JPH0923339A - Method and equipment for picture communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a satisfactory picture by appropreately restoring only a normally received picture part in a proper position even at the time of the occurrence of transmission error and reducing the influence of transmission error upon the whole of the reproduced picture. SOLUTION: A compression condition and an MCU number are added to each of encoded data obtained by information source encoding in the unit of MCU, and this data is transmitted. On the reception side, encoded data in the MCU unit in a normally received frame is subjected to information source decoding in accordance with the added compression condition, and decoded picture data is restored in a position corresponding to the added MCU number.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image communication method and an image communication apparatus used for transmitting a still image, and more particularly to an image communication method capable of reproducing a good image by reducing the influence of a transmission error on a reproduced image. And an image communication device.

[0002]

2. Description of the Related Art First, FIG.
I will explain using. FIG. 4 is a configuration block diagram of a conventional image communication device. As shown in FIG. 4, the conventional image communication apparatus has a transmitting side composed of an information source encoder 1 ', an error correction encoder 2 and a communication controller 3', and a receiving side a communication controller 5 '. And an error correction decoder 6 ', an information source decoder 7', and an interpolator 8 ', and the transmission side and the reception side are connected via a transmission line 4.

Next, each section of the conventional image communication apparatus will be described. The information source encoder 1'is an information source encoding of digitally converted input image data. The information source encoding method in the conventional image communication apparatus is JPEG (Jo
int Photographic Experts Group) method was used.

The JPEG system will be briefly described with reference to FIG. FIG. 5 is an explanatory diagram showing an outline of the JPEG system. In the JPEG method, an original image is encoded block of, for example, 8 pixels × 8 pixels, that is, an MCU (Minimum
Code unit), block-based division, coding block (MCU) -based DCT conversion, quantization using a quantization table, and information source coding (compression code) by entropy coding using a coding table ), M
Create encoded data in CU units. Also, on the receiving side, entropy decoding using the same encoding table as the information source encoding performed on the transmitting side, dequantization using a quantization table, and information source decoding on a MCU basis by inverse DCT transform are performed. The image is reproduced by performing encoding (decompression / decoding).

In the JPEG system, the compression rate is variable, and the number of pixels, the thinning rate, the quantization table, and the like, which are highly likely to depend on the device, are expressed in a few bytes as a compression condition (called a marker code). , Is transmitted prior to image data. That is, the marker code is first output from the information source encoder 1 ′ to the error correction encoder 2, and subsequently the encoded data in units of MCU is output.

The error correction encoder 2 detects a transmission code error in the data output from the information source encoder 1 ',
In some cases, error correction coding (Forward Error Correction: FEC) for adding an error correction code for correction is performed.

Here, as an example of the error correction coding, a CRC (Cyclic Redundancy Checks) code known to be able to detect both an independent error in which an error independently occurs and a burst error in which errors continuously occur. The details are described in “Computer Communication and Network” by Kunio Fukunaga, Kyoritsu Shuppan Co., Ltd., p78-p82. There are also codes with higher error detection capability and various codes that can correct errors as well as detection. “Image band compression and coding technology” by Yuichi Ninomiya Nikkan Kogyo Shimbun, Ltd.
141.

The communication controller 3'includes coded data that has been error-correction coded in coded block units and incorporates it into the HDL.
A transmission frame of the C (High level Data Link Control) procedure is created, modulated into a signal suitable for the transmission line 4, and the transmission line 4 is modulated.
To be sent. Here, the HDLC procedure is a synchronous protocol capable of transmitting variable-length data in bit units, and details are described in "Computer Communication and Network" by Kunio Fukunaga, Kyoritsu Shuppan Co., Ltd. p113-p1.
30.

A transmission frame (packet), which is a transmission unit in the HDLC procedure, is a control for setting a flag for detecting the start of the frame and a command and response according to the transmission destination and the procedure as shown in FIG. A field, a variable length data to be transmitted, that is, a data field for setting a marker code and encoded data in MCU unit here, and an error correction code (CRC in the example of FIG. 6).
Code) and a flag for detecting the end of the frame. FIG. 6 is an explanatory diagram showing the transmission frame format of the HDLC procedure.

Then, as shown in FIG. 7, the transmission data sent from the communication controller 3'to the transmission line 4 is preceded by the HD before the marker code and the variable length encoded data of each MCU.
A flag for the LC procedure and a control field (the two are collectively called a header) are added, and a CRC is added after the encoded data.
A frame in which the code and the flag (footer) are added is continuously sent to the transmission line 4 as a packet. FIG. 7 is an explanatory diagram showing a format of transmission data in the conventional image communication apparatus.

The communication controller 5'demodulates the data received from the transmission line 4, performs processing according to the HDLC procedure, and
The header and the footer of the DLC are removed and the encoded data and the error correction code portion are extracted and output to the error correction decoder 6 '.

The error correction decoder 6'detects an error from the error correction code of the received data, corrects the error if correctable, and normally receives the error-free data and the error-corrected data. Information source decoder 7'as data
Output to On the other hand, data that cannot be error-corrected is discarded,
Information source decoder 7'by replacing with decodable alternative data
Output to

The information source decoder 7 ′ performs information source decoding on the normally received data or the alternative data received from the error correction decoder 6 according to the marker code (compression condition) received prior to the image data. Then, the reverse of the information source coding performed by the information source encoder 1'is performed.

The interpolator 8'represents the image data of the frame which is replaced by the substitute data by the error correction decoder 6 in the image data for one screen decoded by the information source decoder 7 '. Interpolation is performed from the normally received image data around it. The interpolation method is, as the simplest method, a method of setting the same value as the MCU immediately before the missing MCU, or a method of performing linear interpolation or curve interpolation from pixel values around the missing MCU, There is a method of interpolating by weighting depending on the distance between a pixel to be corrected and a normal pixel to be referred by utilizing the correlation between adjacent pixels.

Next, the operation of the conventional image communication apparatus will be described with reference to FIG. In a conventional image communication apparatus, when image data of an image to be transmitted is input, a marker code indicating a compression condition is first output from an information source encoder 1'to an error correction encoder 2 and then an information source code. In the encoder 1 ', the source data is encoded in MCU units and the image data is output to the error correction encoder 2 and the error correction encoder 2
Is error-correction-coded by the communication controller 3 ', incorporated in the HDLC frame by the communication controller 3', further modulated, and transmitted to the transmission path 4.

On the receiving side, the data received from the transmission line 4 is demodulated by the communication controller 5'and further processed in accordance with the HDLC procedure, the HDLC header and footer are removed, and an error occurs in the encoded data portion. The correction code portion is taken out and output to the error correction decoder 6 ', error-corrected and decoded by the error-correction decoder 6', and the frame that cannot be error-corrected is replaced with substitute data to be an information-source decoder. 7 ', and the information source decoder 7'decodes the information source based on the marker code received prior to the image data.

Then, the image data of the frame which has been error-correctable in the error-correction decoder 6'and which has been replaced with the alternative data is interpolated by the interpolator 8 to output the image data.

[0018]

However, in the above-described conventional image communication method and image communication apparatus, even if the packet including the compression condition (marker code) transmitted prior to the image data is not normally received, Even if the subsequent image data can be normally received, there is a problem that the image cannot be properly restored.

The present invention has been made in view of the above circumstances. Even if a transmission error occurs, a normally received image portion can be properly restored to an appropriate position, and the transmission error affects the entire reproduced image. An object of the present invention is to provide an image communication method and an image communication apparatus that can reduce the influence and reproduce good images.

[0020]

According to a first aspect of the present invention for solving the above-mentioned problems of the prior art, an image is encoded by an information source in an encoding unit and transmitted, and an information source is decoded by a receiving side. In the image communication method for reproducing an image, the transmitting side adds the compression condition indicating the encoding condition and the position information of the encoding unit to the encoded data and transmits the data, and the receiving side transmits the image data. The information source decoding of the coded data is performed according to a compression condition, and the decoded image data is restored to a position corresponding to the position information to reproduce an image, and a transmission error occurs. However, since only the image portion of the normally received transmission data is properly decoded and can be restored to the proper position, the influence of the transmission error on the entire reproduced image can be reduced and a good image can be reproduced.

In order to solve the problems of the above-mentioned conventional example, the invention according to claim 2 is an information source encoder which encodes an image by an information source in an encoding unit and outputs encoded data, and the encoded data. An error correction encoder for performing error correction coding, a transmission side communication controller for creating transmission data from the error correction coded data and transmitting the transmission data, and a reception side communication controller for receiving the transmission data And an error correction decoder that performs error correction decoding of the received data that is received and outputs normal reception data, an information source decoder that performs information source decoding of the normal reception data, and In an image communication device having an interpolator for interpolating image data of a coding unit that has not existed, the information source coder is a compression condition indicating a condition of information source coding in the coded data, With location information Is an information source encoder for outputting, and the information source decoder performs information source decoding according to a compression condition included in the normal reception data, and the information source decoded image data is the normal reception data. It is characterized by being an information source decoder that restores to the position corresponding to the position information included in, and even if a transmission error occurs, only the image part of the normally received transmission data is properly decoded. Since the data can be restored to an appropriate position, the influence of the transmission error on the entire reproduced image can be reduced and a good image can be reproduced.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the claimed invention will be described with reference to the drawings. According to the image communication method of the present invention, a compression condition and an MCU number are added to each encoded data source-encoded in the unit of MCU for transmission, and the receiving side receives the MCU in the frame normally received.
For the encoded data of the unit, the information source decoding is performed according to the added compression condition, and the added MC
Since the decoded image data is restored to the position corresponding to the U number, even if a transmission error occurs, only the normally received image data can be properly restored to the proper position and the transmission error is reproduced. Reduce the effect on the entire image,
A good image can be reproduced.

First, the configuration of the image communication apparatus (present apparatus) according to the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the configuration of an image communication apparatus according to the present invention. still,
Parts having the same configuration as in FIG. 4 will be described with the same reference numerals.

The basic structure of this device is the same as the conventional one.
The transmission side includes an information source encoder 1, an error correction encoder 2,
The communication controller 3 and the communication controller 5 on the receiving side.
And an error correction decoder 6, an information source decoder 7, and an interpolator 8, and the transmission side and the reception side are connected via a transmission line 4.

Next, each part of this apparatus will be specifically described. The information source encoder 1 is a conventional information source encoder 1 '.
Similarly to the above, the digital-converted input image data is information-source coded in coding block (MCU) units to create coded data. The compression condition (marker code), which is a condition for the information source coding, is used. And the encoded MCU
This is different from the conventional information source encoder 1 ′ in that the MCU number is added before the encoded data in units of MCU and is output to the error correction encoder 2.

Since the information source coding method is the same as the conventional one, its explanation is omitted here. The compression condition is a combination pattern of the quantization table, the thinning rate, and the number of pixels when the information source is encoded, which is represented by 4 bits, for example.

Further, the MCU number is a serial number corresponding to the position of the MCU in the image of one screen, and is calculated by the counter in the information source encoder 1 by counting for each encoding unit. For example, when an image having 640 × 480 pixels is thinned out at a thinning rate of 4: 2: 2 and then encoded by an information source and transmitted, the MCU becomes 16 × 8 pixels, and the total number of MCUs becomes 2400. Therefore, 12 bits are sufficient to represent the MCU number (0 to 2399). 1M per packet
When transmitting with CU encoded data, the MCU number is the same as the packet number.

The error correction encoder 2 is similar to the conventional one, and an error is added to the data output from the information source encoder 1 to detect a transmission code error and add an error correction code for correction in some cases. Correction coding is performed.

The communication controller 3 is suitable for the transmission line 4 after adding a flag for detecting the start and end of a packet to the data with the error correction code output from the error correction encoder 2 The modulated signal is transmitted to the transmission line 4. As a result, one transmission frame output from the communication controller 3 includes a flag for detecting the start of the frame, the compression condition, the MCU number, and the MCU as shown in FIG.
It is composed of a variable-length data field composed of encoded data in units, an error correction code (CRC code in the example of FIG. 2), and a flag for detecting the end of the frame. FIG. 2 is an explanatory diagram showing a transmission frame format of this device.

The transmission data sent from the communication controller 3 to the transmission path 4 is, as shown in FIG. 3, a flag, a compression condition and an MCU before the variable length encoded data of each MCU.
A number is added, and a CRC code is added after the encoded data,
The frame to which the flag is added becomes a packet and is continuously transmitted to the transmission line 4. FIG. 3 is an explanatory diagram showing the format of transmission data in this device.

The communication controller 5 demodulates the data received from the transmission line 4, removes the flags before and after the frame, extracts the data field and the error correction code, and outputs them to the error correction decoder 6.

The error correction decoder 6 detects an error from the error correction code of the received data, corrects the error if it can be corrected, and outputs the error-free data and the error-corrected data to the normally received data. Is output to the information source decoder 7, while the data that cannot be error-corrected is discarded.

The information source decoder 7 is an error correction decoder 6
The normal reception data received from the source is decoded according to the compression condition added to the coded data, and the image data decoded from the information source is restored to the position corresponding to the MCU number added to the coded data. Therefore, the information source encoding performed by the information source encoder 1 is reversed. The position corresponding to the MCU number is such that the correspondence between the MCU number and the pixel position can be calculated in advance from the image size, the thinning rate, the MCU size, or the like, or the MCU number and the pixel position can be calculated. The correspondence table with and is set in advance, and the pixel position is referred to from the MCU number when decoding.

The interpolator 8 includes an error correction decoder 6 in the image data for one screen decoded by the information source decoder 7.
With respect to the image data of the frame that cannot be corrected and is discarded, the interpolation is performed from the normally received image data of the periphery thereof. The interpolation method is the same as the conventional one.

Next, the operation of this apparatus will be described with reference to FIG.
I will explain using. In this device, when image data of an image to be transmitted is input, the MCU in the information source encoder 1
Image data is source-coded in units, a marker code (compression condition) and MCU number are further added, and the resulting data is output to the error correction encoder 2 and error-correction encoded by the error correction encoder 2 for communication control. A flag is added by the device 3, further modulated and transmitted to the transmission line 4.

On the receiving side, the data received from the transmission line 4 is demodulated by the communication controller 5, the flag is further removed, the coded data and the error correction code portion are taken out, and the error correction decoder 6 corrects the error. Frames that have been decoded and whose error cannot be corrected are discarded, while only normal frames are output to the information source decoder 7 and based on the compression conditions added to the encoded data received by the information source decoder 7. MCU decoded by the information source and added to the received encoded data
It is restored to the position corresponding to the number.

When the information source decoder 7 completes the information source decoding of the image data for one screen, the error correction decoder 6 interpolates the image data of the discarded frame which cannot be error-corrected. The interpolation processing is performed by the device 8 and the image data is output.

According to the image communication method and the image communication apparatus according to the present invention, the compression condition and the MCU number are added to the encoded data which is source coded in the unit of MCU by the information source encoder 1, and the error correction code is added. The error correction code is encoded by the decoder 2 and transmitted as one frame, and the error correction decoder 6 is transmitted on the receiving side.
The information source decoder 7 performs information source decoding on the MCU that has been normally received or error-corrected according to the compression condition added to the encoded data, and decodes at the position of the MCU number added to the encoded data. Even if a transmission error occurs, the image data of the normally received frame can be properly restored to an appropriate position because the image data that has been converted is restored, and the influence of the transmission error on the entire reproduced image is reduced. However, there is an effect that a good image can be reproduced.

Further, according to the image communication method and the image communication apparatus of the present invention, the error correction decoder 6 simply discards the frames that cannot be error-corrected. There is an effect that can be simplified.

Further, according to the image communication method and the image communication apparatus according to the present invention, the image data of the frame discarded by the error correction decoder 6 is calculated by the interpolator 8 from the normally received image data in the vicinity. Since interpolation is performed, there is an effect that a better image can be reproduced.

[0041]

According to the first and second aspects of the present invention, the compression condition indicating the information source coding condition and the position information of the coding unit are added to the coded data which is information source coded in the coding unit. Is added and transmitted, the receiving side performs information source decoding according to the compression condition added to the encoded data, and the information source is decoded at the position corresponding to the position information added to the encoded data. Since the image communication method and the image communication apparatus restore the reproduced image data and reproduce the image, even if a transmission error occurs, only the image portion of the normally received transmission data is properly decoded, and the image is properly transmitted. It is possible to restore the position, reduce the influence of transmission errors on the entire reproduced image, and have the effect of reproducing a good image.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an image communication apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a transmission frame format of this device.

FIG. 3 is an explanatory diagram showing a format of transmission data in this device.

FIG. 4 is a configuration block diagram of a conventional image communication device.

FIG. 5 is an explanatory diagram showing an outline of a JPEG system.

FIG. 6 is an explanatory diagram showing a transmission frame format of an HDLC procedure.

FIG. 7 is an explanatory diagram showing a format of transmission data in a conventional image communication device.

[Explanation of symbols]

1, 1 '... Information source encoder, 2 ... Error correction encoder,
3, 3 '... communication controller, 4 ... transmission line, 5, 5' ...
Communication controller, 6, 6 '... Error correction decoder, 7, 7'
... source decoder, 8,8 '... interpolator

Front page continuation (72) Inventor Hiroyo Sato 3-14-20 Higashi-Nakano, Nakano-ku, Tokyo Kokusai Electric Co., Ltd.

Claims (2)

[Claims] 1. An image communication method in which an image is encoded by an information source and transmitted, and a receiving side decodes the information source to reproduce an image, in which the transmitting side adds the encoded data to the encoded data. The compression condition indicating the coding condition and the position information of the coding unit are added and transmitted, and the receiving side performs the information source decoding of the coded data according to the compression condition, and the position corresponding to the position information is obtained. An image communication method, which reproduces an image by restoring the decoded image data. 2. An information source encoder that encodes an image as an information source in encoding units and outputs encoded data, an error correction encoder that performs error correction encoding of the encoded data, and the error correction code. A transmission side communication controller that creates and transmits transmission data from the converted data, a reception side communication controller that receives the transmission data, and error correction decoding of the received data received An error correction decoder that outputs received data, an information source decoder that performs information source decoding of the normal received data, and an interpolator that interpolates image data of a coding unit that was not normally received In the image communication device, the information source encoder is an information source encoder that adds the compression condition indicating the condition of the information source encoding to the encoded data and the position information of the encoding unit and outputs the information. Source decoder An information source decoder that performs information source decoding according to a compression condition included in normal reception data and restores the information source decoded image data to a position corresponding to position information included in the normal reception data. An image communication device characterized by the above.