JP2604058B2 - Image encoding and decoding device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image encoding and decoding apparatus that encodes a moving image signal and decodes the encoded image signal.

(Prior Art) As one of communication systems, there is a packet communication system. That is, communication is performed by dividing a transmission code into a certain size, adding a code (header) indicating a destination and contents to each of them, compiling them as packets (cells), and exchanging these cells on a network. That's what I mean. Since the packet communication system and the communication processing of voice, image, and data can be handled in a unified and large amount, it is attracting attention as a next-generation communication system.

However, packet communication systems also have disadvantages. That is, when the total number of cells exceeds the processing capacity of the network due to network congestion, a phenomenon called cell discard occurs. When cell loss occurs,
In the case of image communication, image quality is degraded, for example, a part of an image is lost.

Therefore, in the case where an image is encoded and transmitted by the packet communication method, the image encoding method must be a method that takes this cell discard into account.

Therefore, conventionally, image encoding and decoding in consideration of the packet communication system have been performed by the following methods shown in FIGS. 2 (a) and 2 (b) (for example, literature: Hamano, Sakai, Matsuda:
“A Study on Image Coding Method with Resistance to Cell Discard”,
IEICE, Technical Committee on Image Engineering, Image Coding Symposium PCSJ89 PP97-98 (1989.10), etc.).

First, conventional image coding will be described with reference to FIG.

FIG. 2A is a block diagram showing an example of a conventional image encoder. In the figure, an original image is converted into an electric signal representing a light and shade distribution by scanning of an image pickup tube of a TV camera 201, and further converted into an analog / digital converter (hereinafter, A / D).
It is called a converter. ) 202 to sample into pixels and convert them into digital image signals. The digital image signal is input to a discrete cosine converter (hereinafter, referred to as a DCT converter) 203. The DCT converter 203 converts the input image code into several processing blocks (for example, a processing block including 16 × 16 pixels).
And obtains a transform coefficient block for each processing block.

The transform coefficient obtained by the DCT converter 203 is input to the adder 204, and the difference between the transform coefficient of the previous frame and the transform coefficient stored in the frame memory 209 is obtained. The residual signal obtained by taking this difference is input to the quantizer (Q) 205. The quantizer 205 quantizes the residual signal (transform coefficient) with, for example, 8 bits, and outputs the quantized transform coefficient to the variable length coder (VLC) 210. The variable length encoder 210 encodes the code of the transform coefficient with an unequal length code such as a Huffman code,
Output to the packet assembling circuit (PAD) 211. The packet assembling circuit 211 divides the output code of the variable-length encoder 210 into an appropriate size, attaches the header, combines the cells into cells, and sends the cells to the packet communication network 212. The quantized transform coefficient output from the quantizer 205 is also input to the inverse quantizer 206, where it is inversely quantized and input to the adder 207.
The adder 207 adds the transform coefficient of one frame before subtracted to the transform coefficient that has been dequantized, and outputs a local decoded signal. The local decoded signal is input to a frame memory (FM) 209 after being multiplied by a leak coefficient α by a multiplier 208 and stored as a prediction signal of the next frame.

Next, conventional image decoding will be described with reference to FIG.

FIG. 2 (b) is a block diagram showing an example of a conventional image decoder. This image decoder corresponds to the image encoder shown in FIG.

In FIG. 7B, the packet disassembly circuit 213 receives cells from the packet communication network 212 and outputs the cells to the variable length decoders 214, respectively. The variable length decoder 214 decodes the unequal length code into a transform coefficient code, and outputs the transform coefficient code to the inverse quantizer 215. The inverse quantizer 215 inversely quantizes the input code into transform coefficients and outputs the result to the adder 216. Adder 216 is
A transform coefficient of the frame memory 218 is added to the inversely quantized transform coefficient, and the decoded signal is output to a discrete cosine inverse transformer (hereinafter, referred to as a DCT inverse transformer) 219 and a multiplier 217. The multiplier 217 multiplies the decoded signal output from the adder 216 by a leak coefficient α, and
Output to The frame memory 218 stores this signal as a prediction signal of the next frame. DCT inverse transformer 219
The reproduced signal (decoded signal) is subjected to orthogonal inverse transform to be converted into a reproduced image signal. The reproduced image signal is thereafter converted into an analog image signal by a digital / analog converter (hereinafter, referred to as a D / A converter) 220 and output to the image monitor 221.

Here, in the encoder of FIG. 2A, a DCT transformer 203 is used as an orthogonal transform, and predictive coding in a transform coefficient domain, that is, an adder 204 calculates an inter-frame difference for a transform coefficient. It is characterized by taking. Further, the encoders and decoders shown in FIGS. 2A and 2B are provided with multipliers 208 and 217 for multiplying leak coefficients α (0.0 <α <1.0), respectively. In these multipliers 208 and 217, the output of the local decoder of the block 200 portion (the local decoded signal which is the output of the adder 207) indicated by the one-dot chain line in FIG.
The outputs of the adders 216 (the outputs of the adders 207 and 216 are DCT transform coefficients (discrete cosine transform coefficients) to be reproduced) are selectively multiplied by a leak coefficient α to obtain the following (1) and (2). 2), and an encoding / decoding system suitable for packet communication is realized.

(1) By multiplying the DCT transform coefficient by the leak coefficient α, the influence of past frames can be discarded little by little. Therefore, even if the cell is discarded, the reproduced image of the decoder is momentarily disturbed, but is automatically recovered with the passage of time.

(2) The frequency component of the image can be selectively multiplied, such as 0.99 for the conversion coefficient corresponding to the DC component of the image and 0.9 for the conversion coefficient corresponding to the AC component of the image. Therefore, unlike the conventional leak of the inter-frame difference in the time domain, the coding rate does not extremely increase due to the decrease in the prediction gain.

(Problems to be Solved by the Invention) However, the above-described conventional image coding and decoding methods have the following problems.

(1) A DCT converter is applied to an image signal, and a simple inter-frame difference is obtained for the transform coefficient. Therefore, motion compensation prediction coding, which is a prediction coding method in the time domain, cannot be used, resulting in poor coding efficiency.

(2) In order to prevent a decrease in prediction gain, when performing leak selection, a plurality of multipliers must be prepared.
Processing becomes complicated.

Therefore, an object of the present invention is to solve the above-described problems, and to simply perform predictive coding in the time domain, and not to reduce the prediction gain, to achieve high coding efficiency, and even to cause cell discard. Playback image quality automatically recovers over time,
An object of the present invention is to provide an excellent image encoding and decoding apparatus.

(Means for Solving the Problems) A first aspect of the present invention provides a discrete cosine transform of a residual signal between a moving image signal and a predicted image signal from a first frame memory,
In an image coding apparatus having an inter-frame predictive encoder that quantizes and encodes the transform coefficient and sends out an output code, the inter-frame predictive encoder includes the inter-frame predictive encoder and the output code from the first frame memory. With the predicted image signal,
A local decoder for obtaining a locally decoded image signal, and a locally decoded image signal from the local decoder are divided into processing blocks of a predetermined size, and for each processing block,
The average value in the processing block is obtained, the average value in the processing block is subtracted from the pixels in the same processing block, the difference is multiplied by a leak coefficient, and the average value in the processing block is added again. A first leakage circuit for outputting the leakage-added locally decoded image signal to the first frame memory so as to store the locally decoded image signal to the first frame memory as a predicted image signal of the next frame. Things.

According to a second aspect of the present invention, the coded image signal is inversely quantized, the inverse discrete cosine transform is performed, and a prediction signal from the second frame memory is added to the obtained reproduction residual signal to generate a reproduction image signal. In an image decoding apparatus having an inter-frame predictive decoder for outputting, the inter-frame predictive decoder divides the reproduced image signal into processing blocks of a predetermined size, and for each processing block, An average value is obtained, the average value in the processing block is subtracted from the pixels in the same processing block, the difference is multiplied by a leak coefficient, and the leakage addition obtained by adding the average value in the processing block again is obtained. Outputting the reproduced image signal to the second frame memory so as to be stored in the second frame memory as a prediction signal of the next frame. It is made and a second leakage circuit.

According to a third aspect of the present invention, a residual cosine transform between a moving image signal and a predicted image signal from the first frame memory is performed by discrete cosine transform, and the transform coefficient is quantized and coded to output an output code. In an image encoding apparatus having a predictive encoder, the inter-frame predictive encoder includes a local decoder that obtains a local decoded image signal from the output code and a predicted image signal from the first frame memory. And a predetermined value is subtracted from the locally decoded image signal from the local decoder, a leakage coefficient is obtained by multiplying the result of the subtraction by a leak coefficient, and adding the predetermined value again. Outputting a locally decoded image signal to the first frame memory for storage in the first frame memory as a predicted image signal of a next frame;
Further, the fourth invention dequantizes the coded image signal, performs an inverse discrete cosine transform, and converts the obtained reproduction residual signal into a second frame memory. In the image decoding apparatus having an inter-frame predictive decoder that outputs a reproduced image signal by adding the predicted signal from the inter-frame predictive decoder, the inter-frame predictive decoder subtracts a predetermined value from the reproduced image signal, and subtracts the predetermined value. The leaked reproduction image signal obtained by multiplying the result by a leak coefficient and adding the predetermined value again is stored in the second frame memory as the prediction signal of the next frame. And a fourth leakage circuit for outputting to the second frame memory.

According to a fifth aspect of the present invention, a residual signal between a moving image signal and a predicted image signal from a first frame memory is subjected to discrete cosine transform, and its transform coefficient is quantized and coded to output an output code. An image encoding device having a predictive encoder, an inverse quantization of an encoded image signal supplied from the image encoding device via a communication line, and an inverse discrete cosine transform to obtain an obtained reproduction residue; An image decoding apparatus having an inter-frame prediction decoder for adding a prediction signal from a second frame memory to the difference signal and outputting a reproduced image signal; An encoder configured to determine a local decoded image signal from the output code and the predicted image signal from the first frame memory; and a local decoded image from the local decoder. The signal is divided into processing blocks of a predetermined size, an average value within the processing block is obtained for each processing block, and the average value within the processing block is subtracted from the pixels within the same processing block. The leaked local decoded image signal obtained by multiplying by the leak coefficient and adding the average value within the processing block again is stored in the first frame memory as a predicted image signal of the next frame. A first leakage circuit for outputting to the first frame memory, wherein the inter-frame predictive decoder divides the reproduced image signal into processing blocks of a predetermined size, and for each processing block, The average value in the processing block is obtained, and the average value in the processing block is subtracted from the pixels in the same processing block. The leaked reproduction image signal obtained by multiplying the average value in the processing block by multiplying the leakage coefficient by the leak coefficient is again stored in the second frame memory as the prediction signal of the next frame. And a second leakage circuit for outputting to the frame memory.

According to a sixth aspect of the present invention, there is provided a method for performing a discrete cosine transform on a residual signal between a moving image signal and a predicted image signal from a first frame memory, quantizing and encoding the transform coefficient, and outputting an output code between frames. An image encoding apparatus having a predictive encoder, and an inverse quantization of an encoded image signal supplied from the image encoding apparatus via a communication line, and further performing an inverse discrete cosine transform to obtain a reproduction residual obtained. An image decoding apparatus having an inter-frame prediction decoder for adding a prediction signal to a signal from a second frame memory and outputting a reproduced image signal, wherein the inter-frame prediction coding is performed. A local decoder for obtaining a local decoded image signal from the output code and the predicted image signal from the first frame memory; and a local decoded image signal from the local decoder. The leaked local decoded image signal obtained by multiplying the result of the subtraction by a leak coefficient and adding the predetermined value again is stored in the first frame memory. The first frame is stored as a predicted image signal of the next frame.
A third leakage circuit that outputs the predetermined value to the frame memory, the inter-frame predictive decoder subtracts the predetermined value from the reproduced image signal, and multiplies the subtracted result by a leak coefficient; A fourth leakage output to the second frame memory for storing a leakage-added reproduced image signal obtained by adding the predetermined value again, as a predicted signal of a next frame in the second frame memory. And a circuit.

(Operation) The image encoding device includes an inter-frame prediction encoder.
The inter-frame prediction encoder performs leakage addition on a local decoder and a locally decoded image signal from the local decoder, and converts the leakage-added local decoded image signal into a first frame. There is a leakage circuit (first leakage circuit or third leakage circuit) for storing the predicted image signal of the next frame in the memory. The inter-frame predictive encoder performs a discrete cosine transform of a residual signal between the moving image signal and the predicted image signal from the first frame memory, quantizes and encodes the transform coefficient, and sends out an output code.

On the other hand, the image decoding apparatus has an inter-frame predictive decoder, and the inter-frame predictive decoder performs leakage addition on the reproduced image signal, and converts the leakage-added reproduced image signal into a second image. A leakage circuit (a second leakage circuit or a fourth leakage circuit) is stored in the frame memory as a prediction signal of the next frame.
The inter-frame predictive decoder inversely quantizes the coded image signal supplied from the image decoding device via the communication line, performs inverse discrete cosine transform, and converts the resultant reproduced residual signal into a second signal. And outputs a reproduced image signal by adding a prediction signal from the frame memory.

As described above, since the image encoding apparatus performs predictive encoding of an image in the time domain, motion-compensated inter-frame prediction can be performed, and encoding can be performed with high encoding efficiency. In addition,
In the process of adding leakage by the fourth leakage circuit, the DC component of the locally decoded signal or the reproduced image signal is protected, and the AC component is selectively leaked.
The prediction gain does not decrease and the coding efficiency is high. Further, in the case where an image is coded and transmitted by the packet communication method, even if the cell is discarded, the image quality can be automatically recovered from deterioration.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an image encoding / decoding apparatus according to the present invention. FIG. 1 (a) shows an embodiment of an image encoding apparatus according to the present invention, and FIG. () Shows an embodiment of the image decoding apparatus according to the present invention.

First, the image coding apparatus according to the present invention shown in FIG.

The original image is converted into an electric signal representing the light and shade distribution by scanning the imaging tube of the TV camera 101, and further sampled into pixels by the A / D converter 102, and converted into a digital image signal. This input digital image signal is analyzed by an analysis filter (QM
F) Entered in 103. The digital image signals band-divided by the analysis filter 103 are respectively coded by encoders 104a to 104a.
Entered in 104d. Each of the encoders 104a to 104d encodes the digital image signal by an inter-frame predictive encoding method. The codes output from the encoders 104a to 104d are input to the variable length encoders 105a to 105d, respectively.
The variable-length encoders 105a to 105d encode the codes from the encoders 104a to 104d into Huffman codes and run-length codes, and output the codes to the packet assembling circuit 106. Packet assembly circuit 106
Is a circuit for combining output codes of the variable length encoders 105a to 105d into a determined cell length, adding a header, and assembling the cells into cells. The cells assembled by the packet assembling circuit 106 are sent out to the packet communication network 107.

Next, the image decoding apparatus that receives cells from the packet communication network 106 will be described with reference to FIG.

Cells from the packet communication network 107 are separated into variable length codes of each band by a packet decomposing circuit 108. Each of these variable-length codes is a variable-length decoder.
The data is decoded by 109a to 109d and input to decoders 110a to 110d. The decoders 110a to 110d reproduce the band-divided image signals using inter-frame prediction. The reproduced image signals of the respective bands are synthesized into a reproduced image by a synthesis filter (QMF) 111. This reproduced image is converted into an analog image signal by the D / A converter 112 and output to the image monitor 113.

Next, a specific configuration showing one embodiment of the encoders 104a to 104d in FIG. 1A will be described with reference to FIG.

FIG. 3 is a block diagram showing one embodiment of each of the encoders 104a to 104d in FIG. 1 (a). Each encoder 10 shown in FIG.
4a to 104d are constituted by a motion compensation inter-frame predictive encoder as shown in FIG.

In FIG. 3, reference numeral 301 denotes an encoder input terminal to which a digital image signal that has been subjected to band division by the analysis filter 103 is supplied. From this encoder input terminal 301, a band-divided digital image signal is input. Then, the motion vector detector (MV) 311 performs block matching between the input image signal and the image signal of the frame memory 310 using, for example, a processing block of 16 × 16 pixels to detect a motion vector. . The motion vector detected by the motion vector detector 311 is output to the frame memory 310 and the encoder output terminal 305. The adder 302 calculates a difference between the image signal (predicted value) and the input image signal based on the motion vector from the frame memory 310, and outputs the obtained residual signal to the DCT transformer 303. The DCT transformer 303 performs a discrete cosine transform on the residual signal using, for example, a processing block of 8 × 8 pixels, and converts the transform coefficient into a quantizer 30.
Output to 4. The quantizer 304 quantizes the transform coefficient,
Encode and output code to encoder output terminal 305, inverse quantizer
Output to 306. The inverse quantizer 306 reproduces the code into an inversely quantized value, and outputs the code to the DCT inverse transformer 307.

The DCT inverse transformer 307 inversely transforms the reproduced transform coefficient into a reproduced residual signal. The reproduction residual signal obtained by the DCT inverse transformer 307 is added with the image signal (prediction value) from the frame memory 310 by an adder 308 to become a locally decoded image signal. The leakage circuit 309 receives an output of the local decoder 312 (which indicates a block 312 indicated by a dashed line), that is, a local decoded image signal output from the adder 308, and Then, the following processes (1) to (3) are performed.

(1) A locally decoded image signal is converted to a certain size (for example, 16 × 16
(Pixels).

(2) determining the mean value A _B processing block B.

(3) Average value from pixels in the processing block as follows
A _B is separated, multiplied by a leak coefficient, and A _B is added again to obtain a locally decoded image signal block _BL .

B _L (i, j) = α (B (i, j) −A _B ) + A _B where α: leak coefficient (0 <α <1.0) A _B : average value of processing block B B (i , j): Pixels in the locally decoded image signal block B _L (i, j): Pixels in the locally decoded image signal block with leakage This leakage allows the effects of past frames to be discarded little by little. When the cell is discarded, it is possible to automatically recover the image quality deterioration (recover the synchronization between the encoder and the decoder).

The locally decoded image signal to which leakage is added, which is an output signal of the leakage circuit 309, is stored in the frame memory 310 as a prediction signal of the next frame.

Next, a specific configuration of each of the decoders 110a to 110d in FIG. 1B will be described with reference to FIG.

FIG. 4 is a block diagram showing one embodiment of each of the decoders 110a to 110d in FIG. 1 (b). Each decoder 110a to 110d
Is constituted by a motion compensation inter-frame prediction decoder as shown in FIG.

Reference numeral 401 denotes a corresponding variable length decoder 109i shown in FIG.
(I is a corresponding one of a to d) is a decoder input terminal to which the output code is supplied, and when the output code is supplied to the decoder input terminal 401, an inverse quantizer 402
Reproduces the code into an inverse quantized value and outputs it to the DCT inverse transformer 403. Further, the motion vector from the decoder input terminal 401 is sent to the frame memory 406.

The DCT inverse transformer 403 inversely transforms the inversely quantized transform coefficient into a reproduction residual signal. The reproduction residual signal obtained by the DCT inverse transformer 403 is added with a prediction value based on the motion vector from the frame memory 40b by the adder 404, and becomes a reproduced image signal, which is output from the decoder output terminal 407. It is output to the synthesis filter 111 of FIG.

The output (reproduced image signal) of the adder 404 is also input to the leakage circuit 405. The leakage circuit 405 performs the following processes (1) to (3) in the same manner as in the encoder of FIG. 3 described above, and transfers the reproduced image signal to which the leakage has been added to the frame memory 406 for the next frame. Is output as a prediction signal.

(1) The reproduced image signal is divided into processing blocks B of a certain size (for example, 16 × 16 pixels).

(2) An average value _AB is obtained for the processing block B.

(3) Average value from pixels in the processing block as follows
A _B is separated, multiplied by a leak coefficient, and the average value A _B is added again to obtain a reproduced image signal block _BL .

B _L (i, j) = α (B (i, j) −A _B ) + A _B where α: leak coefficient (0 <α <1.0) A _B : average value of processing block B B (i , j): Pixels in the reproduced image signal block B _L (i, j): Pixels in the reproduced image signal block to which leakage is added In the embodiment of FIGS. 3 and 4, the leakage is performed by the leakage circuits 309 and 405. It is subtracted in the processing block average value a _B, or added (above, see formula) operation that is meant to make the removal of significant DC component in the image, an additional. For this reason, the encoder of FIG.
The leak of the decoder shown in the figure is mainly performed for the AC component of the image signal. Therefore, the prediction gain does not significantly deteriorate. Since the average value A _B in the processing block is determined from the local decoded signal of the encoder and the decoded signal of the decoder, a special parameter is exchanged between the encoder and the decoder. It is not necessary.

Further, FIG. 3, in the embodiment of FIG. 4, in leakage circuit 309,405, although seeking each processing block average value A _B, instead of obtaining the processing block average value A _B, it is pre-fixed The value A may be substituted. In this case, it is preferable that the fixed value A is set near the average value of the input image signals in consideration of the above description. If the input image signal fluctuates evenly in the range of 8 bits and 0 to 255, the fixed value A may be set to 128 in each of the encoder and the decoder. Thus, the encoder leakage circuit 309 and the decoder leakage circuit 40
If the fixed value A is set to the same value in each of 5,
No special parameters need to be transmitted from the encoder to the decoder.

The present invention is not limited to the present embodiment, and various applications and modifications can be considered without departing from the gist of the present invention. For example, in the present embodiment, the input image signal is divided into a plurality of bands using the analysis filter 103, and the encoding and decoding are performed in each band. However, the present invention is not limited to this. Without dividing the input image signal into a plurality of bands by the analysis filter 103, and
3 and the synthesis filter 111 are removed, and the encoder and the decoder are replaced by a plurality of encoders 104a to 104d and a plurality of decoders 110a to 110d as shown in FIGS. 1 (a) and 1 (b), respectively. May be provided one by one, and the image signal may be directly input to the one encoder.

(Effects of the Invention) As described above, the present invention has the following various effects.

(1) Since predictive coding of an image is performed in the time domain, motion-compensated inter-frame prediction can be performed, and coding can be performed with high coding efficiency.

(2) Each of the image encoding device and the image decoding device has an inter-frame predictive encoder and an inter-frame predictive decoder, and performs local decoding in a process of adding leakage in the first to fourth leakage circuits. By subtracting the average value (or predetermined value) in the processing block from the signal or the reproduced image signal, the DC component is automatically protected, and the leakage is selectively performed on the AC component, so that the prediction gain does not decrease. , And the coding efficiency is high. In addition, there is no need to exchange special parameters between the image encoding device and the image decoding device because of the average value and the predetermined value in the processing block used for the leakage adding process, and the process is simplified.

(3) Due to the leakage, the past influence can be discarded little by little as in the prior art, and even if cell discarding occurs, image quality degradation can be automatically recovered (for cell discarding). Also strong).

(4) In the process of adding leakage, only one multiplier is required, and the process is simple.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing a conventional example, and FIGS. 3 and 4 are each an embodiment of the encoder and decoder of FIG. FIG. 104a-104d: encoder, 110a-110d: decoder, 302,404 ... adder, 303 ... DCT converter, 304 ... quantizer, 306,402 ... inverse quantizer, 307,403 ... DCT Inverter, 309,405 ... leakage circuit, 310,406 ... frame memory, 311 ... motion vector detector, 312 ... local decoder.

Claims (6)

(57) [Claims] A discrete cosine transform of a residual signal between a moving picture signal and a predicted picture signal from a first frame memory, and an inter-frame predictive coding for quantizing and coding the transform coefficient and transmitting an output code. In the image encoding device having a decoder, the inter-frame prediction encoder includes: a local decoder that obtains a locally decoded image signal from the output code and a predicted image signal from the first frame memory; The locally decoded image signal from the local decoder is divided into processing blocks of a predetermined size, an average value within the processing block is calculated for each processing block, and the average value within the processing block is determined by a pixel within the same processing block. , And the leakage-added local decoding obtained by multiplying the result of the subtraction by a leak coefficient and adding the average value in the processing block again. The outputs an image signal, to the first frame memory to be stored in the first frame memory as a predicted image signal of the next frame 1
And a leakage circuit. 2. A frame for inversely quantizing an encoded image signal, performing an inverse discrete cosine transform, adding a prediction signal from a second frame memory to an obtained reproduction residual signal, and outputting a reproduction image signal. In an image decoding apparatus having an inter-frame prediction decoder, the inter-frame prediction decoder divides the reproduced image signal into processing blocks of a predetermined size, and calculates an average value in a processing block for each processing block. The leakage value obtained by subtracting the average value in the processing block from the pixels in the same processing block, multiplying the subtracted result by a leak coefficient, and adding the average value in the processing block again is obtained. Outputting a reproduced image signal to the second frame memory so as to store the reproduced image signal in the second frame memory as a prediction signal of a next frame; Image decoding apparatus being characterized in that a leakage circuit. 3. An inter-frame predictive coding for performing a discrete cosine transform of a residual signal between a moving image signal and a predicted image signal from a first frame memory, quantizing and encoding the transform coefficient, and transmitting an output code. In the image encoding device having a decoder, the inter-frame prediction encoder includes: a local decoder that obtains a locally decoded image signal from the output code and a predicted image signal from the first frame memory; A predetermined value is subtracted from the locally decoded image signal from the local decoder, the result of the subtraction is multiplied by a leak coefficient, and the result is obtained by adding the predetermined value again.
The leaked local decoded image signal is converted to the first
And a third leakage circuit that outputs the predicted image signal to the first frame memory so as to be stored in the frame memory as a predicted image signal of the next frame. 4. A frame for inversely quantizing an encoded image signal, performing an inverse discrete cosine transform, adding a prediction signal from a second frame memory to an obtained reproduction residual signal, and outputting a reproduction image signal. In an image decoding apparatus having an inter prediction decoder, the inter frame prediction decoder subtracts a predetermined value from the reproduced image signal, multiplies a result of the subtraction by a leak coefficient, and again performs the predetermined operation. A fourth leakage circuit for outputting a leakage-added reproduced image code obtained by adding a value to the second frame memory so as to be stored in the second frame memory as a prediction signal of a next frame; An image decoding device comprising: 5. An inter-frame predictive coding for performing a discrete cosine transform on a residual signal between a moving picture signal and a predicted picture signal from a first frame memory, quantizing and coding the transform coefficient, and transmitting an output code. An image encoding device having a device, and supplied from the image encoding device via a communication line.
An inter-frame predictive decoder that inversely quantizes the encoded image signal, performs inverse discrete cosine transform, adds a prediction signal from a second frame memory to the obtained reproduction residual signal, and outputs a reproduction image signal In the image encoding / decoding apparatus configured with the image decoding apparatus having the above, the inter-frame predictive encoder includes a local decoded image based on the output code and a predicted image signal from the first frame memory. A local decoder for obtaining a signal; a local decoded image signal from the local decoder is divided into processing blocks of a predetermined size, and for each processing block, an average value within the processing block is calculated. By subtracting the average value from the pixels in the same processing block, multiplying the result of the subtraction by a leak coefficient, and adding the average value in the processing block again. Resulting Te, first outputs a local decoded image signal leakage added, in the first frame memory to be stored in the first frame memory as a predicted image signal of the next frame 1
Wherein the inter-frame predictive decoder divides the reproduced image signal into processing blocks of a predetermined size, obtains an average value within the processing block for each processing block, The leaked playback image signal obtained by subtracting the inner average value from the pixels in the same processing block, multiplying the subtracted result by a leak coefficient, and adding the processing block average value again, An image encoding / decoding apparatus, comprising: a second leakage circuit that outputs the predicted signal of the next frame to the second frame memory so as to be stored in the second frame memory. 6. An inter-frame predictive coding for performing a discrete cosine transform on a residual signal between a moving picture signal and a predicted picture signal from a first frame memory, quantizing and coding the transform coefficient, and transmitting an output code. An image encoding apparatus having an encoder, inversely quantizes an encoded image signal supplied from the image encoding apparatus via a communication line, and performs inverse discrete cosine transform to obtain an obtained reproduction residual signal. And an image decoding device having an inter-frame prediction decoder that outputs a reproduced image enhancement signal by adding a prediction signal from the second frame memory. A local decoder for obtaining a locally decoded image signal from the output code and the predicted image signal from the first frame memory; and a local decoded image signal from the local decoder. It is obtained by subtracting a predetermined value, multiplying a result of the subtraction by a leak coefficient, and adding the predetermined value again.
The leaked local decoded image signal is converted to the first
And a third leakage circuit that outputs the predicted value to the first frame memory so as to be stored in the frame memory as a predicted image signal of the next frame, wherein the inter-frame predictive decoder outputs the predetermined value from the reproduced image signal. , And a leakage image obtained by multiplying the result of the subtraction by a leak coefficient and adding the predetermined value again is used to predict the next frame in the second frame memory. A fourth leakage circuit that outputs the signal to the second frame memory to store the signal as a signal.