CN1658674A - Method and device for encoding and decoding intra-frame prediction mode for video or image compression - Google Patents

Abstract

The invention discloses a method and device for encoding and decoding an intra-frame prediction mode for video or image compression. The present invention allows to use a type signal to indicate whether to transmit the intra prediction mode of each block in the set of blocks one by one. When the type signal indicates the direct intra-frame mode, the prediction mode of all blocks in the block set is the codec end's default, and there is no need to transmit the intra-frame prediction modes of each block in the block set one by one. This approach increases the flexibility of intra prediction and improves coding efficiency. The present invention is not limited to the field of video or image codec, and can also be extended to other signal processing applications.

Description

Method and device for encoding and decoding intra-frame prediction mode for video or image compression

technical field

The present invention relates to an electric digital data processing technology, in particular, to a method and device for encoding and decoding an intra-frame prediction mode applied to video or image compression.

Background technique

Traditional video coding standards such as H.261, H.263, H.26L, and H.264 standards formulated by the International Telecommunication Union ITU and MEPG-1, MPEG-2, and MPEG formulated by the International Organization for Standardization ISO's Motion Picture Experts Organization MPEG -4, etc. are all based on the Hybrid Coding framework. The so-called hybrid coding framework is a coding framework that comprehensively considers prediction, transformation and entropy coding methods, and has the following main features: 1. Use prediction to remove redundancy in the time domain; 2. Use transformation to remove redundancy in the space domain; 3. Statistical redundancy is removed by entropy coding.

The above-mentioned video coding standards all have intra-coded frames, namely I frames, and inter-frame coded frames, namely P frames, and I frames and P frames adopt different coding methods. The encoding process of the I frame is as follows: perform two-dimensional transformation on the original image data or the residual block obtained by intra-frame prediction; then quantize the transformation coefficient in the transformation domain; scan the two-dimensional transformation coefficient block obtained by quantization to make it Become a one-dimensional transformation coefficient sequence; finally entropy coding, that is, Huffman coding or arithmetic coding, etc. The encoding process of the P frame is as follows: use motion estimation to obtain the motion vector, then use inter-frame prediction based on motion compensation, and then perform two-dimensional transformation on the residual block obtained by inter-frame prediction, and then quantize the transform domain coefficients, and quantize the obtained Scan the two-dimensional residual block coefficients to make it into a one-dimensional residual coefficient sequence, and finally carry out entropy coding.

During intra-frame prediction, there are different modes according to different intra-frame prediction directions. As in H.264, there are a total of 9 modes for intra prediction. The information of these modes needs to be transmitted in the code stream, only in this way can the decoder decode correctly. In order to improve the efficiency of encoding in the intra-frame mode, the encoding in the intra-frame prediction mode needs to be predicted. According to the information of the adjacent blocks, the maximum possible prediction mode (mostporbably mode) of the current block can be obtained. A one-bit prediction mode flag (pre_mode_flag) is equal to 1 if the mode of the current block is equal to the maximum possible prediction mode. Otherwise, if not the same, the prediction mode flag is equal to 0, and then a value representing the intra prediction mode is passed. The decoder can obtain the actual intra prediction mode of the current block through the prediction mode flag and the value of the intra prediction mode when the prediction mode flag is 0.

In the existing method, when all prediction mode flags are 1 in a set of blocks including one block or more, each set needs N bits to indicate that all intra prediction modes in this block group are is the predicted maximum possible prediction mode. This is relatively wasteful.

Contents of the invention

The purpose of the present invention is to provide a video or image compression intra-frame prediction mode encoding and decoding method for the deficiencies of the prior art.

The object of the invention is achieved through the following technical solutions: a method for encoding and decoding intra-frame prediction mode for video or image compression, in which there is at least one set of blocks, the number of blocks contained in it is greater than 1 , and it uses a type signal to indicate how the intra-frame prediction mode information of each block exists in the code stream; if this signal indicates that the set of blocks adopts the direct intra-frame mode, then the intra-frame prediction mode information of each block is no longer transmitted in the code stream Prediction mode information. If this signal indicates that the set of blocks adopts the non-direct intra-frame mode, the intra-frame prediction mode information of each block in the set of blocks needs to be transmitted in the code stream.

Further, the encoding process includes:

1) The encoder determines whether the set of blocks adopts the direct intra mode according to the optimization strategy, and expresses it with a type signal in the code stream.

2) If this signal indicates that the set of blocks adopts the direct intra-frame mode, then the mode information of each block is not transmitted in the code stream. The mode of these blocks is the codec default mode.

3) If this signal indicates that the set of blocks adopts the non-direct intra-frame mode, then there is also a signal representing the intra-frame prediction mode information of each block in the code stream after this type of signal.

The decoding process includes:

1) According to the type signal in the code stream, it is judged whether the set of blocks adopts the direct intra-frame mode.

2) If the direct intra-frame mode is adopted, the intra-frame prediction mode of each block in the set of blocks is the codec default mode.

3) If the non-direct intra-frame mode is adopted, then the intra-frame prediction mode of each block in the set of blocks needs to be decoded from the subsequent code stream.

Another object of the present invention is to provide an encoding device for encoding and decoding intra-frame prediction mode for video or image compression.

The object of the invention is achieved through the following technical solutions, the encoding device includes: a switch K1. A judging device, which selects which intra-frame prediction mode to use according to a certain rule, thereby controlling the switch K1. A first predictive coding device, which adopts the direct intra-frame prediction mode to perform coding in the intra-frame prediction mode. A second predictive coding device, which adopts the non-direct intra-frame prediction mode to perform coding in the intra-frame prediction mode. The judging device is connected to the switch K1. The switch K1 is connected to the first predictive encoding device and the second predictive encoding device.

Further, the judging means first calculates the cost required by the direct intra prediction mode and the cost required by the indirect mode, and then judges whether the cost required by the direct intra mode is less than the cost required by the indirect mode. If yes, control the switch K1 to select the first predictive encoding device, and if not, control the switch K1 to select the second predictive encoding device. The first predictive encoding device is a direct intra-mode predictive device, and is used at the encoding end to perform prediction in the direct intra-mode.

The purpose of the present invention is also to provide a decoding device for intra-frame prediction mode coding and decoding of video or image compression.

The object of the invention is achieved through the following technical solutions. The decoding device includes: a switch K2 for judging whether to use the first predictive decoding device or the second predictive decoding device according to the type signal in the code stream. A first predictive decoding device, which uses the direct intra-frame prediction mode to decode the intra-frame prediction mode. A second predictive decoding device, which uses the indirect intra-frame prediction mode to decode the intra-frame prediction mode. The switch K2 is connected with the first predictive decoding device and the second predictive decoding device.

Further, the first predictive decoding device is a prediction device for direct intra-frame mode, and is used at the decoding end to perform prediction in the case of direct intra-frame mode.

The present invention has the following technical effects: the present invention can greatly improve the performance of encoding and decoding without increasing the complexity of encoding and decoding.

Description of drawings

Fig. 1 is the coding device block diagram of present existing method;

Fig. 2 is the block diagram of the decoding device of existing method at present;

Fig. 3 is a block diagram of an encoding device according to Embodiment 1 of the present invention;

FIG. 4 is a block diagram of a decoding device according to Embodiment 1 of the present invention;

Fig. 5 is the coding flowchart of embodiment 1 of the present invention;

Fig. 6 is a decoding flow chart of Embodiment 1 of the present invention.

Detailed ways

The present invention will be described in detail below according to the accompanying drawings.

Figure 1 shows an existing encoding device for intra-frame prediction, including a first prediction device.

The prediction device 1 uses a common intra-frame prediction method to perform intra-frame prediction on the current macroblock.

Fig. 2 shows an existing decoding device for intra prediction, including a first prediction device.

The prediction device 2 uses a common intra-frame prediction method to perform intra-frame prediction on the current macroblock.

The disadvantage of the existing method is that a lot of intra-frame mode information still needs to be transmitted for blocks with accurate mode prediction, and the overhead is relatively large. For flat areas and severe quantization, the coding efficiency is not high. In view of the deficiencies of the existing methods, the present invention will be described in detail below with reference to the accompanying drawings.

Example 1

Accompanying drawing 3 shows a coding device for intra-frame prediction applied to video or image compression, including: a second mode selection device for trying direct intra-frame prediction mode, a first mode selection device for trying normal intra-frame prediction mode A mode selection device, a second prediction device for direct intra-mode intra-frame prediction, a first prediction device for normal intra-frame intra-mode intra-frame prediction, a switch K1 for selecting the prediction device according to a control signal, and which intra-frame prediction is used for judging A device for judging the encoding method.

First, through the first mode selection device and the second mode selection device, the cost of the best mode under these two modes is obtained. Compare these two costs in the judging device, and choose a good one as the mode to use. According to this mode, it is selected to use the first prediction device or the second prediction device for intra prediction.

Accompanying drawing 4 shows a decoding device for intra-frame prediction applied to video or image compression, including: a second prediction device for direct intra-frame prediction mode, a first prediction device for common intra-frame prediction mode, Switch K2 for selecting the prediction mode.

The type information in the code stream controls which prediction method is selected by the switch K2. If the direct intra-frame prediction mode is selected, the second prediction device is used for intra-frame prediction, and if the common intra-frame prediction mode is selected, the first prediction device is selected for intra-frame prediction.

Example 2

Fig. 5 shows a coding process for intra-frame prediction applied to video or image compression. First calculate the cost of direct intra mode and normal intra mode, and then determine which mode has the lowest cost. If the cost of direct intra mode is small, use direct intra mode for encoding, and if the cost of normal intra mode is low, use normal intra mode to encode.

Figure 6 shows a decoding process for intra-frame prediction applied to video or image compression. First determine what mode the type signal represents. If it is a direct intra-frame mode, use the direct intra-frame mode for decoding, and if it is a normal intra-frame mode, use the normal intra-frame mode for decoding.

Example 3

An encoding device for intra-frame prediction applied to video or image compression, there is lbit in the code stream to indicate whether the macroblock is in the direct intra-frame mode. When the prediction modes of the 16 4×4 blocks are all the maximum possible prediction modes, the macroblock type is set to 0, that is, the direct intra-frame mode. At this time, the information of the prediction modes of the 16 4×4 blocks does not need to be written into the code separately. flow. Otherwise, the macroblock type is set to 1, and the mode information of each block is transmitted in the code stream.

A decoding device for intra-frame prediction applied to video or image compression, if the macroblock type of the received intra-frame prediction block is 0, that is, direct intra-frame mode, the prediction mode of all 4×4 blocks in the current macroblock All are maximum possible prediction modes, and there is no need to continue to read the mode information of each block from the code stream. Otherwise, continue to read the mode information of each block from the code stream.

Example 4

An encoding device for intra-frame prediction applied to video or image compression, there is lbit in the code stream to indicate whether the macroblock is in the direct intra-frame mode. When the prediction modes of the 16 4×4 blocks all use the same prediction mode (for example, dc is used), the macroblock type is set to 0, that is, the direct intra-frame mode. At this time, the prediction modes of the 16 4×4 blocks The information does not need to be written into the code stream separately, only the patterns shared by these blocks are transmitted in the code stream. Otherwise, the macroblock type is set to 1, and the mode information of each block is transmitted in the code stream.

A decoding device for intra-frame prediction applied to video or image compression. If the macroblock type of the received intra-frame prediction block is 0, that is, the direct type, the prediction modes of all 4×4 blocks in the current macroblock are all For the common mode (for example, dc is used for both), it is no longer necessary to read the mode information of each block of the prediction mode from the code stream, but only need to read the common mode of these blocks transmitted in the code stream. Otherwise, continue to read the mode information of each block from the code stream.

Claims (10)

1. a method that is used for the intra prediction mode encoding and decoding of video or image compression is characterized in that,

1) have the set of a piece at least, the number of the piece that it comprises is greater than 1, and it uses a type signal to indicate the existing way of intra prediction mode information in code stream of each piece.

2) if this signal indicates the set of this piece to adopt direct frame mode, no longer transmit the intra prediction mode information of each piece so in the code stream, if this signal indicates the set of this piece to adopt non-direct frame mode, then need to transmit the intra prediction mode information of each piece in the set of this piece in the code stream.

2. the method for intra prediction mode encoding and decoding according to claim 1 is characterized in that, cataloged procedure comprises:

1) whether encoder adopts direct frame mode according to the set of optimisation strategy decision piece, and represents with a type signal in code stream.

2) if this signal indicates the set of this piece to adopt direct frame mode, no longer transmit the pattern information of each piece so in the code stream.The pattern of these pieces is the pattern of encoding and decoding acquiescence.

3) if this signal indicates the set of this piece to adopt non-direct frame mode, in code stream behind this type signal, represent the signal of the intra prediction mode information of each piece so in addition.

3. the method for intra prediction mode encoding and decoding according to claim 2 is characterized in that, in the described step (2), the pattern of encoding and decoding acquiescence is meant that each piece all uses its maximum possible predictive mode.

4. the method for intra prediction mode encoding and decoding according to claim 1 is characterized in that, decode procedure comprises:

1) according to the type signal in the code stream, whether the set of decision block adopts direct frame mode.

2) if adopt direct frame mode, the intra prediction mode of each piece is the pattern of encoding and decoding acquiescence in the set of this piece.

3) if adopt non-direct frame mode, the intra prediction mode of each piece need be decoded from follow-up code stream and obtained in the set of this piece so.

5. the method for intra prediction mode encoding and decoding according to claim 4 is characterized in that, in the described step (2), the pattern of encoding and decoding acquiescence is meant that each piece all uses its maximum possible predictive mode.

6. an application rights requires the code device of the method for 1 described intra prediction mode encoding and decoding, it is characterized in that it comprises:

One K switch 1.

One judgment means selects to use which kind of intra prediction mode according to certain rule, thus control switch K1.

One first predictive coding device adopts direct intra prediction mode to carry out the coding of intra prediction mode.

One second predictive coding device adopts non-direct intra prediction mode to carry out the coding of intra prediction mode.

Judgment means links to each other with K switch 1.K switch 1 links to each other with the first predictive coding device, the second predictive coding device.

7. code device according to claim 6, it is characterized in that, in the described judgment means, judgment means is to calculate earlier cost that needs with direct intra prediction mode and the cost that needs with non-Direct Model, judges that then the cost that direct frame mode needs is the cost that needs less than non-Direct Model.If then control switch K1 chooses the first predictive coding device, choose the second predictive coding device if not control switch K1 then.

8. code device according to claim 6 is characterized in that, the described first predictive coding device is the prediction unit of direct frame mode, is used for directly predicting under the frame mode situation at coding side.

9. an application rights requires the decoding device of the method for 1 described intra prediction mode encoding and decoding, it is characterized in that it comprises:

One K switch 2 is used for the type signal according to code stream, judges whether to adopt the first prediction decoding device or adopts the second prediction decoding device.

One first prediction decoding device adopts direct intra prediction mode to carry out the decoding of intra prediction mode.

One second prediction decoding device adopts non-direct intra prediction mode to carry out the decoding of intra prediction mode.

K switch 2 links to each other with the first prediction decoding device, the second prediction decoding device.

10. decoding device according to claim 9 is characterized in that, the described first prediction decoding device is the prediction unit of direct frame mode, is used for directly predicting under the frame mode situation in decoding end.

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