JP2002354488A - Moving picture transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moving picture transmission device in which motion compensation is made to be more highly precise by appropriately selecting a candidate of motion compensation prediction to be applied to a block unable to be decoded due to discarded cells or transmission errors from among blocks corresponding to the blocks adjacent to this block. SOLUTION: The device for encoding/decoding a moving picture signal block by block is provided with the following on its transmission side: a means for detecting errors in reception encoded data to output a detected signal, a means for identifying a block to be unable to be decoded on the basis of the detected signal, a means for motion compensation predicting pixel values in the vicinity of block able to be decoded according to each of the motion vectors and a motion compensation method of a plurality of block able to be decoded in the vicinity of the block, a means for calculating respective motion compensation prediction error values of the predicted result, a means for selecting the vector to be applied to the block unable to be decoded from among the plurality of motion vectors on the basis of the error value, and a means for correcting the block able to be decoded by motion compensation using the selected motion vector, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving picture transmitting apparatus for transmitting a moving picture signal, and more particularly to a moving picture transmitting / receiving apparatus which performs coding / decoding using motion compensation prediction in block units.

[0002]

2. Description of the Related Art When an image signal is packed in a packet such as a cell in an ATM network and transmitted, when a cell is discarded, a part of the image signal cannot be decoded until the synchronization of variable-length decoding is restored. Large deterioration occurs. Similarly, if an error occurs in the bit stream on the transmission path, decoding becomes impossible until synchronization is restored. Therefore, as an error compensation method for reducing image quality deterioration due to cell discard or transmission path error, a method of replacing a block that cannot be decoded on the receiving side with a decoded image signal has been studied. In the following description, a case where a cell is discarded will be described, but the same can be said for a case where a transmission path error occurs.

In general, a cell discard compensation technique in a moving picture decoding apparatus using motion compensation prediction replaces an image signal lost by cell discard with an image signal stored in a frame memory (or a field memory). (Called concealment).

An example of a conventional cell loss compensation method will be described with reference to FIG. The image signal of the block A in the coded image, which cannot be decoded due to cell discard, is concealed using the motion vector of a block (for example, block B) adjacent to the block A and which can be decoded. In particular,
Concealment is performed by performing motion compensation prediction on the image signal of block A ′ in the reference image indicated by the motion vector of block B with respect to block A. That is, since the correlation between motion vectors between adjacent blocks is generally high,
A block A that cannot be decoded due to cell discarding is subjected to motion compensation prediction using a motion vector of a block B adjacent to the block A, so that image quality deterioration is reduced.

[0005] For example, in the 1992 Image Coding Symposium (PCSJ92), 6-1 "ATM Image Coding System Having Cell Loss Tolerance", as shown in FIG. (Maximum of eight) are set for motion vectors, weighted majority values of motion vectors are obtained independently in the horizontal and vertical directions, and concealment is performed by motion compensation prediction using the largest number of motion vectors. Here, the weight used for the majority decision is set so that a motion vector closer to the block A is more easily selected as shown in FIG. If the correlation between the motion vectors is too low to make a sufficient majority decision, the majority of motion vectors are re-determined by increasing the number of motion vector candidates as shown in FIG. In this case, for example, even if the correlation of the motion vectors between the blocks 1 to 8 adjacent around the block A is low, if the correlation of the motion vectors between the blocks 9, 11, and 12 is high, the block A is the block 9, The concealment is performed using any one of the motion vectors 11 and 12. However, since the correlation between the motion vector of the block A and the motion vector of the blocks 9, 11, and 12 is not always high, if there is no correlation between the motion vectors of the adjacent blocks, It is difficult to select a motion vector used for highly reliable concealment by using only the value. Further, when there are a plurality of motion compensation prediction modes (for example, MP
In EG, there are forward, backward and bidirectional predictions. Reference: Hiroshi Yasuda, "International Standard for Multimedia Coding," Maruzen)
In this case, since the degree of freedom of the motion compensation prediction is increased, it is difficult to select one candidate from the eight motion compensation prediction candidates by majority decision.

Also, in the 1991 Image Coding Symposium (PCSJ91), 9-2, "Study of ATM Image Coding Method", as shown in FIG. Since the motion vector is detected between the immediately preceding reproduced image and the motion vector used for the motion compensation prediction of the block A is indirectly detected, the block A is concealed. Concealed. However, this method requires a large amount of calculation to detect a motion vector.

Furthermore, cell discarding occurs in the first I picture of a sequence (an image in which all blocks are intra-coded), or cell discarding occurs in a picture after a scene change but before a scene change as a reference picture. If this occurs, there is no image data to be used for concealment in the reference image, so concealment using the above-described motion compensation prediction cannot be performed.

[0008] More specifically, an image in which a cell is discarded in the first I picture of the sequence or an image for which motion compensation prediction is performed using an image before a scene change (frame # n-1 in FIG. 22A) as a reference image. (Frame #n in FIG. 22A)
In the case where cell discarding occurs in the above, there is no image signal that can be used for concealment (can be used for motion compensation), so that there is a problem that concealment by motion compensation cannot be performed. Therefore, as shown in FIG. 22B, a pixel value in a non-decodable block is used by using a pixel value in a decodable block adjacent to a block (a shaded block) that has become undecodable due to cell discard. Is concealed by interpolation. At this time, the inter-frame correlation between frame #n and frame # n + 1 in FIG. 22A is high (when the motion compensation prediction error is almost 0), and blocks with a wide band cannot be decoded due to cell discard. In this case, as shown in FIG.
Since the block concealed by pixel interpolation in has only a very narrow band component and the prediction error signal added thereto is almost 0, refer to the above concealed block in frame # n + 1 on the receiving side. The band of the reproduced image is still only a low-frequency signal. Further, if the inter-frame correlation is high even in the subsequent frames, the high-frequency components are not restored, and some blocks with a narrow band remain, so that visual deterioration continues in the subsequent frames. There was a problem. Here, hatched portions in FIGS. 23A to 23C are signal components.

Also, the first I picture of the sequence,
Since the amount of information generated in a frame is large in an image in which an image before a scene change is used as a reference image, the number of image data cells in these frames increases compared to other frames,
There is a problem that is easily affected by cell discard.

[0010] On the other hand, in the conventional refreshing by intra slice or intra column, when motion compensated prediction is performed on a block belonging to the refreshed area 2 in FIG. , The search range of the motion vector is limited so as not to refer to the above. Therefore, when concealment using the motion vector is executed on the receiving side, a highly reliable motion vector cannot be obtained.

For example, in the 1992 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers, D-162, “Study of Low Delay Interframe Predictive Coding”, as shown in FIG. Lines (hatched portions in FIG. 24) are set periodically (this is called an intra slice).
Assuming that a diamond-shaped region surrounded by intra-slices is defined as region 1 and region 2 as shown in FIG. In area 1
By restricting the search range of the motion vector so as not to be referred to, it is possible to suppress the image quality deterioration due to an error occurring in the area 1 from propagating to the area 2 and thereafter. However, when concealing a block that cannot be decoded due to an error using a motion vector, the motion vector whose search range is limited cannot be said to have a high correlation with the actual motion of the block. However, reduction in image quality deterioration due to concealment cannot be expected. Similarly, instead of forcibly setting the intra-frame coding line in the horizontal direction, the same applies when the intra-frame coding line is forcibly set in the vertical direction (this is called an intra column). is there. Also, see Nikkei Electronics May 10, 1993 issue (no. As shown in 63 to 64, in MPEG2, a motion vector can be added to a macroblock to be intra-coded as an error resilience function.

[0012]

In the conventional method for compensating for cell discards and transmission line errors, a motion compensation prediction suitable for an undecodable block is selected from among motion compensation predictions used in adjacent blocks. When selecting a candidate, a motion vector to be used for concealment is selected by comparing only the values of the motion vectors of the surrounding blocks using the correlation of the motion vectors between adjacent blocks. Therefore,
When the correlation between the motion vectors between adjacent blocks is small, it is difficult to select an appropriate motion vector, and there is a problem that the performance of cell discard compensation is reduced.

Furthermore, cell discarding occurs in the first I picture of a sequence (image in which all blocks are intra-coded), or cell discarding occurs in a picture after a scene change but before a scene change as a reference picture. If this occurs, there is no image data to be used for concealment in the reference image, so concealment using the above-described motion compensation prediction cannot be performed. In addition, since the amount of information generated in a frame is large in an I-picture at the beginning of a sequence or in an image using an image before a scene change as a reference image, the number of image data cells in these frames increases compared to other frames. Thus, there is a problem that is easily affected by cell discard.

In conventional refreshing using intra-slices or intra-columns, when motion compensation prediction is performed on a block belonging to a refresh area, an image signal belonging to an area other than the refresh area is not referred to.
Since the search range of the motion vector was limited, a highly reliable motion vector could not be obtained when concealment using the motion vector was performed on the receiving side.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to make a block which cannot be decoded due to cell discard or a transmission path error perform motion compensation prediction of another block adjacent to the block. And a motion-compensation prediction apparatus that performs motion-compensation prediction using a motion-correction prediction method. It is an object of the present invention to provide a moving image transmission apparatus that can select a candidate and makes motion compensation prediction more accurate.

[0016]

In order to achieve the above object, according to the present invention (claim 1), there is provided a moving picture transmitting apparatus for transmitting data obtained by coding a moving picture signal in units of blocks using motion compensation prediction. A moving image receiving apparatus that receives the encoded data and decodes the encoded data in block units, wherein the moving image receiving apparatus detects an error in the received encoded data and outputs an error detection signal. , An identification unit for identifying a block that cannot be decoded due to the error based on the error detection signal, and a plurality of decoding units near the block identified as undecodable by the identification unit. According to each of the motion vector of the possible block and the method of motion compensation, a plurality of pixel values belonging to a decodable block near the block identified as undecodable are calculated. Motion compensation prediction means for compensating and predicting, error value calculation means for calculating a motion compensation prediction error value for each of the results of the motion compensation prediction, and the plurality of motion vectors and motion compensation based on the motion compensation prediction error value. Selecting means for selecting a motion vector and a motion compensation method to be applied to the block identified as undecodable among the methods, and identifying the undecodable using the selected motion vector and the motion compensation method. Correction means for correcting the block obtained by motion compensation.

In order to achieve the above object, according to the present invention (claim 2), a moving picture transmitting apparatus for transmitting data obtained by coding a moving picture signal in units of blocks using motion compensation prediction,
A moving image receiving apparatus that receives the encoded data and decodes the encoded data in block units, wherein the moving image receiving apparatus detects an error in the received encoded data and outputs an error detection signal. An error detecting means for outputting, an identifying means for identifying a block which cannot be decoded due to the error based on the error detecting signal, a motion compensation prediction error signal of each block and a corresponding motion vector and motion from the encoded data. Decoding means for decoding a compensation method; motion compensation prediction means for generating a motion compensation prediction signal of a corresponding block using the decoded motion vector and the motion compensation method; and an activity of the motion compensation prediction error signal. First calculating means for calculating, activity calculating means for calculating the activity of the motion compensated prediction signal, and Third calculating means for calculating a ratio between the activity of the error signal and the activity of the motion-compensated prediction signal; and motion compensation of a plurality of decodable blocks near the block identified as undecodable by the identifying means. Determining means for determining the reliability based on the value of the ratio of the activity to each block; and a motion vector and a motion compensation method corresponding to the decodable block based on the determined reliability. Selecting means for selecting a motion vector and a motion compensation method to be applied to the block identified as undecodable,
And a correction means for correcting the block identified as undecodable by motion compensation using the selected motion vector and the method of motion compensation.

According to the present invention (claim 1), blocks which cannot be decoded due to packet discarding or transmission path errors (FIG. 2)
Decodable blocks adjacent to X) in FIG.
The motion compensation prediction (prediction mode such as forward prediction and backward prediction and motion vector) used in (A) A to H) is set as a candidate of the motion compensation prediction used when concealing the block, When selecting an appropriate motion compensation prediction to be used for the block, a motion compensation prediction error of each candidate is calculated using a signal of a decodable block adjacent to the block, and the motion compensation prediction that minimizes the error evaluation value is calculated. By selecting, even when the correlation between the motion vectors between adjacent blocks is small, an appropriate one is selected from the motion compensation prediction candidates. Therefore, the prediction accuracy of an image obtained by concealing the undecodable block can be improved.

According to the present invention (claim 2), a block which cannot be decoded due to packet discard or transmission path error (FIG. 2)
Decodable blocks adjacent to X) in FIG.
The motion compensation prediction (prediction mode such as forward prediction and backward prediction and motion vector) used in (A) A to H) is set as a candidate of the motion compensation prediction used when concealing the block, When selecting an appropriate motion compensation prediction to be used for the block, a ratio between the activity of the motion compensation prediction error signal and the activity of the motion compensation prediction signal in a decodable block adjacent to the block is calculated, and the motion compensation prediction is performed. By evaluating the reliability and selecting the motion compensation prediction with the highest reliability, even when the correlation between the motion vectors between adjacent blocks is small, an appropriate motion compensation prediction candidate is selected. Become like Therefore, the prediction accuracy of an image obtained by concealing the undecodable block can be improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, a moving picture transmission apparatus according to a first embodiment of the present invention will be described. FIG.
1 is a block diagram showing a moving image receiving device according to the present embodiment.

The moving picture transmitting apparatus according to the present embodiment is based on ITU (formerly CCITT) standard H.264. Any coding device that uses motion compensation for a moving image such as 26X in block units may be used.

In this embodiment, first, a block that cannot be decoded due to packet discard or transmission path error (FIG. 2A)
X) adjacent to a decodable block (A in FIG. 2A).
To H) (motion prediction and prediction modes such as forward prediction and backward prediction) are set as candidates for motion compensation prediction used for concealment. Next, each motion compensation prediction candidate is applied to a pixel value in a block adjacent to the block X, and a motion compensation prediction error value is calculated for each candidate. And concealment of the block X is performed using the motion compensation prediction.

First, an example of the error detection circuit 100 shown in FIG. 1 will be described with reference to FIG.

As shown in FIG. 3A, when a packet is supplied via a line 10, the packet is decomposed in a packet decomposing circuit 101 and the bit stream is transmitted to a demultiplexer / variable-length decoding circuit 102. At the same time, the packet discard detection is detected from the packet discard identification information (sequence number in the case of the ATM cell), and the packet discard information is supplied to the non-decodable identification information flag circuit 103. The bit stream supplied to the demultiplexer / variable length decoding circuit 102 is subjected to a discrete cosine transform (DCT).
After being separated into coefficients and side information, variable-length decoding is performed.
The signal (for example, a motion vector) sent as the difference data is returned to the original form and then supplied to the decoder 110. At this time, if an error in the syntax of the bit stream such that a code that does not exist in the variable length code table appears, the information is supplied to the non-decodable identification information flag circuit 103. The undecodable identification information flag circuit 103 sets an address and an undecodable identification information flag for a block that cannot be decoded due to an error detected in the packet decomposing circuit 101 and the demultiplexer / variable-length decoding circuit 102. Output via line 20.

On the other hand, as shown in FIG.
When the bit stream is supplied via the “0”, the error correcting circuit 104 corrects the correctable error in the bit stream.
02. Demultiplexer / variable length decoding circuit 1
02 is separated into discrete cosine transform (DCT) coefficients and side information, and then subjected to variable-length decoding. A signal (eg, a motion vector) transmitted as differential data is restored to its original form. After returning, it is supplied to the decoder 110. At this time, if an error in the bit stream syntax such that an error cannot be completely corrected or an erroneous correction has been made, and a code not present in the variable length code table appears, the error is detected. An address of a block that cannot be decoded is set with a non-decodable identification information flag and output via a line 20.

In the decoder 110 of FIG. 1, the DCT coefficient supplied from the error detection circuit 100 is
The side information including the motion vector and the motion compensation prediction mode is supplied to the motion compensation prediction circuit 113 and the motion compensation information memory 120 via the line 30.

In the inverse quantization circuit 111, the inversely quantized DC
The T coefficient is supplied to the inverse DCT circuit 112. On the other hand, the motion compensation prediction circuit 113 reads a reference image signal from the frame memory 130 via the line 40 in accordance with the mode of motion compensation prediction for each block, creates a prediction value, and supplies the prediction value to the adder 114. However, in the block in the intra-frame encoding mode, the predicted value input to the adder 114 is 0. The adder 114 adds the prediction error supplied from the inverse DCT circuit 112 and the prediction value supplied from the motion compensation prediction circuit 113, and adds the result to the frame memory 1 via a line 50.
30.

The decoder of this embodiment may have another configuration as long as it includes the motion compensation prediction circuit 113.

When the concealment circuit 140 conceals the block X shown in FIG. 2 using the information of the blocks A to H, the motion compensation information memory 120 stores the hatched block shown in FIG. , The mode of the motion compensation prediction and the value of the motion vector supplied via the line 30 and the error detection circuit 1
The non-decodable identification information flag supplied via line 20 from 00 will be stored. Further, the frame memory 130 stores image signals of the blocks hatched in FIG. That is, until the decoding of the block H is completed and the signal of the block H is stored in the motion compensation information memory 120 and the frame memory 130,
After the signal of block X is delayed, it is concealed and output. However, the non-decodable identification information flag is supplied via the line 20, and it is not necessary to rewrite the motion compensation information and the image data of the block recognized as non-decodable.

In the concealment circuit 140, first, in the first motion compensation circuit 141, the motion compensation of the blocks A to H stored in the motion compensation information memory 120 that are decodable and are not intra-frame coded. A prediction value for a pixel value near block X is created from the reference image read from frame memory 130 using the information, and is supplied to error evaluation value calculation circuit 142.

A motion compensation error evaluation circuit (hereinafter, referred to as an MC error evaluation circuit) 142 reads a reproduced image of a pixel in the vicinity of the block X from the frame memory 130, and outputs the block X supplied from the first motion compensation prediction circuit 141. After calculating an error evaluation value (sum of absolute value or sum of squares of the error signal) with the prediction value of the neighboring pixel, the error evaluation value is selected by the selection circuit 14.
Supply 3 However, among the pixels near the block X, the motion compensation prediction error of the pixels included in the undecodable block is not evaluated.

In the selection circuit 143, the MC error evaluation circuit 1
The motion compensation prediction which is supplied from 42 and has the smallest error evaluation value is selected, the corresponding motion compensation information is read from the motion compensation information memory 120, and the second motion compensation circuit 14
4

The second motion compensation circuit 144 uses the most appropriate motion compensation prediction selected by the selection circuit 143 to read the motion compensation prediction value (concealment image) of the block X from the frame memory 130 as a reference image. It is created from the signal and supplied to the selector 150. Note that a block adjacent to block X cannot be decoded,
If motion compensation information cannot be obtained because the block is not a motion compensation mode (for example, an intra-frame encoding mode), for example, the same position as the block X in the reference image stored in the frame memory 130 is used. May be read and supplied to the selector 150.

In the selector 150, if the block (block X) is a decodable block based on the non-decodable identification information flag supplied from the motion compensation information memory 120, the block X stored in the frame memory 130
Is output via a line 60, and if the block cannot be decoded, the concealment image supplied from the second motion compensation prediction circuit 144 is output via a line 60. Here, the encoding of the block H is completed, and the information is stored in the frame memory 130 and the motion compensation information memory 1.
After being stored in the block 20, the image of the block X is delayed and output from the selector 150 via the line 60.

As described above, the error-compensated image signal output via the line 60 is stored in the frame memory 130 as a reference image of the next frame.

Note that the block X in the above embodiment is
FIG. 2B does not evaluate the motion compensation prediction error values of all pixels included in blocks A to H as neighboring pixels.
The hardware scale can be reduced by using a group of pixels (pixel group) close to the block X (having a strong correlation between pixels). However, since the influence of an error propagates in the horizontal direction, when the block X cannot be decoded due to an error, the blocks D and E are also often undecodable, and the error is evaluated only with the pixels in these blocks. Better not.

As another embodiment of the concealment circuit 140, the following is conceivable. That is, as shown in FIG. 4, a pixel value interpolation circuit 145 and a mode determination circuit 146 are provided, and an output obtained by performing motion compensation prediction on the block X by the second motion compensation circuit 144 in the same manner as in the above embodiment, An output obtained by interpolating and predicting the inside of the block X using the pixel values near the block X in the insertion circuit 145 is
Each of the outputs is supplied to the selector 147, and an output determined to be appropriate for concealing the block X by the mode determination circuit 146 is output via the selector 147. Specifically, in the pixel value interpolation circuit 145, for example, a pixel value adjacent to the block X of the blocks A to H stored in the frame memory 130 (when the block size is n × n pixels, each block has n pixels) , N: integers, pixels indicated by oblique lines in FIG. 2C) from the frame memory 130, and weighting and interpolating the pixel values in the block X by linear combination of the pixel values according to the distance between the pixels. Create an interpolated image. However, the pixel values in the undecodable block are not used when creating an interpolated image of the block X. As an interpolation image creation method for the block X, another interpolation method such as using an average value of surrounding blocks may be used. Further, in the mode determination circuit 146, in a predetermined case, for example, when all the motion compensation modes of the decodable blocks stored in the motion compensation information memory 120 are the intra-frame encoding, the selector 147 Value interpolation circuit 145
Supplies a signal that selects the output of

As another embodiment for setting a pixel for evaluating a motion compensation error value, an attribute determination circuit 148 is provided in a concealment circuit 140 as shown in FIG. The first motion compensation prediction circuit 14 detects a luminance gradient (for example, an edge) of a pixel group to be used and uses a pixel group in a region (for example, an edge portion) having a large luminance gradient.
1 and the MC error evaluation circuit 142 may be used to obtain a motion compensation prediction error evaluation value. As a specific example, block A
ＨH are detected, and the motion compensation prediction error is evaluated using the pixels in the block including the edge. Further, as in the embodiment of FIG. 4 described above, the second motion compensation prediction circuit 14
4 and the output of the pixel value interpolation circuit 145 may be switched.

(Second Embodiment) Next, a moving image transmission apparatus according to a second embodiment of the present invention will be described. FIG.
1 is a block diagram illustrating a moving image receiving device according to the present embodiment.

Referring to FIG. 6, in the error detection circuit 100,
As in the first embodiment, the coded data supplied via the line 10 is separated into discrete cosine transform (DCT) coefficients and side information, and then subjected to variable length decoding. 111, the motion compensation information such as a motion vector (hereinafter referred to as MV) is stored in the first motion compensation prediction circuit 22.
0 and the motion compensation information memory 240. In addition, an address and an undecodable identification information flag are set for a block that cannot be decoded and are output via a line 20.

In the inverse quantization circuit 111, the inversely quantized DC
The T coefficient is supplied to the inverse DCT circuit 112. The prediction error signal output from the inverse DCT circuit 112 is supplied to the first activity calculation circuit 200, and the activity of the prediction error signal (such as the sum of squares or the sum of absolute values) is used as an index of the amount of information included in the signal. ) Is calculated. In the second activity calculation circuit 210, the first activity compensation circuit 20
A predicted signal of the same block as the block whose activity is calculated at 0 is supplied, and the activity of this signal (the sum of squares or the sum of absolute values of signals obtained by separating the average value) is calculated.

The reliability determination circuit 230 receives the activity of the prediction error signal and the activity of the prediction signal calculated by the activity calculation circuits 200 and 210, respectively, and determines the reliability of the MV. For example, when the luminance gradient of the prediction signal is small even if the power of the prediction error signal is small, there is a possibility that an MV detection error may occur due to noise or the like at the time of MV detection on the transmission side. On the other hand, when the luminance gradient of the prediction signal is large, the reliability of the MV is high unless the power of the prediction error signal is extremely large. Therefore,
The ratio E / of the activity E of the prediction error signal (output of 200) and the activity P of the prediction signal (output of 210)
This value is supplied to the motion compensation information memory 240, assuming that MV is more reliable as P is smaller.

When estimating the motion compensation information of the block X shown in FIG. 2 using the motion compensation information of the blocks A to H, the motion compensation information memory 240
For the hatched block (a), the mode of motion compensation prediction and the value of the motion vector supplied via the line 30 and the undecodable identification information supplied via the line 20 from the error detection circuit 100 The flag and the reliability of the MV supplied from the reliability determination circuit 230 are stored. Here, if the block (block X) is a decodable block, the motion compensation information of the block is supplied to the second motion compensation prediction circuit 113. If the block is not decodable, the block A The motion compensation information of the block having the MV with the highest reliability among H to H is supplied to the second motion compensation prediction circuit 113. The average value of the MV with the highest reliability and the average value of the MV with the second highest reliability among the blocks A to H are calculated by the second motion compensation prediction circuit 113.
May be supplied.

The second motion compensation prediction circuit 113 reads a reference image signal from the Fourem memory 130 in accordance with the mode of motion compensation prediction supplied from the motion compensation information memory 240 for each block, creates a prediction value, and generates an adder. 11
4 However, in the block in the intra-frame encoding mode, the predicted value input to the adder 114 is 0.

In the adder 114, when the value of the block X is supplied from the second motion compensation prediction circuit 113, the inverse DCT circuit is added to the delay circuit 250 until the value up to the block H is stored in the motion compensation information memory 240. After delaying the output of 112, the value is added and the frame memory 130
To supply. However, if the block cannot be decoded, the delay circuit 250 resets the value of the prediction error signal.

(Third Embodiment) Next, a moving picture transmission apparatus according to a third embodiment of the present invention will be described. FIG.
1 is a block diagram illustrating a moving image receiving device according to the present embodiment.

In FIG. 7, in the error detection circuit 100,
As in the first embodiment, the coded data supplied via the line 10 is separated into discrete cosine transform (DCT) coefficients and side information, and then subjected to variable length decoding. At 111, motion compensation information such as MV is supplied to the motion compensation information memory 300. Further, an address and a non-decodable identification information flag are set for the non-decodable block and output via a line 20.

When the motion compensation information of the block X shown in FIG. 2 is estimated using the motion compensation information of the blocks A to H, the motion compensation information memory 300
For the hatched block (a), the mode of motion compensation prediction and the value of the motion vector supplied via the line 30 and the undecodable identification information supplied via the line 20 from the error detection circuit 100 The flag will be stored. Here, the motion compensation estimating circuit 310 stores the motion compensation information of the block (block X) in the motion compensation information memory 300 if the block is a decodable block and stores the motion compensation information of the block if the block is a non-decodable block. An appropriate motion compensation is selected from the motion compensation information of the blocks A to H, and the motion compensation information is supplied to the motion compensation prediction circuit 113.

In the inverse quantization circuit 111, the inversely quantized DC
The T coefficient is supplied to the inverse DCT circuit 112. The prediction error signal output from the inverse DCT circuit 112 is delayed by the delay circuit 350 as in the second embodiment,
The signal is supplied to the frame memory 130 after being added to the prediction signal supplied from the motion compensation prediction circuit 113. Here, the prediction error signal of the block that cannot be decoded in the delay circuit 320 is reset to zero.

In the pixel value interpolation circuit 330, similarly to the circuit of FIG. 4 explained in the first embodiment, for example, the block X of the blocks A to H stored in the frame memory 130 is used.
Are read from the frame memory 130 (when the block size is n × n pixels, n pixels for each block, n is an integer), and the pixel values in the block X are determined by the linear combination of the pixel values. An interpolation image is created by performing weighted interpolation according to, and is supplied to the weighted averaging circuit 350.

In the weighted averaging circuit 350, the signal supplied from the frame memory 130 and the pixel value interpolation circuit 33
A weighted average value with the interpolation signal supplied from 0 is calculated based on the signal supplied from the mode determination circuit 340. For example, when the mode determination circuit 340 determines that the block X stored in the motion compensation information memory 300 is decodable, the frame memory 130
When the input from is determined that the block X cannot be decoded and the modes of motion compensation of the blocks that can be decoded among the blocks A to H adjacent thereto are all intra-frame coding, After calculating the input from the pixel value interpolation circuit 330 and, in other cases, the average of the input from the frame memory 130 and the input from the pixel value interpolation circuit in the weighted averaging circuit 350, the line 40 is The data is output to the frame memory 130 as well as output through the frame memory 130.

As described above, when a block that cannot be decoded is concealed by motion compensation, even if the correlation of the low-frequency component with an adjacent block is small and block-like distortion occurs, pixel value interpolation is performed. By taking an average value of an adjacent block created in the circuit 330 and a signal whose block boundary is smoothly connected, block-like distortion is reduced.

The concealment circuit 140 shown in FIG. 4 is changed as shown in FIG.
In 6, when it is determined that all of the motion compensation modes of the blocks that can be decoded among the blocks A to H adjacent to the block X are the intra-frame coding, the input from the pixel value interpolation circuit 330 is input. In other cases, the same effect can be obtained by calculating the average value of the input from the frame memory 130 and the input from the pixel value interpolation circuit in the weighted averaging circuit 350 and outputting the result to the selector 150.

(Fourth Embodiment) Next, a moving picture transmission apparatus according to a fourth embodiment of the present invention will be described. FIG.
1 is a block diagram illustrating a moving image receiving device according to the present embodiment.

In FIG. 9, in the error detection circuit 100,
As in the first embodiment, the coded data supplied via the line 10 is separated into discrete cosine transform (DCT) coefficients and side information, and then subjected to variable length decoding. At 111, motion compensation information such as MV is supplied to the motion compensation information memory 400. Further, an address and a non-decodable identification information flag are set for the non-decodable block and output via a line 20.

When estimating the motion compensation information of block X shown in FIG. 2 using the motion compensation information of blocks A to H, the motion compensation information memory 300
For the hatched block (a), the mode of motion compensation prediction and the value of the motion vector supplied via the line 30 and the undecodable identification information supplied via the line 20 from the error detection circuit 100 The flag will be stored. Here, the motion compensation estimation circuit 410 stores the motion compensation information of the block (block X) in the motion compensation information memory 400 if the block is a decodable block and stores the motion compensation information in the motion compensation information memory 400 if the block is a non-decodable block. An appropriate motion compensation is selected from the motion compensation information of the blocks A to H, and the motion compensation information is supplied to the motion compensation prediction circuit 113.

In the inverse quantization circuit 111, the inversely quantized DC
The T coefficient is supplied to the inverse DCT circuit 112. The prediction error signal output from the inverse DCT circuit 112 is delayed by the delay circuit 420 in the same manner as in the second embodiment.
The signal is supplied to the frame memory 130 after being added to the prediction signal supplied from the motion compensation prediction circuit 113. Here, the prediction error signal of the block that cannot be decoded by the delay circuit 420 is reset to zero.

In the low-order coefficient prediction circuit 430, reference: H. Su
n, K.Challapali, J.Zdepski, ERRORCONCEALMENT IN DIGI
TAL SIMULCAST AD-HDTV DECODER ”, IEEE Trans.Consume
r Electoronics, Vol. 38, No. 3, Aug. 1992, (see FIG. 10)
, The average value of the DCT block (DC1 to DC1)
Using DC9), low-order coefficients (AC01, AC10, AC02, AC11, AC20) of the DCT block corresponding to DC5
Is predicted on the condition that the amplitude change on the screen is approximated by a quadratic surface. Where DC5, DC6, DC8, DC
If the macroblock including 9 cannot be decoded, the value of DC in an adjacent macroblock (DC2, DC3, etc.)
Is used to perform bilinear interpolation prediction. Note that the dotted line in FIG. 10A indicates the boundary between DCT blocks, and the solid line indicates the boundary between macro blocks.

On the other hand, in the coefficient separation / synthesis circuit 440, in the mode determination circuit 450, the motion compensation information memory 40
Blocks A to A adjacent to the block X stored at 0
If it is determined that the motion compensation modes of the blocks that can be decoded in H are all intra-frame coding, only the input from the low-order coefficient prediction circuit 430 is output. The low-order coefficient of the signal obtained by converting the signal of the block X read from the frame memory 130 supplied from the circuit 460 into the DCT coefficient is converted into a low-order coefficient prediction circuit 43
A signal replaced with the count supplied from 0 is output. The output of the coefficient separating / combining circuit 440 is output to the inverse DCT circuit 470
, And is supplied to the selector 480. The selector 480 outputs a signal of the block X supplied from the frame memory via the line 40 if the block X is a decodable block, and supplies a signal from the inverse DCT circuit if the block X is not decodable. The resulting signal is output via line 40 and the output of line 40 is provided to frame memory 130.

As described above, when a block that cannot be decoded is concealed by motion compensation, the low-order component of the DCT is reduced even if block-like distortion occurs due to a low correlation between adjacent blocks. Since the low-order coefficient prediction circuit 430 replaces the block with a coefficient predicted so as to smoothly connect an adjacent block and a block boundary, block-like distortion is reduced.

The concealment circuit 140 shown in FIG. 4 described above is modified as shown in FIG. 11, and in the coefficient separation / combination circuit 440, in the mode determination circuit 146, among the blocks A to H adjacent to the block X, When it is determined that the motion compensation modes of the decodable blocks are all intra-frame coding, the input from the low-order coefficient prediction circuit 430 is output as it is, and in other cases, the DCT circuit 4
60, a signal obtained by replacing the low-order coefficient of the signal obtained by converting the signal of the block X read from the frame memory 130 supplied from the frame memory 130 into a DCT coefficient with the coefficient supplied from the low-order coefficient prediction circuit 430 is output. The same effect can be obtained by performing an inverse transform in the DCT circuit 470 and outputting the result to the selector 150.

The low-order coefficient prediction circuit 430, DCT circuit 460, and inverse DCT circuit 470 may be replaced by circuits other than DCT and adapted to orthogonal transform or band division filters.

(Fifth Embodiment) Next, a moving picture transmission apparatus according to a fifth embodiment of the present invention will be described. FIG.
FIG. 2 is a block diagram showing a moving image transmitting apparatus according to the present embodiment.

In FIG. 12, an input image is stored in a plurality of frame memories 500. Motion vector detection circuit 5
In 10, after detecting a motion vector between frames stored in the frame memory 500, the sum of the absolute value of the error signal (determined at the time of detecting the motion vector) for each block and the time when the frame performs motion compensation on another frame are detected. A signal for identifying whether or not to be a reference image is sent to a scene change detection circuit 52.
Supply 0.

The scene change detection circuit 520 calculates the activity of the input image supplied from the frame memory 500 (for example, the sum of absolute values of AC components), and calculates the sum of the absolute value of the error signal supplied from the motion vector detection circuit 510 and Compare. Here, for example, if the number of blocks in which the latter value is larger is half or more of the total number of blocks in the frame, it is determined that a scene change has occurred, and if the frame is a reference image of another frame, The scene change identification signal is converted into a resolution conversion circuit 530 and an encoder 540.
Respectively.

Note that the embodiment of the scene change detection is not limited to the above method, and another method may be used.

In the resolution conversion circuit 530, when the scene change identification signal supplied from the scene change detection circuit 520 is enabled, an image signal whose resolution has been reduced by applying a low-pass filter of the 0th order to the frame is output. It is supplied to the encoder 540.

In the encoder 540, the resolution conversion circuit 5
The image signal supplied from 30 is divided into blocks, and motion compensated prediction encoding is performed for each block using the motion vector supplied from the motion vector detection circuit 510, and then the encoded image signal is output.

As another embodiment for reducing the spatial resolution of a frame immediately after a scene change, as shown in FIG.
Instead of lowering the spatial resolution by the resolution conversion circuit 530, if the scene change identification signal supplied from the scene change detection circuit 520 is enabled, the encoder 560 encodes all the blocks of the frame in a frame, The coefficient is discarded, for example, as shown in FIG.
The spatial resolution may be reduced by encoding only low-order coefficients as shown in FIG.

A scene change identification flag (1 bit) may be added for each frame.

Similarly, in FIG. 13, instead of the resolution conversion circuit 530, a dynamic range conversion circuit 535 is used.
In the case where the scene change identification signal supplied from the scene change detection circuit 520 is enabled, an image signal with a reduced dynamic range of the frame is supplied to the encoder 540 according to the following equation. x ′ = α · (x−128) +128 0 <α <1 Here, x is a pixel value of the frame, and x ′ is a pixel value with a reduced dynamic range.

As another embodiment for reducing the dynamic range, an average value of x may be used instead of 128 in the above equation. This average value may be the average value of the entire frame or the average value of the small area including x.

Further, instead of multiplying the amplitude value by α, the dynamic range of the amplitude value may be limited by a limiter.

The region in which the band and the dynamic range are reduced as described above may be the entire frame, or may be only the region in which information is largely lost due to spatial interpolation. In the latter case, it is necessary to detect an edge portion or a region where the power of the high frequency component is large. Therefore, it is preferable to add an edge portion detection circuit 550 as shown in FIG. In this case, the edge part detection circuit 550
An edge detection filter is applied to the signal of the frame supplied from 0 to detect an edge portion, and a signal for identifying a region including the edge portion is supplied to the dynamic range conversion circuit 535. In the dynamic range conversion circuit 535, the dynamic range is reduced only in the area determined to be an edge by the edge detection circuit 550.

The moving image receiving apparatus can be realized if it has the same configuration as the first to fourth embodiments. For example, in the mode determination circuit 146 of FIG.
If all of the decodable blocks in the block are intra-frame coded, it is determined that a scene change has occurred, and the selector 14
7, the signal from the pixel value interpolation circuit 145 may be output. As shown in FIG. 16, when the scene change identification flag is sent from the transmission side, the input from the pixel value interpolation circuit 145 is always output to the selector 147 in the mode determination circuit 146. What is necessary is just to comprise so that such a signal may be supplied.

(Sixth Embodiment) Next, a moving picture transmission apparatus according to a sixth embodiment of the present invention will be described. FIG.
FIG. 7 is a block diagram showing a moving image transmitting apparatus according to the present embodiment.

In FIG. 17, an input image is stored in a plurality of frame memories 500. Motion vector detection circuit 5
In 10, after detecting a motion vector between frames stored in the frame memory 500, the sum of the absolute value of the error signal (determined at the time of detecting the motion vector) for each block and the time when the frame performs motion compensation on another frame are detected. A signal for identifying whether or not to be a reference image is sent to a scene change detection circuit 52.
Supply 0.

The scene change detection circuit 520 calculates the activity of the input image supplied from the frame memory 500 (for example, the sum of the absolute values of AC components), and calculates the sum of the absolute value of the error signal supplied from the motion vector detection circuit 510 and Compare. Here, for example, if the number of blocks in which the latter value is larger is half or more of the total number of blocks in the frame, it is determined that a scene change has occurred, and if the frame is a reference image of another frame, The scene change identification signal is supplied to the encoder 600. The edge portion detection circuit 550 applies an edge detection filter to the signal of the frame supplied from the frame memory 500 to detect an edge portion, and for each block, identifies whether the block belongs to a region including the edge portion. The encoder 600
To supply.

In the encoder 600, the frame memory 5
The image signal supplied from 00 is divided into blocks, and motion-compensated prediction encoding is performed for each block using the motion vector supplied from the motion vector detection circuit 510, and then the encoded image signal is output. Here, when the scene change identification signal supplied from the scene change detection circuit 520 is enabled (for example, frame #n in FIG. 22A), all the blocks of the frame are intra-coded. Also, a frame using this frame as a reference image for motion compensation prediction (for example, FIG.
In frame # n + 1), the block in which the edge detection circuit 550 determines that the frame belongs to the edge portion is forcibly intra-coded.

The moving image receiving apparatus can be realized if it has the same configuration as the first to fourth embodiments. For example, if all of the decodable blocks among the blocks A to H are intra-frame coded in the mode determination circuit 146 of FIG. 4, it is determined that a scene change has occurred, and the pixel value interpolation circuit 145 is output via the selector 147. It is sufficient to output a signal from When the scene change identification flag is sent from the transmission side as shown in FIG. 16, the mode determination circuit 146 always outputs the input from the pixel value interpolation circuit 145 to the selector 147. What is necessary is just to supply a suitable signal.

As described above, for example, even if cell discarding occurs in frame #n in FIG. 22A and concealment by spatial interpolation lowers the spatial resolution and the edge is blurred,
In the frame # n + 1, the edge portion is forcibly encoded in the frame, thereby eliminating the edge blur.

In the first to seventh embodiments described above, if the input image is an interlaced signal, the type of concealment may be switched for each field.

In all of the above (first to sixth) embodiments, when these embodiments are applied to MPEG, the motion compensation circuits (141, 144, 220) related to concealment are Omits the pixel average value calculation circuit required for 1/2 pixel motion compensation, B picture interpolation prediction mode, etc. (for example, when the motion vector is rounded by one pixel, when the B picture interpolation prediction mode is selected) Concealment using only forward prediction) can also reduce the circuit scale.

(Seventh Embodiment) Next, a moving image transmission apparatus according to a seventh embodiment of the present invention will be described. FIG.
FIG. 8 is a block diagram illustrating the moving image transmitting apparatus according to the present embodiment.

In FIG. 18A, first, the first frame memory 700 stores the video signal supplied for each frame. Next, the motion vector detection circuit 710 detects the MV from the first frame memory 700 and the second frame memory 720 storing the local decoded image, and supplies the MV to the motion compensation prediction circuit 730. The motion compensation prediction circuit 730 creates a prediction image signal from the second frame memory 720 using the MV supplied from the motion vector detection circuit 710, and supplies the prediction image signal to the encoding control circuit 740 and the intra-frame / inter-frame switching circuit 750. I do.

Intra-frame / inter-frame switching circuit 75
At 0, the subtractor 760 sets the optimum prediction value created by the motion compensation prediction circuit 730 when the inter-frame coding is selected, and sets the prediction value to 0 when the intra-frame coding is selected. Is supplied to the adder 770.

In the subtracter 760, an error signal between the input image and the prediction signal is created and supplied to the DCT circuit 780. The prediction error signal converted into the transform coefficient in the DCT circuit 780 is supplied to the quantizer 790. The transform coefficient quantized by the quantizer 790 is output to the inverse quantizer 8
The transform coefficient inversely quantized in 00 is supplied to the inverse DCT circuit 810. In the inverse DCT circuit 810, the transform coefficient is inversely transformed into a prediction error signal and supplied to the adder 770. The adder 770 adds the prediction error signal and the prediction value to create a locally decoded image, and generates a locally decoded image.
To supply. Further, the transform coefficients quantized by the quantizer 790 are also supplied to the variable length coding circuit 820.

In the variable length coding circuit 820, the quantizer 7
At 90, the quantized transform coefficient is subjected to variable-length coding together with additional information including MV, and then supplied to a multiplexing circuit 830.

The multiplexing circuit 830 multiplexes the variable length code supplied from the variable length coding circuit 820, and outputs a coded bit stream via the output buffer 840. In the output buffer 840, the amount of stay of the coded bit stream in the buffer is determined by the coding control circuit 740.
To supply.

The encoding control circuit 740 uses the predicted image signal supplied from the motion compensation prediction circuit 730 and the input image signal supplied from the first frame memory 700 to perform an optimal prediction method (for example, forward prediction). The prediction mode is determined for each block, and the prediction mode is determined. Here, in FIG. 24, when an image signal belonging to the area 1 is referred to when performing motion compensation prediction on a block belonging to the area 2, the intra-frame prediction mode is forcibly set.
Here, when error resilience is required, the mode is switched to a mode in which a motion vector is added in intra-frame prediction coding, and the motion vector information is also supplied to the variable length coding circuit 820.

As described above, the determined intra-frame / inter-frame determination information is supplied to the intra-frame / inter-frame switching circuit 750. Also, the quantization step size is determined from the staying amount of the encoded bit stream supplied from the output buffer 840 so as to adapt to the set code amount, and is supplied to the quantizer 790 and the inverse quantizer 800.

[0093]

According to the present invention, when concealing a block that cannot be decoded due to packet discarding or a transmission path error, the block that cannot be decoded even if the correlation between motion vectors between adjacent blocks is small. Can be appropriately selected from those corresponding to decodable blocks adjacent to the block. This makes it possible to improve the prediction accuracy of an image obtained by concealing the block that cannot be decoded.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a moving image receiving apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining data used for concealment;

FIG. 3 is a block diagram illustrating a configuration example of an error detection circuit in FIG. 1;

FIG. 4 is a block diagram showing another configuration example of the concealment circuit of FIG. 1;

FIG. 5 is a block diagram showing still another configuration example of the concealment circuit of FIG. 1;

FIG. 6 is a block diagram showing a main configuration of a moving image receiving apparatus according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a main configuration of a moving image receiving apparatus according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing another configuration example of the moving image receiving apparatus according to the third embodiment of the present invention.

FIG. 9 is a block diagram showing a main configuration of a moving image receiving apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a diagram for explaining a DCT coefficient prediction method.

FIG. 11 is a block diagram showing another configuration example of the moving image receiving apparatus according to the fourth embodiment of the present invention.

FIG. 12 is a block diagram showing a main configuration of a moving image receiving apparatus according to a fifth embodiment of the present invention.

FIG. 13 is a block diagram showing another configuration example of the moving image receiving apparatus according to the fifth embodiment of the present invention.

FIG. 14 is a block diagram showing still another configuration example of the moving image receiving device according to the fifth embodiment of the present invention.

FIG. 15 is a block diagram showing still another configuration example of the moving image receiving apparatus according to the fifth embodiment of the present invention.

FIG. 16 is a block diagram showing still another configuration example of the moving image receiving device according to the fifth embodiment of the present invention.

FIG. 17 is a block diagram showing a main configuration of a moving image receiving apparatus according to a sixth embodiment of the present invention.

FIG. 18 is a block diagram showing a main configuration of a moving image receiving apparatus according to a seventh embodiment of the present invention.

FIG. 19 is a diagram illustrating the principle of conventional packet discard compensation.

FIG. 20 is a view for explaining a conventional method of selecting a motion vector.

FIG. 21 is a diagram illustrating an example of conventional packet discard compensation.

FIG. 22 is a view for explaining concealment by spatial interpolation in a frame;

23 is a view for explaining the effect of the band of frame #n on the transmission side in FIG. 22 on the band of frame # n + 1 on the reception side;

FIG. 24 is a view for explaining a method of setting an intra slice in a frame to limit a search range of a motion vector.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 error detection circuit 101 packet disassembly circuit 102 demultiplexer / variable-length decoding circuit 103 undecodable identification flag circuit 104 error correction circuit 110 decoder 111 inverse quantization circuit 112, 470 inverse DCT circuit 113 141, 144, 220 ... motion compensation circuit 114 ... adder 120, 240, 300, 400 ... motion compensation information memory 130, 500 ... frame memory 140 ... concealment circuit 142 ... motion compensation error evaluation circuit 143 ... selection circuit 145, 330 ... Pixel value interpolation circuit 146,340,450 ... Mode judgment circuit 148 ... Attribute judgment circuit 150,147,480 ... Selector 200,210 ... Activity calculation circuit 230 ... Reliability judgment circuit 250,320,420 ... Delay circuit 310, 410: Motion compensation estimation time Path 350 delay circuit 430 low-order coefficient prediction circuit 440 coefficient separation / synthesis circuit 460 DCT circuit 510 motion vector detection circuit 520 scene change detection circuit 530 resolution conversion circuit 535 dynamic range conversion circuit 540, 560, 600: encoder 550: edge portion detection circuit 700, 720 frame memory 710: motion vector detection circuit 730: motion compensation prediction circuit 740: coding control circuit 750: intra-frame / inter-frame switching circuit 760: subtractor 770: addition Unit 780: discrete cosine transform circuit 790: quantizer 800: inverse quantizer 810: inverse discrete cosine transform circuit 820: variable length coding circuit 830: multiplexing circuit 840: output buffer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C059 MA00 MA23 MC11 ME01 PP06 PP07 RB02 RF02 RF07 SS06 TA06 TA61 TA76 TB08 TC03 TC10 TC14 TC42 TD06 UA02 UA05 5J064 AA01 BA09 BA13 BA16 BB03 BC01 BC02 BC08 BC14 BC25 BD02

Claims (2)

[Claims] A moving picture transmitting apparatus for transmitting data obtained by coding a moving picture signal in units of blocks using motion compensation prediction, and a moving picture receiving apparatus for receiving the coded data and decoding the blocks in block units. In the moving picture transmission apparatus, the moving picture receiving apparatus detects an error in the received coded data and outputs an error detection signal. Identification means for identifying a block that can be decoded; and a motion vector and a motion compensation method for a plurality of decodable blocks near the block identified as undecodable by the identification means. Motion compensation prediction means for motion compensation prediction of a plurality of pixel values belonging to a decodable block near the identified block, and a result of the motion compensation prediction, Error value calculating means for calculating a motion compensated prediction error value, and a motion to be applied to the block identified as undecodable among the plurality of motion vectors and motion compensation methods based on the motion compensated prediction error value. Selecting means for selecting a vector and a method of motion compensation; and correcting means for correcting the block identified as undecodable by motion compensation using the selected motion vector and the method of motion compensation. Characteristic moving image transmission device. 2. A moving image transmitting apparatus for transmitting data obtained by encoding a moving image signal in units of blocks using motion compensation prediction, and a moving image receiving apparatus for receiving the encoded data and decoding the blocks in units of blocks. In the moving picture transmission apparatus, the moving picture receiving apparatus detects an error in the received coded data and outputs an error detection signal. Identification means for identifying a possible block; decoding means for decoding the motion compensation prediction error signal of each block and the corresponding motion vector and motion compensation method from the encoded data; and the decoded motion vector and motion compensation Motion-compensated prediction means for generating a motion-compensated predicted signal of a corresponding block using the method of Second calculating a first calculating means for calculating the activity of the motion compensated prediction signal
Calculating means for calculating the ratio of the activity of the motion-compensated prediction error signal to the activity of the motion-compensated prediction signal; and Determining means for respectively determining the reliability of the motion compensation of the decodable block based on the value of the ratio of the activity to each block; and the motion corresponding to the decodable block based on the determined reliability. Selecting means for selecting a motion vector and a motion compensation method to be applied to the block identified as undecodable from vectors and motion compensation methods, and using the selected motion vector and motion compensation method, Correction means for correcting a block identified as undecodable by motion compensation. Transmission equipment.