JP2867807B2 - Video signal encoding / decoding system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal encoding / decoding system, and more particularly to a video signal encoding / decoding system employing an inter-frame difference orthogonal transform coding system which combines inter-frame difference prediction and orthogonal transform. Related to chemical systems.

[0002]

2. Description of the Related Art In a conventional moving picture signal encoding / decoding system of this type, a frame memory in a moving picture signal decoding apparatus is periodically refreshed in order to prevent image quality deterioration on the receiving side due to transmission path errors. Is done. In the case of the inter-frame difference orthogonal transform coding method or the direct conversion inter-frame coding method, since the contents of the frame memory are the transform coefficients after the orthogonal transform, the orthogonal transform is applied to the video signal input to the video signal encoding device. The quantized signal is transmitted as a signal for refreshing, for example, one block line per frame, and the signal refreshes one screen of the frame memory in the moving picture signal decoding apparatus at a constant period. . For example, when encoding is performed in units of two-dimensional blocks of I lines × J pixels, signals for I lines are collectively referred to as one block line.

FIG. 8 is a signal timing diagram illustrating the above-described periodic refresh in a conventional moving picture signal encoding / decoding system. Screen is divided into two-dimensional blocks consisting of a plurality of lines and a plurality of pixels, it is given a block number from the first block B1 to the ^N-th block B ^N along the line. FIG. 8 shows an example in which K blocks are refreshed for each frame from the first frame period T ¹ to the p-th frame T ^P (N = P ·
K). For example, in the first frame period T ¹ , the first block B ¹ to the K-th block ^BK are refreshed, but this refresh is abbreviated as {B ^{1 -K} }. In each frame period, during a period other than the transmission period of the refresh signal, a signal obtained by performing interframe coding including orthogonal transform on the moving image signal is transmitted.

The above-mentioned conventional moving picture signal encoding / decoding system is described in NTT Review Vol. 2, No. 199.
May 2000 [NTT REVIEW VOL. 2, NO.
3, May, 1990] (pp. 110-117), "International Standardization of Video Code for ISDN Video Conferencing and Videophone Services" (Inter.
national Standardization
of Video Codes for ISDN V
videoconferencing and Video
opphoneServices).

[0005]

In the conventional moving picture signal encoding / decoding system described above, the orthogonal transform is applied to the moving picture signal inputted to the moving picture signal encoding apparatus, and all the transform coefficients of the encoded signal are obtained. The components are collectively used as a refresh signal. However, image quality degradation on the receiving side due to a transmission path error is usually caused by a partial error in a transform coefficient. In the conventional video signal encoding / decoding system, components that do not need to be refreshed are collectively refreshed, so that there is a problem that there is much waste. Furthermore, in the conventional moving picture signal encoding / decoding system, refresh is often performed in units of block lines, in which case the ratio of refresh information per frame is high, and the coding efficiency is limited. There is also a problem.

[0006]

According to a first aspect of the present invention, there is provided a moving picture signal encoding apparatus for orthogonally transforming an input moving picture signal for each block composed of a plurality of pixels, Subtraction means for subtracting a first prediction signal from a signal to output a prediction error signal; first quantization means for quantizing the prediction error signal to output a first quantization signal; Adding means for adding a quantized signal and the first prediction signal to output a local decoded signal; and a second means for quantizing the local decoded signal and outputting a second quantized signal.
, A first switch for selectively connecting one of the local decoded signal and the second quantized signal, and a signal selectively connected by the first switch for a predetermined number of frames. A first frame memory that outputs the first prediction signal with a delay, a second switch that selectively connects one of the first and second quantized signals, and a moving picture signal decoding device When the second frame memory is refreshed, the first and second switch means are instructed to selectively connect the second quantized signal, and when the second frame memory is not refreshed, Switching control for instructing the first switch means to selectively connect the local decoded signal and the second switch means to selectively connect the first quantized signal. Switching control means for instructing selective connection so that the block is refreshed for each group consisting of a plurality of transform coefficients and having substantially different frequency domains at the time of the refresh, and the second switch means is selected. A code conversion means for code-converting and transmitting the first and second quantized signals and the switching control signal.

[0007] A first moving picture signal decoding apparatus of the present invention comprises:
Code inverse transform means for inversely transforming the code sequence transmitted from the first video signal encoding device to separate and reproduce the first or second quantized signal and the switching control signal; Adding means for adding a second prediction signal to the first quantized signal reproduced by the conversion means; and the second quantum signal if the switching control signal reproduced by the code inverse conversion means is an instruction at the time of refreshing. A third switching means for selectively connecting the added signal of the adding means if the instruction at the time of non-refreshing, and a signal selected and connected by the third switching means delayed by a predetermined number of frames. The second frame memory, which is output as a second prediction signal, and the signal selectively connected by the third switch means is subjected to inverse transformation with respect to the orthogonal transformation to convert the moving image signal. Comprising the inverse orthogonal transform means for raw.

A first moving picture signal encoding / decoding system according to the present invention comprises the first moving picture signal encoding apparatus and the second moving picture signal encoding apparatus.
And a moving image signal decoding device.

[0009] A second moving picture signal encoding apparatus of the present invention comprises:
Subtraction means for subtracting a first prediction signal from an input video signal to output a prediction error signal; and a motion for detecting a motion vector signal by performing block matching between frames on the video signal A detection circuit, a first orthogonal transform unit for orthogonally transforming the prediction error signal for each block including a plurality of pixels, and a first quantum for quantizing a result of the orthogonal transform and outputting a first quantized signal A first adding means for adding the first quantized signal and the orthogonal transform signal to output a local decoded signal; and a second adding means for quantizing the local decoded signal and outputting a second quantized signal. 2
, A first switch for selectively connecting one of the local decoded signal and the second quantized signal, and a predetermined number of frames for the signal selectively connected by the first switch. A first frame memory that outputs the second predicted signal as a second predicted signal after being delayed by an amount, a first orthogonal inverse transform circuit that returns the second predicted signal from the transform domain to the spatial domain, and the first orthogonal inverse transform A variable delay circuit for giving a delay corresponding to the motion vector signal to the signal returned to the spatial domain by the circuit to generate the first prediction signal;
A second orthogonal transformation circuit that performs orthogonal transformation on the first prediction signal to generate the orthogonal transformation signal, and a second orthogonal connection circuit that selectively connects one of the first quantization signal and the second quantization signal.
When refreshing the second frame memory incorporated in the moving picture signal decoding apparatus, and instructing the first and second switch means to selectively connect the second quantizing means. If the second frame memory is not refreshed, the local decoding signal is sent to the first switch, and the quantized signal of the first quantizer is sent to the second switch. , Respectively, giving a switching control signal instructing to selectively connect,
Switching control means for instructing selective connection so that the block is refreshed for each group of a plurality of transform coefficients and substantially different frequency domains at the time of the refresh, and a quantized signal selectively connected by the second switch; And code conversion means for performing variable-length coding on the motion vector signal and coding and transmitting the motion vector signal and the switching control signal.

A second moving picture signal decoding apparatus according to the present invention comprises:
Code inverse transform means for inversely transforming the code sequence transmitted from the code transform means of the second video signal encoding apparatus to separate and reproduce the quantized signal, the switching control signal, and the moving vector signal; Second adding means for adding a third prediction signal to the reproduced first quantized signal;
The second quantized signal is selectively connected if the reproduced switching control signal is an instruction at the time of refreshing, and the added signal of the adding means is selectively connected if the reproduced switching control signal is an instruction at the time of non-refreshing. Switch means, and the third
A second frame memory for delaying a signal selectively connected by the switch means by a predetermined number of frames, a second orthogonal inverse transform circuit for orthogonally transforming an output signal of the frame memory and returning the signal to a spatial domain, A variable delay circuit for providing a delay corresponding to the reproduced motion vector signal to the signal returned to the spatial domain by the orthogonal inverse transform circuit, and a quadrature transform of the signal delayed by the variable delay circuit A third orthogonal transform circuit for generating a third predicted signal; and a third orthogonal inverse transform circuit for performing an inverse transform on the orthogonal transform on the signal selectively connected by the third switch means to reproduce the moving image signal. And

According to a second moving picture signal encoding / decoding system of the present invention, the second moving picture signal coding apparatus and the second
Of the moving picture signal decoding apparatus.

A third moving picture signal encoding apparatus according to the present invention comprises:
Subtraction means for subtracting a first prediction signal from an input moving image signal to output a prediction error signal; orthogonal transformation means for orthogonally transforming the prediction error signal for each block composed of a plurality of pixels; A first quantization means for quantizing the result of (1) to output a first quantized signal, and a first addition for adding the first quantized signal and the second prediction signal and outputting a local decoded signal Means, and second quantizing means for quantizing the local decoded signal and outputting a second quantized signal;
First switching means for selectively connecting one of the local decoded signal and the second quantized signal, and delaying the signal selectively connected by the first switching means by a predetermined number of frames. A first frame memory that outputs the second prediction signal, a first orthogonal inverse transform unit that performs an inverse transform on the orthogonal transform on the second prediction signal and outputs the result as the first prediction signal, A second switch for selectively connecting one of the first quantized signal and the second quantized signal; and a second switch for refreshing a second frame memory incorporated in the video signal decoding apparatus. Instruct the first and second switch means to selectively connect the second quantization means, and if the second frame memory is not refreshed, the first switch means A switching control signal for instructing the local switching signal to selectively connect the quantized signal of the first quantizing means to the second switching means is provided to the second switching means. Switching control means for instructing selective connection so that refresh is performed for each group of frequency domains substantially different from each other, and the first or second quantized signal selectively connected by the second switch means and the switching. Code conversion means for code-converting and transmitting the control signal.

A third moving picture signal decoding apparatus according to the present invention comprises:
Code inverse transforming means for inversely transforming the code sequence transmitted from the code transforming means of the third video signal encoding apparatus to separate and reproduce the quantized signal and the switching control signal; and Second adding means for adding a third prediction signal to the first quantized signal; and, if the reproduced switching control signal is a refresh instruction, the second quantizing signal is replaced with the reproduced switching signal. If the control signal is a non-refresh instruction, the third switching means for selectively connecting the addition signal of the adding means, and the signal selectively connected by the third switching means are delayed by a predetermined number of frames. And a second frame memory for outputting the predicted signal of the second frame memory, and a second signal for performing an inverse transform of the orthogonal transform on the signal selectively connected by the third switch means to reproduce the moving image signal. Comprising a 交逆 conversion circuit.

According to a third moving picture signal encoding / decoding system of the present invention, the third moving picture signal
Of the moving picture signal decoding apparatus.

In a fourth moving picture signal encoding / decoding system according to the present invention, the first moving picture signal encoding apparatus is a first transmitting section, and the second moving picture signal decoding apparatus is a first transmitting section. A first station as a receiving unit, a second moving image signal encoding device as a second transmitting unit, and a second moving image signal decoding device as a second receiving unit. And a first station.
A moving image signal encoding / decoding system configured to transmit a code sequence from the transmitting unit to the second receiving unit and to transmit a code sequence from the second transmitting unit to the first receiving unit; A defect indicating that, when a transmission path error occurs during transmission from the first station to the second station, correct decoding becomes impossible in the code inverse conversion circuit of the second station. Information is transmitted from the code inverse conversion circuit to the switching control circuit of the second station, and in response to the defect information, the switching control circuit sends a refresh transmission request signal to the first station to the second station. Output to the code conversion circuit of
The code conversion circuit transmits the request signal to the first station, and the code conversion circuit of the first station that has received the refresh transmission request signal converts the signal into the first signal.
To the switching control circuit of the first station, and in response thereto, the switching control circuit outputs the local decoded signal of the first station as a refresh signal to the code conversion circuit of the first station. The code conversion circuit performs a variable length encoding on the local decoded signal for refreshing, and along with a signal obtained by encoding the refresh control signal given from the switching control circuit, passes through a transmission path. The code inversion circuit, which has transmitted to the second station and received the refresh control signal, writes a refresh signal following the signal into the frame memory of the second station.

According to a fifth moving picture signal encoding / decoding system of the present invention, the second moving picture signal encoding apparatus is a first transmitting section, and the second moving picture signal decoding apparatus is a first transmitting section. A first station as a receiving unit, a moving image signal encoding device according to claim 7 as a second transmitting unit, and a moving image signal decoding device according to claim 8 as a second receiving unit. And two stations,
Moving image signal encoding / decoding configured to transmit a code sequence from the first transmission unit to the second reception unit and to transmit a code sequence from the second transmission unit to the first reception unit In the system, when a transmission path error occurs during transmission from the first station to the second station, correct decoding becomes impossible in the code inverse conversion circuit of the second station. Is transmitted from the code inverse conversion circuit to the switching control circuit of the second station, and in response to the defect information, the switching control circuit sends a refresh transmission request signal to the first station to the first station. Output to the code conversion circuit of the second station, the code conversion circuit transmits the request signal to the first station, and the code reverse conversion circuit of the first station receiving the refresh transmission request signal. Transmits this signal before the first station. A switching control circuit for transferring the local decoded signal of the first station as a refresh signal to the code conversion circuit of the first station in response to the transfer to the switching control circuit; The code conversion circuit performs variable length coding on a refresh local decoding signal, and transmits the second station through a transmission path together with a signal obtained by coding the refresh control signal given from the switching control circuit. The code inversion circuit that has received the refresh control signal and transmits the refresh control signal to the frame memory of the second station.

In a sixth moving picture signal encoding / decoding system according to the present invention, the third moving picture signal encoding apparatus is a first transmitting unit, and the third moving picture signal decoding apparatus is a first transmitting section. A first station as a receiving unit, a second moving image signal encoding device as a second transmitting unit, and a third moving image signal decoding device as a second receiving unit. And a first station.
A moving image signal encoding / decoding system configured to transmit a code sequence from the transmitting unit to the second receiving unit and to transmit a code sequence from the second transmitting unit to the first receiving unit; A defect indicating that, when a transmission path error occurs during transmission from the first station to the second station, correct decoding becomes impossible in the code inverse conversion circuit of the second station. Information is transmitted from the code inverse conversion circuit to the switching control circuit of the second station, and in response to the defect information, the switching control circuit sends a refresh transmission request signal to the first station to the second station. Output to the code conversion circuit of
The code conversion circuit transmits the request signal to the first station, and the code conversion circuit of the first station that has received the refresh transmission request signal converts the signal into the first signal.
To the switching control circuit of the first station, and in response thereto, the switching control circuit outputs the local decoded signal of the first station as a refresh signal to the code conversion circuit of the first station. The code conversion circuit performs a variable length encoding on the local decoded signal for refreshing, and along with a signal obtained by encoding the refresh control signal given from the switching control circuit, passes through a transmission path. The code inversion circuit, which has transmitted to the second station and received the refresh control signal, writes a refresh signal following the signal into the frame memory of the second station.

[0018]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a structural diagram illustrating the blocking of the transform coefficients in the first embodiment.

FIG. 3 is a signal timing chart for explaining a periodic refresh in the first embodiment.

FIG. 4 is a block diagram showing a configuration example of the quantization circuit 7 in the first embodiment.

FIG. 5 is a block diagram showing a second embodiment of the present invention, and shows an example in which a method in which motion compensation is introduced in interframe difference orthogonal transform coding is employed.

FIG. 6 is a block diagram showing a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a fourth embodiment of the present invention employing a demand refresh system using a block structure divided into groups as shown in FIG.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. The video signal encoding device includes an orthogonal transform circuit 1;
Subtractor 2, quantization circuit 3, code conversion circuit 4, quantization circuit 7, frame memory 8, switching control circuit 12
And a switch SW1 and a switch SW2.
The video signal decoding apparatus includes a code inverse transform circuit 14, an adder 15, a frame memory 16, a quadrature inverse transform circuit 17
And a switch SW3.

The operation of the moving picture signal coding apparatus will be described.

The orthogonal transformation circuit 1 converts an input moving image signal into a block composed of a plurality of pixels (details will be described later).
The signal obtained by performing the orthogonal transformation is output to the subtractor 2. The subtracter 2 subtracts the prediction signal provided by the frame memory 8 from the signal output from the orthogonal transformation circuit 1 to generate a prediction error signal in the transformation domain, and outputs the signal to the quantization circuit 3. The quantization circuit 3 outputs a quantized signal obtained by quantizing the prediction error signal to the terminal A1 of the switch SW1 and the adder 6. The adder 6 adds the prediction signal from the frame memory 8 and the quantized signal from the quantizing circuit 3 to generate a local decoded signal.
The signal is output to the terminal A2 of W2 and the quantization circuit 7. The quantization circuit 7 converts a quantized signal obtained by quantizing the local decoded signal into a terminal B1 of the switch SW1 and a switch SW2.
To the terminal B2. The frame memory 8 includes a switch SW
The signal selectively connected in step 2 is written, temporarily stored, and read out after the lapse of one frame period to give a delay to generate the prediction signal.

The code conversion circuit 4 performs variable length coding on the quantized signal selectively connected by the switch SW1, and
The switching control signal supplied from the switching control circuit 12 is encoded and transmitted to the moving picture signal decoding device through the transmission path. The switching control circuit 12 generates the switching control signal that instructs the switch SW1 and the switch SW2 to select which of the two input-side terminals is to be connected to the output-side terminal. When the terminals A1 and A2 are selectively connected, the quantized signal of the prediction error signal output from the quantization circuit 3 is transmitted from the code conversion circuit 4 as a code sequence,
On the other hand, when the terminals B1 and B2 are selected, the quantized signal output from the quantization circuit 7 is transmitted from the code conversion circuit 7 as a refresh code sequence.

Next, the operation of the moving picture signal decoding apparatus will be described.

The code inversion circuit 14 decodes and separates the code sequence received from the transmission path, outputs the prediction error signal or the local decoded signal to the adder 15 and the terminal B3 of the switch SW3, and switches the switching control signal to the switch B3. Output to SW3. The switch SW3 is connected to the terminal A in response to the instruction of the switching control signal, similarly to the switches SW1 and SW2 on the transmission side.
3 and one of the terminals B3 are selectively connected. When the terminal A3 is selectively connected, the prediction error signal output from the code inverse transformation circuit 14 is added to the prediction signal by the adder 15, and then returned to the spatial domain by the orthogonal inverse transformation circuit 17 to reproduce the moving image signal. Is done. The addition result of the adder 15 is temporarily stored in the frame memory 16, read out after one frame period, given a delay, and sent to the adder 15 as a reproduced prediction signal. On the other hand, when the terminal B3 is selectively connected,
The refresh local decoding signal output from the code inverse conversion circuit 14 is written into the frame memory 16 and refresh is performed.

FIG. 2 is a structural diagram illustrating the blocking of the transform coefficients in the first embodiment, and FIG. 3 is a signal timing diagram for explaining the periodic refresh in the first embodiment. .

Referring to FIG. 2, one frame of frame F
Is divided into a two-dimensional block consisting of 8 lines × 8 pixels, and block numbers are sequentially assigned to the first block B ¹ to the N-th block B ^N in the line direction. Each block (for example, the i-th block B ⁱ ) is a two-dimensional block of 8 lines × 8 pixels, and extends from the lower left corner of the lower sequence to the lower right corner of the higher sequence to form a first group G.
It is divided into the first to seventh groups G7. The refresh is performed in the first frame period T as illustrated in FIG.
Between 1 and the m-th frame period T ^m, it is carried out block by block minute L groups for each frame period (N =
Lm). For example, the first frame T ^1, although the first group G ¹ of the first block B ¹ to the L block B ^L are refreshed, which was abbreviated as ^{{G 1 (1) ~1 (} L)} Shown. In each frame period, a signal obtained by encoding the prediction error signal is transmitted during periods other than the transmission period of the refresh signal.

FIG. 4 is a block diagram showing a configuration example of the quantization circuit 7 in the first embodiment. The quantization circuit 7
It is provided to quantize the locally decoded signal so as to match the input value acceptable by the code conversion circuit 4 when transmitting the refresh signal. The local decoded signal given from the adder 6 is
The distribution circuit 70 is distributed to the quantizer 71 to 77 for each group from the first group G ¹ to the seventh group G ^7. Normally, the image quality deterioration due to the quantization error is large in the lower sequence, so that the quantization step of the quantizer 71 is the finest, and the quantizers 72, 73, 74, 75,
In the order of 76 and 77, the closer to the quantizer 77, the coarser the quantization step. The selection circuit 78 receives a switching control signal indicating a group number to be refreshed from the switching control circuit 12, selects a quantized output for the group, and outputs it to the terminal B1 of the switch SW1 and the terminal B2 of the switch SW2.

In the first embodiment described above, (1) Since the local decoded signal is transmitted as the refresh signal, there is no difference in the reception image quality between the refreshed portion and the remaining portion. (2) The block of variable coefficients is further divided into a plurality of groups and the refresh signal is transmitted, so that the time required for refreshing the entire screen becomes longer than before.
Therefore, the amount of information for refresh per unit time is reduced as compared with the conventional case, and the coding efficiency is improved. The first embodiment is a case where each group is refreshed at an equal frequency. However, the refresh frequency of a high-sequence group having little effect on image quality is made lower than that of a low-sequence group. Further, the coding efficiency can be improved.

FIG. 5 is a block diagram showing a second embodiment of the present invention, and shows an example in which a method in which motion compensation is introduced into interframe difference orthogonal transform coding is employed.

The moving picture signal encoding apparatus comprises an orthogonal transform circuit 1
, A subtractor 2, a quantization circuit 3, and a code conversion circuit 4A
A motion detection circuit 5, an adder 6, a quantization circuit 7,
It includes a frame memory 8, an orthogonal inverse transform circuit 9, a variable delay circuit 10, an orthogonal transform circuit 11, and a switching control circuit 12. The video signal decoding apparatus includes a code inverse conversion circuit 1
4A, adder 15, switch SW3, frame memory 16, orthogonal inverse transform circuit 17, variable delay circuit 18
And an orthogonal transform circuit 19 and an orthogonal inverse transform circuit 20.

The operation of the moving picture signal coding apparatus will be described.

A motion detection circuit 5 to which a moving image signal is input
Detects a motion vector signal by block matching between frames. The motion vector signal is transmitted to the code conversion circuit 4
A and output to the variable delay circuit 10. On the other hand, the subtracter 2 outputs to the orthogonal transform circuit 1 a prediction error signal obtained by subtracting a prediction signal output from the variable delay circuit 10 to the other input terminal from a moving image signal supplied to one input terminal. I do. The orthogonal transformation circuit 1 performs an orthogonal transformation on the prediction error signal for each block composed of a plurality of pixels, and outputs the result to the quantization circuit 3. The quantization circuit 3 quantizes the transform coefficient obtained by the orthogonal transform and outputs the quantized transform coefficient to the terminal A1 of the switch SW1 and the adder 6.

The adder 6 adds the signal orthogonally transformed by the orthogonal transformation circuit 11 and the quantized signal output from the quantization circuit 3 to generate a local decoded signal. To the terminal A2 and the quantization circuit 7. The quantization circuit 7 quantizes the local decoded signal, and outputs a signal to a terminal B1 of the switch SW1 and a terminal B2 of the switch SW2.
Output to The frame memory 8 writes and temporarily stores a signal selectively connected by the switch SW2, gives a delay by reading it after one frame period has elapsed, outputs a prediction signal to the orthogonal inverse transform circuit 9, and outputs the predicted signal to the orthogonal inverse transform circuit 9. Returns this prediction signal from the transform domain to the spatial domain. The variable delay circuit 10 subtracts a prediction signal obtained by giving a delay corresponding to a motion vector to an output signal from the orthogonal inverse transformation circuit 9 to the subtracter 2.
And the orthogonal transformation circuit 11. Orthogonal transform circuit 11
Performs orthogonal transform on the prediction signal and outputs the result to the adder 6.

The code conversion circuit 4 A performs variable length coding on the quantized signal selectively connected by the switch SW 1, and converts the motion vector signal supplied from the motion detection circuit 5 and the switching control signal supplied from the switching control circuit 12. The data is encoded and transmitted to the video signal decoding device through the transmission path. The switching control circuit 12 outputs a switching control signal indicating which of the terminals A1 and A2 and the terminals B1 and B2 of the switches SW1 and SW2 is to be selectively connected. When the terminals A1 and A2 are selectively connected, the quantized signal of the prediction error transform coefficient output from the quantizing circuit 3 is coded and transmitted from the code converting circuit 4A, and the local decoded signal is not quantized and is directly stored in the frame memory. 8 is output.
On the other hand, when the terminals B1 and B2 are selectively connected, the quantization circuit 7
, The quantized signal of the local decoded signal is coded and transmitted from the code conversion circuit 4A for refreshing, and is also output to the frame memory 8.

Next, the operation of the moving picture signal decoding apparatus will be described.

The code sequence received from the transmission path is decoded and separated by the code inverse conversion circuit 14A, and the prediction error conversion coefficient or the local error signal is added to the adder 15 and the terminal B3 of the switch SW3.
At this time, the switching control signal is output to the switch SW3 and the motion vector signal is output to the variable delay circuit 18, respectively. The switch SW3 selectively connects one of the terminal A3 and the terminal B3 according to the instruction of the switching control signal, similarly to the switch SW1 and the switch SW2 of the moving picture signal encoding device. When the terminal B3 is selectively connected, the sign inversion circuit 1
4A, a prediction error transform coefficient is output, and a predictive decoded signal obtained as a result of adding the predictive transform coefficient to the predictive error transform coefficient by the adder 15 is returned to the spatial domain by the orthogonal inverse transform circuit 20 to be converted into a moving image signal Will be played as Adder 1
5 is temporarily stored in the frame memory 16,
A delay is given by reading out after one frame period, the signal is returned to the spatial domain by the orthogonal inverse transform circuit 17, a delay corresponding to the motion vector is given by the variable delay circuit 18, and further a prediction transform coefficient is given by the orthogonal transform circuit 19. Are fed back to the adder 15. On the other hand, when the terminal B3 is selectively connected, a local decoding signal for refresh is output from the code inverse conversion circuit 14A and is directly written into the frame memory 16 to perform refresh.

The operations of blocking the transform coefficients and performing the periodic refresh in the second embodiment are the same as those in the first embodiment described with reference to FIGS.

FIG. 6 is a block diagram showing a third embodiment of the present invention.

The third embodiment is configured by removing functions related to motion compensation from the second embodiment.
With this configuration, the same effect as in the second embodiment can be obtained.

FIG. 7 is a block diagram showing a configuration of a fourth embodiment of the present invention employing a demand refresh method using a block structure divided into groups as shown in FIG. In this embodiment, a code sequence is transmitted and received between the station 100 and the station 200. In the moving picture signal coding apparatus of the station 100, the moving picture signal is subjected to orthogonal transform and inter-frame coding by the coding circuit 101, and the code conversion circuit 10
Reference numeral 2 denotes a code inverse transform circuit 2 of the moving picture signal decoding device of the station 200, which performs a variable length coding on the quantized signal output from the coding circuit 101 to form a code sequence.
04. The code inverse transform circuit 204 decodes the code sequence, reproduces a signal subjected to the orthogonal transform and the inter-frame encoding, and decodes the signal into the composite circuit 20
Reference numeral 5 reproduces a moving image signal.

Refresh is not performed unless a transmission path error occurs during transmission of this code sequence. For example, if a transmission path error occurs during transmission from the station 100 to the station 200, correct decoding becomes impossible in the code inverse conversion circuit 204, and the defect information indicating the error is transmitted to the code inverse conversion circuit 204. Is transmitted to the switching control circuit 203. In response to the defect information, the switching control circuit 203 outputs a refresh transmission request signal for the station 100 to the code conversion circuit 202, and the code conversion circuit 202 transmits the request signal to the station 100. The code inverse conversion circuit 104 that has received the refresh transmission request signal converts the signal into the switching control circuit 1
Transfer to 03. In response, the switching control circuit 103
A refresh control signal for outputting the local decoded signal of the encoding circuit 101 to the code conversion circuit 102 as a refresh signal is output. The code conversion circuit 102 performs variable-length coding on the refresh local decoding signal, and transmits the refresh control signal supplied from the switching control circuit 103 to the station 200 through the transmission path together with the coded signal. The code inverse conversion circuit 204 that has received the refresh control signal writes a refresh signal following the signal into the frame memory of the decoding circuit 205,
It controls the decoding circuit 205.

As described above, the frame memory of the decoding circuit 205 is refreshed only when decoding cannot be correctly performed by the code inverse conversion circuit 204 by the cycle of the demand refresh operation. As shown in FIG. Each block of F is further divided into groups G1 to G7, and both the number of the group including the transform coefficient that cannot be decoded and the number of the block are transmitted from the code inverse conversion circuit 204 together with the defect information to the switching control circuit 203 and the code. An instruction is given to the switching control circuit 103 via the conversion circuit 202 and the sign inverse conversion circuit 104, and a refresh signal is transmitted only to the block and group portions that have received the instruction. Therefore, the time occupied by the refresh transmission is very short. When decoding cannot be performed correctly by the code inverse conversion circuit 204, the output value of the code inverse conversion circuit 204 of the group of the block or the decoding circuit 205
By fixing the transform coefficient of the group of the block decoded in step (1) to a predetermined value (for example, 0), the deterioration of the reproduction image quality can be reduced as compared with the case where the decoding circuit 205 decodes the erroneous prediction error signal. Can be suppressed.

The encoding circuits 101 and 201 are shown in FIG. 2 by an orthogonal transformation circuit 1, a subtractor 2, a quantization circuit 3, a code conversion circuit 4, a quantization circuit 7, a frame memory 8, switches SW1, and switches SW2. It is configured as follows.
The code conversion circuits 102 and 202 have the same contents as the code conversion circuit 4 shown in FIG.
3 has the same contents as the switching control circuit 12 shown in FIG. The decoding circuits 105 and 205 include an adder 15, a frame memory 16, an orthogonal inverse transformation circuit 17, and a switch S
It is configured as shown in FIG. 1 by W3. The sign inversion circuits 104 and 204 have the same contents as the sign inversion circuit 14 shown in FIG.

On the other hand, when the motion compensation is combined with the interframe difference orthogonal transform coding method, the coding circuit 10
Reference numerals 1 and 201 denote an orthogonal transformation circuit 1, a subtractor 2, a quantization circuit 3, a code conversion circuit 4, a motion compensation circuit 5, an adder 6, a quantization circuit 7, a frame memory 8, an orthogonal inverse transformation circuit 9, and a variable delay. The circuit 10, the quantization circuit 11, the switch SW1, and the switch SW2 are configured as shown in FIG.
The decoding circuits 105 and 205 are configured as shown in FIG. 5 by the adder 15, the frame memory 16, the orthogonal inverse transform circuit 17, the variable delay circuit 18, the orthogonal transform circuit 19, and the switch SW3.

[0052]

As described above, according to the present invention, the local decoded signal in the transform domain is refresh-transmitted for each component, and the minimum necessary refresh frequency is guaranteed especially for components in which image quality degradation is conspicuous. Accordingly, a refresh effect equivalent to that of the related art can be obtained with less refresh information than that of the related art.

Further, when the demand refresh method is employed, only the components of the group in which an error has occurred in the block in which the error has occurred need be sent as refresh information, and the overall coding efficiency is greatly improved. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a structural diagram illustrating the blocking of transform coefficients according to the first embodiment of the present invention.

FIG. 3 is a signal timing chart for explaining a periodic refresh in the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration example of a quantization circuit 7 according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating a second embodiment of the present invention, illustrating an example in which a method in which motion compensation is introduced is used for inter-frame differential orthogonal transform coding.

FIG. 6 is a configuration diagram showing a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a fourth embodiment of the present invention employing a demand refresh system using a block structure divided into groups as shown in FIG.

FIG. 8 is a signal timing diagram illustrating the above-described periodic refresh in a conventional video signal encoding / decoding system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Orthogonal transformation means 2 Subtraction means 3 Quantization means 4 Code conversion means 5 Motion detection circuit 6 Addition means 7 Quantization means 8 Frame memory 9 Orthogonal inverse transformation circuit 10 Variable delay circuit 11 Orthogonal transformation circuit 12 Switching control means 14, 14A code Inverting means 15 Adding means 16 Frame memory 17 Orthogonal inverse transform means 18 Variable delay circuit 19 Orthogonal transform circuit SW1, SW2, SW3 Switching means 100, 200 station 102 Code conversion circuit 103 Switching control circuit 104 Code inverse conversion circuit 202 Code conversion circuit 203 Switching control circuit 204 Sign reverse conversion circuit

Claims (30)

(57) [Claims] 1. An orthogonal transformation means for orthogonally transforming an input moving image signal for each block composed of a plurality of pixels, and a subtraction for subtracting a first prediction signal from the orthogonally transformed signal to output a prediction error signal. Means, a first quantization means for quantizing the prediction error signal to output a first quantized signal, and a local decoded signal by adding the first quantized signal and the first predicted signal. Adding means for outputting; second quantizing means for quantizing the local decoded signal to output a second quantized signal; and selectively connecting one of the local decoded signal and the second quantized signal. A first switch unit, a first frame memory that delays a signal selectively connected by the first switch unit by a predetermined number of frames and outputs the delayed signal as the first prediction signal, Quantized signal of And a second switch means for selectively connecting one of the first and second switch means, and a second frame memory incorporated in the moving picture signal decoding device, when refreshing the second frame memory, the second quantum means with respect to the first and second switch means. When the second frame memory is not refreshed, the local decoding signal is sent to the first switch means, and the first decoded signal is sent to the second switch means. A switching control signal for instructing the quantization signal to be selectively connected is provided, and the selective connection is instructed so that the block is refreshed for each group including a plurality of transform coefficients and having substantially different frequency domains from each other during the refresh. Switching control means; and the first and second switches selected by the second switch means.
And a code conversion means for code-converting and transmitting the quantized signal and the switching control signal. 2. An orthogonal transformation means for orthogonally transforming an input moving image signal for each block composed of a plurality of pixels, and a subtraction for subtracting a first prediction signal from the orthogonally transformed signal to output a prediction error signal. Means for quantizing the prediction error signal and outputting a first quantized signal;
Adding means for adding the first quantized signal and the first prediction signal to output a locally decoded signal; and second quantizing for quantizing the locally decoded signal and outputting a second quantized signal. Means, first switching means for selectively connecting one of the local decoded signal and the second quantized signal, and delaying the signal selectively connected by the first switching means by a predetermined number of frames. A first frame memory for outputting as the first prediction signal;
A second switch means for selectively connecting one of the quantized signals, and a second frame memory incorporated in the moving picture signal decoding apparatus, for refreshing the first frame memory. When the second frame memory is not refreshed, the local decoding signal is sent to the first switch means, and the second decoded signal is sent to the second switch means. A switching control signal for instructing the first quantized signal to be selectively connected is provided, and the block is selected so as to be refreshed for each group of a plurality of transform coefficients and substantially different frequency domains from each other during the refresh. Switching control means for instructing connection, the first and second quantization signals selected by the second switching means, and the switching control signal. Code conversion means for performing code conversion for transmitting the first or second quantized signal and the switching control signal by performing code inverse conversion on a code sequence transmitted from a video signal coding apparatus having Code inverting means for adding, a adding means for adding a second prediction signal to the first quantized signal reproduced by the code inverting means, and a switching control signal reproduced by the code inverting means being refreshed. If the instruction of the time, the second quantized signal,
A third switch for selectively connecting the added signal of the adding means if the instruction is for non-refreshing; and a second predictor for delaying the signal selectively connected by the third switch by a predetermined number of frames. The second frame memory for outputting as a signal;
A video signal decoding apparatus comprising: an inverse orthogonal transform unit for performing an inverse transform on the orthogonal transform to the signal selectively connected by the switch unit to reproduce the video signal. 3. A moving picture signal coding / decoding system comprising the moving picture signal coding apparatus according to claim 1 and the moving picture signal decoding apparatus according to claim 2. 4. The moving picture signal encoding / decoding system according to claim 3, wherein said blocks are composed of said groups divided according to the order of a sequence. 5. The video signal encoding / decoding system according to claim 3, wherein a refresh frequency is set for each group. 6. The moving picture signal encoding / decoding system according to claim 4, wherein a relatively high refresh frequency is set to said group having a lower sequence. 7. A subtraction means for subtracting a first prediction signal from an input moving image signal to output a prediction error signal, and performing a block matching between frames on the moving image signal to obtain a moving vector A motion detection circuit for detecting a signal; first orthogonal transform means for orthogonally transforming the prediction error signal for each block composed of a plurality of pixels; and quantizing a result of the orthogonal transform to output a first quantized signal. A first quantizing means for adding the first quantized signal and the orthogonal transform signal to output a locally decoded signal; and a second quantizing means for quantizing the locally decoded signal. A second quantizer for outputting a signal; a first switch for selectively connecting one of the local decoded signal and the second quantized signal; a signal selectively connected to the first switch Clear A first frame memory for outputting a second predictive signal by delaying the number of frames determined because, first returning to the spatial domain to the second prediction signal from the transform domain
An orthogonal inverse transform circuit; a variable delay circuit that gives the signal returned to the spatial domain by the first orthogonal inverse transform circuit a delay corresponding to the motion vector signal to generate the first prediction signal; A second orthogonal transformation circuit that performs orthogonal transformation on the first prediction signal to generate the orthogonal transformation signal, and a second switch that selectively connects one of the first quantization signal and the second quantization signal. Means for instructing the first and second switch means to selectively connect the second quantization means when refreshing a second frame memory incorporated in the video signal decoding apparatus; When the second frame memory is not refreshed, the local decoding signal is sent to the first switch means, and the quantized signal of the first quantization means is sent to the second switch means. Yes A switching control signal for instructing selective connection to perform selective connection, and a switching control means for instructing selective connection so as to refresh the block at the time of refreshing, for each group of a plurality of transform coefficients and frequency domains substantially different from each other; A moving picture signal coding apparatus, comprising: code conversion means for performing variable length coding on a quantized signal selectively connected by the second switch, and coding and transmitting the moving vector signal and the switching control signal. 8. A subtraction means for subtracting a first prediction signal from an input moving image signal to output a prediction error signal, and a moving vector by performing block matching between frames on the moving image signal. A motion detection circuit for detecting a signal, first orthogonal transform means for orthogonally transforming the prediction error signal for each block composed of a plurality of pixels, and quantizing a result of the orthogonal transform to output a first quantized signal A first quantizing means for adding the first quantized signal and the orthogonal transform signal to output a locally decoded signal; and a second quantizing means for quantizing the locally decoded signal. A second quantizer for outputting a signal; a first switch for selectively connecting one of the local decoded signal and the second quantized signal; a signal selectively connected to the first switch Set in advance First frame memory for outputting a second predictive signal delayed by a few minutes frames,
A first method of returning the second prediction signal from the transform domain to the spatial domain;
An orthogonal inverse transform circuit, and a variable delay circuit that applies a delay corresponding to the motion vector signal to the signal returned to the space domain by the first orthogonal inverse transform circuit to generate the first prediction signal, A second orthogonal transform circuit that performs orthogonal transform on the first prediction signal to generate the orthogonal transform signal, and a second switch that selectively connects one of the first quantized signal and the second quantized signal Means for instructing the first and second switch means to selectively connect the second quantization means when refreshing a second frame memory incorporated in the moving picture signal decoding apparatus; If the second frame memory is not refreshed, the first
The local decoded signal to the second switch means.
A switching control signal for instructing the switching means to selectively connect the quantized signals of the first quantizing means, respectively. The block is made up of a plurality of transform coefficients at the time of the refresh, and the frequency domain is mutually different. Switching control means for instructing selective connection so as to be refreshed for each substantially different group; and performing variable length coding on the quantized signal selectively connected by the second switch, and converting the moving vector signal and the switching control signal to each other. And performing code inverse conversion on the code sequence transmitted from the code conversion means of the video signal coding apparatus having a code conversion means for coding and transmitting the quantized signal, the switching control signal, and the motion vector signal. Code inversion means for separating and reproducing; second adding means for adding a third prediction signal to the reproduced first quantized signal; A third switch for selectively connecting the second quantized signal if the switching control signal is an instruction at the time of refreshing, and an addition signal of the adding means if the reproduced switching control signal is an instruction for non-refreshing; A second frame memory for delaying a signal selectively connected by the third switch means by a predetermined number of frames; and a second orthogonal inverse that orthogonally transforms an output signal of the frame memory and returns the signal to a spatial domain. A conversion circuit, a variable delay circuit for providing a delay corresponding to the reproduced motion vector signal to the signal returned to the spatial domain by the orthogonal inverse conversion circuit, and a signal delayed by the variable delay circuit. A third orthogonal transformation circuit for converting the signal to generate the third prediction signal; Moving image signal decoding apparatus having a third inverse orthogonal transform circuit for reproducing the moving image signal by performing conversion. 9. A moving picture signal encoding / decoding system comprising the moving picture signal encoding apparatus according to claim 8 and the moving picture signal decoding apparatus according to claim 9. 10. The moving picture signal encoding / decoding system according to claim 9, wherein said blocks are composed of said groups divided according to a high-low sequence of a sequence. 11. The moving picture signal encoding / decoding system according to claim 9, wherein a refresh frequency is set for each of said groups. 12. The moving picture signal encoding / decoding system according to claim 10, wherein a relatively high refresh frequency is set to the group having a lower sequence. 13. A subtraction means for subtracting a first prediction signal from an input moving image signal to output a prediction error signal, and an orthogonal transformation means for orthogonally transforming the prediction error signal for each block including a plurality of pixels. A first quantizing means for quantizing a result of the orthogonal transformation to output a first quantized signal; and adding a first quantized signal and a second prediction signal to output a local decoded signal. A first adder that performs quantization, a second quantizer that quantizes the local decoded signal and outputs a second quantized signal, and outputs one of the local decoded signal and the second quantized signal. A first switch for selectively connecting, a first frame memory for delaying a signal selectively connected by the first switch by a predetermined number of frames and outputting the delayed signal as the second prediction signal; 2 prediction signals A first orthogonal inverse transform unit that performs an inverse transform on the orthogonal transform and outputs the result as the first prediction signal; and a second selectively connects one of the first quantized signal and the second quantized signal. When refreshing a second frame memory incorporated in the moving picture signal decoding apparatus, the switch means instructs the first and second switch means to selectively connect the second quantization means. When the second frame memory is not refreshed, the local decoding signal for the first switch means, the quantized signal of the first quantization means for the second switch means, A switching control signal for instructing selective connection is provided, and the block is refreshed for each group of a plurality of transform coefficients and substantially different frequency domains from each other during the refresh. The switching control means for instructing the selected connection to Gerhard, the second switch means has selected connection 1 or 2
And a code conversion means for code-converting and transmitting the quantized signal and the switching control signal. 14. A subtraction means for subtracting a first prediction signal from an input video signal and outputting a prediction error signal, and an orthogonal transformation means for orthogonally transforming the prediction error signal for each block composed of a plurality of pixels. First quantizing means for quantizing a result of the orthogonal transform and outputting a first quantized signal;
A first adding unit that adds the first quantized signal and the second prediction signal to output a locally decoded signal; and a second that quantizes the local decoded signal and outputs a second quantized signal. Quantizing means, first switch means for selectively connecting one of the local decoded signal and the second quantized signal,
A first frame memory for delaying the signal selectively connected by the first switch means by a predetermined number of frames and outputting the second predicted signal as the second predicted signal; First orthogonal inverse transform means for performing an inverse transform and outputting the result as the first predicted signal, second switch means for selectively connecting one of the first quantized signal and the second quantized signal, When refreshing a second frame memory incorporated in the moving picture signal decoding apparatus, instructing the first and second switch means to selectively connect the second quantization means;
When the second frame memory is not refreshed, the local decoding signal is sent to the first switch means, and the quantized signal of the first quantization means is sent to the second switch means. A switching control signal for instructing a selective connection, and a switching control means for instructing a selective connection so as to refresh the block at the time of refreshing, for each group of a plurality of transform coefficients and substantially different frequency domains, A code conversion means for code-converting and transmitting the first or second quantized signal and the switching control signal selectively connected by the second switch means and transmitting the signal. Code inverse transforming means for inversely transforming the encoded code sequence to separate and reproduce the quantized signal and the switching control signal; and Second adding means for adding a third prediction signal to the first quantized signal; and, if the reproduced switching control signal is an instruction at the time of refreshing, the second quantizing signal is replaced with the reproduced switching signal. If the control signal is a non-refresh instruction, a third switch for selectively connecting the addition signal of the adding means; and a third switch for delaying the signal selectively connected by the third switch by a predetermined number of frames. A second orthogonal memory for outputting the predicted signal of the second frame memory; and a second orthogonal inverse transform circuit for performing an inverse transform on the orthogonal transform on the signal selectively connected by the third switch means to reproduce the moving image signal. A video signal decoding device comprising: 15. A moving picture signal encoding / decoding system comprising the moving picture signal encoding apparatus according to claim 11 and the moving picture signal decoding apparatus according to claim 12. 16. The block according to claim 15, wherein the block is composed of the groups divided according to a high-low sequence.
The moving picture signal encoding / decoding system according to Claim 1. 17. The moving picture signal encoding / decoding system according to claim 15, wherein a refresh frequency is set for each of said groups. 18. The moving picture signal encoding / decoding system according to claim 16, wherein a relatively high refresh frequency is set to the group having a lower sequence. 19. A first station, wherein the video signal encoding device according to claim 1 is a first transmitting unit, and the video signal decoding device according to claim 2 is a first receiving unit. A second station that uses the moving picture signal encoding device according to claim 1 as a second transmitting unit and the moving picture signal decoding device according to claim 2 as a second receiving unit; A moving image signal encoding / decoding system configured to transmit a code sequence from a transmission unit to the second reception unit and to transmit a code sequence from the second transmission unit to the first reception unit; Failure information indicating that, when a transmission path error occurs during transmission from the first station to the second station, correct decoding becomes impossible in the code inverse conversion circuit of the second station. Is transmitted from the code inverse conversion circuit to the switching control circuit of the second station. The switching control circuit outputs a refresh transmission request signal for the first station to the code conversion circuit of the second station, and the code conversion circuit transmits the request signal to the first station;
The code inverse conversion circuit of the first station that has received the refresh transmission request signal transfers the signal to the switching control circuit of the first station, and accordingly, the switching control circuit A refresh control signal for outputting the local decoded signal of one station as a refresh signal to the code conversion circuit of the first station is output. The code conversion circuit converts the local decoded signal for refresh into a variable-length local decoded signal. After performing the encoding, the refresh control signal given from the switching control circuit is transmitted to the second station through a transmission path together with the encoded signal, and the code inverse conversion circuit that receives the refresh control signal outputs the signal. A moving picture signal encoding / decoding system for writing a refresh signal subsequent to the video signal to the frame memory of the second station. 20. A first station, wherein the moving picture signal encoding device according to claim 7 is a first transmitting unit, and the moving picture signal decoding device according to claim 8 is a first receiving unit. A second station that uses the moving picture signal encoding device according to claim 7 as a second transmitting unit and the moving picture signal decoding device according to claim 8 as a second receiving unit; A moving image signal encoding / decoding system configured to transmit a code sequence from a transmission unit to the second reception unit and to transmit a code sequence from the second transmission unit to the first reception unit; Failure information indicating that, when a transmission path error occurs during transmission from the first station to the second station, correct decoding becomes impossible in the code inverse conversion circuit of the second station. Is transmitted from the code inverse conversion circuit to the switching control circuit of the second station. The switching control circuit outputs a refresh transmission request signal for the first station to the code conversion circuit of the second station, and the code conversion circuit transmits the request signal to the first station;
The code inverse conversion circuit of the first station that has received the refresh transmission request signal transfers the signal to the switching control circuit of the first station, and accordingly, the switching control circuit A refresh control signal for outputting the local decoded signal of one station as a refresh signal to the code conversion circuit of the first station is output. The code conversion circuit converts the local decoded signal for refresh into a variable-length local decoded signal. After performing the encoding, the refresh control signal given from the switching control circuit is transmitted to the second station through a transmission path together with the encoded signal, and the code inverse conversion circuit that receives the refresh control signal outputs the signal. A moving picture signal encoding / decoding system for writing a refresh signal subsequent to the video signal to the frame memory of the second station. 21. A first station, wherein the video signal encoding device according to claim 13 is a first transmitting unit, and the video signal decoding device according to claim 14 is a first receiving unit. A second station that uses the moving picture signal encoding device according to claim 13 as a second transmitting unit, and the moving picture signal decoding device according to claim 14 as a second receiving unit; A moving image signal encoding / decoding system configured to transmit a code sequence from a transmission unit to the second reception unit and to transmit a code sequence from the second transmission unit to the first reception unit; Failure information indicating that, when a transmission path error occurs during transmission from the first station to the second station, correct decoding becomes impossible in the code inverse conversion circuit of the second station. Is transmitted from the code inverse conversion circuit to the switching control circuit of the second station. The switching control circuit outputs a refresh transmission request signal for the first station to the code conversion circuit of the second station, and the code conversion circuit sends the request signal to the first station. Send,
The code inverse conversion circuit of the first station that has received the refresh transmission request signal transfers the signal to the switching control circuit of the first station, and accordingly, the switching control circuit A refresh control signal for outputting the local decoded signal of one station as a refresh signal to the code conversion circuit of the first station is output. The code conversion circuit converts the local decoded signal for refresh into a variable-length local decoded signal. After performing the encoding, the refresh control signal given from the switching control circuit is transmitted to the second station through a transmission path together with the encoded signal, and the code inverse conversion circuit that receives the refresh control signal outputs the signal. A moving picture signal encoding / decoding system for writing a refresh signal subsequent to the video signal to the frame memory of the second station. 22. The block according to claim 19, wherein the block is composed of the groups divided according to a high-low sequence.
The moving picture signal encoding / decoding system according to Claim 1. 23. The video signal encoding / decoding system according to claim 19, wherein a refresh frequency is set for each of said groups. 24. The moving picture signal encoding / decoding system according to claim 22, wherein a relatively high refresh frequency is set to the group having a lower sequence. 25. The block according to claim 20, wherein the blocks comprise the groups divided according to a high-low order of a sequence.
The moving picture signal encoding / decoding system according to Claim 1. 26. The moving picture signal encoding / decoding system according to claim 20, wherein a refresh frequency is set for each group. 27. The moving picture signal encoding / decoding system according to claim 24, wherein a relatively high refresh frequency is set to the group having a lower sequence. 28. The block according to claim 21, wherein the blocks are composed of the groups divided according to a high-low sequence.
The moving picture signal encoding / decoding system according to Claim 1. 29. The moving picture signal encoding / decoding system according to claim 21, wherein a refresh frequency is set for each of said groups. 30. The moving picture signal encoding / decoding system according to claim 28, wherein a relatively high refresh frequency is set for the group having a lower sequence.