JPH06245205A - Method and device for coding interlace picture - Google Patents

Abstract

PURPOSE:To encode an interlace picture with a high efficiency and high quality. CONSTITUTION:A prediction error signal 52 is obtained by subtracting a prediction signal 60 from an input picture signal 51, picture elements of a luminance block included in a macro block in a picture are properly rearranged at a block rearrangement section 21, picture elements of a quantized signal 53 is subjected to oblique zigzag scanning or simple vertical scanning at a scanning selection device 24, and variable length code data 54 are outputted from a Huffman coder 25. The signal 53 is subjected to inverse quantization and inverse transformation, picture elements of a block are rearranged by a block rearrangement device 33, a quantization error signal 55 is obtained and it is added to the signal 60, a decoded signal is stored in frame memories 38,39, motion compensation is executed in motion compensation circuits 42,43, to obtain an interpolation prediction signal 66 and the prediction signal 60. Thus, adaptive prediction of a field/frame, block rearrangement, and oblique zigzag scanning or simple vertical scanning are properly selected and the purpose is attained with a minimum quantity of the hardware.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interlaced image signal encoding method and apparatus. Specifically, it is intended to provide an image coding method and apparatus for reducing the value of large prediction error data that is likely to occur when predictively coding and transmitting an interlaced image signal.

[0002]

2. Description of the Related Art In videophones and video conferences,
The moving image signal to be transmitted has a huge amount of information. Therefore, conventionally, various methods have been used to efficiently encode a moving image signal by encoding the moving image signal. By utilizing the correlation between the pictures (frames or fields) of the image signal, the one used for this high efficiency encoding,
There is inter-picture predictive coding that predicts the current picture from the previous or subsequent picture. The difference value for each pixel between the image signal of the current picture and the image signal of the immediately preceding picture is obtained as prediction error data, and only the obtained prediction error data is encoded and transmitted. This allows
The information amount of the image to be encoded and transmitted is reduced.

However, when the object to be imaged has no motion or the motion is small, the inter-picture predictive coding can be an effective high-efficiency coding means because the inter-picture correlation is high, but when the moving area is large. Since the correlation between pictures is low, there is a drawback that large prediction error data is generated and the image quality is deteriorated. Motion-compensated inter-picture predictive coding is used as a means for correcting this. In motion-compensated inter-picture encoding, a motion vector, which is the amount of movement of an imaging target between the current picture and the previous picture, is detected before obtaining prediction error data between pictures. When the motion vector is obtained, the prediction error data with respect to the current picture at the position shifted according to the motion vector in the previous picture is obtained. The obtained prediction error data is transmitted to the receiving side together with the motion vector.

Here, a motion vector in motion-compensated inter-picture predictive coding will be described with reference to FIG. In FIG. 4, reference numeral 100 denotes a current picture, and assuming that the picture is composed of, for example, 1 line of 704 dots and 480 lines, the current picture 100 is divided into blocks of, for example, 16 × 16 pixels. Therefore, assuming that the block 103 is a block for detecting a motion vector, 8 pixels in each of the horizontal direction and the vertical direction relative to the block (broken line) at the same position in the picture 101 immediately before the block 103, + A block that is larger by 7 pixels in the direction, that is, a 31 × 31 pixel search region 104 (one-dot chain line) that includes a block with a broken line in the center is set as a region in which a block having the highest degree of correlation with the block 103 is searched. Therefore, in the search area 104, the block 103 is sequentially shifted by one pixel in the horizontal direction and the vertical direction to obtain the difference for each corresponding pixel, and the degree of correlation with the block 103 is determined from the obtained difference value. The evaluation value of is calculated. As the evaluation value, for example, a sum of absolute values of difference values or a sum of squares of difference values is used. Evaluation area calculation result, search area 1
If the block 102 has the smallest evaluation value in 04, the vector 109 from the center of the block indicated by the broken line at the same position as the block 103 to the center of the block 102 is set as the motion vector for the block 103.

If the prediction error data between pictures corrected using the motion vector thus obtained is coded and transmitted, the amount of transmission information is greatly reduced as compared with the interframe coding without motion compensation. To be done. In the above, 1
The same effect can be obtained by using the previous (front) picture 101, but using the next (back) picture.

However, when the picture is completely changed and there is no correlation between the pictures as in the scene change, inter-picture predictive coding is performed.
The prediction error data may be larger than the data of the current picture only. Therefore, in a scene change or the like, it is desirable to use intra-picture encoding that encodes data of only the current picture, not inter-picture predictive encoding.

When inter-picture predictive coding using motion compensation is performed, it may be determined that a motion vector has occurred due to the noise included in the image signal although there is no actual motion part. . In such a case, inter-picture predictive coding that does not use motion compensation is more suitable.

Therefore, in order to realize more effective coding of image signals, the coding mode to be used for each unit block to be coded is between intra-picture coding and forward (past) pictures. It is effective to determine the inter-picture predictive coding, the inter-picture predictive coding with the backward (future) picture, and the interpolative predictive coding using both the forward and backward pictures.

Interpolation predictive coding will be described with reference to FIG. Each picture is processed in block units as described in FIG. I picture (In
In trapicture), intra-picture coding is performed on all blocks included in the picture. P picture (Pred
ictive picture), one of the inter-picture predictive coding and the intra-picture code having the smaller prediction error data is selected for each block. The image used for prediction is the decoded signal stored in the buffer memory.

In a B picture (Bidirectional picture), not only a forward (past) I or P picture can be used for detecting prediction error data, but also a backward (future) I or P picture can be used for prediction. . When the rear I and P pictures are used, the decoded signals once stored in the buffer memory are used for the front I, P pictures, B pictures and the rear I, P pictures.

When the interpolative prediction coding for detecting the prediction error data using the forward and backward I and P pictures is selected, two forward and backward I and I for one block in the B picture are selected. Two pieces of motion vector information are obtained by referring to the P picture. The values of these two motion vector information are
It is independently obtained in the respective search areas (see 104 in FIG. 4) in the I and P pictures which are the forward and backward reference pictures.

An image signal motion-compensated by a motion vector obtained by referring to the forward I and P pictures is R, and the backward I and P pictures are
If the image signal motion-compensated by the motion vector obtained by referring to the P picture is S, the internally predicted signal for interpolation prediction encoding of the block that is the target of prediction of the target B picture is (R + S) / As 2, the internal prediction signal for interpolation prediction encoding of the block that is the target of the current B picture prediction is obtained.

A moving picture coding apparatus using such a prediction signal is roughly classified into a moving picture coding apparatus for communication and a moving picture coding apparatus for storage media. There are some differences in the motion compensation prediction structure between the two.
Real-time encoding is important for the moving picture coding device for communication, and the image used for prediction is one of the past ones.
It is one reproduced image (forward I, P picture). On the other hand, in the moving image coding apparatus for storage media, the reference images used for prediction are two reproduced images (forward and backward I and P pictures). One of the two (back I, P
For the (picture), the original order of the images is different from the processing order, so the future order is used for the screen order.

First, an outline of a conventional moving image coding prediction structure for communication will be described, and then an outline of a conventional moving image coding prediction structure for a storage medium will be described as an extension thereof. In the following description, the term prediction means prediction including compensation by a motion vector, that is, motion compensation.

1) Predictive structure of moving picture coding for communication The moving picture coding apparatus for communication is defined by CCITT (International Telegraph and Telephone Consultative Committee) H.261, and the coding screen is 16 × 16.
Encoding is performed for each unit called a macro block corresponding to a luminance signal unit of a pixel. One macroblock includes four luminance blocks in a luminance signal unit of 8 × 8 pixels and two color difference blocks for a total of six blocks. The 8 × 8 pixels in the luminance block included in the macro block are arranged as shown in the box in FIG. 7, and are scanned in diagonal zigzag according to the order shown by the numbers in the box in FIG. 6 of each block. Orthogonal transform, for example, discrete cosine transform, quantized, and the quantized value is "0,0,0, ..., 0" followed by a length (run) and a value (level) that is not "0", Variable Length Code as a function of both
Is encoded as a sequence of. This is also called a run-level two-dimensional variable length code (see CCITT H.261).

A plurality of macro blocks
A method such as prediction is switched according to the type of macroblock by classifying into types. When the macroblock types are classified according to the prediction method, there are two types: intra-frame (Intra frame) coded macroblocks and interframe (Inter frame) predictive coded macroblocks.

When a prediction error from a past picture such as a scene change becomes large, intraframe coding is used for processing a macroblock, and the signal of the current picture is subjected to discrete cosine transform and further quantized. .

When there are many parts in which the current picture is similar to the past picture, interframe predictive coding is selected, and the motion vector is used in the macroblock from the position of the current macroblock in the past picture. Then, prediction is performed from the image at the displaced position, and the prediction error is quantized by, for example, discrete cosine transform.

2) Predictive structure of moving picture coding for storage media In the case of a moving picture coding apparatus for storage media (ISO IS 11172-2), two screens are used for prediction (forward and backward I, P). Picture) is allowed. Using a set of several images so that it can be played back from the middle of the moving image,
This is called an image group (Group of Pictures). There are the following three types of screens in the image group.

I screen: Intra frame coding screen P screen: Inter frame (Predictive) predictive coding screen B screen: Bidirectional predictive coding screen

The I screen is a screen in which all macroblocks are intra-frame coded, and is required to be used as a reference for prediction in the image group, which enables processing within the image group. Therefore, this type is used to maintain the independence of the image groups.

In the P screen, intraframe coding (Intra) and interframe predictive coding (Inter) can be selected for each macroblock as in the function of moving picture coding for communication.

The B screen is a unique screen type newly set in the image coding for storage media, and not only the past (forward) I and P screens are used for prediction but also the future (rearward) I and P screens. The screen is also a screen that can be used for prediction.

The rear I and P pictures have already been processed and are stored in the buffer, and they are in the future in the order of the screen. The use of the past (forward) and future (backward) images for prediction is called bidirectional prediction or interpolation prediction. Also, prediction from past reproduced images is called forward prediction, and prediction from future images is called backward prediction.

The types of each macroblock included in the screen are intraframe coding (intra) that does not use both forward and backward, forward predictive coding that uses forward, backward predictive coding that uses backward, and forward and backward. It can be classified into four types of interpolation predictive coding using both.

The motion vector of this screen is 0 for intra-frame coding, 1 for inter-frame predictive coding with forward or backward, and 1 for both forward and backward interpolating predictive codes for each macroblock. In the case of conversion, two will be attached. This B screen is not only subjected to passive interpolation, but the prediction error that occurs therein is coded in the same manner as in the P screen.

The processing order of the frames is different from the order of the screens, and some B screens are skipped in the screen order and the P
After processing the screen, process the skipped B screen. The purpose of this peculiar frame structure of video coding for storage media is to improve prediction accuracy by bidirectional prediction (interpolation prediction). This frame structure of moving picture coding for storage media also has a period of I and P screens (M, m in the case of FIG. 5).
If the value of + n) is small, it can be used for communication as well. Therefore, the coding structure of the interlaced image will be described below by using the structure of the moving image coding for storage media.

3) Coding structure of interlaced image Regardless of whether it is for communication or for storage media, a moving image has a basic structure of almost interlaced fields and a frame consisting of two fields. To avoid confusion with the term frame for a field, the following description will avoid the term frame in the sense of an image and use the term picture for that. A field is an image in which the time interval is half the frame time interval and the vertical resolution of the image is half the frame. Fields which are numbered from 0 and are adjacent to each other are called even field and odd field.

A frame is an image obtained by compounding (interlacing) two adjacent field images for each horizontal scanning line. Therefore, the vertical resolution of the frame is twice that of the field.

The interlace is 1 / the vertical resolution.
This is an image scanning method that scans two field images at twice the frequency in time to reduce flicker (flicker) of the image and to secure the vertical resolution.

As found for communication and storage media, video encoders have developed picture structures for improved predictive power. Interlacing is generally used for scanning a moving image, and an image coding apparatus needs to effectively apply interlacing to a structure for predicting moving image coding to improve prediction accuracy. The development of the mechanism was an important issue. In interlaced image coding, there are roughly two types of prediction structures, a field structure and a frame structure, which will be described below.

(1) Field Structure It has an image to be encoded and a plurality of (0 to 4) images used for prediction, and they are all field images. The prediction there may be done "between fields" or "between frames". The "between fields" means that the field intervals are odd, and the "between frames" means that the field intervals are even. The prediction between "frames" and "fields" depends on which picture memory is used for prediction. This can be adaptively changed for each macroblock.

(2) Frame structure It has an image to be coded and reference images used for a plurality of predictions, and they are all frame images. Since the reference image is a frame, if the y-direction component of the motion vector used for prediction is an even number, the prediction will be from an even field to an even field or from an odd field to an odd field. When the motion vector used for the prediction has an odd number in the y direction, the prediction is called from the odd field to the odd field or from the odd field to the even field, and is called different parity prediction. These can be selected by the value of the y-direction component of the motion vector.

In the frame structure, using one motion vector per macroblock is called frame prediction. It is called field prediction to use two motion vectors per macroblock for two blocks belonging to an even field and two blocks belonging to an odd field among four luminance blocks. Frame prediction and field prediction can be adaptively changed for each macroblock. This is called frame / field adaptive prediction.

In any adaptive prediction, the DCT
The selection of two types of block arrangements has an effect in dividing a macro block into blocks to apply (discrete cosine transform). This is a frame / field adaptation D
Call CT. The arrangement of these two types of blocks is shown in FIG. 7 and FIG.
Is shown in.

FIG. 7 shows the arrangement of luminance pixels (frame type division) during frame processing, and 8 × 8 luminances included in each of the four luminance blocks included in one macroblock. For each pixel, each circle has a block number 0 (even block), a triangular block has a block number 1 (even block), a square has a block number 2 (odd block), and a hexagon has a block number 3 ( (Odd block)
Represents a luminance pixel, and a macro block is divided into four luminance blocks in a cross shape. Such an arrangement is called a cross-shaped arrangement of luminance blocks.

FIG. 8 shows an arrangement (field type division) of luminance pixels at the time of field processing, and 8 × 8 pixels included in each of four luminance blocks included in one macroblock. 7 are represented by circles, triangles, squares, and hexagons for each luminance block as in the case of FIG. Here, the luminance pixel of block number 0 (even block) represented by a circle and the luminance pixel of block number 2 (odd block) represented by a square are alternately arranged in a row in the left half. And the luminance pixel of the block number 1 (even block) represented by the triangular mark and 6
Luminance pixels of block number 3 (odd block) represented by square marks are alternately arranged in horizontal rows in the right half. Such an arrangement is called an alternate arrangement of luminance blocks.

The field structure and frame structure of (1) and (2) above are not fixed and can be adapted for each picture (ISO-IEC / JTC1 / SC29 / WG11 NO328).
TM3 (Test Model 3) of the CCITT SGXV Working Party XV / 1 Expe
rts group on ATM Video Coding AVC-400 also has description).

As described above, in the frame structure, frame / field adaptive prediction and frame / field adaptive DCT (block rearrangement) are the main techniques. In the field structure, prediction selection from a plurality of fields and averaging are performed. It can be said to be the main adaptive prediction technology. Next, the coding technique after DCT and quantization will be described.

(3) Scan selection mechanism In any prediction structure, any adaptive prediction, and any block arrangement, it is effective to adaptively switch the scan order within a block of DCT (discrete cosine transform) coefficients. There is. Because, in the field structure and the frame structure, when the frame / field adaptive DCT selects a field, what is encoded is a field image, but the field image becomes a horizontally long image with an aspect ratio of pixel intervals of 1: 2. This is because the DCT coefficients after DCT are distributed longer in the vertical direction.

Further, when the frame DCT having the frame structure is selected, the motion causes a horizontal comb shape in the encoded frame image, and the prediction error is also likely to take a comb shape in the horizontal direction. , DCT coefficients are likely to exist in the vertical direction up to high frequencies. In addition, since the block layout selection mechanism and the scan selection mechanism have a complementary relationship with each other, when the block layout selection mechanism is omitted, or when the block layout is fixed to the frame type (cross-shaped array),
Furthermore, the effect of scanning selection is great. To do this,
Conventionally, switching between the diagonal zigzag scanning already described with reference to FIG. 6 and the vertical zigzag scanning shown in FIG. 9 has been performed. Similar to FIG. 6, FIG. 9 shows the arrangement of 8 × 8 pixels in the luminance block included in the macro block, and the scanning is performed in vertical zigzag according to the order indicated by the numbers in the box.

In general, when coding is performed in the moving area of an interlaced image, the high frequency component of the DCT (discrete cosine transform) coefficient in the vertical direction appears strongly not only in the input image but also in the prediction error signal. Therefore, normal DC
If the T (discrete cosine transform) coefficient is encoded by the diagonal zigzag scanning in FIG. 6, the encoding efficiency will be reduced.

[0043]

Whether the field structure is applied or the frame structure is applied, generally, in coding an interlaced image, not only the input image signal but also the prediction error signal is subjected to the discrete cosine. Since the high frequency component of the transform coefficient in the vertical direction appears strongly, there remains a problem to be solved that the coding efficiency is lowered by the coding using the diagonal zigzag scanning.

However, in order to solve this problem, when switching between diagonal zigzag scanning and vertical zigzag scanning, the amount of scanning hardware is about twice as large as when fixed to diagonal zigzag scanning. There was a task to be done.

[0045]

An interlaced image signal that forms one frame by two fields including many macroblocks each including a macroblock of 16 × 16 pixels including four luminance blocks of 8 × 8 pixels as a processing unit. The subtractor for obtaining the prediction error signal by taking the difference between a certain input signal and the prediction signal, the first block rearranger for changing the arrangement of the luminance blocks in the prediction error signal, and the arrangement of the blocks have been changed. A converter for discrete cosine transforming the prediction error signal to output a transformed signal, a quantizer for quantizing the transformed signal to obtain a quantized signal, and a 8 × 8 pixel signal in the luminance block. A scan selector for selecting the scan order, a Huffman encoder for obtaining variable-length code data from the scan-selected pixel signals, and a quantizer output from the quantizer. An inverse quantizer for receiving the received signal and inversely quantizing it to output an inversely quantized signal; an inverse transformer for inversely transforming the inversely quantized signal by discrete cosine and outputting an inversely transformed signal; Second block rearrangement unit for returning the arrangement of the luminance blocks rearranged by the block rearrangement unit to the original arrangement and outputting as a quantization error signal, and the quantization error signal and the prediction signal are added. And a first selector switch for switching the output of the adder according to the frame of the image, and an output of the non-linear filter corresponding to the switching of the first selector switch. And the first and second frame memories for respectively storing the motion compensation macro blocks and the motion-compensated macro blocks from the signals stored in the first and second frame memories according to the instruction of the motion vector obtained from the input signal. First and second motion compensating circuit of outputting the first and second motion compensated signals removed, respectively, first and second
, One of the first and second motion-compensated signals, the interpolated prediction signal, and no signal. And a second changeover switch for outputting the prediction signal to be applied to the subtractor.

[0046]

In the first block rearranger, rearrangement is performed so that the block arrangement is optimum for frame processing and field processing. In the scan selector, an optimum scan that minimizes the generated code amount is selected from the diagonal zigzag scan or simple vertical scan for the 8 × 8 pixels in the luminance block. The scan output is converted into variable length code data by the Huffman encoder and output. By selecting one of the simple vertical scanning and the oblique zigzag scanning, the above-mentioned problem to be solved is solved without expanding the hardware.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A circuit configuration diagram of an embodiment of the present invention will be described with reference to FIG. In this embodiment, all pictures have fields / fields.
The frame adaptive DCT is performed, and the scan changing function is performed for all pictures.

Reference numeral 50 denotes an image signal input terminal, and the input image signal 51 input from this terminal subtracts the prediction signal 60 by the subtracter 20 to obtain a prediction error signal 52. The prediction error signal 52 passes through the block rearranger 21 and the converter 22.
Outputs a signal 53 that is orthogonally transformed, for example, discrete cosine transformed, quantized by the quantizer 23, and quantized, and the scan selector 24 selects a scan type and outputs a variable-length code. The Huffman encoder 25 outputs the run and level two-dimensional variable-length code data 54. The quantized signal 53 is inversely quantized by the inverse quantizer 31 and inversely transformed by the inverse transformer 32, and the quantized error signal 55 is obtained through the block rearranger 33. The adder 34 adds the quantized error signal 55 and the prediction signal 60 to obtain a decoded signal 56.
The decoded signal 56 is applied to the changeover switch 36.

The decoded signal 56 is sent to the frame memory 38 or 39 via the terminal e or f of the changeover switch 36.
Applied and stored. An image signal of a B frame is applied to the input terminal 50, the changeover switch 36 is connected to the terminal g when processing a B picture, and an image signal of a front or rear I or P picture is applied to the input terminal 50. The changeover switch 36 is connected to the terminal e or f when processing the forward or backward I and P pictures. Therefore, the composite signal 56 of the front or rear I and P pictures is stored in the frame memories 38 and 39, and the input image signal 51 is stored in the motion compensation circuits 42 and 43.
An image of a block motion-compensated from the forward or backward I or P picture stored in the frame memory 38 or 39 according to the instructions of the vector signals 62 and 63 output from the motion vector detector 46 that detects the motion vector from the Read the signal to obtain a motion compensated signal 64 or 65,
This is applied to the terminals a and c of the interpolation circuit 44 and the changeover switch 45. When the B picture is processed, it is not stored in the frame memories 38 and 39.

The interpolation circuit 44, which receives the motion-compensated signals 64 and 65 from the forward or backward I and P pictures,
The interpolation prediction signal 66 is calculated and output, and this is applied to the terminal b of the changeover switch 45.

When the terminal a or c is selected by the changeover switch 45, a motion-compensated signal is selected from the forward or backward I and P pictures, and the predicted signal 60 is selected.
Will be output as. When the terminal b is selected, the interpolation prediction signal 66 is output as the prediction signal 60. When the grounded terminal d is selected, “0” is output as the prediction signal 60. The changeover switch 45 is changed over by a control signal from the outside (not shown) in which an optimum mode is selected for each luminance block included in a macroblock in the image.

In the changeover switch 45, the terminal b is selected when the B picture is processed and when the interpolation prediction is selected for the macro block.

Either one of the terminals e and f of the changeover switch 36 is alternately selected at the time of processing the forward or backward I and P pictures, which will be described with reference to FIG.

In FIG. 2, B pictures are B1, B2.
B3 ..., I, P pictures are I1, I2, I
, 3, and B pictures and I pictures (I, P pictures) are alternately arranged.

When the I1 picture is processed, the terminal e of the changeover switch 36 is selected, and the noise-removed signal 57 of the I1 picture which is the picture preceding the B1 picture is stored in the frame memory 38. Next, the changeover switch 36 is switched to the terminal f, and the noise-removed signal 57 of the I2 picture, which is the picture behind the B1 picture, is stored in the frame memory 39. Then, the prediction signal 60 of the B1 picture is obtained from the switch 45.

Next, the changeover switch 36 is switched to the terminal e, and the noise-removed signal 57 of the I3 picture, which is the picture behind the B2 picture, is output to the frame memory 3.
The prediction signal 60 of the B2 picture is obtained from the switch 45 by using this and the I2 picture already stored in the picture memory 39 as the picture preceding the B2 picture. In the following B3 picture as well, the changeover switch 36 is similarly changed over by a control signal not shown.

There is one type of macroblock type MB1 in the I picture, and when the macroblock type MB1 is selected, the changeover switch 45 is at the position of the terminal d. Also in this case, the block rearrangement is independently performed and the frame / field DCT is performed. Scan selection is also performed independently.

In the P picture, the macroblock type can be selected from two types of macroblock types MB1 and MB2, including one type of I picture. In the macroblock type MB2, the prediction frame and the reproduction frame are different. When the changeover switch 36 is the terminal e, the changeover switch 45 selects the position of the terminal c, and when the changeover switch 36 is the terminal f, the changeover switch 45 selects the position of the terminal a.

When the field prediction is selected for the macroblock type MB2, the vector signal 62 or 63 is different between two even and odd blocks, and the prediction is performed separately. Also in the P picture, the block rearrangement is independently performed, and the frame / field DCT is performed.
Scan selection is also performed independently.

In the B picture, the changeover switch 45 is the intra-picture prediction at the position of the terminal d, the forward (or backward) prediction is at the position of the terminal c, and the terminal b, similar to the conventional storage media encoding processing. Interpolation prediction at the position of, terminal a
At the position of, backward (or forward) prediction is selected.

In the B picture, the same processing as the conventional storage media encoding processing is performed, and there are four macroblock types, MB3 to MB6. Macro block
In the type MB3, the changeover switch 45 is at the position of the terminal d, and there is intra-picture prediction, macroblock type MB4.
In (MB5), the changeover switch 45 is at the position of the terminal c (a), and is forward (backward) prediction, macroblock type MB.
6, the changeover switch 45 is at the position of the terminal b, and the interpolation prediction is selected. Also in B pictures, block rearrangement is performed independently, and frame / field DC
T is performed. Scan selection is also performed independently.

The above macroblock types MB1 to M
B6 for picture type, field / frame processing,
Sorting by the number of motion vectors V and the processing of encoding,

For I picture, MB1: frame / field DCT, V = 0, intra picture coding

In P picture, MB1: frame / field DCT, V = 0, intra picture coding MB2: frame / field adaptive prediction, V = 1,
2, frame / field DCT

For B pictures, MB3: frame / field DCT, V = 0, intra-picture coding MB4: frame / field adaptive prediction, frame / field
Field DCT, V = 1, 2, forward predictive coding MB5: frame / field adaptive prediction, frame /
Field DCT, V = 1, 2, backward predictive coding MB6: frame / field adaptive prediction, frame /
Field DCT, V = 2, 4, interpolative prediction coding. In each picture, the macroblock type with the smallest value of the prediction error signal 52 is selected.

In the block rearranger 21 shown in FIG.
1 of one macroblock included in the prediction error signal 52
6 × 16 luminance pixels (during intra-picture prediction) or luminance prediction error pixels (during inter-picture prediction) are rearranged as shown in the cross arrangement in FIG. 7 or the alternate arrangement in FIG.

The block rearrangement unit 21 is a mechanism for selecting two types of block arrangements, that is, a cross arrangement and an alternating arrangement, and the selection is made by an instruction from the control unit not shown in FIG. In accordance with a control signal from this control unit, one of the two block arrangements is arranged and passed to the quantizer 23 in block units.

In order to select these two kinds of block arrangements by an instruction of a control unit (not shown), a publicly known method (TM of the above-mentioned document ISO-IEC / JTC1 / SC29 / WG11 NO328) is selected.
3 (see Test Model 3)).

The cruciform array (FIG. 7) and the alternating array (FIG. 8) of the luminance blocks represent the spatial position within the macroblock i.
(0 ≦ i ≦ 15) and j (0 ≦ j ≦ 15), and X _ij
Is the luminance pixel of the macroblock, and the luminance block number is k
21 + k is expressed by (0 ≦ k ≦ 1) and l (0 ≦ l ≦ 1), and the spatial position in each luminance block is m (0 ≦ m ≦ 7).
And n (0 ≦ n ≦ 7), and B _klmn is the pixel of four luminance blocks, the cross-shaped array of luminance blocks at the time of frame processing shown in FIG. 7 is B _klmn = X _{m + 8k} , _n It can be expressed as _{+ 8l} .

The alternate arrangement of the luminance blocks during the field processing shown in FIG. 8 can be expressed as B _klmn = X _{m + 8k} , _{2n + l} .

The block rearrangement unit 33 reverses the rearrangement performed by the block rearrangement unit 21 to restore the array of the quantization error signal 55 to the array of the prediction error signal 52.

In the scan selector 24, 8 in the luminance block
Diagonal zigzag scanning is performed on the x8 luminance pixels in the order shown by the numbers in the box in FIG. 6, or the 8 × 8 luminance pixels shown in FIG. 3 is simply shown by the numbers in the box in FIG. A simple vertical scan for vertically scanning from the top or a scan that will reduce the code amount is selected, one of the scans is performed, and the output is applied to the Huffman encoder 25.

Whether the scan selector 24 (FIG. 1) selects diagonal zigzag scanning, which is the pixel processing order, or simple vertical scanning is determined by a control signal from a control unit (not shown in FIG. 1). Either one of the processing order of these two pixels is selected, and the pixel signal is sent to the Huffman encoder 25 in the processing order.

There is the following method for the control unit (not shown) to select the processing order of these two pixels.

There is an a priori method of selecting the smaller sum of the runs (zero run + 1) of each block in the macroblock when both processing orders are taken. This is based on the assumption that the code amount increases as the run increases, but the effect is hardly reduced as compared with the method of comparing the code amounts. The amount of calculation is small, but it is not the method that gives the best results.

Next, the features of the simple vertical scanning shown in FIG. 3 will be described. This simple vertical scanning can be realized with a smaller amount of hardware than the vertical zigzag scanning of FIG. 9, and has the advantage that its verticality is completely retained. The reason is that the data (quantized DCT coefficients) arranged in the memory in the normal horizontal scanning order is VLC (variable length coding).
This means that the amount of address conversion hardware that gives the processing order can be significantly reduced. In this simple vertical scanning, since the lower 3 bits of the address are used as they are for the vertical address and the next 3 bits are used for the horizontal address, almost no hardware is required for address conversion.

This is usually DCT (discrete cosine transform)
It is simpler than the diagonal zigzag scanning (FIG. 6) and the vertical zigzag scanning (FIG. 9) used for encoding, and affects the hardware amount of the entire selection mechanism of the diagonal zigzag scanning and the simple vertical scanning. The selection mechanism for diagonal zigzag scanning and vertical zigzag scanning is twice the amount of hardware for diagonal zigzag scanning alone, but the selection mechanism for diagonal zigzag scanning and simple vertical scanning is the amount of hardware for diagonal zigzag scanning alone. It can be realized with almost the same amount of hardware. Thus, the new simple vertical scan has the advantage of being a simple mechanism. The properties of simple vertical scanning are almost the same as those of vertical zigzag scanning. As described above, the new simple vertical scan is a scan order that enables simple hardware implementation while maintaining the scan selection mechanism.

[0078]

As is apparent from the above description, the present invention has the following effects. That is, a new scan was prepared as the type of macroblock to be encoded. There, since the means for switching the scanning order of the encoded discrete cosine transform block from the normal diagonal zigzag scanning to the simple vertical scanning is provided, the coding efficiency is improved in the case of the conventional diagonal zigzag scanning. We solved the problem of deterioration with a simple hardware configuration. Because of such advantages, the effect of the present invention is extremely large.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a picture position diagram showing a position of a picture for explaining a switching operation of two frame memories which are components of FIG.

FIG. 3 is a processing sequence diagram showing a processing order of 8 × 8 pixels included in one luminance block used in the present invention.

FIG. 4 is a principle diagram for explaining an operation principle of conventional motion vector detection.

FIG. 5 is a picture position diagram for explaining an operation of detecting a motion vector from conventional forward and backward pictures.

FIG. 6 is a processing sequence diagram showing a processing order of 8 × 8 pixels included in one conventional luminance block.

FIG. 7 is a block layout diagram when performing frame processing of four blocks in a macroblock.

FIG. 8 is a block layout diagram when performing field processing of four luminance blocks in a macroblock.

FIG. 9 is a processing sequence diagram showing another processing order of 8 × 8 pixels included in one conventional luminance block.

[Explanation of symbols]

 20 subtractor 21 block rearranger 22 converter 23 quantizer 24 scan selector 25 Huffman encoder 31 inverse quantizer 32 inverse converter 33 block rearranger 34 adder 36 changeover switch 38, 39 frame memory 42, 43 Motion compensation circuit 44 Interpolation circuit 45 Changeover switch 46 Motion vector detector 50 Input terminal 51 Input image signal 52 Prediction error signal 53 Quantized signal 54 Variable length code data 55 Quantization error signal 56 Decoded signal 60 Prediction signal 62,63 Vector signal 64,65 Motion compensated signal 66 Interpolation prediction signal 100,101 picture 102,103 block 104 search area m, n picture interval

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Wataru Kameyama Wataru Kameyama 7-5 Minami-Aoyama, Minato-ku, Tokyo Column 6th floor Minami-Aoyama GC Technology Co., Ltd.

Claims (2)

[Claims] 1. A number of macroblocks including four 8 × 8 pixel luminance blocks and 16 × 16 pixel macroblocks including a plurality of color difference signal blocks as processing units.
A prediction error signal (52) is obtained by taking a difference between an input signal (51) which is an interlaced image signal forming one frame by two fields and a prediction signal (60) which may be zero, and the prediction error signal (52) A pixel is rearranged to obtain a rearranged first luminance block signal (21), the first luminance block signal is orthogonally transformed (22), and quantized to obtain a quantized signal (23). In the quantized signal, one of oblique zigzag scanning and simple vertical scanning included in the scan type of the 8 × 8 pixels included in the luminance block is selected and scanned to obtain a scan output ( 24), variable length code data (54) is obtained from the scan output, the quantized signal is inversely quantized (31), and inverse orthogonal transformation is performed to obtain an inverse transformed signal (32). Oke The arrangement of the luminance blocks is returned to the arrangement before obtaining the first luminance block signal to obtain a quantized error signal (55) (33), and the error signal and the prediction signal are added to obtain a decoded signal ( 56) is obtained (34), the decoded signal is stored (38, 39) and motion compensated to obtain first and second motion compensated signals (64, 65) (42, 43, 46). An interpolation prediction signal (66) is obtained from the first and second motion-compensated signals (44), and the first and second motion-compensated signals are switched between the interpolation signals and no signals. And an interlaced image coding method for obtaining the prediction signal (60). 2. A large number of macroblocks including four 8 × 8 pixel luminance blocks and a 16 × 16 pixel macroblock including a plurality of color difference signal blocks as a processing unit.
Subtraction means (20) for obtaining a prediction error signal (52) by taking a difference between an input signal (51) which is an interlaced image signal forming one frame by two fields and a prediction signal (60) which can be zero. First block rearrangement means (21) for rearranging the pixel arrangement of the luminance block in the prediction error signal to obtain the rearranged first luminance block signal, and orthogonally transforming the first luminance block signal. And a quantizing means (2) for quantizing the signal orthogonally transformed by the converting means to obtain a quantized signal (53).
3) and, in the quantized signal, one of oblique zigzag scanning and simple vertical scanning included in the scanning type of the 8 × 8 pixels included in the luminance block is selected and scanned for scanning. Scan selection means (24) for obtaining output, variable length coding means (25) for obtaining variable length code data (54) from the scan output, and for dequantizing the quantized signal And the inverse transforming means (3) for inverse orthogonally transforming the signal inversely quantized by the inverse quantizing means to obtain an inverse orthogonally transformed signal.
2), and second block rearrangement means () for obtaining the quantization error signal (55) by returning the arrangement of the luminance blocks in the inverse orthogonal transform signal to the arrangement before obtaining the first luminance block signal. 33), adding means (34) for adding the error signal and the prediction signal to obtain a decoded signal (56), and storing the decoded signal and performing motion compensation to obtain the first and second signals.
Motion compensation means (38, 39, 42, 43, 46) for obtaining the motion-compensated signal (64, 65) and the interpolated prediction signal (66) from the first and second motion-compensated signals. ) For obtaining the prediction signal (60) by switching between the first and second motion-compensated signals, the interpolation signal and no signal. An interlaced image encoding device including switch means (45).