JPH06292028A - High efficient encoding and decoding device - Google Patents

Abstract

PURPOSE:To suppress propagation of an error and to attain high compression by making a code quantity constant. CONSTITUTION:An inter-frame prediction section 53 discriminates the similarity between inputted block data and a reference block to generate the reference clock thereby obtaining a prediction error. A compression mode selection section 50 gives data of an in-frame compression area to an orthogonal transformation section 16 as they are and data of an inter-frame compression area give a prediction error from the inter-frame prediction section 53 to the orthogonal transformation section 16. A quantization section 58 has an in-frame compression quantization table and an inter-frame compression quantization table, a quantization device selection section 54 selects a quantization means to quantize an orthogonal transformation coefficient. Since the inter-frame compression is adopted, high compression is attained.

Description

Detailed Description of the Invention

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high efficiency coding / decoding device using orthogonal transform.

[0002]

2. Description of the Related Art In recent years, digital compression of images has been studied. In particular, various standardization proposals have been proposed for high-efficiency coding using DCT (discrete cosine transform). The high-efficiency coding technique is for coding image data at a smaller bit rate in order to improve the efficiency of digital transmission and recording. In this method, one frame is divided into a plurality of small blocks (m pixels × n horizontal scanning lines), DCT processing is performed, and coordinate axis components are converted into orthogonal spatial frequency components (orthogonal components), whereby the spatial axis direction Redundancy can be reduced. The orthogonally transformed components are quantized to reduce the redundancy of the small block signal.

Further, variable length coding such as Huffman coding is applied to the quantized output to further reduce the data amount. Huffman coding performs coding based on the result calculated from the statistical code amount of the quantized output, assigning short bits to data with a high appearance probability and long bits to data with a low appearance probability. The variable length coding to be assigned reduces the total amount of data.

As described above, since variable length coding is adopted in high efficiency coding, if an error occurs even in 1 bit on the way, the code synchronization is lost and it becomes impossible to decode the subsequent data, so that the picture quality is improved. Is significantly deteriorated. Further, in the variable length coding, the compression code amount differs depending on the pattern. Therefore, when recording the compressed data in the storage medium, feedback control is performed according to the pattern in order to make the code amount constant for each frame. However, if there is a difference in the fineness of the picture between the first half and the second half of the screen, the position on the screen of the compressed data cannot be grasped from the recording position.

As a solution to these problems, in Japanese Patent Laid-Open No. 4-91587, one large block is formed by sample data at a plurality of discrete positions on the screen, and the code amount is made constant in units of this large block. A device for doing so has been proposed.

FIG. 10 is a block diagram showing this proposal.

The input digital video signal is given to the large block forming section 14. The large block forming unit 14 forms an input video signal into a frame and then into a large block. That is, the image data of each pixel is divided into macroblock units, which are a group of horizontal and vertical 8 × 8 pixel small blocks.
As shown in, a large block is composed of macroblocks (hatched portions) at a plurality of discrete positions on the screen. Figure 1
1 shows an example in which the screen is divided into five parts I0 to I4 and one macroblock of each part I0 to I4 is collected to form one large block. Other large blocks are similarly constructed. Since each small block is shuffled to form each large block, the amount of information in each large block is considered to be substantially the same regardless of the pattern.

The data of a large block is supplied to the small block forming unit 15 and converted into small blocks, and then supplied to the orthogonal transforming unit 16. The orthogonal transformation unit 16 orthogonally transforms the input data in small block units and outputs the transform coefficient to the quantization unit 20 via the buffer 17 and also to the data length estimation unit 18.

The quantizing unit 20 has a plurality of quantizers for quantizing with a plurality of quantizing widths for each band, and uses a quantizer designated by the quantizer selecting unit 19 for buffering. 17
Quantizes the transform coefficient from and outputs it to the variable length coding unit 21. The data length estimation unit 18 calculates the data amount when the transform coefficient is quantized with a predetermined quantization width for each large block, and outputs it to the quantizer selection unit 54.

This amount of data can be controlled by changing the quantization width. For example, if the quantization width is made coarse, the information deteriorates, but the dynamic range of the quantized output becomes small and the code amount also becomes small. Quantizer selection unit 19
Selects the quantizer of the quantizer 20 based on the output of the data length estimation unit 18 to make the code amount constant in large block units. The buffer 17 delays the orthogonal transform coefficient until the quantizer of the quantizer 20 is selected.

The quantized output from the quantization unit 20 is given to the variable length coding unit 21, the variable length coding unit 21 variable length codes the quantized output, and outputs the coded output via the transmission unit 22. . In this way, since the code amount is made constant in units of large blocks, the correspondence between the position of the encoded data and the screen position becomes clear, and even if an error occurs, the subsequent data can be reproduced, and the VTR Special playback is also possible.

FIG. 12 is an explanatory diagram for explaining a method of recording coded data of each large block.
No. 156792. Figure 1
Reference numerals 2 (a) to 2 (c) show first to third sync blocks, respectively.

The large block is composed of 2n small blocks, and 3 sync blocks (synchronous blocks) are allocated to the recording of the large block. A1 to An and B1 to Bn of the first sync block and the second sync block indicate the recording ranges of the small blocks. The fixed data amount of each block is recorded in each recording range. In the first and second sync blocks, the low band data to the high band data of each block are sequentially recorded. First and second
The high-frequency data that could not be written in the sync block of No. 3 is written in the third sync block. The recording ranges An 'and Bn' of the third sync block represent the high frequency data of the An and Bn blocks, respectively.

By recording in this way, even if an error occurs, or even if all recorded data of a predetermined sync block is not reproduced as in the case of high speed reproduction of a VTR, etc., the effective reproduced sync is reproduced. The screen can be reproduced by using the block data.

By the way, in order to further reduce the code amount,
Predictive coding that performs coding by using the correlation with other image data may be adopted. In this predictive coding, the difference between the previous frame and the current frame (prediction error) is obtained by utilizing the fact that the image data of the preceding and following frames have a correlation, and the prediction error is coded to determine the data amount. It is reducing more.

However, the apparatus of FIG. 10 is a method of shuffling small blocks in one image, and it is not possible to adopt interframe compression as it is. For this reason, when high compression is required, such as when compressing an image with a large amount of information on the screen such as high-definition television broadcasting, the quantization width is extremely large in order to sufficiently reduce the data amount. However, there is a problem that the quality of the reproduced image is deteriorated.

[0017]

As described above, in the conventional apparatus in which the code amount is made uniform in a large block unit by the shuffling, the predictive coding cannot be adopted and the high compression is required. There is a problem that the reproduced image is extremely deteriorated.

According to the present invention, it is possible to achieve high compression by inter-frame compression, to suppress error propagation by making the code amount constant in large block units, and to improve the image quality during special reproduction of VTR. An object is to provide a high efficiency encoding / decoding device.

[Structure of the Invention]

A high-efficiency coding / decoding apparatus according to the present invention sets an intra-screen compression area and a prediction compression area within a screen, and sets the positions of these intra-screen compression area and prediction compression area. A region control unit that periodically changes, a large block forming unit that forms a large block by a plurality of sample data of the in-screen compression region and the prediction compression region, and a conversion unit that divides the large block into a plurality of conversion units. If it is based on the in-screen compression area, it is orthogonally transformed, and if it is based on the prediction compression area, it is orthogonal transformation means that orthogonally transforms the prediction error and outputs transform coefficients, and the in-screen compression area Quantizing means for quantizing the transform coefficient based on the quantization width according to the intra-screen compression and quantizing the transform coefficient based on the prediction compression region with the quantization width corresponding to the predictive compression; Control means for stabilizing the code amount of the coded output based on the output of the quantizing means in units of the large blocks, and further, it has an intra-screen compression area and a predictive compression within the screen. And an encoding means for setting the area and encoding the data of the in-screen compression area and the predictive compression area area by in-screen compression or predictive compression, respectively, and assigning the encoded output of this encoding means to a plurality of sync blocks. , An output based on the in-screen compression is recorded in a predetermined recording range of the sync block, and an output based on the in-screen compression left unrecorded is recorded in another unused recording range, and based on the in-screen compression A recording means for recording the output based on the predictive compression in a recording range in which no output is recorded is provided, and one in-screen compressed screen for n screens and (n-1) predicted pressures are provided. Screen setting means for setting a screen, and large block forming means for forming a large block by sample data at discrete positions of the in-screen compressed screen and forming a large block by sample data at discrete positions of the predictive compression screen When the large block is divided into a plurality of conversion units and the conversion unit is based on the intra-screen compression screen, the orthogonal conversion is performed as it is, and when the conversion unit is based on the prediction compression screen, the prediction error is orthogonally converted. An orthogonal transform unit for outputting a transform coefficient, and a transform coefficient based on the intra-screen compression area is quantized with a quantization width corresponding to intra-screen compression, and a transform coefficient based on the prediction compression area is quantized according to the prediction compression. Quantizing means for quantizing,
Quantization control means for controlling the quantization width to make the code amount of the encoded output based on the output of the quantization means constant in large block units based on the intra-picture compression and large block units based on the predictive compression. It is equipped with.

[0020]

In the present invention, the in-screen compression area and the prediction compression area are set in the screen, and the large block is constructed by the sample data of these areas. The quantization control unit controls the quantization width to make the code amount constant in large block units. For the data in the prediction compression area, the code amount is reduced by orthogonally converting the prediction error.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a high efficiency coding / decoding device according to the present invention. In this embodiment, intraframe compression and interframe compression are adopted.

The input digital video signal is given to the large block forming section 14. The large block formation unit 14 forms a large block by a plurality of macro blocks at discrete positions on the screen, and outputs image data to the small block formation unit 15 in units of large blocks. The macroblock is composed of, for example, four luminance small blocks and two color difference small blocks.

The small block forming section 15 outputs the large block data to the terminal a of the switch 52 in small block units and also to the inter-frame predicting section 53. The output of the inter-frame prediction unit 53 is given to the terminal b of the switch 52. switch
52 is controlled by the compression mode selection unit 50. The compression mode selection unit 50 has a switch 52 when the intra-frame compression mode is selected.
To select the terminal a and apply the block data from the small block forming unit 15 to the orthogonal transform unit 16 as it is. Further, the compression mode selection unit 50 causes the switch 52 to select the terminal b when the interframe compression mode is selected, and gives the output of the interframe prediction unit 53 to the orthogonal transformation unit 16. The compression mode selection unit 50 causes the switch 53 to select the terminal a when the data from the small block formation unit 15 is data corresponding to the intra-frame compression area described later, and the data corresponding to the inter-frame compression area described later. If so, the terminal b is selected. Note that the inter-frame prediction unit 53 outputs a prediction error with respect to the image data of the previous frame, as will be described later.

The output of the switch 52 is given to the orthogonal transformation section 16. The orthogonal transformation unit 16 orthogonally transforms the data in small block units to obtain orthogonal transformation coefficients by the data length estimation unit 57 and the buffer 17.
Output to. The data length estimation unit 57 has a predetermined quantization table for the intra-frame compression block and a predetermined quantization table for the inter-frame compression block. In the intra-frame compression mode, the data length estimation unit 57 quantizes the transform coefficient using the quantization table for the intra-frame compression block to calculate the code amount. Also, the data length estimation section
In the inter-frame compression mode, 57 quantizes the transform coefficient using the quantization table for the inter-frame compression block to obtain the code amount. The data length estimation unit 57 gives the obtained code amount to the quantizer selection unit 54 in units of large blocks. The quantizer selection unit 54 is configured to select the optimum quantization unit of the quantization unit 57 based on the output of the data length estimation unit 57 in order to suppress a large block to a constant code amount.

FIG. 2 is an explanatory diagram for explaining the transform coefficients from the orthogonal transform unit 16. Tables 1 and 2 below show the quantization table for intraframe compression and the quantization frame for interframe compression of the quantization unit 58, respectively. It is for explaining the conversion table.

[0026]

[Table 1]

[Table 2] The quantizer 58 includes quantizers 1 to 8, and the quantizers 1 to 8 quantize the transform coefficient using the intra-frame compression quantization table or the inter-frame compression quantization table. Has become.

As described above, the spatial coordinate components from the switch 52 are transformed into frequency components by orthogonal transformation. The conversion coefficient has a DC component and an AC component indicating the average of the conversion coefficients, and is arranged from the horizontal and vertical low band to the high band as shown in FIG. The intra-frame compression quantization table is used for the transform coefficient in the intra-frame compression mode, and the quantization width is set for each horizontal and vertical band of the transform coefficient. As shown in FIG. 2, the conversion coefficient is divided into four bands a, b, c, from the horizontal and vertical low band to the high band.
When divided into d, for example, the quantizing means 3 has a quantization width Q1 for the transform coefficients in the bands a and b as shown in Table 1 in the intra-frame compression mode, and a quantum for transform coefficients in the bands c and d. The conversion width is Q2. The quantization widths Q1 to Q4 have a relationship of Q1 <Q4, and the quantization width is set smaller as the conversion coefficient in the lower frequency band. Further, the quantizing means 1 has a smaller quantizing width, and the quantizing means 8 has a larger quantizing width. That is, the code amount of the quantized output increases as the quantizing unit 1 decreases, and the code amount decreases as the quantizing unit 8 decreases.

On the other hand, the quantizers 1 to 8 use the interframe compression quantization table for the transform coefficients in the interframe compression mode. The inter-frame compression quantization table has the same structure as the intra-frame compression quantization table, and the quantization widths q1 to q4 are set according to the band of the transform coefficient. The quantization widths q1 to q4 have a relationship of q1 <q4. For example, in the interframe compression mode, the quantizing means 1 quantizes the transform coefficients in all the bands with the quantizing width q1 as shown in Table 2, and the quantizing means 8 performs the quantization in the bands a, b, c. The transform coefficient is quantized with a quantization width q3, and the transform coefficient in the band d is quantized with a quantization width q4.
Quantize with.

Generally, the difference between the quantization widths of the low-frequency component and the high-frequency component of the transform coefficient is set smaller in the inter-frame compression quantization table than in the intra-frame compression quantization table. Often.

In Tables 1 and 2, the combination of the quantization widths Q1 to Q4 and the combination of the quantization widths q1 to q4 are matched, but it is not necessary to match them.

The quantized output of the quantizing unit 58 is a variable length coding unit.
Give to 21. The variable length coding unit 21 is adapted to, for example, Huffman-code the quantized output and output the variable-length coded output via the transmission unit 22.

Further, the quantized output is output to the inverse quantizer 55 to create reference image data for inter-frame compression. The inverse quantizer 55 performs an inverse quantization process on the quantized output, restores the data before quantization, and outputs it to the inverse orthogonal transformer 56. The inverse orthogonal transformer 56 inversely orthogonally transforms the output of the inverse quantizer 55 into data before orthogonal transformation, and the interframe prediction unit 53
Output to.

FIG. 3 is a block diagram specifically showing the structure of the inter-frame predicting section 53 in FIG.

At the time of inter-frame prediction, a prediction error is obtained by subtracting the image of the previous frame from the image of the current frame as a reference image, and the amount of data is reduced by encoding only the prediction error. That is, the block data of the previous frame from the inverse orthogonal transformer 56 is given to the adder 60 of the interframe prediction unit 53. At the time of inter-frame prediction, the block data input to the adder 60 is a prediction error,
As will be described later, the adder 60 receives the block data of the previous frame from the switch 61 and adds the two inputs to reproduce the image data of the previous frame and output it to the frame buffer 62.

The frame buffer 62 delays the input block data for one frame period and supplies it to the frame memory 63 as reference block (reference image) data. The frame memory 63 stores the reference block data and supplies it to the predictor 64.

The block data of the current frame is given to the predictor 64 from the small block forming section 15. The input of the predictor 64 may be a small block, which is a unit for performing orthogonal transformation, or a set unit of a plurality of small blocks. Block data at discrete positions on the screen are sequentially input to the predictor 64. The predictor 64 refers to the reference block data stored in the frame memory 63, determines which position of the reference frame the input block data is most similar to, and creates reference block data. . In this case, the predictor 64 also creates a motion vector indicating which block of the reference frame is the reference block.

The reference block from the predictor 64 is given to the subtractor 65 and also to the adder 60 via the switch 61. The subtractor 65 subtracts the reference block data from the block data of the current frame from the small block forming unit 15 to obtain a prediction error, and outputs it to the terminal b of the switch 52. The subtractor 65 may perform the subtraction in units of a plurality of small blocks. The switch 61 is turned on only during inter-frame prediction, and supplies the reference block data from the predictor 64 to the adder 60. That is, in the intra-frame compression mode, since the block data from the inverse orthogonal transformer 56 does not have a prediction error, the adder 60 outputs it to the frame buffer 62 without adding it to the reference block.

Next, the operation of the embodiment thus constructed will be described with reference to the explanatory view of FIG. FIG. 4 shows a video frame.

The input video signal is converted into a large block in the large block conversion section 14 and further into a small block in the small block conversion section 15. The block data from the small blocking unit 15 is given to the terminal a of the switch 52 as it is, and the inter-frame prediction unit 53 obtains a prediction error from the previous frame and gives it to the terminal b of the switch 52.

The compression mode selection unit 50 divides the screen into a plurality of parts and determines for each part whether to select the intra-frame compression mode or the inter-frame compression mode. Regions I0 to I5 and P0 to P5 in FIGS. 4, 7 and 8 indicate units for switching compression modes, I0 to I5 indicate regions for intraframe compression, and P0 to P5 indicate regions for interframe compression. Is shown.

Now, in the x-th frame, the large block forming section 14 makes the areas I0 to I2, P3, P4 shown in FIG. 4 (a).
1 macroblock (broken line portion) is collected from 5 macroblocks to form one large block. The compression mode selection unit 50 causes the switch 52 to select the terminal a when the small blocks in the regions I0 to I2 of the large block of the xth frame are output from the small block formation unit 15. Further, the compression mode selection unit 50 causes the switch 52 to select the terminal b when the small blocks in the regions P3 and P4 are output from the small block formation unit 15.

The orthogonal transform section 16 is provided with the small block data of the areas I0 to I2 as it is, and the small block data of the areas P3 and P4 is provided with only the prediction error from the previous frame. That is, when the small block data of the areas P3 and P4 is input to the inter-frame prediction unit 53, the inter-frame prediction unit 53 compares the reference block of the previous frame with the input small block data and displays the screen of the small block data. By analogy with the upper position, the contents of the frame memory 63 are read and reference block data is created. The subtractor 65 subtracts the reference block data from the small block data to obtain the prediction error, and the switch 52
The signal is output to the orthogonal transformation unit 16 via the terminal b. Orthogonal transformation unit
16 orthogonally transforms the input data, outputs the transform coefficient to the quantizing unit 58 via the buffer 17, and supplies it to the data length estimating unit 57.

The data length estimation unit 57 is arranged in each of the areas I0 to I2.
Also, the amount of code when the transform coefficients for the regions P3 and P4 are quantized and variable-length coded is obtained, and the data length is output in a large block unit. The quantizer selecting unit 54 causes the quantizing unit 58 to select one of the quantizing units 1 to 8 based on the data length obtained in a large block unit.

When any of the selected quantizing means 1 to 8 receives the transform coefficient corresponding to the region I0 to I2, it quantizes the transform coefficient using the quantization table shown in Table 1, and then, When the transform coefficients corresponding to the areas P3 and P4 are input, the transform coefficients are quantized using the quantization table shown in Table 2 and output to the variable length coding unit 21. The variable length coding unit 21 performs variable length coding on the quantized output and outputs it via the transmission unit 22.

On the other hand, the quantized output is also given to the inverse quantizer 55 to create a reference image for the next frame. Inverse quantizer
Reference numeral 55 inversely quantizes the quantized output, and inverse orthogonal transformer 56 inversely orthogonally transforms the inverse quantized output and provides the result to interframe prediction unit 53.
The inter-frame prediction unit 53 creates reference block data based on the image data of the previous frame and stores it in the frame memory 63 (FIG. 3). As described above, the inter-frame prediction unit 53
The predictor 64 creates a reference block based on the similarity between the reference block stored in the frame memory 63 and the input block, and the subtractor 65 outputs the difference between the input block and the reference block as a prediction error.

In this way, the inter-frame prediction section 53 obtains a prediction error by subtracting the data of the corresponding blocks (blocks at the same position when the motion vector is 0) of the previous frame and the current frame. , The code amount of the prediction error coded output is extremely small.

In the next (x + 1) th frame, FIG.
As shown in (b), the large block forming unit 14 has the areas P0 and P0.
One macroblock (broken line portion) is collected from 1 and I2 to I4 to form one large block. The compression mode selection unit 50 selects the terminal a when the small block data of the areas P0 and P1 is applied to the switch 52, and the area I is selected.
When the small block data of 2 to I4 is applied to the switch 52, the terminal b is selected. Other operations are the same as in the x-th frame.

Next, the structure of the sync block by the encoded output will be described with reference to FIGS. 5 and 6. FIG. 5 shows the structure of a sync block by the coded output of the xth frame in FIG. Further, FIG. 6 shows areas I01 and I of FIG.
The specific data sequences of 02 and I03 are shown.

As described above, the x-th frame includes the intra-frame compression areas I0 to I2 and the inter-frame compression area P3,
It is composed of P4 sample data. I in FIG.
pq indicates an area in which the encoded outputs of the small blocks q included in the intra-frame compression area Ip are arranged. These regions Ipq are sequentially arranged from the low and middle frequency components of the code to the high frequency components. Codes that could not be written in these areas Ipq are arranged in portions that are not used in other areas. An inter-frame compression area P is set in the remaining area after arranging these data.
Arrange the encoded output of the small block q contained in p.

For example, as shown in FIG. 6A, in the area I01 of the first sync block, first, the encoded outputs of the small blocks 1 of the intra-frame compression area I0 are sequentially arranged from the low band to the high band. . Further, the encoded output of the small block 1 of the inter-frame compression area P3 is arranged in the remaining part of the area I01. In the area I02 of the first sync block shown in FIG. 6B, the small block 2 of the intra-frame compression area I0 is recorded.
The encoded outputs of are arranged in order from the low frequency range. In the area I03,
As shown in FIG. 6C, first, the intra-frame compression area I
All the components from the low band to the high band of the small block 0 of 0 are arranged, and in the remaining part, the high band components of the small block 2 of the intra-frame compression area I0 that could not be written in the area I02 are arranged. Further, the encoded output of the small block 2 of the inter-frame compression area P3 is arranged in the remaining area.

In this way, the codes in the intra-frame compression area are preferentially arranged, and if the codes cannot be arranged in the designated area, the middle and low compression areas of the intra-frame compression area are set in the remaining parts of other areas. In the case where data of all sync blocks cannot be played back like high speed playback of VTR by arranging the band component, high band component and inter-frame compression area in order of priority and configuring the sync block However, it is possible to reproduce a wide area on the screen by using the reproduced data of the compressed block in the frame.

As described above, in this embodiment, a large block is formed by a plurality of small blocks at discrete positions on the screen, the data length is obtained in units of large blocks, the quantizing means is selected, and the code amount is determined. In addition to homogenizing, the inter-frame prediction unit 53 creates the reference block data by determining the similarity between the input small block and the block data of the previous frame, thereby enabling inter-frame prediction and high compression. ing.

Further, a large block is formed by mixing a plurality of small blocks for intra-frame compression and a plurality of small blocks for inter-frame compression, and the code amount of the large block can be made substantially constant. . Further, the reference block of the inter-frame compression block is made to be the intra-frame compression block by changing the intra-frame compression area and the inter-frame compression area in a two-frame cycle and always making the screen center area the intra-frame compression area. The error can be prevented from propagating to the next frame.

In FIG. 4, the intra-frame compression area and the inter-frame compression area are changed in two frame cycles, but they may be changed in other cycles. Also, FIG.
In the above, the screen is equally divided into five, but other division methods may be used.
For example, as shown in FIG. 7, the central area may be further divided into two areas, an inter-frame compression area and an intra-frame compression area. Further, for example, as shown in FIG. 8, the screen may be divided into five parts in the left-right direction and two parts in the up-and-down direction, and the intra-frame compression region and the inter-frame compression region may be switched at a two-frame cycle. .

By the way, in the above embodiment, the intra-frame compression area and the inter-frame compression area are set in one frame. However, a predetermined frame of a plurality of frames is constituted by the intra-frame compression area, and the remaining frames are It may be composed of an inter-frame compression area. FIG. 9 shows an example in which intraframe compressed frames and interframe compressed frames are alternately provided every other frame.

The x-th frame shown in FIG. 9A is divided into five intra-frame compression areas, and one macro block (hatched portion) in each area constitutes a large block. Further, the (x + 1) th frame shown in FIG. 9B is divided into five inter-frame compression areas, and one macroblock (hatched portion) in each area constitutes a large block.

As described above, in the intra-frame compression and the inter-frame compression, the inter-frame compression has higher coding efficiency and high compression is possible. Therefore, when the usable code amount is the same, the high image quality can be obtained by the inter-frame compression. Therefore, in order to make the image quality of the intra-frame compressed frame and the inter-frame compressed frame uniform, it may be better to use different code amounts in the frames. In this case, the operation of the quantizer 58 is different from that of the embodiment shown in FIG.

That is, by changing the quantization width of the quantization unit 58 for the same pattern between the intra-frame compression frame and the inter-frame compression frame, the code amount of the large block of the inter-frame compression frame is changed to that of the intra-frame compression frame. It is smaller than the code amount of a large block. This reduces the code amount of the inter-frame compressed frame and allocates the code amount to the intra-frame compressed frame, thereby homogenizing and improving the image quality. In this case, the frame buffer 62 of FIG. 3 may be omitted.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the screen is divided into five areas and sample data is collected from each area to form a large block. The number of screen divisions is not limited. Also, the screen division method is not limited. Further, in the present embodiment, one reference frame is used in the inter-frame prediction, but a plurality of reference frames may be used. In this case, if a plurality of frame memories 63 of FIG. 3 are prepared. It is possible.

[0060]

As described above, according to the present invention, high compression is possible by inter-frame compression, the code amount is made constant in a large block unit to suppress error propagation, and VTR special reproduction is performed. There is an effect that the image quality at the time can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a high efficiency encoding / decoding device according to the present invention.

FIG. 2 is an explanatory diagram for explaining an example.

FIG. 3 is a block diagram showing a specific configuration of an interframe prediction unit in FIG.

FIG. 4 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 5 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 6 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 7 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 8 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 9 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 10 is a block diagram showing a conventional high efficiency encoding / decoding device.

11 is an explanatory diagram for explaining the conventional example of FIG.

12 is an explanatory diagram for explaining the conventional example of FIG.

[Explanation of symbols]

14 ... Large block conversion unit, 16 ... Orthogonal transformation unit, 50 ... Compression mode selection unit, 52 ... Switch, 53 ... Inter-frame prediction unit, 54 ... Quantizer selection unit, 58 ... Quantization unit

Claims (4)

[Claims] 1. An area control unit for setting an in-screen compression area and a prediction compression area in a screen and periodically changing the positions of these in-screen compression area and prediction compression area, and the in-screen compression area and prediction. A large block forming means for forming a large block by a plurality of sample data of a compressed area, and dividing the large block into a plurality of conversion units, and if the conversion unit is based on an in-screen compressed area, performs orthogonal transform as it is and predicts Orthogonal transform means for orthogonally transforming the prediction error to output a transform coefficient when it is based on the compression region, and quantizing the transform coefficient based on the in-screen compression region with a quantization width according to the in-screen compression, Quantizing means for quantizing the transform coefficient based on the predictive compression region with a quantization width according to the predictive compression; and a coding output code based on the output of the quantizing means by controlling the quantization width. Wherein the amount high-efficiency coding and decoding apparatus characterized by comprising a quantization control means for constant at atmospheric block. 2. The area control means always sets an in-screen compression area in the center of the screen.
A high-efficiency coding / decoding apparatus according to item 1. 3. An encoding means for setting an in-screen compression area and a prediction compression area in a screen and encoding the data of these in-screen compression area and prediction compression area area by intra-screen compression or prediction compression, respectively. The encoded output of the encoding means is assigned to a plurality of sync blocks, the output based on the intra-screen compression is recorded in a predetermined recording range of the sync block, and the output based on the intra-screen compression left unrecorded is used. And a recording means for recording the output based on the predictive compression in a recording range where the output based on the intra-frame compression is not recorded. . 4. An in-screen compressed screen and (n-
1) A screen setting means for setting one predictive compressed screen, and a large block composed of sample data at discrete positions of the intra-compressed screen, and a large block made up of sample data at discrete positions of the predictive compressed screen. A large block forming unit that configures the large block, and if the large block is divided into a plurality of conversion units and the conversion unit is based on an in-screen compressed screen, orthogonal transform is performed as it is An orthogonal transformation unit that orthogonally transforms an error and outputs a transformation coefficient, and a transformation coefficient based on the intra-frame compression area is quantized with a quantization width according to intra-picture compression to transform the transformation coefficient based on the prediction compression area into prediction compression. Quantizing means for quantizing with a corresponding quantizing width, and controlling the quantizing width to compress the code amount of the coding output based on the output of the quantizing means in the screen. A high-efficiency coding / decoding device comprising: a large block unit based on the above and a quantization control unit that makes constant in the large block unit based on the predictive compression.