JPH04119793A - Coder for video signal - Google Patents

Abstract

PURPOSE:To decrease an error at a block border by providing a 1st coding means which classifies small divided blocks into two groups and applies 1st coding to a block belonging to the 1st group and a 2nd coding means which applies coding of a difference between a predicted value and a true value to each of blocks belonging to the 2nd group to the device which divides a pattern into small blocks and applies coding to them. CONSTITUTION:Blocks in a buffer memory 2 are subject to coding and decoding sequentially by an orthogonal transformation device 6, a quantizer 7, an inverse quantizer 8 and an inverse orthogonal transformation device 9 as the 1st coding. A difference between a predicted value and a true value is calculated by a subtractor 11 and the difference is coded by an orthogonal transformation (discrete sine transformation) device 12 and a quantizer 13 as the 2nd coding. A quantized data of a part coded by the 1st coding is read and stored in a buffer memory 15 and the stored data is decoded by using the inverse quantizer 8 and the inverse orthogonal transformation device 9 as the 1st decoding. Then the difference in each block is decoded by the inverse quantizer 17 and the inverse orthogonal transformation device 18 as the 2nd decoding.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a video signal encoding device.

One of the conventional high-efficiency encoding methods for video signals is based on orthogonal transformation.

This divides the screen into small blocks, orthogonally transforms each block, and encodes the coefficients. In general, video signals have strong correlations between pixels, and when orthogonal transformation is applied to a signal divided into small blocks, coefficients with large values are concentrated in the low frequency part, that is, in the upper left part when expressed as a two-dimensional matrix. There is a tendency to Further, when a characteristic frequency component within a block is observed, the coefficient of the portion corresponding to that frequency appears large. By limiting the range of quantization to only the vicinity of concentrated coefficients or by making the quantization width variable, the number of bits required for encoding coefficients can be reduced.

FIG. 5 is a block diagram of an encoder and a decoder for explaining a conventional method of encoding a video signal using orthogonal transform.

In the figure, (a) is a block diagram of the encoder, and the image signal stored in the buffer memory 23 is divided by the block generator 22 into blocks such as 8 pixels vertically by 8 pixels horizontally.

The signals of each block are sequentially encoded by an orthogonal transformer 25 and a quantizer 26. The quantized result is stored in the buffer memory 24 and then output as an encoded output.

FIG. 5(b) is a block diagram of the decoder. In the figure, the encoded input signal is stored in a buffer memory 27 and then decoded by an inverse quantizer 28 and an inverse orthogonal transformer 29. The decoded result is stored in the buffer memory 31, and then returned to the original arrangement by the deblocker 30 and output.

Problems to be Solved by the Invention However, in conventional methods, when the amount of encoded data is reduced, high-frequency components cannot be restored correctly, discontinuity occurs between each block, and image deterioration called block noise occurs. arise.

In view of the above, it is an object of the present invention to provide a video signal encoding method that makes block noise less noticeable and is more efficient than the conventional method.

Means for Solving the Problems The present invention provides an apparatus that divides a screen into small blocks and performs encoding.The divided small blocks are classified into two groups, and blocks belonging to the first group are classified into two groups.
The encoding means of the above is applied to obtain encoded data, and the first decoding means corresponding to the first encoding means is provided to obtain decoded data of the block, and the decoded data of the block belonging to the second group is obtained. For each, all or part of the decoded data of the block that has been encoded and decoded in the first group and the decoded data of the blocks that have already been encoded and decoded among the blocks belonging to the second group. A means for calculating a predicted value in a block using a second encoding means for obtaining a predicted value and encoding a difference value between the predicted value and the true value; A second decoding means is provided to encode one screen, and similarly, when decoding, the first decoding means is provided for blocks belonging to the first group.
The decoding means is applied to obtain decoded data, and for each of the remaining groups, a means for calculating the predicted value in the block is provided in the same way as during encoding to obtain the predicted value. At the same time, a decoding means corresponding to the second encoding means is provided to obtain decoded data of the difference value, and the decoding of one screen is executed by calculating the sum of the predicted value and the decoded data of the difference value. This is a video signal encoding device that divides the screen into small blocks and performs encoding. applying the first encoding means to obtain encoded data, and
A first decoding means corresponding to the first encoding means is provided to obtain decoded data of the block, and for each of the blocks belonging to the remaining groups, each k is further divided into a plurality of sub-blocks. , the decoded data of the blocks that have been encoded and decoded in the first group, the decoded data of the blocks that have already been encoded and decoded among the blocks belonging to the second group, and the decoded data of the blocks that have already been encoded and decoded in the blocks that are to be encoded. Using all or part of the decoded data of encoded and decoded subblocks, a means is provided to sequentially calculate a predicted value in each subblock to obtain a predicted value, and calculate the difference between the predicted value and the true value. A second encoding means for encoding a difference value and a decoding means corresponding to the second encoding means are provided to execute encoding of one screen, and similarly, upon decoding,
The first decoding means is applied to blocks belonging to the first group to obtain decoded data, and for each block belonging to the remaining groups, predicted values within the blocks are calculated in the same way as during encoding. By providing means to obtain a predicted value, providing a decoding means corresponding to the second encoding means to obtain decoded data of the difference value, and calculating the sum of the predicted value and the decoded data of the difference value. This is a video signal encoding device characterized by executing decoding of one screen.

Effect of the Invention With the above-described device, the present invention can suppress errors at block boundaries to a small extent and perform encoding with higher efficiency.

Furthermore, by performing the first decoding and predicting the remaining blocks, it is possible to easily reproduce the screen without performing the second decoding, so it is possible to realize an encoding method suitable for special video reproduction such as fast forwarding.

Embodiment FIG. 1 is a block diagram of an encoder and a decoder for explaining a video signal encoding method in a first embodiment of the present invention. In the figure, (a) is a block diagram of the encoder, and the block generator 1 divides the screen into blocks each having 8 pixels vertically by 8 pixels horizontally. The divided blocks are sorted into the arrangement shown in FIG. 2 by the switch 4 and stored in the buffer memories 2 and 3, respectively.

As the first encoding, the blocks in the buffer memory 2 are sequentially encoded and decoded by an orthogonal transformer 6, a quantizer 7, an inverse quantizer 8, and an inverse orthogonal transformer 9. The quantized result is stored in the buffer memory 14 and then output, while the decoded result is stored in the buffer memory 2 again and used for prediction of the block stored in the buffer memory 3.

Next, the block stored in the buffer memory 3 is encoded.

For each block read from the buffer memory 3, the positions surrounding it on any of its four sides, that is, the blocks 1 block before, 1 block after, h blocks before, and h blocks after the original block position. Among them, the decoded ones are read out from the buffer memory 2 and the buffer memory 34 based on the address from the address generator 5.

Based on the signal value of the block read from the buffer memory 2, the signal value of the desired block is predicted using the interpolation signal generator 10.

As second encoding, the difference between the predicted value and the actual value is calculated by the subtracter 11, and the difference value is encoded by the orthogonal transform (discrete sine transform) device 12 and the quantizer 13. In this case, since peripheral information is used for interpolation, the difference value is considered to be small near the block boundary and large near the center. Discrete sine transformation approximates using a sine function, so it is suitable for approximating a signal that is 0 at the boundary and becomes large at the center. Therefore, efficient quantization can be achieved by using discrete sine transform in the orthogonal transformer 12.

The encoded result is stored in the buffer memory 14 and then output. Furthermore, an inverse quantizer 17 and an inverse orthogonal transformer 1
8 to decode the difference value. The decoded difference value is added to the predicted signal value by the adder 20 to form the decoded value of the same block, and is stored in the buffer memory 34.

FIG. 1(b) is a block diagram of a decoder in a first embodiment of the present invention. In the figure, after reading out the quantized data of the part encoded by the first encoding and storing it in the buffer memory, the inverse quantizer 8 performs the first decoding.
, decoded by the inverse orthogonal transformer 9. The decrypted results are stored in the buffer memo January 9th.

Based on the signal value of the decoded block, the interpolation signal generator 10 is used to predict the signal value of a neighboring block, as in the case of encoding.

Next, in the second decoding, the quantized data of the part encoded by the second encoding is read out and stored in the buffer memory, and then the inverse quantizer 17 and the inverse orthogonal transformer 18 Decode the difference value. The decoded difference value is added to the predicted signal value by the adder 20 in the same way as during encoding to obtain a decoded value. The decoding result of each block is stored in the buffer memory 19, and is returned to the original arrangement by the deblocker 21 together with the first decoding result and then output.

Here, by sending the first decoding result and the prediction result of the remaining blocks directly to the buffer memory and outputting it, the second decoding procedure, namely reading the encoded input, dequantization The screen can be easily reproduced without performing steps such as , inverse orthogonal transformation, and addition. In this case, the time required for simple playback is approximately half that of normal playback for both the data read time and calculation time, making it possible to realize an encoding method suitable for special playback such as fast forwarding.

FIG. 3 is a block diagram of an encoder and a decoder for explaining a video signal encoding method in a second embodiment of the present invention. In the figure, (a) is a block diagram of the encoder, and the block generator 1 divides the screen into blocks each having 8 pixels vertically by 8 pixels horizontally. The divided blocks are sorted into the arrangement shown in FIG. 4 by the switch 4 and stored in the buffer memories 2 and 3, respectively.

As the first encoding, the blocks in the buffer memory 2 are sequentially encoded and decoded by the orthogonal transformer 6, the quantizer 7, the inverse quantizer 8, and the inverse orthogonal transformer 9. The quantized result is stored in the buffer memory 14 and then output as an encoded output.

The decoded result is put into buffer memory 2 again,
It is used to predict blocks stored in the buffer memory 3.

Next, the block stored in the buffer memory 3 is encoded.

For each block read from the buffer memory 3, the position surrounding it on any of its four sides, that is, the block before the block, after l block, before h block, and after h block at the original block position. The decoded data is read from the buffer memory 2 and the buffer memory 34 based on the address from the address generator 5.

At the same time, the blocks read from buffer memory 3 are
The subblock generator 32 divides the image into four subblocks as shown in FIG.

Based on the signal values of the four blocks read from the buffer memory 2, the interpolation signal generator 10 is used to predict the signal value of the desired sub-block.

As second encoding, the difference between the predicted value and the actual value is calculated by the subtracter 11, and the difference value is encoded by the orthogonal transform (discrete sine transform) device 12 and the quantizer 13.

The encoded result is stored in the buffer memo 4 and then output as an encoded output. Furthermore, the inverse quantizer 17
, the difference value is decoded by the inverse orthogonal transformer 18. The decoded difference value is added to the predicted signal value by the adder 20 to form the decoded value of the same sub-block, and is stored in the buffer memory 34.

As for the remaining sub-blocks, as shown in FIG. Prediction is performed from signal values of encoded and decoded subblocks. A subtracter 11 calculates the difference between the predicted value and the measured value, and the orthogonal transformer 12 and quantizer 13 encode the difference value.

FIG. 3(b) is a block diagram of a decoder in the first embodiment of the present invention. In the figure, after reading out the part encoded by the first encoding, that is, the block part where r + J is an even number and storing it in the buffer memory 15, the inverse quantizer 8 and the inverse orthogonal transform are used as the first decoding. The encoder 9 decodes the data. The decrypted results will be stored in Hanwha Memo January 9th.

Based on the signal values of the decoded blocks, the interpolation signal generator 10 predicts the signal values of the blocks surrounded by the four blocks.

Next, as second decoding, after reading out the part encoded by the second encoding, that is, the block part where 1+J is an odd number and storing it in the buffer memory 16, the inverse quantizer 17,
The inverse orthogonal transformer 18 decodes the difference value in each subblock. The decoded difference value is added to the predicted signal value by the adder 20 in the same way as during encoding to obtain a decoded value. The decoded result of each sub-block is restored to the original block arrangement by the deblocker 33 and then stored in the buffer memory 19, and then restored to the original arrangement by the deblocker 21 along with the first decoded result. Output after being returned.

In addition, in this example, the division method into subblocks is as follows:
Although it was divided into four equal parts as shown in FIG. 2(b), the number of divisions and the shape are arbitrary.

In the above embodiments, the blocks were divided into 8x8 pixels, but the size of the blocks may be arbitrary. Any method may be used. Also, although an orthogonal transformer is provided before the quantizer, other methods such as a predictive encoder may be used for this, and the second transform method uses a discrete sine transform. However, other methods may also be used.

As described in detail, according to the present invention, block noise is less noticeable and more efficient encoding can be performed.

Furthermore, by performing the first decoding and predicting the remaining blocks, it is possible to easily reproduce the screen without performing the second decoding, so it is possible to realize an encoding method suitable for special video reproduction such as fast forwarding.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an encoder and a decoder for explaining the video signal encoding method in the first embodiment of the present invention, and FIG.
The figure is a diagram for explaining the block classification method in the first and second embodiments of the present invention, and FIG. 3 is an encoder for explaining the video signal encoding method in the second embodiment of the present invention. , a block diagram of a decoder, FIG. 4 is a diagram for explaining the block classification method and sub-block division method in the second embodiment of the present invention, and FIG. 5 is a conventional orthogonal transform video signal encoding method. FIG. 2 is a configuration diagram of an encoder and a decoder for explaining. 1...Blocker, 2.3.14.15.1
6.19.34...Buffer memory, 4...
...Switcher, 5...Address generator, 6
．． 12... Orthogonal transformer, 7.13...
Quantizer, 8.17... Inverse quantizer, 9.18
...Inverse orthogonal transformer, 10...Interpolation signal generator, 11...Subtractor, 20...Adder, 21...・Deblocker, 32...
...Subblock generator, 33...Reverse subblock generator. Name of agent: Patent attorney Akira Kokaji and 2 others No. 1 (b)

Claims (4)

[Claims] (1) In a device that divides a screen into small blocks and performs encoding, the divided small blocks are classified into two groups, and the first encoding means is applied to the blocks belonging to the first group. , obtain encoded data and provide a first decoding means corresponding to the first encoding means to obtain decoded data of the block, and for each block belonging to the second group, the first decoding means is provided. Prediction within a block using all or part of the decoded data of the block that has been encoded and decoded and the decoded data of the block that has already been encoded and decoded among the blocks belonging to the second group. A means for calculating a value is provided to obtain a predicted value, a second encoding means for encoding a difference value between the predicted value and the true value, and a second decoding means corresponding to the second encoding means. Similarly, during decoding, the first decoding means is applied to blocks belonging to the first group to obtain decoded data, and each of the blocks belonging to the remaining groups is , a means for calculating the predicted value within the block is provided in the same way as during encoding to obtain the predicted value, and a decoding means corresponding to the second encoding means is provided to obtain decoded data of the difference value. A video signal encoding device that executes decoding of one screen by calculating the sum of the predicted value and the decoded data of the difference value. (2) In a device that divides a screen into small blocks and performs encoding, the divided small blocks are classified into two groups, and the first encoding means is applied to the blocks belonging to the first group. , while obtaining encoded data, providing a first decoding means corresponding to the first encoding means to obtain decoded data of the block, and further decoding each of the blocks belonging to the remaining groups. Decoded data of a block that has been divided into multiple sub-blocks and subjected to first encoding and decoding, and decoded data and encoding of blocks that have already been encoded and decoded among blocks belonging to the second group. A means is provided to sequentially calculate a predicted value in each sub-block using all or part of the decoded data of the sub-blocks that have already been encoded and decoded in the block to be processed, and the predicted value is obtained. A second encoding means for encoding the difference value between the predicted value and the true value and a decoding means corresponding to the second encoding means are provided to execute encoding of one screen, and similarly, when decoding , obtain decoded data for blocks belonging to the first group using the first decoding means, and for each block belonging to the remaining groups, predict values in the blocks in the same way as during encoding. Providing a calculating means to obtain a predicted value, providing a decoding means corresponding to the second encoding means to obtain decoded data of the difference value, and calculating the sum of the predicted value and the decoded data of the difference value. A video signal encoding device that performs decoding of one screen. (3) The video signal encoding device according to claim 1 or 2, wherein orthogonal transformation is used in the first and second encoding means and decoding means according to claim 1 or 2. (4) The video signal encoding device according to claim 1 or 2, wherein the second encoding means and decoding means according to claim 1 or 2 use discrete sine transformation.