JPH07135657A - Method and device for coding - Google Patents

Abstract

PURPOSE:To prevent the deterioration in picture quality due to a prediction error and to attain more efficient coding by arranging processing frames so that a frame with low correlation such as a scene change is not in existence between inter-frame coding processing frames. CONSTITUTION:Picture information is received by a picture input section 100. When a scene change detection section 101 detects a frame with small correlation between frames, a frame arrangement decision section 102 arranges processing frames so as not to refer the frame with low correlation. The coding method of each frame is tentatively stored in a frame arrangement storage section 103. Then a frame processing order revision section 104 reads frame data according to frame arrangement information in the frame arrangement storage section 103 and provides an output to a motion vector detection section 105. The processing after the stage of the motion vector detection section 105 is conducted by a usual method and the resulting data are outputted from a coding data output section 114.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving picture coding system, and more particularly to a moving picture coding method suitable for a moving picture coding recording / reproducing apparatus and a moving picture coding apparatus to which the coding method is applied. It is a thing.

[0002]

2. Description of the Related Art As a moving image encoding method, a method of compressing by utilizing correlation in the time axis direction is known. The encoding method is a method that uses the correlation between frames and between frames. In general, the coding using inter-frame correlation can improve the compression rate compared to the intra-frame coding, but when an error etc. occurs, it is propagated in the time axis direction, so the intra-frame coding is performed at a predetermined cycle. Refresh is needed.

FIG. 7 shows the relationship between the predicted frame and the frame to be processed in the method of compressing a moving image by utilizing the correlation in the time axis direction. In FIG. 7, I is an intra-frame coding processing frame, P is an inter-frame coding processing frame whose previous frame is a prediction frame, and B is a preceding and following frame and an interpolation frame generated from the preceding and following frames are prediction frames. This represents a frame interpolation coding processing frame. I is a frame that is compressed using only the correlation within the frame, and is used as a predicted frame in the subsequent P and B frame processing. P frame is the previous I frame,
Alternatively, the previous P frame is referred to as a prediction frame. The B frame refers to the preceding and following I and P frames and the interpolated image generated from the I and P frames as a prediction frame.

FIG. 8 shows a state in which the frames in FIG. 7 are rearranged in processing order. As the encoding process, first, the I-0 frame is intra-frame encoded. Next processed I-
P-3 frame is inter-coded with 0 frame as a prediction frame. Next processed I-0 frame,
The P-3 frame and the interpolated image generated from the I-0 and P-3 frames are B-1 frames as prediction frames.
The frame B-2 is frame-interpolated. Next, the P-6 frame is interframe-coded with the processed P-3 frame as a prediction frame. Next, the processed P
-3 frame, P-6 frame and interpolated image generated from P-3 and P-6 frame as a prediction frame B
-4 frames and B-5 frames are subjected to frame interpolation coding. The processing order of each frame is determined by the type of encoding processed in this way.

FIG. 9 shows an outline of the generated code amount of each frame when each frame is encoded in the order of FIG. As shown in the figure, generally, when obtaining the same image quality in each frame, the code amount of each frame increases in the order of B frame, P frame, and I frame.

Further, in the case of a system that handles moving images, the compression rate (rate) of encoded data must be suppressed below the data transfer rate of the recording medium. In this case, a buffer is provided in the output stage, and the quantization step is controlled by the untransmitted code amount in the buffer to control the code amount. Further, a virtual buffer having a different capacity is assumed depending on the type of encoding method in each frame, and the code amount is controlled by the virtual buffer. As shown in FIG. 9, when the same image quality is generally obtained, B frame, P
Since the generated code amount increases in the order of frames and I frames, this is used to change the virtual buffer capacity for each type of processing of each frame and control so that the buffer does not overflow or underflow as a whole. Is.

FIG. 21 shows a block diagram of a conventional moving picture coding apparatus. In FIG. 21, reference numeral 2100 denotes an image input unit, 2
Reference numeral 101 denotes an intra-frame coding processing frame that is coded by intra-frame processing, an inter-frame coding processing frame that uses the previous frame as a prediction frame, a preceding frame and a preceding frame, and an interpolating frame generated from the preceding and following frames as a prediction frame. A frame arrangement setting unit 2102 for setting the arrangement of frame interpolation coding processing frames to be processed is a frame processing order changing unit 2103 for changing the frame order to be processed according to the frame arrangement information set by the frame arrangement setting unit 2101. A motion vector detection unit 2104 for detecting a motion vector between a target frame and an already-processed frame, which is a prediction frame of the processing target frame, in block units, calculates a difference value for each block between the processing target frame and the prediction frame. This is a subtraction unit to be obtained.

Reference numeral 2105 denotes 1 of orthogonal transformation for the difference value.
The DCT unit 2106 that performs the DCT, and the DCT unit 2106
A quantizer for quantizing the transform coefficient obtained in 105;
Reference numeral 07 denotes an encoding unit that encodes the coefficient quantized by the quantization unit 2106 (for example, Huffman encoding), 2108 denotes an encoding method for each frame set in the frame arrangement setting unit 2101, and an encoding unit 2107. A code amount control unit for controlling the quantization step according to the generated code amount from 2), 2109 an inverse quantization unit, 2110 an inverse DCT unit, 2111 a frame memory unit for temporarily storing the processed frame, 21
Reference numeral 12 is an encoded data output unit.

The detailed operation of FIG. 21 when encoding with the frame arrangement shown in FIG. 8 will be described below. First,
The frame processing order changing unit 2102 sets the I-0 frame to D
It is sent to the CT unit 2105. Here, since the I-0 frame is intra-frame encoded, the motion vector detecting unit 210
3, the subtraction unit 2104 does not perform the process, and the DCT unit 21
At 05, DCT processing is performed for each block (for example, 8 × 8) to transform into the frequency domain. In the quantizer 2106, FIG.
Quantization is performed using a quantization table weighted for each frequency band as shown in FIG.

In general, an image has a strong correlation between adjacent pixels, so that energy is concentrated on low frequency components. Therefore,
As shown in FIG. 22, the low-frequency components are weighted so that the quantization step is small and the high-frequency components are large. The quantized coefficient is encoded by the encoding unit 21.
Entropy-encoded at 07, and the code data output unit 21
It is output from 12. In addition, the code amount control unit 2108 provides information about the intra-frame coding and the coding unit 2
The quantization step is controlled by the generated code amount of 107,
It is given to the quantizer 2106.

The quantizing unit 2106 calculates a new quantizing step based on the quantizing table shown in FIG. 22 and the quantizing step provided by the code amount controlling unit 2108, and quantizes each block. In FIG. 23, the code amount control unit 210
When the quantization step output from 8 is “2”, the quantization table newly calculated by the quantization unit 2106 is shown.

Further, quantized by the quantizer 2106,
The inverse quantization unit 2109 inversely quantizes the coefficient of each block,
The inverse DCT unit 2110 performs the inverse DCT process, and is temporarily stored in the frame memory unit 2111. The frame is referred to as a prediction frame in the subsequent processing.

Next, the frame processing order changing unit 2102 reads the P-3 frame. Since the P-3 frame is an inter-frame coded frame in which the I-0 frame is the prediction frame, the I-0 frame is read from the frame memory unit 2111 and the block unit ( For example, the motion vector is detected in 8 × 8). The subtraction unit 2104 uses the motion vector calculated for each block to calculate the difference value between the blocks.

In the DCT unit 2105, D is calculated for each block.
CT is performed, and the encoding unit 2107 performs entropy encoding. The code amount control unit 2108 controls the quantization step based on the information indicating that it is interframe coding and the generated code amount of the encoding unit 2107, and gives it to the quantization unit 2106. Further, the coefficients of each block quantized by the quantizer 2106 are inversely quantized and inverse DC by the inverse quantizer 2109.
Inverse DCT processing is performed by the T unit 2110, the motion vector information with the previous I-0 frame is referred to, added in block units, and temporarily stored in the frame memory unit 2111. The frame is referred to as a prediction frame in the subsequent processing. In this way, encoding is performed according to the information of the frame arrangement setting unit 2101.

[0015]

However, in the above-mentioned conventional coding method, interframe coding is performed when a frame having a small correlation between frames exists in a moving picture sequence due to a scene change or the like. Conversely, the image quality may deteriorate. In addition, there is a method of controlling so that intraframe coding is performed without taking a difference between frames in a frame having a low correlation, but the interframe coding processing frame and the frame interpolation coding processing frame are Since the virtual buffer size is set smaller than that of the processing frame, a large amount of code cannot be allocated and the image quality deteriorates.

In view of the above point, the present invention has an object to propose an encoding method capable of suppressing deterioration of image quality even if there is a frame having no correlation in the time axis direction.

[0017]

In order to achieve the above object, the present invention provides (1) an intra-frame coding processing frame, an inter-frame coding processing frame using the intra-frame coding processing frame as a prediction frame, and a frame. The inter-frame coding process frame and the frame are processed so that there is no frame having a low correlation such as a scene change between the inter-frame coding process frame and the next inter-frame coding process frame using the inter-frame coding process frame as a prediction frame. This is a configuration in which an inter-coding processing frame and a frame interpolation coding processing frame are arranged.

(2) The moving picture sequence is divided into a frame group composed of at least one frame having a strong correlation between each frame, and an intra-frame coding processing frame is formed for each frame group. This is a configuration in which the arrangement of the inter-frame coding processing frame and the frame interpolation coding processing frame is changed.

(3) In each frame group composed of a plurality of frames having strong correlation between each frame, a frame belonging to the frame group immediately preceding in time is not set as a predicted frame of a frame belonging to the frame group. As described above, the intra-frame coding processing frame, the inter-frame coding processing frame, and the frame interpolation coding processing frame are arranged.

(4) The moving picture sequence is divided into a frame group composed of at least one arbitrary number of frames, and in each frame group, an intra-frame coding processing frame, an inter-frame coding processing frame,
And a means for setting the arrangement of frame interpolation coding processing frames, a means for detecting a frame position with a low correlation between each frame in each frame group, and a means for detecting a frame with a low correlation between the frames before the frame with a low correlation. The intra-frame coding process frame, the inter-frame coding process frame, and the frame interpolation coding process frame are rearranged so that the frame is not referred to as a prediction frame in the subsequent inter-frame coding process frame.

(5) A means for detecting a frame having a low correlation between each frame in the moving picture sequence,
When performing the inter-frame coding process between the frames having low correlation detected by the means, the code amount control means in the inter-frame coding process frame controls the code amount in the inter-frame coding process frame from the inter-frame coding process frame. The configuration is switched to.

(6) In the moving image sequence, means for calculating the activity of the intra-frame coding processing frame, means for calculating the strength of correlation between the inter-frame coding processing frame and the prediction frame, and frame interpolation coding processing A unit for calculating the strength of correlation between a frame and a prediction frame, the activity of the intra-frame coding processing frame, the strength of correlation between the inter-frame coding processing frame and the prediction frame, frame interpolation coding processing It has a means for controlling the quantization step depending on the strength of the correlation between the frame and the predicted frame and the amount of untransmitted code in the transmission buffer, and switches the code amount control method for each processing frame.

(7) In the moving picture sequence, means for detecting frames with low correlation between each frame and strength of intraframe correlation in a plurality of frames before and after frames with low correlation detected by the interframe correlation detecting means , And a means for calculating the strength of inter-frame correlation, and the strength of intra-frame correlation and the strength of inter-frame correlation between the plurality of frames before the low-correlation frame and the plurality of frames after the low-correlation frame. , And the quantization step is controlled by the amount of untransmitted codes in the transmission buffer.

(8) If the video after the frame having a low correlation between the frames has stronger intra-frame correlation and inter-frame correlation than the video before the frame, the quantization step of the processing frame before the frame is performed in the transmission buffer. If the intra-frame and inter-frame correlations of the video after the frame are weaker than the video before the frame, the quantization step before the frame is controlled to be smaller than the quantization step calculated from the untransmitted code amount of The configuration is such that it is controlled to be larger than the quantization step calculated from the untransmitted code amount in the transmission buffer.

(9) The encoding processing unit is a field.

[0026]

According to the present invention having the above-described configuration, (1) inter-frame coding processing frames, inter-frame coding processing frames having the intra-frame coding processing frame as a prediction frame, and inter-frame coding processing frames and The intra-frame coding processing frame, the inter-frame coding processing frame, and the inter-frame coding processing frame are set so that there is no frame having a low correlation such as a scene change between the next inter-frame coding processing frames having the inter-frame coding processing frame as the prediction frame. Since the frame interpolation coding processing frame is arranged, a frame having low correlation in one-way prediction such as inter-frame coding processing frame is not used as a prediction frame, so that image quality deterioration due to prediction error can be prevented and one-way prediction frame Is performed only on highly correlated frames, so less degradation Perform gastric encoding.

(2) The moving picture sequence is divided into a frame group composed of at least one or more frames having strong correlation between each frame, and an intra-frame encoding processing frame is divided for each frame group, Since the arrangements of the inter-frame encoding processing frame and the frame interpolation encoding processing frame can be changed, it is possible to perform encoding with a frame arrangement suitable for each frame group and to perform encoding with less deterioration.

(3) In each frame group composed of a plurality of frames having strong correlation between each frame, a frame belonging to the frame group immediately preceding in time is not set as a predicted frame of a frame belonging to the frame group. As described above, since the intra-frame coding processing frame, the inter-frame coding processing frame, and the frame interpolation coding processing frame are arranged, a frame having low correlation in one-way prediction such as the inter-frame coding processing frame is set as a prediction frame. Since it does not, it is possible to prevent image quality deterioration due to prediction error and
Since the frame for which the directional prediction is performed is performed only for the frame having a strong correlation, the coding with less deterioration is performed.

(4) Low-correlation frame In order to prevent a frame before the frame from being referred to as a prediction frame in a subsequent inter-frame coding process frame, an intra-frame coding process frame, an inter-frame coding process frame, and a frame interpolation code Since the rearrangement of the processing frame is performed,
Image quality deterioration due to a prediction error can be prevented, and the frame in which the one-way prediction is performed is performed only for the frame having a strong correlation, so that encoding with less deterioration is performed.

(5) When performing inter-frame coding processing between frames having low correlation, the code amount control means in the inter-frame coding processing frame changes from the inter-frame coding processing frame to the intra-frame coding processing frame. Since control is switched to control, when a frame with low correlation is set as a prediction frame in an inter-frame coding processing frame, processing can be performed as intra-frame coding, and control can be performed so as to allocate a large code amount to the frame. Also, deterioration of the image quality of a processing frame having the frame as a prediction frame is prevented.

(6) Activity of intra-frame coding processing frame, strength of correlation between inter-frame coding processing frame and prediction frame, strength of correlation between frame interpolation coding processing frame and prediction frame, and in the transmission buffer Since the code amount control method is switched for each processing frame depending on the untransmitted code amount, the more optimal code amount can be assigned to each processing frame.

(7) Intra-frame correlation strength and inter-frame correlation strength between a plurality of frames before the low correlation frame and a plurality of frames after the low correlation frame,
Since the quantization step is controlled by the amount of untransmitted code in the transmission buffer, deterioration of image quality is prevented in the scenes before and after the scene change.

(8) If the video after the frame having a low correlation between the frames has stronger intra-frame correlation and inter-frame correlation than the video before the frame, the quantization step of the processing frame before the frame is performed in the transmission buffer. If the intra-frame and inter-frame correlations of the video after the frame are weaker than the video before the frame, the quantization step before the frame is controlled to be smaller than the quantization step calculated from the untransmitted code amount of Since the control is performed so as to be larger than the quantization step calculated from the untransmitted code amount in the transmission buffer, image quality deterioration is prevented in scenes before and after a scene change or the like.

(9) By using a field as a unit of coding processing, coding with less deterioration is performed in a sequence with a lot of motion.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A moving picture coding system according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a moving picture coding apparatus according to a first embodiment of the present invention.

In FIG. 1, 100 is an image input unit and 10 is an image input unit.
Reference numeral 1 is a scene change detection unit for detecting frames having a small correlation between frames, and 102 is a scene change detection unit 10
According to the information of 1, the intra-frame coding processing frame to be coded by the intra-frame processing, the inter-frame coding processing frame whose previous frame is the prediction frame, the preceding and following frames, and the interpolation frame generated from the preceding and following frames are generated. A frame placement determination unit that determines the placement of the frame interpolation coding processing frame to be a prediction frame, 103 a frame placement storage unit that temporarily stores the frame placement information obtained by the frame placement determination unit 102, and 104 a frame placement storage unit A frame processing order changing unit that changes the order of frames to be processed according to the frame arrangement information 103, and 105, in units of blocks, motion vectors of a processing target frame and an already processed frame that is a prediction frame of the processing target frame. The motion vector detection unit 106 detects a frame to be processed. Subtracting unit for obtaining a difference value between each block of the measurement frame, 107 DCT section for performing is one DCT orthogonal transform on the difference value, 108 DCT unit 1
A quantizer for quantizing the transform coefficient obtained in 07;
Is a coding unit that codes the coefficient quantized by the quantization unit 108 (for example, Huffman coding), 110 is a coding method of each frame stored in the frame arrangement storage unit 103, and a coding unit 109 Code amount control unit for controlling the quantization step according to the generated code amount of
Reference numeral 12 is an inverse DCT unit, 113 is a frame memory unit for temporarily storing processed frames, and 114 is an encoded data output unit.

Hereinafter, FIG. 10, FIG. 11, FIG. 12, FIG.
The operation of the block shown in FIG. 1 will be described in detail with reference to FIGS. 14 and 15. In FIG. 1, first, frame data is input from the image input unit 100 in the display order. The scene change detection unit 101 calculates a correlation between each frame input from the image input unit 100, and detects a frame having a low frame correlation as a scene change. The frame arrangement determination unit 102 arranges each frame process based on the scene change information detected by the scene change detection unit 101 so that a frame having a low correlation is not referred to as a predicted frame of an inter-frame encoding processing frame. The coding method of each frame determined by the frame placement determination unit 102 is temporarily stored in the frame placement storage unit 103. Next, the frame processing order changing unit 104 reads out frame data according to the frame arrangement information in the frame arrangement storage unit 103 and outputs the frame data to the motion vector detection unit 105.

The operations of the frame arrangement determining unit 102 and the frame processing order changing unit 104 will be described below.

FIG. 10 is a diagram showing, in the order of display, how the processing of each frame is performed by a preset encoding method. In FIG. 10, I represents an intra-frame coding processing frame, P represents an inter-frame coding processing frame, and B represents a frame interpolation coding processing frame, and the numbers indicate the display order in the same sequence. For example, P-9 indicates an inter-frame encoding processing frame, and the display order is the ninth. A case where the scene is changed from the fifth frame in the figure will be described.

FIG. 11 shows each frame in FIG.
The state where the frame processing order changing unit 104 arranges the frames in the encoding processing order is shown. As shown in the figure, as the encoding processing order, first, inter-frame encoding is performed with the P-0 frame as the previous frame as the prediction frame. Next, the I-3 frame is intra-frame encoded. Next, the preprocessed P-0 frame, I-3 frame, and the interpolated frame generated from P-0 and I-3 frames are set as B as the prediction frame.
-1 frame and B-2 frame are subjected to frame interpolation coding. Next, the P-6 frame is interframe-coded with the I-3 frame that has been processed as a prediction frame. next,
The B-4 frame and the B-5 frame are frame-interpolated by using the I-3 frame, the P-6 frame, and the interpolated frame generated from the I-3 and P-6 frame which have been processed as the prediction frame.

FIG. 12 shows the capacity of the virtual buffer for each processing frame for controlling the code amount of each frame in the encoding processing order of FIG. In this way, the virtual buffer capacity of the intra-frame coding processing frame in which a large amount of code is generated is the largest, the inter-frame coding processing frame, and the frame interpolation coding processing frame have the smallest virtual buffer capacity. The generated code amount is controlled. Using such a virtual buffer, the code amount control unit 11
At 0, the quantization step given to the quantization unit 108 is controlled by the untransmitted code amount in the virtual buffer. However, in the figure, due to the scene change, there is no correlation I-3
In a P-6 frame (point a) in which interframe coding is performed using a frame as a prediction frame, the interframe coding processing frame is controlled by the code amount control by the virtual buffer regardless of the fact that intraframe coding is actually performed. Since the code amount is controlled as, the image quality is significantly deteriorated.

On the other hand, in the frame arrangement determining unit 102 in FIG. 1, the information from the scene change detecting unit 101 that the scene has changed from the fifth frame is used in FIG.
Arrange the frame as shown in. FIG. 14 shows a state in which the frame arrangement shown in FIG. 13 is arranged in the encoding processing order by the frame processing order changing unit 104. In Figure 15,
14 shows the capacity of the virtual buffer for each processing frame for controlling the code amount of each frame in the encoding processing order of FIG. In this way, B-
In 5 frames, since the interpolated frames generated from the P-3 frame and the I-6 frame, and the P-3 and I-6 frames are used as the prediction frames, it is considered that a large prediction error does not occur. In addition, since the fifth frame whose image quality is deteriorated by the scene change in FIG. 12 is processed as the intra-frame encoding processing frame as shown in FIG. 15, the image quality is not deteriorated by the scene change. Further, in the frame after the scene change, the frame before the scene change is used as the prediction frame and the inter-frame coding is not performed, so that the image quality deterioration due to the scene change can be suppressed.

Regarding the processing after the motion vector detecting unit 105, the same processing as the conventional example of FIG. 21 is performed. In this way, the intra-frame coding processing frame and the inter-frame coding processing frame using the intra-frame coding processing frame as the prediction frame, and the inter-frame coding processing frame and the inter-frame coding processing frame as the prediction frame The intra-frame coding process frame, the inter-frame coding process frame, and the frame interpolation coding process frame are arranged so that there is no frame with a low correlation such as a scene change between the following inter-frame coding process frames.
Encode.

Next, a moving picture coding system according to another embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram of a moving picture coding apparatus according to the second embodiment of the present invention.

In FIG. 2, reference numeral 200 denotes an image input unit, and 20
Reference numeral 1 is a frame correlation detection unit that detects frames with a small correlation between frames, 202 is a frame group formation unit that forms a frame group composed of a plurality of frames with strong correlation between frames, and 203 is an interframe correlation detection unit 201
According to the frame group forming unit 202, it is generated from an intra-frame coding processing frame that is coded by intra-frame processing, an inter-frame coding processing frame that uses the previous frame as a prediction frame, a preceding and following frame, and a preceding and succeeding frame. And a frame arrangement determination unit that determines the arrangement of the frame interpolation coding processing frame in which the interpolation frame to be used as the prediction frame.

Reference numeral 204 denotes a frame layout storage unit for temporarily storing the frame layout information obtained by the frame layout determination unit 203. Reference numeral 205 denotes a frame processing order for changing the processing frame order according to the frame layout information in the frame layout storage unit 204. A change unit, 206 is a motion vector detection unit that detects a motion vector of a processing target frame and a processed frame that is a prediction frame of the processing target frame in block units, and 207 is a processing target frame and a prediction frame. A subtraction unit for obtaining a difference value for each block, 208 is a DC for performing DCT which is one of orthogonal transformations on the difference value
A T unit 209 is a quantization unit that quantizes the transform coefficient obtained by the DCT unit 208.

Reference numeral 210 denotes a coding unit for coding the coefficients quantized by the quantization unit 209 (for example, Huffman coding), 2
Reference numeral 11 denotes a code amount control unit for controlling the quantization step according to the coding method of each frame stored in the frame arrangement storage unit 204 and the generated code amount from the coding unit 210, and 21.
Reference numeral 2 is an inverse quantization unit, 213 is an inverse DCT unit, 214 is a frame memory unit for temporarily storing processed frames, and 21
Reference numeral 5 is an encoded data output unit.

The detailed operation of FIG. 2 will be described below with reference to FIGS. The moving image sequence input from the image input unit 200 is the interframe correlation detection unit 201.
Then, a frame with low correlation is detected. The frame group forming unit 202 forms a frame group composed of a plurality of frames having a strong correlation. The frame arrangement determining unit 203 determines the frame arrangement in the frame group based on the information of the inter-frame correlation detecting unit 201 and the information of the frame group forming unit 202.

FIG. 16 shows a state in which the moving picture sequence is divided into a frame group composed of a plurality of frames having a strong correlation. FIG. 16 is a diagram showing how frames are arranged in the same frame cycle in each frame group. In frame group 2, BBIBBBBP is one cycle, and in frame group 3, BIBP is 1
Frames are arranged as one cycle. This is because, for example, when the correlation strength extends over a plurality of frames within the same frame group where the correlation is strong to some extent, the frame group 2
As described above, by arranging a large number of B frames between I and P frames, more efficient encoding can be realized. On the other hand, when the correlation strength does not extend over a large number of frames, the frame group 3 This is because it is more effective to shorten the frame period as described above.

Further, as shown in FIG. 17, the frame period may be changed in the same frame group. In this way, the coding information of each frame obtained by the frame arrangement determination unit 203 is stored in the temporary frame arrangement storage unit 204. The frame processing order changing unit 205 sequentially reads the frame data according to the frame arrangement storage unit 204 and encodes the frame data. For the subsequent processing, the same processing as the conventional example of FIG. 21 is performed. In this way, the moving image sequence is divided into frame groups composed of at least one or more frames having strong correlation between each frame, and the intra-frame coding processing frame and the inter-frame processing are performed for each frame group. Coding is performed by changing the arrangement of the coding processing frame and the frame interpolation coding processing frame.

Next, a moving picture coding system according to still another embodiment of the present invention will be described with reference to the drawings. Figure 3
FIG. 9 is a block diagram of a moving picture coding apparatus according to a third embodiment of the present invention.

In FIG. 3, reference numeral 300 denotes an image input unit, and 30
Reference numeral 1 is a scene change detection unit that detects a frame having a small correlation between frames, 302 is a frame arrangement setting unit that presets an encoding method of each frame, 303 is a frame arrangement setting unit 302, and a scene change detection unit 301
According to the information of 1., the intra-frame coding processing frame to be coded by the intra-frame processing, the inter-frame coding processing frame whose previous frame is the prediction frame, the preceding and following frames and the interpolated frames generated from the preceding and following frames are predicted. A frame rearrangement unit that redetermines the arrangement of the frame interpolation coding processing frames to be frames.

Reference numeral 304 denotes a frame processing order changing unit for changing the order of frames to be processed in accordance with the frame arrangement information of the frame rearrangement unit 303, and 305 denotes a processing target frame and the processing target frame is a predicted frame, which has already been processed. A motion vector detection unit that detects a motion vector with respect to a frame in block units, a subtraction unit 306 that obtains a difference value for each block between the processing target frame and the prediction frame, 307
Is a DCT unit that performs DCT, which is one of orthogonal transforms on the difference value, and 308 is a quantizer that quantizes the transform coefficient obtained by the DCT unit 307.

Reference numeral 309 denotes a coding unit for coding the coefficient quantized by the quantization unit 308 (for example, Huffman coding), 3
10 is a code amount control unit for controlling the quantization step according to the coding method of each frame determined by the frame rearrangement unit 303 and the generated code amount from the coding unit 309, 311 is an inverse quantization unit, and 312 is an inverse unit. The DCT unit, 313 is a frame memory unit for temporarily storing the processed frames, and 314 is an encoded data output unit.

The detailed operation of FIG. 3 will be described below with reference to FIG. First, prior to the encoding process, the frame placement setting unit 302 sets the encoding method for each frame. FIG. 18A shows an example in which the coding method of each frame is set. In the figure, the encoding method of each frame is set so that encoding is performed in the cycle of BBIBBPBBP. In the moving image sequence input from the image input unit 300, the inter-frame correlation detection unit 301 detects a frame with low correlation. If there is a scene change between the prediction frame and the inter-frame coding processing frame as shown in FIG. 18A, the frame rearrangement unit 303 changes the frame layout to the prediction frame as shown in FIG. 18B. And inter-frame coding process Dynamically change so that there is no scene change between frames.

As described above, in the normal processing, the coding is performed at the cycle of BBIBBPBBP set in the frame arrangement setting unit 302, and the interframe coding in which the frame having a small correlation is set as the prediction frame occurs due to a scene change or the like. In this case, the frame arrangement is dynamically changed so that there is no scene change between the prediction frame and the inter-frame coding processing frame. After that, each frame is encoded in the same manner as in the conventional example of FIG. In this way, when a frame with low correlation is detected, the frame before the frame with low correlation is coded so that the frame before the frame is not referred to as a prediction frame in the subsequent inter-frame coding processing frame The processing frame and the frame interpolation coding processing frame are rearranged for coding.

Next, a moving picture coding system according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram of a moving picture coding apparatus according to the fourth embodiment of the present invention.

In FIG. 4, 400 is an image input unit, 40
Reference numeral 1 denotes an inter-frame correlation calculation unit that detects a correlation between frames, 402 denotes a frame arrangement setting unit that presets an encoding method for each frame, and 403 indicates a frame order to be processed according to the frame arrangement information of the frame arrangement setting unit 402. A frame processing order changing unit to change, 404 is a motion vector detection unit that detects a motion vector of a processing target frame and a processed frame that is a prediction frame of the processing target frame in block units, and 405 is a processing target frame Is a subtraction unit that obtains a difference value for each block between the prediction frame and the prediction frame.

Reference numeral 406 denotes a DCT section which performs DCT which is one of orthogonal transformations on the difference value, and 407 denotes the DCT section 406.
The quantizing unit 411 for quantizing the transform coefficient obtained in step 411 encodes the coefficient quantized by the quantizing unit 407 (for example, Huffman coding), and 412 is set by the frame arrangement setting unit 402. A coding amount control unit 408 that controls the quantization step based on the coding method of each frame, the strength of the inter-frame correlation calculated by the inter-frame correlation calculation unit 401, and the generated code amount from the coding unit 411. Is an inverse quantization unit, 409 is an inverse DCT unit, 410 is a frame memory unit for temporarily storing processed frames, and 413 is an encoded data output unit.

Hereinafter, referring to FIGS. 10, 11, and 19,
The operation of FIG. 4 will be described in detail. In FIG. 4, the frame layout setting unit 402 sets the coding method for each frame. FIG. 10 shows an example in which the coding method of each frame is set. In the figure, the encoding method of each frame is set so that encoding is performed in the cycle of BBIBBPBBP.

FIG. 11 is a diagram showing a state in which FIG. 10 is rearranged in the encoding processing order. The moving image sequence input from the image input unit 400 is the interframe correlation calculation unit 401.
Then, the frame with low correlation is detected. While the frame with low correlation is not detected, the frame processing order changing unit 403 reads out and processes the image data according to the information of the frame arrangement setting unit 402 in the encoding processing order. As shown in FIG. 10, when the scene changes from the B-5 frame, the interframe correlation calculation unit 401 gives this frame position to the code amount control unit 412.

In the code amount control unit 412, the I-3 frame including the scene change is set as the prediction frame, and P-
When the inter-frame coding process of 6 frames is started, as shown in FIG. 19, the capacity of the virtual buffer is changed from the inter-frame coding to the virtual buffer capacity for intra-frame coding to control the code amount. To do. After that, each frame is encoded in the same manner as in the conventional example of FIG. Thus, in the inter-frame coding processing frame, when a frame with low correlation is set as a prediction frame, processing is performed as intra-frame coding, control is performed so as to allocate a large code amount to the frame, and coding is performed. .

Next, a moving picture coding system according to the fifth embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram of a moving picture coding apparatus according to the fifth embodiment of the present invention.

In FIG. 5, reference numeral 500 denotes an image input unit, 50
1 is an activity calculation unit that calculates an activity that represents the fineness of an image in a frame, 502 is an interframe correlation calculation unit that detects correlation between frames, and 503 is a frame arrangement setting that presets the coding method of each frame. 504 is a frame processing order changing unit that changes the order of frames to be processed according to the frame arrangement information of the frame arrangement setting unit 503, and 505 is a processing target frame, and a processed frame whose prediction frame is the processing target frame. Is a motion vector detection unit that detects a motion vector for each block, and 506 is a subtraction unit that calculates a difference value for each block between the processing target frame and the prediction frame.

Reference numeral 507 denotes a DCT section for performing DCT which is one of orthogonal transformations on the difference value, and 508 denotes a DCT section 507.
The quantizing unit 512 quantizes the transform coefficient obtained in step 502. The quantizing unit 512 encodes the coefficient quantized by the quantizing unit 508 (for example, Huffman coding). The coding unit 513 is set by the frame arrangement setting unit 503. The encoding method of each frame, the intra-frame correlation strength obtained by the activity calculation unit 501, the inter-frame correlation strength calculated by the inter-frame correlation calculation unit 502, and the encoding unit 512 A code amount control unit for controlling the quantization step according to the generated code amount, 5
Reference numeral 09 is an inverse quantization unit, 510 is an inverse DCT unit, 511 is a frame memory unit for temporarily storing processed frames, 5
Reference numeral 14 is an encoded data output unit.

The operation of the code amount control unit 513 will be described below with reference to FIG. In FIG. 20, the line (d) indicates the conventional virtual buffer capacity for each encoding processing frame according to the frame arrangement setting unit 503. In the figure, the line (c) indicates the coding method of each frame set by the frame placement setting unit 503 and the activity calculation unit 5.
FIG. 10 is a diagram showing a state in which the capacity of the virtual buffer is variably controlled by the intra-frame correlation strength obtained in 01 and the inter-frame correlation strength calculated by the inter-frame correlation calculation section 502.

In the case of the figure, the sequence in the first half is a video image in which the correlation between frames is relatively strong, that is, a video image which is relatively easy to compress. By reducing the virtual buffer capacity, the code of each frame is coded. Control to reduce the amount. On the other hand, since the sequence in the latter half is a video in which the correlation between frames is weak, that is, it is difficult to compress, the virtual buffer capacity is increased in order to allocate a larger code amount to each frame.

As described above, the code amount control unit 513 controls the quantization step by the virtual buffer variably controlled for each frame and the code amount generated from the encoding unit 512. After that, each frame is encoded in the same manner as in the conventional example of FIG. In this way, the activity of the intra-frame coding processing frame, the strength of the correlation between the inter-frame coding processing frame and the prediction frame, the strength of the correlation between the frame interpolation coding processing frame and the prediction frame, and the The code amount control method is switched for each processing frame according to the transmission code amount, an optimal code amount is assigned to each processing frame, and encoding is performed.

Next, a moving picture coding system according to the sixth embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram of a moving picture coding apparatus according to a sixth embodiment of the present invention.

In FIG. 6, reference numeral 600 denotes an image input unit, 60
1 is an activity calculation unit that calculates an activity that represents the fineness of an image in a frame, 602 is an interframe correlation calculation unit that detects correlation between frames, and 603 is an activity that temporarily stores the activity calculated by the activity calculation unit 601. A storage unit, 604 is an interframe correlation storage unit that temporarily stores the interframe correlation information calculated by the frame correlation calculation unit 602, and 605 is a frame arrangement setting unit that presets the encoding method of each frame,
A frame processing order changing unit 606 changes the order of frames to be processed according to the frame arrangement information of the frame arrangement setting unit 605.

Reference numeral 607 denotes a motion vector detection unit for detecting, in block units, motion vectors of a processing target frame and an already processed frame which is a prediction frame of the processing target frame, and 608 denotes a processing target frame and a prediction frame. A subtraction unit for obtaining a difference value for each block, 609 is a DCT that performs DCT, which is one of orthogonal transforms, on the difference value
The unit 610 is a quantizer for quantizing the transform coefficient obtained by the DCT unit 609, and the reference numeral 611 is a coding unit for coding the coefficient quantized by the quantizer 610 (for example, Huffman coding).

Reference numeral 615 denotes the encoding method of each frame set by the frame arrangement setting unit 605, the activity for several frames stored in the activity storage unit 603, and the number stored in the inter-frame correlation storage unit 604. A code amount control unit for controlling the quantization step based on the inter-frame correlation information for the frames and the generated code amount from the encoding unit 615, 612 an inverse quantization unit, 613 an inverse DCT unit, 6
Reference numeral 14 is a frame memory unit for temporarily storing the processed frames, and 616 is an encoded data output unit.

The operation of the code amount control unit 615 will be described below. The code amount control unit 615 uses the inter-frame correlation storage unit 60.
Based on the inter-frame correlation information of 4, a frame with low inter-frame correlation is detected. Further, according to the inter-frame correlation information of the inter-frame correlation storage unit 604 and the intra-frame correlation information of the activity storage unit 603, the video after the frame having a low correlation between the frames is compared with the intra-frame correlation and the frame before the video before the frame. If the correlation is strong,
The quantization step of the processing frame before the frame is controlled to be smaller than the quantization step calculated from the untransmitted code amount in the transmission buffer obtained by the encoding unit 611, and the video after the frame is controlled to be the frame. If the intra-frame and inter-frame correlation is weaker than the previous video, the quantization step before the frame is controlled to be larger than the quantization step calculated from the untransmitted code amount in the transmission buffer.

In this way, when the scene changes greatly,
The code amount is controlled by the characteristics of the video before and after the scene change and the current untransmitted code amount. After that, each frame is encoded in the same manner as in the conventional example of FIG.

[0075]

As described above, according to the present invention, the following excellent effects are obtained. (1) Since a frame having low correlation in one-way prediction is not set as a prediction frame, image quality deterioration due to a prediction error can be prevented, and a frame in which one-way prediction is performed is performed only for a frame having strong correlation, which is more efficient. Encoding can be done. (2) The video sequence has a strong correlation between each frame,
It is divided into a frame group composed of at least one or more frames, and an intra-frame coding processing frame, an inter-frame coding processing frame,
Also, since the arrangement of the frame interpolation encoding processing frames can be changed, it is possible to perform encoding with a frame arrangement suitable for each frame group and perform more efficient encoding. (3) Since a frame with low correlation is not used as a prediction frame in one-way prediction, deterioration of image quality due to a prediction error can be prevented, and a frame for one-way prediction is performed only for a frame with strong correlation, which is more efficient. Encoding can be done. (4) Intra-frame coding processing frame, inter-frame coding processing frame, and frame-interpolation coding processing frame so that the frame before the low correlation frame is not referred to as a prediction frame in the subsequent inter-frame coding processing frame. Is dynamically performed, real-time processing is possible, image quality deterioration due to prediction error can be prevented, and the frame in which the one-way prediction is performed is performed only for the frame with strong correlation. Efficient encoding can be performed. (5) In the inter-frame coding processing frame, when a frame with low correlation is set as a prediction frame, processing can be performed as intra-frame coding, and control can be performed so as to allocate a large code amount to the frame. It is possible to prevent deterioration of the image quality of the processing frame in which the frame is the prediction frame. (6) Activity of intra-frame coding processing frame, strength of correlation between inter-frame coding processing frame and prediction frame, strength of correlation between frame interpolation coding processing frame and prediction frame, and non-transmission in transmission buffer Since the code amount control method is switched for each processing frame depending on the code amount, an optimum code amount can be assigned to each processing frame. (7) Quantization step according to intraframe correlation strength, interframe correlation strength, and untransmitted code amount in the transmission buffer between a plurality of frames before the low correlation frame and a plurality of frames after the low correlation frame Is controlled, it is possible to prevent image quality deterioration in the scenes before and after a scene change or the like. (8) The video after the frame where the correlation between frames is low,
If the intra-frame correlation and the inter-frame correlation are stronger than the video before the frame, the quantization step of the processing frame before the frame is controlled to be smaller than the quantization step calculated from the untransmitted code amount in the transmission buffer. ,
If the video after the frame has weaker intra-frame and inter-frame correlation than the video before the frame, the quantization step before the frame is larger than the quantization step calculated from the untransmitted code amount in the transmission buffer. Since it is controlled as described above, it is possible to prevent the image quality from being deteriorated in the scenes before and after the scene change or the like. (9) By using the field as the encoding processing unit, it is possible to more efficiently perform encoding in a sequence in which the motion is intense.

[Brief description of drawings]

FIG. 1 is a block diagram of an encoding device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an encoding device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of an encoding device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of an encoding device according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of an encoding device according to a fifth embodiment of the present invention.

FIG. 6 is a block diagram of an encoding device according to a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between prediction frames in encoding using inter-frame prediction.

FIG. 8 is a diagram showing a state in which frames are arranged in encoding order.

9 is a diagram showing the generated code amount of each frame when each frame is encoded in the order of FIG.

FIG. 10 is a diagram showing a state in which a coding method of each frame is set.

FIG. 11 is a diagram showing a state in which frames are arranged in encoding order.

FIG. 12 is a diagram showing the capacity of a virtual buffer for each processing frame.

FIG. 13 is a diagram showing a state in which a coding method of each frame is set.

FIG. 14 is a diagram showing a state in which frames are arranged in encoding order.

FIG. 15 is a diagram showing the capacity of a virtual buffer for each processing frame.

FIG. 16 is a diagram showing a state in which a moving image sequence is divided into a plurality of frame groups.

FIG. 17 is a diagram showing a state in which a moving image sequence is divided into a plurality of frame groups.

FIG. 18 is a diagram showing how the processing frame configuration of a frame group is changed when a scene change exists in a moving image sequence.

FIG. 19 is a diagram showing the capacity of the virtual buffer for each processing frame.

FIG. 20 is a diagram showing the capacity of the virtual buffer for each processing frame.

FIG. 21 is a block diagram of a conventional encoding device.

FIG. 22 is a diagram showing a quantization table.

FIG. 23 is a diagram showing a quantization table.

[Explanation of symbols]

 100 image input unit 101 scene change detection unit 102 frame arrangement determination unit 103 frame arrangement storage unit 104 frame processing order change unit 105 motion vector detection unit 106 subtraction unit 107 DCT unit 108 quantization unit 109 encoding unit 110 code amount control unit 111 Inverse quantization unit 112 Inverse DCT unit 113 Frame memory unit 114 Code data output unit

Claims (9)

[Claims] 1. Intra-frame coding for coding a moving image by intra-frame processing, inter-frame coding for using a previous frame as a prediction frame, and preceding and following frames and interpolation frames generated from the preceding and following frames. A coding method for performing coding by combining frame interpolation coding as a prediction frame, comprising interframe coding processing frames between intraframe coding processing frames and intraframe coding processing frames as prediction frames, and between frames In order not to have a frame with low correlation such as a scene change between the next inter-frame coding process frame in which the coding process frame and the inter-frame coding process frame are prediction frames,
An encoding method comprising arranging an intra-frame encoding processing frame, an inter-frame encoding processing frame, and a frame interpolation encoding processing frame. 2. A moving picture sequence is divided into a frame group composed of at least one or more frames having a strong correlation between each frame, and an intra-frame coding processing frame and a frame are divided for each frame group. An encoding method characterized by changing the arrangement of inter-coded frames and frame-interpolated coded frames. 3. In each frame group composed of a plurality of frames having strong correlation between each frame, a frame belonging to a frame group immediately preceding in time is not set as a prediction frame of a frame belonging to the frame group. 3. The encoding method according to claim 1, wherein an intra-frame encoding processing frame, an inter-frame encoding processing frame, and a frame interpolation encoding processing frame are arranged. 4. A motion picture sequence is divided into frame groups composed of at least one or more arbitrary number of frames, and in each frame group, an intra-frame coding processing frame, an inter-frame coding processing frame, and Frame interpolation coding processing A means for setting the arrangement of frames and a means for detecting a frame position with low correlation between each frame in each frame group are used to detect a frame with low correlation, The intra-frame coding process frame, the inter-frame coding process frame, and the frame interpolation coding process frame are rearranged so that this frame is not referred to as a prediction frame in a subsequent inter-frame coding process frame. Encoding method. 5. In each frame of an intra-frame coding processing frame, an inter-frame coding processing frame, and a frame interpolation coding processing frame, the frame is divided into at least one or more processing blocks, and each processing block is divided. For each moving image data, a code amount control means for controlling a quantization step according to an untransmitted code amount in a transmission buffer is provided for each frame processing, and the code amount control means is switched for each processing frame. A coding device for controlling the code amount for each frame, in the moving image sequence, having detection means for detecting a frame with low correlation between each frame, between frames with low correlation detected by the detection means, When performing interframe coding processing, the code amount control means in the interframe coding processing frame is set to the interframe coding processing frame. Encoding apparatus characterized by switching the code amount control in the intraframe coding processing frame from. 6. In a moving picture sequence, a means for calculating the activity of an intra-frame coding processing frame, a means for calculating the strength of correlation between an inter-frame coding processing frame and a prediction frame, and a frame interpolation coding processing frame. Means for calculating the strength of the correlation between the prediction frame and the intraframe coding processing frame, the strength of the correlation between the interframe coding processing frame and the prediction frame, the frame interpolation coding processing frame and the prediction An encoding device having means for controlling a quantization step according to the strength of correlation with a frame and the amount of untransmitted code in a transmission buffer, and switching the code amount control method for each processing frame. 7. In a moving image sequence, means for detecting frames with low correlation between each frame, and strength of intraframe correlation in a plurality of frames before and after the frames with low correlation detected by the interframe correlation detection means, And a means for calculating the strength of interframe correlation, a plurality of frames before the low correlation frame, the strength of intraframe correlation in the plurality of frames after the low correlation frame, the strength of interframe correlation, And an encoding device which controls the quantization step according to the amount of untransmitted code in the transmission buffer. 8. If the video after a frame with a low correlation between frames has stronger intra-frame correlation and inter-frame correlation than the video before a frame, the quantization step of the processing frame before the frame is untransmitted in the transmission buffer. It is controlled to be smaller than the quantization step calculated from the code amount, and if the video after the frame has weaker intra-frame and inter-frame correlation than the video before the frame, the quantization step before the frame is not stored in the transmission buffer. 8. The encoding apparatus according to claim 7, wherein the encoding step is controlled to be larger than the quantization step calculated from the transmission code amount. 9. The encoding method according to claim 1, wherein the encoding processing unit is a field.