data is separated, and the compressed image data is processed by the video processing unit 3 via the bus.
In addition to being stored in the RAM 33, the compressed voice data is stored in the RAM 62 of the voice processing unit 6 via the bus. The RAM 72 is a program used in the program processing executed by the CPU 71,
It is a semiconductor memory that stores data, compressed image data, audio data, and the like. Further, the GA 73 is the CPU 7
This is a collection of random logics that form one peripheral circuit, and forms, for example, an input signal receiving circuit from the remote controller 10 that controls the present videophone device.

Next, the modem section 8, as shown in FIG.
DSP (Digital Signal Process) that controls modulation and demodulation
ssor) 81, A / D conversion, D / A conversion, filter processing,
AFE (Analog Front End) 82 for controlling NCU 5 and interface processing with CPU, ROM 83,
And RAM 84. The DSP 81 and the AFE 82 have a function as a modulator that converts the compressed image / audio data multiplexed by the CPU 71 into a transmission signal (analog signal) that can be transmitted through a communication line and transmits the signal. Conversely, the transmission signal (analog signal) sent via the communication line
Is again provided with a function as a demodulator (demodulator) for returning to a digital signal that can be decoded by the CPU 71, and can be used as a communication line used by the NCU 5 on a general subscriber line. . RO
The M83 is a semiconductor memory that stores programs used by the DSP 81, data, and the like. RAM84 is a ROM
It is a semiconductor memory that is booted from 83 and stores a program executed by the DSP 81, and is also used as a program used in the program processing executed by the DSP 81, a buffer that stores transmission / reception data, and the like.

The modem unit 8 and the NCU unit 5 in this embodiment are V. It is compliant with 32 bis and has a transmission speed of 9600 bps (bit per seco) on an analog public line.
nd) or 14400 bps data transmission is possible, and as a processing unit, image data, audio data, or control data is transmitted in a time-divisional manner as each packet configuration. At this transmission speed, normal image data for one screen (simple image data) can be transmitted as an intermittent image at a rate of one frame for about 3.5 seconds.
In the case of fine image data, it can be transmitted at a rate of one frame in about 30 seconds. This data transmission method will be described later. Further, in this videophone device, the voice can always be transmitted and received in both directions, so that there is no interruption during simple image communication / fine image communication.
Controlled.

A-2. Connection Configuration of Videophone Device and Peripheral Equipment Next, the connection configuration of the above-described videophone device and peripheral equipment will be described with reference to FIG. FIG. 8 is a schematic diagram showing a connection configuration between a videophone device and peripheral devices. The parts corresponding to those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In the figure, a display device 20 such as a normal television receiver (CRT) is connected to the image output terminal OUT as a monitor of the NCU 5 of the present video telephone device.
The display device 20 may be an LCD display. In the display device, the video image (face) of the user and the video image (face) of the user of the other party captured by the videophone device are displayed on a screen divided into four. An image that is always transmitted and received during communication with a videophone device is called a simple image. Further, as described above, a fine image having a resolution higher than that of the simple image is prepared, and the fine image is transmitted when the user operates the transmission button of the remote controller 10 which will be described later.
Further, a telephone 21 for making a telephone call is connected to the NCU 5 of the present video telephone device by a normal modular cable. A conversation by voice is conducted by the telephone 21. In addition, this telephone 21 has a so-called slave unit 22.
May be provided. Further, the NCU 5 of the present videophone device is connected to a communication line (in this case, an analog public line) via the modular jack 23.

Further, in the figure, the remote controller 10 is provided with a button switch for sending various instructions to the present video telephone apparatus. In particular, SW1 is a video circuit section 2 from the external input terminal IN. This is a camera / video changeover switch for instructing whether to capture the image signal of or the image signal from the camera unit 1. Also, SW2
Is a start / stop button that is operated prior to making a call while exchanging images with each other after the line connection with the other party is secured. Further, SW3 has the same function as the start / stop button SW2, and is provided in the main body of the present videophone device.

A-3. Data Configuration Next, FIG. 9 is a schematic diagram showing a format of data transmission in a normal time in the video telephone device. In the figure, in the present videophone device, as described above, image data, audio data, and control data are time-divisionally transmitted in packet units. Each data has a header and CRC
The code is added, and the image data actually effective for transmission is about 7,000 bps, and the voice data is about 7,000 bps.
Has become. In other words, as the image data, as in the present embodiment, when color image data of 4096 colors (12 bits) with 112 × 128 pixels in one screen is handled, the pixel data amount of one screen is 112 × 128 × 12 = 17203.
Although it is 2 bits (about 21.5 kilobytes), the data can be compressed to about 1/7 by image compression processing. Therefore, an intermittent still image is transmitted at a rate of 1 frame every 24500 bits of image data divided by the number of bits that can be transmitted per second (about 7,000 bits), that is, 24500 ÷ 7000≈3.5 seconds. Become. In this way, in actuality, 49152-bit image data obtained by dividing 172032 bits by 3.5 seconds is compressed to about 1/7 and transmitted as about 7000-bit image data. On the other hand, audio data is treated as digital data sampled at 12 bits and 8 kHz, and this 12 × 8
The audio data of 000 = 96000 bits is compressed to about 1/14 and transmitted as audio data of about 7000 bits.

B. Operation of Embodiment Next, the operation of the above-described embodiment will be described. B-1. Internal operation of videophone device First, the internal operation of the videophone device at the start of a call and during a call will be described. When a call is made to the other party or a call is received from the other party, the power of this videophone device is automatically turned on, and the following processing is executed on each of the videophone device on the transmitting side and the receiving side. .
First, in the videophone device on the transmission side, the video signal supplied from the camera unit 1 or the external input terminal IN is converted into the video circuit unit 2 and the A / D / D / A converter 3 of the video processing unit 3.
1. After being temporarily stored in the RAM 33 as image data via the image input control circuit 32, the image compression / expansion circuit 3
4 is compressed by a predetermined compression method. The compressed image data is read by the CPU 71 via the bus, packetized by the CPU 71 such as adding an image header to the compressed image data, and then sent to the modem unit 8 via the bus. The modem unit 8 adds CRC to the compressed image data to which the header has been added and modulates the data, and then transmits the compressed image data to the other party via the public line.

On the other hand, in the video telephone apparatus on the receiving side, the image data (packet) received via the public line is N
It is demodulated by the modem unit 8 via the CU unit 5 and read by the CPU 71 via the bus. CPU71
Confirms that the image data is image data by discriminating the image header. Then, after converting the packetized data into image data of one screen, it is supplied to the video processing unit 3 via the bus and temporarily stored in the RAM 33. Next, the image data temporarily stored in the RAM 33 is expanded by the image compression / expansion circuit 34, and then the video circuit 2
Is sent to the image output terminal OUT via. This video signal is displayed on the external display device 20.

B-2. Transmission / Reception Operation of Image Data Packet Next, the transmission / reception operation of the image data packet by the present video telephone will be described with reference to FIGS. 10 to 15. (A) Transmission / reception operation when there is no transfer error First, transmission / reception when the line condition is good and there is no transfer error will be described. FIG. 10 is a conceptual diagram showing transmission and reception of image data packets between the videophone devices on the transmitting side and the receiving side when the line condition is good and there is no transfer error. First, the total number of bytes of image data for one screen to be transmitted from the video telephone device on the transmission side is transmitted to the video telephone device on the reception side, and subsequently, the image data packets (1) to (n) are transmitted to the reception side. Sequentially send to the videophone device. Upon completion of receiving the image data packets (1) to (n) indicated by the total number of bytes, the video telephone device on the receiving side expands the image data for one screen received so far according to the above-mentioned operation, It is displayed on the external display device 20. In the same manner, the transmitting side video telephone device sequentially transmits the total number of bytes and the image data packet for each screen to the receiving side video telephone device. When the reception of the image data packet is completed, the operation of expanding the received image data for one screen and displaying it on the external display device 20 is repeated.

(B) Transmission / reception operation when transfer error occurs Next, transmission / reception when the line condition is bad and a transfer error occurs will be described. FIG. 11 is a conceptual diagram showing transmission and reception of image data packets between the videophone devices on the transmitting side and the receiving side when the line state is poor and a transfer error occurs.
First, from the videophone device on the transmitting side, data is transmitted from now on 1
The total number of bytes of the image data for the screen is transmitted to the receiving side video telephone device, and subsequently the image data packets are sequentially transmitted to the receiving side video telephone device. In this transmission / reception process, as shown in the figure, even if a transfer error occurs in the image data packet (2), the video telephone device on the transmitting side continues the image data packets (3) to (n-1), (n).
To the end, that is, one screen of image data packet indicated by the total number of bytes is transmitted. On the other hand, even if a transfer error occurs, the videophone device on the receiving side sequentially receives the next image data packet (3) and subsequent packets, and finally receives the image data packet for one screen. However,
In this case, since a transfer error has occurred in the middle, even if the reception of the image data for one screen indicated by the total number of bytes is completed, it is not expanded, and all the image data for one screen received so far is discarded. .

Here, the line condition deteriorates, and the occurrence frequency of the transfer error (CRC error) is a predetermined value (for example, 1).
(Once every 0 seconds), the videophone device on the transmitting side / receiving side transmits / receives image data packets according to the flowcharts shown in FIGS. 12 and 13.

(C) Transmission / reception operation when the frequency of transfer errors increases 1. Operation of the transmitting side videophone device First, the operation of the transmitting side videophone device will be described. FIG. 12 is a flow chart for explaining the operation of the videophone device on the transmission side when the frequency of occurrence of transfer errors exceeds a predetermined value. In step S10, the videophone device on the transmission side first transmits the total number of bytes of the image data for one screen to be transmitted to the reception side, and also sets the variable x indicating the packet number to be transmitted to "0".
To Next, in step S12, the retransmission request RE
It is determined whether or not Q is received. This resend request REQ
Is only when the frequency of occurrence of transfer error (CRC error) exceeds a predetermined value (for example, once in 10 seconds),
When a transfer error occurs, the videophone device on the receiving side transmits the videophone device on the transmitting side. If the retransmission request REQ has not been received, the determination result in step S12 is "NO", and the process proceeds to step S14. In step S14, the image data packet (x) indicated by the variable x is transmitted.

On the other hand, if the retransmission request REQ is received, the result of the determination in step S12 is "YES", and the process proceeds to step S16. In step S16, the image data packet corresponding to the resend request REQ is retransmitted. Next, when the process of step S14 or step S16 is completed, the process proceeds to step S18, and it is determined whether or not the transmission of all packets is completed. Then, if the transmission of all packets is not yet completed, step S
The determination result in 18 is "NO", and step S2
Go to 0. In step S20, the variable x is incremented by "1", and the process returns to step S12. Hereinafter, steps S12 to S20 are repeatedly executed to transmit the image data packet for one screen.

In the above-mentioned image data packet transmission processing, when transmission of all packets is completed, step S1
The determination result in 8 is "YES", and step S2
Proceed to 2. In step S22, it is determined whether or not the all-packet completion notification END from the receiving-side videophone device has been received. As with the retransmission request REQ, this all-packet completion notification END completes the reception of all packets only when the occurrence frequency of transfer errors (CRC errors) exceeds a predetermined value (for example, once every 10 seconds). At that point, the videophone device on the receiving side transmits to the videophone device on the transmitting side. Then, all packet completion notification E
When ND is not received, the determination result in step S22 is "NO", and the process proceeds to step S24.
In step S24, it is determined whether the retransmission request REQ has been received. Here, it is judged whether or not the retransmission request REQ has been received. If the next image data is transmitted before the all packet completion notification END is received, the retransmission request REQ for the previous image data is generated. This is because the receiving videophone device may receive the next image data packet before receiving the corresponding image data packet.

When the resend request REQ is received, the result of the determination in step S24 is "YES", and the process proceeds to step S26. In step S26, the image data packet corresponding to the resend request REQ is retransmitted to the videophone device on the receiving side, and then the process returns to step S22. On the other hand, when the retransmission request REQ is not received,
The determination result in step S24 is "NO", and the process returns to step S22 without doing anything. Hereinafter, steps S22 and S2 are performed until the all packet completion notification END is received.
4 or steps S22, S24 and 26 are repeatedly executed. Then, when receiving the all-packet completion notification END from the receiving-side videophone device, the determination result in step S22 becomes "YES", and the process returns to step S10. At this point, the transmission of the image data for one screen is completed. Hereinafter, steps S10 to S26 are repeatedly executed to transmit the next image data in packet units.

2. Operation of Receiving Side Video Telephone Device Next, the operation of the receiving side video telephone device will be described. FIG. 13 is a flowchart for explaining the operation of the videophone device on the receiving side when the frequency of occurrence of transfer errors is higher than a predetermined value. In step S30, the videophone device on the receiving side receives the total number of bytes transmitted from the videophone device on the transmitting side, and the variable x
Is set to "0". Next, in step S32, the variable x
The image data packet (x) indicated by is received. In step S34, it is determined whether or not a CRC error has occurred in order to determine whether or not the image data packet (x) received in step S32 is normally received.
If a CRC error occurs, step S
The determination result in 34 is "YES", and step S
Proceed to 36. In step S36, a resend request REQ is sent to the videophone device on the sending side to resend the corresponding image data packet (x) in which the CRC error has occurred.
As described above, the resend request REQ has a transfer error (CRC error) occurrence frequency of a predetermined value (for example, 1
Sent once every 0 seconds).

When the processing of step S36 is completed,
It proceeds to step S38. On the other hand, if no CRC error occurs, nothing is done and the process directly proceeds to step S38.
In step S38, it is determined whether reception of all the packets is completed. If the reception of all the packets is not completed, the determination result in step S38 is "NO".
Then, the process proceeds to step S40. In step S40,
After incrementing the variable x by "1", step S
Return to 32. Hereafter, until the reception of all packets is completed,
Repeat steps S32 to S40 to
The image data packet for the screen is received.

In the above-mentioned image data packet reception processing, when reception of all packets is completed, step S3
The determination result in 8 is "YES", and step S4
Proceed to 2. In step S42, an all-packet completion notification END indicating that all the packets have been received is transmitted to the videophone device on the transmitting side, and then the process returns to step S30. At this point, the reception of the image data for one screen is completed. Hereinafter, steps S30 to S42 are repeatedly executed to receive the next image data in packet units.

3. Transmission / Reception of Image Data Packets Next, a state of transmission / reception of image data packets when the frequency of occurrence of transfer errors exceeds a predetermined value will be described with reference to the above-described flowchart. 14 and 15
FIG. 9 is a conceptual diagram showing transmission and reception of image data packets between the videophone devices on the transmission side and the reception side when the frequency of occurrence of the transfer error exceeds a predetermined value. When the frequency of occurrence of the transfer error becomes higher than a predetermined value, the receiving side video telephone device, as shown in FIG. 14, when the CRC error occurs (in this case, at the time of receiving the image data packet (2)), that is, , Step S36 shown in FIG. 13 described above.
Then, a resend request REQ is sent to the videophone device on the sending side so as to resend the corresponding image data packet. on the other hand,
Upon receiving the resend request REQ, the videophone device on the transmitting side, as shown in FIG. 14, completes the transmission of the image data packet currently being transmitted (in this case, the image data packet (3)), and then executes the above-mentioned steps. In S16, the image data packet (in this case, the image data packet (2)) in which the retransmission request REQ is issued is transmitted again to the videophone device on the receiving side. As described above, when the occurrence frequency of the transfer error is higher than the predetermined value and the CRC error occurs, the videophone device on the reception side transmits the resend request REQ to the transmission side, and the videophone device on the reception side receives the retransmission request REQ. The videophone device retransmits the corresponding image data packet.

Then, the receiving side video telephone device is shown in FIG.
As shown in FIG. 4, when the reception of all the image data packets is completed, in step S42 described above, the all packet completion notification END indicating that the reception of all the packets is completed is transmitted to the transmitting side videophone device. On the other hand, as shown in FIG. 14, the videophone device on the transmitting side does not transmit the next image data until it receives the all-packet completion notification END. This is the step S22 shown in FIG.
It is realized by the processing of step S26. This is because, as shown in FIG. 15, if the total number of bytes relating to the next image data or the image data packet is transmitted before receiving the all-packet completion notification END, as described above, This is because there is a possibility that an image data packet corresponding to the retransmission request REQ for data may be received.

As described above, in this embodiment, when the line condition is good and the transfer error does not occur, the image data packet is transmitted and received as it is, but the line condition is bad and the occurrence frequency of the transfer error is less than the predetermined value. In some cases, the received image data packet is ignored, and the image data packet in which the transfer error occurs is transmitted again only when the transfer error occurs when the frequency of the transfer error exceeds a predetermined value. Since whether to restore the image data is switched according to the frequency of occurrence of the transfer error, the image data can be transmitted / received at the minimum time interval according to the line state.

In the above-mentioned embodiment, the compression method of image data is not limited to the JPEG algorithm, but may be, for example, a block coding method, a predictive coding method, or the like, and a compression method of audio data. as,
Not limited to the CELP algorithm, for example, AD / PCM
(Adaptive Differential Pulse Code Modulation) method, VSELP (Vector Sum Excited Liner Predictio)
n) method may be used.

C. Detailed Technical Description In the above-described embodiment, the packet configuration and the data transmission procedure are simplified in order to facilitate understanding of the operation of the videophone device. Below, the transmission method, packet structure, data transmission sequence, and the like according to the present embodiment will be described in detail.

C-1. Connection Protocol In the videophone device according to the present invention, V. A transmission protocol conforming to 32 bis is used, and a calling side, that is, a person who makes a call is "CALLER", and a called side, that is, a person who receives a call is "ANSWER". In addition, the communication speed is 14400 bps (bit per
second) and 9600 bps, and synchronous communication is performed. Also, the HDLC frame is adopted.

Further, due to the influence of the communication line state, V. 32bi
Considering the case where the connection of s cannot be made or one of them has not started the connection, if the connection is not completed within 30 seconds from the start of the connection, the connection will be interrupted at that point. There is.

C-2. Packet Basic Configuration In the present videophone device, as described above, image data,
The voice data and the control data are time-divisionally transmitted in packet units. In the above explanation, the packet is the header,
Although it has been described that it is composed of data and a CRC code, it actually has the structure shown in FIG. In the figure, a packet is basically composed of a flag, a header, data, an FCS, and a flag. The flag has 8 bits and is “7E”. The header is 8 bits, and 00 to 09 (H) is unused (NOP when receiving), 0A is a voice packet, 0B is an image packet, 0C is a command packet, 0D is a retransmission command packet, and 0E to FE are not. It is used (NOP when receiving). Then the data is variable length in bytes,
The contents will be described later. The FCS is 16 bits and the X. 25 CRCs (X ¹⁶ + X ¹² + X ⁵ +1) are used.

C-3. Configuration of Various Packets (a) Voice Packet Data FIG. 17 (a) is a conceptual diagram showing the configuration of voice packet data. In the figure, the voice packet data is 1
It is composed of a voice packet header of bytes and variable length data of 1 to 88 bytes. The voice packet header is data such as voiced / non-voiced data of the packet (details will be described later).

(B) Image Packet Data FIG. 17 (b) is a conceptual diagram showing the structure of image packet data. In the figure, the image packet data is composed of an image packet header of 1 byte and fixed length data of 32 bytes. In the image packet header, a packet # (number), a checksum, and a head packet flag of a frame (four packets form one frame) are written.

(C) Command Packet Data FIG. 17 (c) is a conceptual diagram showing the structure of command packet data. In the figure, the command packet data includes a 1-byte data length, a 1-byte command, and 0
.About.20 bytes of variable length data. The data length indicates the number of bytes of the command and data that follow. The contents of commands and data will be described later.

(D) Retransmission command packet data FIG. 17 (d) is a conceptual diagram showing the structure of retransmission command packet data. In the figure, the resend command packet data is composed of a 1-byte block # (number) and a 1-byte frame # (number). This resend command packet data is sent when a resend request occurs during image data reception.

C-4. Packet Transmission Method The videophone device according to the present embodiment sends four types of packets (voice, image, command, resend command) every predetermined time t (every 48 msec in the illustrated example) as shown in FIG. Then, the voice, the resend command, the command, and the image are transmitted in this order. The time t of the transmission interval is
It is determined from the size of the data buffer (RAM 84) of the modem unit 8 side and the size of the execution time of the software of the entire software that packetizes the data and writes the data in the modem unit 8. However, a packet with no data to be transmitted is not transmitted. The transmission means the modem unit 8
Is to write to the transmission buffer (RAM84) of
It is not actually sent on the line.

In particular, for voice packets, command packets, and resend command packets, one packet is always sent every 48 msec as long as data exists. On the other hand, with respect to the image packet, one packet is not always transmitted every 48 msec, but 0 packet to 2 packet is transmitted depending on the data amount of another packet (voice, command, resend command) as shown in FIG. Change between That is, first, a voice packet, a command packet, and a resend command packet are transmitted, and at that time, 4
If the amount of data that can be transmitted in 8 msec is exceeded, no image packet is transmitted. If it has not exceeded, one image packet is transmitted, and if an underrun has occurred last time, one image packet is further transmitted. Here, the underrun is a time when no transmission data is sent.

The reason for doing this is as follows. First, since the voice data is a continuous amount, it must be transmitted at regular intervals. Therefore, the voice data may always be preferentially transmitted, and the image data may be transmitted with a margin. However, the packet of voice data has a variable length, and its size changes from moment to moment depending on the input voice. In an extreme example, when there is no voice input, that is, when no voice is spoken, only the information that the voice is currently silent needs to be transmitted, and the packet length of the voice data in that case is the shortest. On the other hand, for image data,
Since the present videophone device needs to transmit as many still images as possible, when the voice data is small and the transmission data amount has a margin, as much image data as possible should be transmitted. For this reason, the data transmission method described above is adopted.

C-5. Negotiation The videophone device according to the present embodiment is a V.V. After the 32 bis negotiation is completed, the negotiation is performed to notify the other party of the model name of each other. This videophone device can be connected to all models using the connection request command and the connection response command.
When it is recognized that the other party is the host, the subsequent operation is set to the host connection mode. In the host connection mode, images are transmitted / received and displayed only by an instruction from a host of a connection partner, and the attached remote controller 10
This is the mode in which the control in (3) is stopped.

Here, FIG. 20 is a conceptual diagram showing a connection sequence between the videophone device on the calling side and the videophone device on the called side. In the figure, first, the videophone device on the calling side is V. According to 32bis, the connection request is transmitted to the videophone device on the called side. On the contrary,
The videophone device on the called side receives the connection request and transmits a connection response to the videophone device on the calling side. Upon receiving the connection response, the videophone device on the calling side starts the image communication as described above. As described above, in the videophone device, the transmission of the simple image is started immediately after the exchange of the connection request / response is completed, but in order to transmit the first simple image in the shortest time, depending on the connection speed at that time 1
No sound is transmitted for 2 seconds at 4.4K and for 4 seconds at 9.6K.

FIG. 21 is a conceptual diagram showing a connection sequence when the connection response to the connection request is not received, that is, when the connection response times out. As shown in the figure, consider the case where a connection request or connection response was not received due to the influence of noise mixed in the communication line. , Send a connection request. The above operation is repeated until the connection response is received.

C-6. Image Transmission / Reception Next, a method of transmitting / receiving image data by the present video telephone will be described in detail. As described above, the present videophone device uses two types of methods as the image data transfer sequence. The difference between the two methods is that when an error occurs in the received image data due to noise superimposed on the telephone line, the image 1 including the data in which the error occurred
The difference is whether all images are invalidated or only that image packet is invalidated and the image packet in which the error has occurred is transmitted again (retransmission). In the following, the method of invalidating all one image will be referred to as no retransmission, and the method of retransmitting will be referred to as retransmission.

As described above, in this video telephone device,
It is equipped with two types of image data transfer methods: simple images and fine images. In the simple image transmission / reception, when an error occurs, two methods are appropriately used, namely, no retransmission in which the image data is not retransmitted and no retransmission in which the image data is retransmitted. That is, regarding the simple image, 32b
Immediately after the connection by is, it will be sent without retransmission,
If it is determined that the line condition is bad and the frequency of occurrence of received data error is high, switching to retransmission is performed.
However, when a resend is received by the resend control command, communication is always performed with resent.

Without retransmission, the sender does not monitor or wait for a response from the receiver. On the other hand, when there is retransmission, the sender waits for a response from the receiver, or when the receiver cannot receive data normally, it sends a resend request requesting the transmission of image data again, and the sender When the resend request is received, the image data is sent again. Therefore, without retransmission, no handshake operation is performed, and if the received image data contains an error, all the image data is discarded as described above. Further, with respect to a fine image, communication is always performed with retransmission.

That is, in the system with retransmission, the videophone device on the transmitting side cannot transmit the next data until the receiving side confirms that the data can be received reliably. Therefore, even if no communication error occurs, there is a timing at which data cannot be transmitted (a state of waiting for a response from the other party). From the above, the advantages of the method without retransmission and the method with retransmission
The shortcomings are summarized as follows. In the case of no resend method Advantage: The sender does not have to wait for a response from the receiver. Cons: The image is discarded when a communication error occurs. In case of resending method Advantage: Do not discard the image when a communication error occurs. Disadvantage: The sender has a response waiting state for the receiver.

Therefore, in the video telephone device according to the present invention, as described above, there are used the non-retransmission and the re-transmission. That is, in the case of a simple image, it is continuously transmitted from one to the next, so if an error rarely occurs, even if one image is discarded, its effect is small, If you do not resend and there are many errors,
If the image is discarded each time an error occurs, it may happen that the image from the other party cannot be displayed, so the method with retransmission is adopted. On the other hand, in the case of a fine image, it takes a relatively long time to send one piece of image data, and when the sending side operates the send button instead of sending it one after another as in a simple image. Only one image is transmitted, and the image cannot be discarded due to the occurrence of an error. Therefore, the method with retransmission is adopted.

There are the following two conditions for determining that there is a retransmission due to the poor line condition in the above-mentioned simple image. 3 seconds,
When no normal packet (packet without CRC error) can be received, no normal packet can be received for 4 (M) times or more for 1 (L) seconds or more in 30 (N) seconds. That is the case.

Next, the transmission / reception sequence of image data in the present video telephone will be described. When starting the image transmission, the transmitting side transmits an image reception request in advance so as to notify the control data such as a display location (which region of the four-division screen is displayed) and the compressed image data size. When there is retransmission, the receiving side must send an image receiving response as a response to the image receiving request, and the transmitting side must wait for the reception of the image receiving response. Here, if the image reception response cannot be received for one second after the image reception request is transmitted, the image reception response must be transmitted again and the reception of the image reception response must be waited.

On the transmitting side, the image reception request is transmitted without retransmission, and the image data transmission is started after the image reception response is received with retransmission. The image data is divided into one block in the simple image and a plurality of blocks in the fine image, and each block is given a number of 0 as a block # (number). The size of the block varies depending on the amount of the image data, but in the case of the present videophone device, the maximum size is 3 Kbytes (excluding the header portion of the packet). A block consists of multiple frames,
A frame # (number: 0) is given to each. 1
The frame is divided into 4 packets (1 packet = 33 bytes) and sent.

(A) Image data and frame information FIG. 22 is a conceptual diagram showing the contents of image data of one frame. In the figure, C1 to C4 are 8-bit checksums with C1 as the higher order. This is image data for 4 packets, 128 bytes (32 bytes x 4 packets)
Is the value of the lower 8 bits of the two's complement of each sum of. F1
~ F4 is 16-bit frame information with F1 as the higher order. This is a value obtained by allocating several kinds of information of the frame to the bit field, and the allocation is as shown in FIG. As shown, 4 of F1
Bit is unused. The upper 1 bit of F2 is a retransmission flag, and "0" usually indicates retransmission and "1" indicates retransmission.
Also, 4 bits consisting of the lower 3 bits of F2 and the upper 1 bit of F3 are a block # (number). And F
7 bits including the lower 3 bits of 3 and all 4 bits of F4 are a frame # (number).

When a data error occurs during data reception, a resend request command is transmitted to notify the transmitting side of the block # (number) and frame # (number) in which the error occurred. On the other hand, on the transmitting side, when the retransmission request command is received, the block #
Retransmit the image data of (number) and frame # (number). The conditions that are considered as a data error during data reception are listed below. When the sequence of frame # is deviated (when frame # is missing) When the sequence of block # is deviated When the frame checksums do not match When the expected frame does not come for a certain period of time (timeout)

(B) Image transfer sequence of simple image If a CRC error occurs in the packet at the packet reception stage, the packet is regarded as unsuccessful, and therefore the resend request is transmitted without the checksums matching. Will be done. When there is retransmission, the receiving side transmits a block completion command to the transmission partner in order to notify the partner that the reception of all the image data of one block (corresponding to one screen of the simple image) has been completed correctly. Upon receiving the block completion command, the transmitting side determines that all the frames of the block have been correctly received by the receiving side. The transmitting side suspends the transmission of the image data when the time from the transmission start of one block of image frame to the transmission end exceeds 30 seconds. In this case, the receiving side is still in the receiving state, but the transmitting side transmits an image reception request for new image data, and the receiving side receives the request, whereby the receiving side starts receiving new image data. The image transfer sequence by each transfer method will be described in detail below.

1. Image Transfer Sequence Without Retransmission FIG. 24 is a conceptual diagram showing an image transfer sequence without retransmission. In the figure, the videophone device on the transmission side transmits an image reception request command (no retransmission) to the reception side. The videophone device on the receiving side receives the image reception request command and recognizes that the image transfer is without resending. Next, the videophone device on the transmitting side sequentially transmits the image frames to the receiving side, and finally transmits the final image frame. The videophone device on the receiving side sequentially receives the image frames and finally receives the final image frame. Image data for one screen is transmitted and received by the above sequence.

2. Image Transfer Sequence with Resending Next, FIG. 25 is a conceptual diagram showing an image transfer sequence with resending. In the figure, the videophone device on the transmission side transmits an image reception request command (with retransmission) to the reception side. The videophone device on the receiving side receives the image reception request command, recognizes that the image transfer is due to resending, and then transmits the image reception response command to the transmitting side. On the other hand, when the videophone device on the transmission side receives the image reception response command, it sequentially transmits the image frames to the reception side, and finally transmits the final frame of the image. The videophone device on the receiving side sequentially receives the image frames, finally receives the last frame of the image, and confirms that all the image data of one block (corresponding to one screen of the simple image) is correctly received. Send a block completion command to the other party to notify. Upon receiving the block completion command, the transmitting side determines that all the frames of the block have been correctly received by the receiving side. According to the above sequence, image data for one screen is transmitted and received.

3. Image Transfer Sequence with Retransmission (When Receiving Response Timeout) Next, FIG. 26 is a conceptual diagram showing an image transfer sequence with retransmitting (when receiving response timeout). In the figure, the videophone device on the transmitting side first transmits an image reception request command to the receiving side. On the other hand, if the image reception response command is not transmitted from the receiving side videophone device within 1 second, that is, if the time-out occurs, the transmitting side videophone device again sends the image reception request command to the receiving side. Send. On the other hand, when the image reception response command is received from the videophone device on the receiving side,
Similar to the image transfer sequence shown in FIG. 25 described above, image frames are sequentially transmitted.

4. Image Transfer Sequence (When One Block Transmission Times Out) Next, FIG. 27 is a conceptual diagram showing an image transfer sequence (when one block transmission times out) with retransmission. In the figure, the videophone device on the transmission side receives the image reception request command and recognizes that the image transfer is due to resending, as in the image transfer sequence described above. The image reception response command is transmitted to the transmission side. On the other hand, when the videophone device on the transmission side receives the image reception response command, it sequentially transmits the image frames to the reception side, and finally transmits the final frame of the image.

At this time, the transmitting side video telephone device is set to 1
If the time from the start of transmission of the image frames for blocks to the end of transmission does not exceed 30 seconds, the image frames are transmitted as they are. The videophone device on the receiving side sequentially receives the image frames and finally receives the final image frame. On the other hand, if the time from the start of transmission of the image frame for one block to the end of transmission exceeds 30 seconds, at that point,
The transmission of the image data is interrupted. In this case, the videophone device on the receiving side is still in the receiving state, but the transmitting side transmits the image reception request command for the new image data, and the receiving side receives the command, so that the receiving side receives the new image data. Start receiving.

5. Image Transfer Sequence with Retransmission (When Retransmission Request Due to Frame Loss or Data Error) Next, FIG. 28 is a conceptual diagram showing an image transfer sequence with retransmission (when retransmission request due to frame loss or data error). . The image transfer sequence is the same as the sequence shown in FIG. FIG.
In, the transmitting videophone device transmits an image reception request command, as in the image transfer sequence described above. The videophone device on the receiving side receives the image reception request command, recognizes that the image transfer is due to resending, and then transmits the image reception response command to the transmitting side.
On the other hand, when the videophone device on the transmitting side receives the image reception response command, it sequentially transmits the image frames to the receiving side.

At this time, if a frame loss or a data error occurs in the third frame as shown in the figure, the receiving side video telephone device receives the fourth frame and then sends a resend request command to the third frame. To the sender.
When the videophone device on the transmission side receives the resend request command, the videophone device preferentially resends the third frame.
The image is sequentially transmitted to the receiving side, and finally the final frame of the image is transmitted. The videophone device on the receiving side receives the image frames in sequence, receives the last frame of the image at the end, and confirms that all the image data of one block (corresponding to one screen of the simple image) has been correctly received. Send a block complete command to the sender to notify.

6. Image Transfer Sequence with Retransmission (When Retransmission Request with Frame Wait Timeout) Next, FIG. 29 is a conceptual diagram showing an image transfer sequence with retransmission (when a retransmission request with frame wait timeout is requested). In the figure, the videophone device on the transmitting side is
As with the image transfer sequence described above, the image reception request command is transmitted. The videophone device on the receiving side receives the image reception request command, recognizes that the image transfer is due to resending, and then transmits the image reception response command to the transmitting side. On the other hand, when the videophone device on the transmitting side receives the image reception response command, it sequentially transmits the image frames to the receiving side.

At this time, as shown in the figure, it is assumed that a frame loss or data error occurs in the third frame. The videophone device on the receiving side transmits a resend request command to the transmitting side when the image frame is not received for more than 1.5 seconds, that is, when it times out. In this case, the retransmission request command is transmitted for the third frame. When the videophone device on the transmission side receives the retransmission request command, the videophone device preferentially retransmits the third frame, and then sequentially transmits to the reception side, and finally transmits the final frame of the image. The videophone device on the receiving side receives the third frame which has timed out, and finally after receiving the last frame of the image,
One block (corresponding to one screen of a simple image) In order to notify the other party that all image data has been correctly received, a block completion command is transmitted to the other party. In the illustrated example, when the third frame that has timed out is the final frame, the block completion command is transmitted immediately after receiving the third frame.

7. Image Transfer Sequence with Retransmission (Retransmission Wait Timeout for Retransmission Request) Next, FIG. 30 is a conceptual diagram showing an image transfer sequence with retransmission (retransmission wait timeout for a retransmission request). In the figure, the videophone device on the transmission side transmits an image reception request command, as in the image transfer sequence described above. The videophone device on the receiving side receives the image reception request command, recognizes that the image transfer is due to resending, and then transmits the image reception response command to the transmitting side. On the other hand, when the videophone device on the transmitting side receives the image reception response command, it sequentially transmits the image frames to the receiving side.

At this time, as shown in the figure, it is assumed that frame loss or data error occurs in the third frame. Since the videophone device on the receiving side recognizes (discovers) that the third frame is missing when it receives the fourth frame, it transmits a retransmission request command to the transmitting side and waits for 0.5 seconds. On the other hand, when the videophone device on the transmission side receives the resend request command, it resends the corresponding image frame, that is, the third frame. If not received, the timeout occurs and the resend request command is sent to the sending side again. In the illustrated example, the videophone device on the transmission side retransmits the third frame, but the frame loss or data error has occurred again, so that the videophone device on the reception side has timed out.

When the videophone device on the transmitting side does not receive the resend request command from the receiving side, the image frames are sequentially transmitted to the receiving side, and finally the final frame of the image is transmitted, as in the above-described sequence. The videophone device on the receiving side completes the block in order to notify the other party that the image data of all one block (corresponding to one screen of the simple image) has been correctly received after the last image final frame is received. Send a command to the recipient.

(C) Image Transfer Sequence for Fine Image Transmission of a fine image is performed by dividing it into a plurality of blocks. The transmission / reception method of each block is exactly the same as that of the simple image, but in the fine image, as described above, there is always retransmission. However, a simple image is always composed of one block, but a fine image is composed of a plurality of blocks, so a special exchange is performed when the next block is started after transmission / reception of a certain block is completed. May occur. That is, even if the receiving side completes the reception of all the frames of a certain block and transmits the block completing command, the block completing command cannot be normally received by the transmitting side. In that case, since the transmission side is in a waiting state for receiving the block completion command, the reception side transmits the block completion command, and if no frame of the next block is received even after waiting for 3 seconds, the transmission block # Send the update request command. When this is received by the sender, it must start sending the frame of the next block. After sending the send block # update request command, if no frame of the next block can be received even after waiting for 3 seconds, send the send block # update request again to receive the frame of the next block. I'm waiting.

1. Fine Image Transfer Sequence FIG. 31 is a conceptual diagram showing a detailed image transfer sequence. In the figure, the videophone device on the transmission side transmits an image reception request command to the reception side. Upon receiving the image reception request command, the videophone device on the reception side transmits an image reception response command to the transmission side. On the other hand, when the videophone device on the transmission side receives the image reception response command, first, the image frames of the first block are sequentially transmitted to the reception side, and the final image frame is transmitted at the end of the first block. The video telephone device on the receiving side sequentially receives the image frame of the first block, and when the last frame of the image is received, transmits a block completion command to the transmitting side. Upon receiving the block completion command, the videophone device on the transmission side sequentially transmits the image frames of the next block, that is, the second block to the reception side, and transmits the final image frame at the end of the second block. The videophone device on the receiving side sequentially receives the image frame of the second block, and when receiving the final frame of the image, transmits a block completion command to the transmitting side. Similarly, 3
By sequentially transmitting / receiving the image data of the block, the fourth block, ..., And the final block, the image data of one screen of fine screen is transmitted / received.

2. Fine image transfer sequence (at the time of waiting for data in the next block) FIG. 32 is a conceptual diagram showing a transfer sequence of detailed images (at the time of waiting for data in the next block). In the figure, the videophone device on the transmission side transmits an image reception request command (no retransmission) to the reception side. Upon receiving the image reception request command, the videophone device on the reception side transmits an image reception response command to the transmission side. On the contrary,
Upon receiving the image reception response command, the videophone device on the transmission side first sequentially transmits the image frames of the first block to the reception side, and transmits the final frame of the image at the end of the first block. The video telephone device on the receiving side sequentially receives the image frame of the first block, and when the last frame of the image is received, transmits a block completion command to the transmitting side.

Here, it is assumed that an error occurs and the block completion command cannot be normally received by the transmitting videophone device. After transmitting the block completion command, the receiving side video telephone device transmits a transmission block # update request command to the transmitting side video telephone device if no frame of the next block is received even after waiting for 3 seconds.
Upon receiving the update request command, the videophone device on the transmitting side preferentially receives the next block (in this example, 2 blocks).
The transmission of the image frame of the (block) is started. After transmitting the transmission block # update request command, if the video telephone device on the reception side cannot receive any frame of the next block even after waiting for 3 seconds, the transmission block # is transmitted again.
Send an update request and wait for the next block of frames to be received. In the same manner, the image data of the third block, the fourth block, ...

C-7. Line Status Monitoring and Correspondence In the present videophone apparatus, the line status is determined by the number of packets received and the number of CRC errors. First, the retransmission of the simple image is started according to the occurrence frequency of the CRC error. Also, when there is no normal received packet, the video mode is cut off and the analog telephone mode by only normal voice transmission is restored. less than,
The operation of monitoring the CRC error and the number of normal packets will be described.

FIG. 33 is a flow chart showing the monitoring operation by the present videophone device. In the figure, in step S50, it is determined whether or not a CRC error occurs four times or more in 30 seconds or continuously. One CRC error occurs for each packet. Further, FIG. 34 shows a method of detecting a CRC error. In FIG. 34, the horizontal axis represents time, and when a plurality of CRC errors occur within one second, it is regarded as one. Further, the occurrence of three CRC errors is regarded as continuous occurrence.
Furthermore, even if it occurs intermittently, if it occurs four times or more in 30 seconds, it is considered as four or more single occurrences in 30 seconds.

When the CRC error occurs four times or more in 30 seconds or continuously, the determination result in step S50 becomes "YES", and the mode shifts to the simple image retransmission mode. On the other hand, if the CRC error does not occur the predetermined number of times or more, the determination result in step S50 is "NO", and the process proceeds to step S52. In step S52, it is determined whether or not no normal packet was found in 3 seconds. The number of packets generated per second is constantly changing because each packet number has a variable length. The minimum (MIN) is 42 and the maximum (MA).
In X), the production quantity of 65 pieces can be taken. Then, when no normal packet is found in 3 seconds, that is, usually 126 to 190 (42 to 65 ×) in 3 seconds.
3) If there is no normal packet generated, the determination result in step S52 is "YES", and the video mode is disconnected at that time. The normal packet indicates that the CRC value of the portion composed of the packet flag to the data immediately before the next packet flag is correct. On the other hand, when even one normal packet can be found in 3 seconds, the determination result in step S52 is "N".
"O" and the process ends.

C-8. Commands Next, various commands used in this videophone device will be described. (A) Connection request / connection response / connection refusal The connection request command is a command transmitted to the other party to recognize itself during negotiation with the other party's videophone device. Further, the connection response command is a command transmitted when the connection request command is received, to notify the other party that the connection request command has been recognized. Also, the connection refusal command is
This is a command that is sent when it cannot connect to the other party.

(B) Image reception request / image reception response The image reception request command is a command transmitted to the other party when starting image transmission. The data field of the image reception request command includes information such as the data amount and display position of image data to be transmitted. Further, the image reception response command is a command transmitted to notify the other party that the image reception request command is received when the image reception request command is received. (C) Simple Image Retransmission Control As described above, the simple image retransmission control command is a command for causing the other party to switch between retransmission and non-retransmission in the simple image performed according to the transmission status and the like. When this simple image resend control command is received, it is necessary to switch to the presence / absence of resending according to the content indicated by the data field of this simple image resend control command in the subsequent simple image transmission / reception.

(D) Block Completion Command The block completion command is sent to the other party when all the image data of one block (corresponding to one screen in the simple image) is normally received during the image transfer in the resending mode. This is a command sent to the other party for notification. (E) Image transmission request / image transmission refusal The image transmission request command is a command transmitted when requesting the transmission of an image to the other party. When this image transmission request command is received, transmission of predetermined image data must be started. The image transmission refusal command is a command transmitted when the image transmission request command for the memory screen is received and the image is not stored in the memory.

(F) Image display request / image display refusal The image display request command is a command transmitted when it is desired to display the clip image or the memory image of the partner on the screen of the partner. When this image display request command is received, predetermined image data must be displayed on the screen. The image display refusal command is a command transmitted when the image display request command for the memory screen is received and the image is not stored in the memory. (G) Character display The character display command is a command for displaying a predetermined character string line by line on the partner side.

(H) Screen display control The screen display control command is a command for allowing the other party to switch to a predetermined screen display mode (multi-full, etc.). (I) Color back control The color back control command is a command for switching on / off of the color back for each of the four screens according to the contents of the data field. (J) Color back color control The color back color control command is a command for changing the brightness and color difference data of the other party's color back.

(K) Double Sampling Request / Double Sampling End The double sampling request command is, as shown in FIG. 35, a command for causing the other party to perform image sampling in both simple image and fine image modes. As shown in FIG. 35, the double sampling end command is a command for notifying the other party of the end after the double sampling. (L) Transmission block #update request The transmission block #update request command is a command transmitted when the image frame of the next block cannot be received after the transmission of the block completion command described above. When this transmission block # update request command is received, the transmission of the next block must be started even if the block completion command is not received.

(M) Remote Control A remote control command is sent according to the pressed switch when the remote controller 10 attached to the present videophone device or the start / stop switch SW3 of the main body is turned on. Is. (N) Memory Write The memory write command is a command for writing predetermined data in 1-byte units to a predetermined address of the CPU controlling the partner video-phone device. (O) Memory read request, memory read response The memory read request command is a command for reading the data at the predetermined address of the CPU controlling the other party's TV telephone device in 1-byte units, and is a memory read response. It is sent to the other party by command.

(P) Program Call The program call command is a command for making a subroutine call to a predetermined address of the CPU controlling the videophone device on the other side. (Q) Video Input Switching Request The video input switching request command is a command for switching the video input of the other party to either CAM or AUX. (R) Voice transmission control request / line connection confirmation The voice transmission control request command is a command for suspending / resuming voice transmission according to the content of the data. While voice transmission is stopped, packets may not be sent to the other party at all, and the other party may disconnect (set to analog telephone mode).
A line connection confirmation command is sent every 0 msec. However, if another command or another packet is being transmitted when the line connection confirmation command is transmitted, it is not necessary to transmit the line connection confirmation command.

Although the above-mentioned commands are used for the functions of ordinary video telephone devices, these abundant commands can also be effectively used in the image information center, the image message system and the like. The image information center is a user who can obtain various kinds of image data by connecting to the image information center having an image database by the user of the videophone device. The image message system is a message system including image data as well as voice. In the system as described above, it is necessary for the information center and the message system side to be able to variously control the screen state of the television connected to the user's side video telephone apparatus, so these commands are utilized.

As described in the above embodiment, the present invention can obtain a great effect when an analog public telephone line is used, but prevents the use of other communication lines such as ISDN. Not a thing. Also,
In the above-described embodiment, the video telephone device of the type that is used by connecting to the existing television receiver and telephone has been described as an example. It goes without saying that it is also applicable.

[0106]

As described above, according to the present invention,
Even if a communication line such as an analog public line that has a low transmission rate and is prone to transmission errors is used, there is an advantage that image data can be transmitted accurately and at high speed without interruption of voice.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a videophone device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a camera unit of the videophone device according to the present embodiment.

FIG. 3 is a block diagram showing a configuration of a video processing unit of the videophone device according to the present embodiment.

FIG. 4 is a block diagram showing a configuration of a video display unit of the videophone device according to the present embodiment.

FIG. 5 is a block diagram showing a configuration of an audio processing unit of the videophone device according to the present embodiment.

FIG. 6 is a block diagram showing a configuration of a CPU unit of the videophone device according to the present embodiment.

FIG. 7 is a block diagram showing a configuration of a modem unit of the videophone device according to the present embodiment.

FIG. 8 is a schematic diagram showing a connection configuration of a videophone device according to the present embodiment and peripheral devices connected thereto.

FIG. 9 is a schematic diagram showing a format of data transmission in a normal state in the videophone device according to the present embodiment.

FIG. 10 is a conceptual diagram showing transmission / reception of an image data packet between the transmission side and the reception side when the line state is good and there is no transfer error.

FIG. 11 is a conceptual diagram showing transmission / reception of image data packets between a transmission side and a reception side when a line state is poor and a transfer error occurs.

FIG. 12 is a flowchart illustrating an operation on the transmitting side of the videophone device according to the present embodiment.

FIG. 13 is a flowchart illustrating an operation on the receiving side of the present videophone device according to the present embodiment.

FIG. 14 is a conceptual diagram showing transmission and reception of image data packets between the transmission side and the reception side when the frequency of occurrence of transfer errors exceeds a predetermined value.

FIG. 15 is a conceptual diagram showing transmission / reception of an image data packet between a transmission side and a reception side when the frequency of occurrence of a transfer error exceeds a predetermined value.

FIG. 16 is a schematic diagram showing a basic configuration of a packet transmitted and received between the present videophone devices.

17A is a conceptual diagram showing the configuration of voice packet data, FIG. 17B is a conceptual diagram showing the configuration of image packet data, FIG. 17C is a conceptual diagram showing the configuration of command packet data, and FIG. It is a conceptual diagram which shows the structure of retransmission command packet data.

FIG. 18 is a conceptual diagram showing a method of transmitting a packet exchanged between the present video telephone devices.

FIG. 19 is a conceptual diagram showing a method of transmitting a packet transmitted and received between the present video telephone devices.

FIG. 20 is a conceptual diagram showing a connection sequence between a videophone device on the calling side and a videophone device on the called side.

FIG. 21 is a conceptual diagram showing a connection sequence when a connection response to a connection request is not received, that is, when the connection response times out.

FIG. 22 is a conceptual diagram showing the contents of image data of one frame.

FIG. 23 is a conceptual diagram showing the structure of frame information in image data.

FIG. 24 is a conceptual diagram showing an image transfer sequence without retransmission.

FIG. 25 is a conceptual diagram showing an image transfer sequence with retransmission.

FIG. 26 is a conceptual diagram showing an image transfer sequence (when a reception response times out) with retransmission.

[Fig. 27] Fig. 27 is a conceptual diagram showing an image transfer sequence (with one block transmission timed out) with retransmission.

FIG. 28 is a conceptual diagram showing an image transfer sequence with retransmission (when a retransmission request is made due to frame loss or data error).

FIG. 29 is a conceptual diagram showing an image transfer sequence with retransmission (when a retransmission request is made with a frame wait timeout).

FIG. 30 is a conceptual diagram showing an image transfer sequence (retransmission waiting timeout for a retransmission request) with retransmission.

FIG. 31 is a conceptual diagram showing a transfer sequence of detailed images.

[Fig. 32] Fig. 32 is a conceptual diagram showing a detailed image transfer sequence (at the time of waiting for data of the next block).

FIG. 33 is a flowchart showing a monitoring operation by the present videophone device.

FIG. 34 is a conceptual diagram showing a method of detecting a CRC error in the monitoring operation.

FIG. 35 is a conceptual diagram for explaining a double sampling request / double sampling end command.

[Explanation of symbols]

1 camera section (image capturing means) 2 video circuit section 3 video processing section (display control section) 4 video display section 5 NCU 6 audio processing section 7 CPU section (communication control section, transmission control section) 8 modem section (communication control) Means, reception control means, transmission control means, line status monitoring means) 9 key / LED section 10 remote control 11 lens 12 CCD 13 CCD driver 14 A / D / D / A converter 15 DSP 31 A / D / D / A conversion Device 32 Image input control circuit 33 RAM 34 Image compression / expansion circuit 41 Display control circuit 42 RAM 43 OSDC 61 CODEC 62 RAM 63 Audio compression / expansion circuit 71 CPU (communication control means, reception control means, transmission control means) 72 RAM 73 GA 81 DSP 82 AFE 83 ROM 84 RAM (transmission buffer) 20 Display device 21 Telephone 22 Remote unit 23 Modular jack IN Image input terminal OUT Image output terminal SW1 Camera / Video switch SW2, SW3 Start / Stop button

Claims (32)

[Claims] 1. A communication control means for determining whether or not to resend the image data in which a transfer error has occurred, according to the frequency of occurrence of a transfer error in the transfer of image data via a communication line. Videophone device. 2. An image capturing means for capturing at least a user's self-portrait and a partner image from a partner's device connected via a communication line, while the self-portrait captured by the image capturing means is received. Communication control means for transmitting to the device of the other party and for instructing the device of the other party to retransmit the image data in which the transfer error has occurred in accordance with the frequency of occurrence of the transfer error in the transfer of the image data via the communication line. A videophone device comprising: a display control unit for displaying, on a display device, a self-portrait captured by the image capturing unit and a partner image received by the communication control unit from the partner device. 3. The communication control means instructs the device of the other party to retransmit the image data when the frequency of occurrence of a transfer error in data transfer via a communication line is less than or equal to a predetermined value. On the other hand, on the other hand, when the frequency of occurrence of the transfer error is higher than a predetermined value, the videophone device according to claim 1 or 2, which instructs the device of the other party to retransmit the image data. . 4. The communication control means, in a situation where the frequency of occurrence of the transfer error is a predetermined value or less, continues transmission and reception of image data with the device of the other party even if a transfer error occurs, The videophone device according to claim 1 or 2, wherein the series of image data that is finally received is discarded. 5. The reception control means, when receiving all the image data groups to be received, transmits a reception completion instruction notifying that all the image data has been received to the other party's device, 3. The television according to claim 1, further comprising a transmission control unit that transmits the next image data group to the device of the other party only when receiving a reception completion instruction from the device of the other party. Telephone device. 6. The videophone device according to claim 1, wherein the communication control means transmits the total number of bytes of data to be transmitted immediately before transmitting image data to the device of the other party. . 7. The image data is data for one screen transmitted in packet units, and it is determined whether or not the transfer error has occurred in the transfer for the one screen. 7. The videophone device according to any one of Items 1 to 6. 8. A transfer error is determined again according to the frequency of occurrence of the transfer error, and whether or not the data in which the transfer error has occurred is retransmitted. When the frequency of occurrence of the transfer error exceeds a predetermined value, the transfer error occurs again. A data transmission method characterized by transmitting and receiving data. 9. In a situation where the frequency of occurrence of the transfer error is equal to or lower than a predetermined value, even if a transfer error occurs, data transmission / reception with a device of a partner is continued, and a series of finally received data is received. 9. The data transmission method according to claim 8, wherein the data is discarded. 10. The data transmission method according to claim 8, wherein the data is image data transmitted in packet units. 11. The communication control means starts transmission of image data immediately upon receiving a connection response transmitted from a called side in response to a connection request transmitted to a destination at the time of line connection. The videophone device according to any one of 1 to 7. 12. The videophone device according to claim 11, wherein the communication control means transmits the connection request again if a connection response cannot be received for a predetermined time after transmitting the connection request. . 13. An image capturing means for capturing at least a user's self-portrait, and a partner image from a partner device connected via a communication line, while receiving the self-portrait captured by the image capturing means. When the image data that is transmitted and received at the other end is a simple image with a low resolution and the occurrence frequency of the transfer error in the data transfer via the communication line is less than or equal to a predetermined value, the other device And not instructing the image data to be retransmitted to the other side, and on the other hand, when the frequency of occurrence of the transfer error is higher than a predetermined value, communication control means for instructing the other party's device to retransmit the image data Display control means for displaying on the display device the self-portrait captured by the image capturing means and the partner image received from the communication control means from the partner device Videophone apparatus characterized by comprising. 14. The communication control means sets image data to be transmitted / received to a high-definition high-definition image only when instructed by the user, and when a transfer error occurs, the communication control means notifies the other device 14. The videophone device according to claim 13, wherein an instruction to retransmit the image data is always issued. 15. The communication control means determines that the occurrence frequency of a transfer error is higher than a predetermined value when no normal packet is received within a predetermined time. 15. The videophone device according to any one of 4, 13, or 14. 16. The communication control means sets a normal packet 1 times or more M times in N seconds and L (L <M) seconds or more.
4. If not received at all, it is determined that the frequency of occurrence of transfer error is higher than a predetermined value.
15. The videophone device according to any one of 4, 13, or 14. 17. The communication control means, when the time from the start of transmission of image data for one screen to the end of transmission exceeds a predetermined time, suspends transmission of the image data at that time, and the image of the next screen is displayed. 17. The videophone device according to claim 1, wherein transmission of data is started. 18. The communication control means transmits a resend request to the transmission side when it is determined that a transfer error has occurred in the image data, according to any one of claims 1 to 7 or 11 to 17. The videophone device according to. 19. The communication control means, when the image data is not received for a predetermined time even when a resend request is transmitted to the transmitting side at the time when it is determined that a transfer error has occurred in the image data,
The videophone device according to any one of claims 1 to 7 or 11 to 18, wherein the retransmission request is transmitted again to the transmitting side. 20. The communication control means transmits a resend request to a transmission side when image data is not received for a predetermined time.
9. The videophone device according to any one of 9 above. 21. According to the frequency of occurrence of CRC error, it is determined whether or not to retransmit a simple image, and if there is no normal received packet, the videophone operation is cut off and a normal voice is sent. 21. The videophone device according to claim 1, further comprising line state monitoring means for returning to an analog telephone operation by transmission only. 22. The operation of the other side is controlled by setting a predetermined command and exchanging the command between the transmitting side and the receiving side. Alternatively, the videophone device according to any one of 11 to 21. 23. In a videophone system for transmitting voice data and image data via a communication line, the transmission data comprises voice packets containing encoded voice data, image packets containing encoded image data, and control. It is composed of a command packet containing data and a resend request command packet for sending out transmission data again when an error occurs, and these packets are provided at predetermined time intervals with a voice packet, a resend request packet, a command packet,
A videophone system characterized by sending in the order of image packets. 24. In a videophone system for transmitting voice data and image data via a communication line, the transmission data includes voice packets containing encoded voice data, image packets containing encoded image data, and control. It is composed of a command packet containing data and a resend request command packet for sending out transmission data again when an error occurs.
A retransmit command packet is sent one packet at a predetermined time, and the image packet is sent in a packet amount that can be sent within the predetermined time range. 25. The videophone system according to claim 23, wherein a packet having no data among the packets is not transmitted. 26. The voice packet has a variable length,
The videophone system according to claim 23 or 24, wherein the image packet has a fixed length. 27. The videophone system according to claim 23, wherein the command packet has a variable length, and the retransmission command packet has a fixed length. 28. The videophone system according to claim 23, wherein the transmission of the transmission data is a process of writing in the transmission buffer of the modem section. 29. In a videophone system in which a videophone device on the transmitting side and a videophone device on the receiving side are connected to transmit voice data and image data, at the time of connection, after exchanging a connection request and a response. The videophone system characterized in that the voice data is not transmitted for the first predetermined time. 30. In a videophone system in which a videophone device on the transmitting side and a videophone device on the receiving side are connected to transmit voice data and image data, the transmitting side does not monitor and wait for a response from the receiving side.
Mode and the sending side monitors and waits for a response from the receiving side, and when the receiving side cannot receive data normally, it sends a resend request requesting data transmission again, and the sending side sends the resending request. And a second mode in which the data is transmitted again when is received. 31. A videophone system for connecting a videophone device on the transmitting side and a videophone device on the receiving side to transmit audio data and image data, having a simple image transmission mode and a fine image transmission mode, In the simple image transmission mode, the transmission side performs communication control processing in which the transmission side does not monitor and wait for the response from the reception side, and in the fine image transmission mode, the transmission side monitors and waits for the response from the reception side, and the reception side operates normally. A videophone system characterized in that, when data cannot be received, a resend request for sending data is sent again, and when the sending side receives the resend request, it performs communication control processing to send the data again. 32. In the simple image transmission mode,
Due to the increase in the frequency of transmission errors, the sender monitors and waits for a response from the receiver, and when the receiver cannot receive data normally, it sends a resend request to request data transmission again. 32. The videophone system according to claim 31, wherein when the resend request is received, the process is switched to a communication control process for transmitting the data again.