ES2351306T3 - PROCEDURE AND DEVICE FOR THE CODING OF MOVING IMAGES. - Google Patents

Abstract

A video coding method for performing predictive coding by motion compensation in an input video image that has luminance (Y) and two color differences (Cr, Cb) comprising: the selection of a combination from a plurality of indexed combinations of a reference image, a weighting factor prepared for each luminance and two color differences and a displacement prepared for each luminance and two color differences for a block to be encoded from the input video image; obtaining index information (215) indicating the selected indexed combination; the generation of a motion compensation prediction image (212) for the block to be encoded by adding the offset to the reference image multiplied by the weighting factor, according to a motion vector (214) for the block to be encoded; the generation of a prediction error signal for the block to be encoded by calculating an error between the input video image and the motion compensation prediction image; the quantified generation of an orthogonal transformation coefficient (210) for the block to be encoded by subjecting the prediction error signal to orthogonal transformation and quantification; and the coding of the quantified orthogonal transformation coefficient, the motion vector information and the index information.

Description

Technical field

The present invention relates to a method and apparatus for encoding / decoding video that encodes / decodes a melt video and dissolution video, in particular, at high efficiency.

Prior art

Inter-frame coding for motion compensation is used as one of the coding modes in a standard video coding scheme such as ITUTH.261, H.263, ISO / IEC MPEG-2 or MPEG-4. As a predictive model in interframe predictive coding of motion compensation, a model is used that shows the highest predictive efficiency when no change in brightness is used in the direction of time. In the case of a fade video that changes in the brightness of images, there is no known procedure so far that it makes an appropriate prediction against a change in the brightness of images when, for example, a normal image appears from a black image In order to also maintain the image quality in a fade video, a large number of bits is therefore required.

In order to solve this problem, for example, in Japanese Patent No. 3,166,716, "Fader Countermeasure Video Encoder and Encoding Procedure", a part of fade video is detected to change the bit number allocation . More specifically, in the case of a close fade video, a large number of bits is assigned to the fade start portion that changes in luminance. In general, the last part of the closing fade becomes a monochrome image, and with it can be easily encoded. For this reason, the number of bits assigned to this part is reduced. This makes it possible to improve the overall image quality without excessively increasing the total number of bits.

In Japanese Patent No. 2,938,412, "Video luminance change compensation procedure, video encoding apparatus, video decoding apparatus, recording medium in which the video encoding or decoding program is recorded and medium of recording in which video encoded data is recorded ", an encoding scheme is proposed consisting of properly copying a fade video by compensating a reference image according to two parameters, which are, a quantity of luminance change and an amount of contrast change.

In Thomas Wiegand and Berand Girod, "Multi-frame motion-compensated prediction for video transmission", Kluwer Academic Publishers 2001, an encoding scheme based on a plurality of frame buffers is proposed. In this scheme, an attempt has been made to improve the predictive efficiency by selectively generating a prediction image from a plurality of reference frames contained in the buffers.

of frames.

According to conventional techniques, in order to encode a fade video or a dissolution video while maintaining high image quality, a large number of bits is required. Therefore, an improvement in coding efficiency cannot be expected.

Description of the invention

An object of the present invention is to provide a video coding method and apparatus that can encode a video that changes luminance over time, for example, a melt video or dissolution video, in particular, at high efficiency. The invention is defined by claims 1 and 2.

Brief description of the drawings Best way of carrying out the invention

FIG. one

it is a block diagram that shows the configuration of a coding device

video cation according to the first embodiment of the present invention;

FIG. 2

it is a block diagram that shows the detailed configuration of a general

d of prediction images / frame memory in FIG. one;

FIG. 3

is a view that shows an example of a number combination table

of reference frames and predictive parameters, which is used in the first form

of realization;

FIG. 4

is an organization chart that shows an example of a sequence to select a

predictive scheme (a combination of a reference frame number and a

predictive parameter) for each macroblock and to determine a coding mode

fication in the first embodiment;

FIG. 5

it is a block diagram that shows the configuration of a decodi apparatus

video fication according to the first embodiment;

FIG. 6

It is a block diagram showing the detailed configuration of the generator

of prediction images / frame memory of FIG. 5;

FIG. 7

it is a view that shows an example of a table of combinations of parame

other predictors in a case where the number of reference frames is one and

a reference frame number is sent as mode information according to the

second embodiment of the present invention;

FIG. 8

it is a view that shows an example of a table of combinations of parame

other predictive in a case where the number of reference frames is two and

a reference frame number is sent as mode information according to the

second embodiment;

FIG. 9

is a view that shows an example of a number combination table

of reference images and predictive parameters in a case where the number

reference frame number is one according to the third embodiment of the

present invention;

FIG. 10

is a view that shows an example of a table for luminance signals only

according to the third embodiment;

FIG. eleven

is a view that shows an example of a syntax for each block when

will encode index information;

FIG. 12

it is a view that shows a specific example of a bit stream encoded

when a prediction image is to be generated it is using a reference image

rencia;

FIG. 13

it is a view that shows a specific example of a bit stream encoded

when a prediction image is to be generated using two refe images

rencia;

FIG. 14

is a view that shows an example of a table of reference frame numbers

rencia, reference field number and predictive parameters when in

formation to be coded is a higher field according to the fourth form of

embodiment of the present invention; Y

FIG. fifteen

is a view that shows an example of a table of reference frame numbers

rencia, reference field number and predictive parameters when in

formation to be encoded is a lower field according to the fourth area of area

lization of the present invention.

The embodiments of the present invention will now be described with reference to the various views of the attached drawings.

[First embodiment] (On the coding side)

FIG. 1 shows the configuration of a video coding apparatus according to the first embodiment of the present invention. A video signal 100 is introduced into the video coding apparatus, for example, on a frame basis. The video signal 100 is introduced into a subtractor 101. The subtractor 101 calculates the difference between the video signal 100 and a prediction image signal 212 to generate a predictive error signal. A mode select switch 102 selects the predictive error signal or the video signal

100. An orthogonal transformer 103 subjects the selected signal to an orthogonal transformation, for example, a discrete cosine transform (DCT). The orthogonal transformer 103 generates orthogonal transformation coefficient information, for example, DCT coefficient information. The orthogonal transformation coefficient information is quantified by a quantifier 104 and branches into two paths. A quantification information of the orthogonal transformation coefficient 210 branched into two paths is guided towards a codi

variable length marker 111.

The other orthogonal transformation coefficient quantification information 210 branched in the two paths is sequentially processed in reverse to that of quantizer 104 and orthogonal transformer 103 by a reverse quantifier or quantizer 105 and inverse orthogonal transformer 106 to be reconstructed into a signal of predictive error Subsequently, an adder 107 adds the reconstructed predictive error signal to the prediction image signal 212 introduced through a switch 109 to generate a local decoded video signal 211. The local decoded video signal 211 is input into a generator prediction images / frame memory 108.

The prediction image generator / frame memory 108 selects one from a plurality of combinations of reference frame numbers and prepared predictive parameters. The linear sum of the video signal (decoded local video signal 211) of the reference frame indicated by the reference frame number of the selected combination is calculated according to the predictive parameter of the selected combination, and the resulting signal It is added to a shift based on the predictive parameter. With this operation, in this case, a reference image signal is generated on a frame basis. Subsequently, the prediction image generator / frame memory 108 compensates the reference image signal in motion using a motion vector to generate the prediction image signal 212.

In this procedure the prediction image generator / frame memory 108 generates motion vector information 214 and index information 215 indicating a selected combination of a reference frame number and a predictive parameter, and sends information necessary for selection of an encoding mode to a mode selector 110. Motion vector information 214 and index information 215 are input into a variable length encoder 111. The prediction image generator / frame memory 108 will be described in more detail. ahead.

Mode selector 110 selects an encoding mode in a macroblock base based on the predictive information P of the prediction image generator / frame memory 108, that is, selects the intraframe encoding mode or the interframe coding mode predictive compensated, and produces control signals of switch M and S.

In intraframe coding mode, switches 102 and 112 are switched to side A via switch control signals M and S, and input video signal 100 is input into orthogonal transformer 103. In interframe coding mode , switches 102 and 109 are switched to side B by switch control signals M and S. Accordingly, the predictive error signal of the subtractor 101 is input into the orthogonal transformer 103, and the prediction image signal 212 of the prediction imager / frame memory 108 is entered into adder 107. Mode information 213 is produced from mode selector 110 and is entered into variable length encoder 111.

The variable length encoder 111 subjects the orthogonal transformation coefficient quantification information 210, the mode information 213, the motion vector information 214 and the index information 215 to variable length coding. The variable length codes generated by this operation are multiplexed by a multiplier 114. Next, the resulting data is smoothed by an output buffer 115. The encoded data 116 produced from the output buffer 115 is sent to a Transmission system or storage system (not shown).

An encoding controller 113 controls an encoding unit 112. More specifically, the encoding controller 113 monitors the amount of buffer of the output buffer 115, and controls encoding parameters such as the size of the quantizer step of the quantizer 104 to make the amount of buffer constant.

(About prediction image generator / frame memory 108)

FIG. 2 shows the detailed configuration of the prediction image generator / frame memory 108 of FIG. 1. Referring to FIG. 2, the decoded local video signal 211 input from adder 107 in FIG. 1 is stored in a frame memory set 202 under the control of a memory controller 201. The frame memory set 202 has a plurality of (N) frame memories FM1 to FMN to temporarily store the decoded local video signal 211 as a reference frame.

In a predictive parameter controller 203 a plurality of combinations of reference frame numbers and predictive parameters are prepared in advance in the form of a table. The predictive parameter controller 203 selects, on the basis of the video signal 100, a combination of the reference frame number of a reference frame and a predictive parameter that are used to generate the prediction image signal 212, and produces 215 index information indicating the selected combination.

A multi-frame motion evaluator 204 generates a reference image signal according to the combination of the reference frame number and the index information selected by the predictive parameter controller 203. The multi-frame motion evaluator 204 evaluates the amount of movement and the predictive error from this reference image signal and the input video signal 100, and produces the motion vector information 214 that minimizes the predictive error. A multi-frame motion compensator 205 performs motion compensation for each block using a reference image signal selected by the multi-frame motion evaluator 204 according to the motion vector to generate the prediction image signal 212.

Memory controller 201 establishes a frame number of reference to a decoded local video signal for each frame, and stores each frame in one of the memory memories.

5

10

fifteen

twenty

25

30

-6

frame FM1 to FMN of frame memory set 202. For example, the respective frames are numbered in sequence from the frame closest to the input image. The same reference frame number can be set for different frames. In this case, for example, different predictive parameters are used. A frame near the input image is selected from the FM1 to FMN frame memories and sent to the predictive parameter controller 203.

(On table of combinations of reference frame numbers and prediction parameters) FIG. 3 shows an example of the table of combinations of reference frame numbers and predictive parameters, which is prepared in the predictive parameter controller

203. The "index" corresponds to prediction images that can be selected for each block. In this case, there are eight types of prediction images. A reference frame number n is the number of a decoded local video as a reference frame, and in this case, it indicates the number of a decoded local video corresponding to n past frames.

When the prediction image signal 212 is generated using the image signals of a plurality of reference frames stored in the frame memory set 202, a plurality of reference frame numbers is designated, and a (number of reference frames + 1) of coefficients as predictive parameters for each of a luminance signal (Y) and color difference signals (Cb and Cr). In this case, as indicated by equations (1) to (3), n assumes the number of reference frames, n + 1 predictive parameters Di (i =, ..., n + 1) are prepared for the signal of luminance Y; n + 1 predictive parameters Ei (i =, ..., n + 1), for the color difference signal Cb; and n + 1 predictive parameters Fi (i =, ..., n + 1), for the color difference signal Cr:

n

Y = DY + D

t ∑ tt −1 n + 1 i = 1

(one)

n

Cb = E Cb + E

t ∑ tt −1 n + 1 i = 1

(2)

n

Cr = F Cr + F

t ∑ tt −1 n + 1 i = 1

(3)

This operation will be described in more detail with reference to FIG. 3. Referring to FIG. 3, the last number of each predictive parameter represents a shift, and the first number of each predictive parameter represents a weighting factor (predictive coefficient). For index 0, the number of reference frames is given by n = 2, the reference frame number is 1 and the predictive parameters are 1 and 0 for each of the luminance signal Y and the color difference signals Cr and Cb. The fact that the predictive parameters are 1 and 0 as in this case indicates that a decoded local video signal corresponding to the reference frame number "1" is multiplied by 1 and the offset 0 is added. In other words, the Decoded local video signal corresponding to reference frame number 1 is converted to a reference image signal without any change.

For index 1, two reference frames are used as decoded local video signals corresponding to reference frame numbers 1 and 2. According to the predictive parameters 2, -1 and 0 for the luminance signal Y, the signal Decoded local video corresponding to the reference frame number 1 is doubled, and the decoded local video signal corresponding to the reference frame number 2 is subtracted from the resulting signal. Next, offset 0 is added to the resulting signal. That is, the extrapolation prediction is made from the decoded local video signals of two frames to generate a reference image signal. For the Cr and Cb color difference signals, since the predictive parameters are 1, 0 and 0, the decoded local video signal corresponding to the reference frame number 1 is used as the reference image signal without any change. This predictive scheme corresponding to index 1 is especially effective for a dissolution video.

For index 2, according to predictive parameters 5/4 and 16, the decoded local video signal corresponding to reference frame number 1 is multiplied by 5/4 and offset 16 is added. For difference signals Cr and Cb color, as the predictive parameter is 1, the signals of Cr and Cb color differences are converted into reference image signals without any change. This predictive scheme is especially effective for a fade video from a black frame.

In this way, the reference image signals can be selected on the basis of a plurality of predictive schemes with different combinations of the reference frame numbers to be used and the predictive parameters. This makes it possible for this embodiment to properly resolve a fade video and a dissolution video that have suffered deterioration in image quality due to the absence of an appropriate predictive scheme.

(On the sequence of prediction scheme selection and determination of the mode of

coding)

An example of a specific sequence for selecting a predictive scheme (a combination of a number of reference frames and a predictive parameter) for each macroblock and determining an encoding mode in this embodiment with reference to FIG. Four.

First, a maximum acceptable value is set for the variable min_D (step S101). LOOP1 (step S102) indicates a repetition for the selection of a predictive scheme in interframe coding, and the variable i represents the "index" value in FIG. 3. In this case, in order to obtain an optimal motion vector for each predictive scheme, an evaluation value D of each index (each combination of a reference frame number and a predictive parameter) is calculated from the number of bits associated with motion vector information 214 (the number of bits of a variable length code produced from variable length encoder 111 in correspondence with motion vector information 214) and a sum of predictive absolute error values , and a motion vector is selected that minimizes the evaluation value D (step S103). The evaluation value D is compared with min_D (step S104). If the evaluation value D is less than min_D, the evaluation value D is set to min_D, and the index i is assigned to min_i (step S105).

An evaluation value D is then calculated for intraframe coding (step S106). The evaluation value D is compared with min_D (step S107). If this comparison indicates that min_D is less than the evaluation value D, the MODE mode is determined as intraframe coding, and min_i is assigned to index information INDEX (step S108). If the evaluation value D is lower, the MODE mode is determined as intraframe coding (step S109). In this case, the evaluation value D is set as the estimated value of the number of bits with the same quantization stage size.

(On the decoding side)

Next, a video decoding apparatus corresponding to the video coding apparatus shown in FIG. 1. FIG. 5 shows the configuration of the video decoding apparatus according to this embodiment. The encoded data 300 sent from the video encoding apparatus shown in fig. 1 and sent through a transmission system or a storage system are temporarily stored in an input buffer 301 and are demultiplexed by a demultiplexer 302 for each frame based on a syntax. The resulting data is entered in a variable length decoder 303. The variable length decoder 303 decodes the variable length code of each syntax of the encoded data 300 to reproduce an orthogonal quantization transformation coefficient, mode information 413, information of motion vector 414 and index information 415.

From the information reproduced, the quantification orthogonal transformation coefficient is quantified by a quantifier 304 and inverse orthogonal transformed by an inverse orthogonal transformer 305. If the mode information 413 indicates the intraframe coding mode, a signal is produced. Playback video from the reverse orthogonal transformer 305. This signal is then output as a playback video signal 310 through an adder 306.

If the mode information 413 indicates the interframe coding mode, a predictive error signal is produced from the reverse orthogonal transformer 305, and a mode selection switch 309 is activated. The prediction image signal 412 produced from a generator prediction images / frame memory 308 is added to the predictive error signal by means of adder 306. As a consequence, the playback video signal is produced

310. Playback video signal 310 is stored as a reference image signal in the prediction image generator / frame memory 308.

Mode information 413, motion vector information 414 and index information 415 are entered into the prediction imager / frame memory 308. Mode information 413 is also entered into mode selection switch 309 In intraframe coding mode, mode selection switch 309 is deactivated. In interframe coding mode, the switch is activated.

As the prediction image generator / frame memory 108 on the coding side of FIG. 1, the prediction / frame memory image generator 308 includes a plurality of prepared combinations of reference frame numbers and predictive parameters in the form of a table, and selects a combination indicated by index information 415 from the table. The linear sum of the video signal (playback video signal 210) of the reference frame indicated by the reference frame number of the selected combination is calculated according to the predictive parameter of the selected combination, and a offset based on the predictive parameter to the resulting signal. With this operation, a reference image signal is generated. Subsequently, the generated reference image signal is compensated in motion by the use of the motion vector indicated by the motion vector information 414, thereby generating a prediction image signal 412.

(About the 308 prediction / frame memory imager)

FIG. 6 shows the detailed configuration of the prediction image generator / frame memory 308 of FIG. 5. Referring to FIG. 6, the playback video signal 310 produced from adder 306 of FIG. 5 is stored in the frame memory set 402 under the control of a memory controller 401. The frame memory set 402 has a plurality of (N) frame memories FM1 to FMN to temporarily save the playback video signal 310 as reference frame.

A predictive parameter controller 403 has in advance combinations of reference frame numbers and predictive parameters in the form of a table such as that shown in FIG. 3. The predictive parameter controller 403 selects a combination of the reference frame number of a reference frame and a predictive parameter, which are used to generate the prediction image signal 412, based on the index information 415 of the variable length decoder 303 in FIG. 5. A plurality of multi-frame motion compensators 404 generate a reference image signal according to a combination of a reference frame number and index information, which is selected by the predictive parameter controller 403, and performs compensation of motion for each block using this reference image signal according to the motion vector indicated by the motion vector information 414 of the variable length decoder 303 of FIG. 5, thereby generating the prediction image signal 412.

[Second embodiment]

Next, the second embodiment of the present invention will be described with reference to FIG. 7 and 8. Since the overall configurations of a video coding apparatus and video decoding apparatus in this embodiment are almost the same as those of the first embodiment, only the differences with respect to the first will be described embodiment.

In this embodiment, an example of how to express predictive parameters based on a scheme capable of designating a plurality of reference frame numbers according to mode information of a macroblock base is described. For each macroblock a reference frame number is discriminated by mode information. This embodiment therefore uses a table of predictive parameters as shown in FIG. 7 and 8 instead of using a table of combinations of reference frame numbers and predictive parameters as in the first embodiment. That is, the index information does not indicate a reference frame number, and only a combination of predictive parameters is designated.

The table of FIG. 7 shows an example of a combination of predictive parameters when the number of reference frames is one. Predictive parameters are designated (the number of reference frames + 1) parameters, that is, two parameters (a weighting factor and a shift), for each luminance signal (Y) and color difference signals (Cb and Cr).

The table in FIG. 8 shows an example of a combination of predictive parameters when the number of reference frames is two. In this case, as predictive parameters, (the number of reference frames + 1) are designated parameters, that is, three parameters (two weighting factors and one offset), of each luminance signal (Y) and signals of differences of color (Cb and Cr). This table is prepared for the coding side and the decoding side as in the first embodiment.

[Third embodiment]

The third embodiment of the present invention will be described with reference to FIG. 9 and 10. Since the overall configurations of a video coding apparatus and video decoding apparatus in this embodiment are almost the same as those of the first embodiment, only differences with respect to the following will be described below. first and second embodiments.

In the first and second embodiments, a video is treated on a plot basis. However, in this embodiment, a video is treated on an image basis.

If there is a progressive signal and an interlaced signal as input image signals, the images are not necessarily encoded on a frame basis. In consideration of this, an image assumes (a) an image of a frame of a progressive signal, (b) an image of a frame generated by fusing two fields of an interlaced signal, or (c) an image of a field of a signal entwined

If the image to be encoded is an image with a frame structure such as (a) or (b), a reference image used in motion compensation prediction is also treated as a frame regardless of whether the encoded image, which is the reference image, has a frame structure or a field structure. This image is assigned a reference image number. Similarly, if the image to be encoded is an image with a field structure such as (c), a reference image used in motion compensation prediction is also treated as a field regardless of whether the encoded image, which is The reference image has a frame structure or a field structure. This image is assigned a reference image number.

Equations (4), (5) and (6) are examples of predictive equations for reference image numbers and predictive parameters, which are prepared in the predictive parameter controller 203. These examples are predictive equations for generating an image signal. prediction by motion compensation prediction using a reference image signal.

LY −1

Y = clip ((D () i × R () i + 2) >> L + D ())

iY Y 2 i (4) Lc −1

Cb = clip ((E () i × (R () i - 128) + 2) >> L + E () i + 128)

1 Cb C 2 (5) Lc −1

Cr = clip ((F () i × (R () i - 128) + 2) >> L + F () i + 128) (6)

1 Cr C 2

where Y is a prediction image signal of a luminance signal, Cb and Cr are prediction image signal of two color difference signals, RY (i), RCb (i) and RCr

(i) are the pixel values of the luminance signal and two color difference signals of a reference image signal with index i, D1 (i) and D2 (i) are the predictive coefficient and the signal offset of luminance with index i, E1 (i) and E2 (i) are the predictive coefficient and the offset of the color difference signal Cb with index i, and F1 (i) and F2 (i) are the predictive coefficient and the offset of the color difference signal Cr with index i. The index i indicates a value of 0 (the maximum number of reference images -1), and encoded for each block to be encoded (for example, for each macroblock). The resulting data is then transmitted to the video decoding apparatus.

The predictive parameters D1 (i), D2 (i), E1 (i), E2 (i), F1 (i) and F2 (i) are represented by values determined in advance between the video coding device and the recording device. Video decoding or an encoding unit such as a frame, field or section, and are encoded together with encoded data that will be transmitted from the video encoding apparatus to the video decoding apparatus. With this operation, these parameters are shared

Two for both devices.

Equations (4), (5) and (6) are predictive equations in which the powers of 2, that is, 2, 4, 8, 16, ... are selected as denominators of predictive coefficients by which they multiply The reference image signals. Predictive equations can eliminate the need for division and be calculated by arithmetic shifts. This makes it possible to avoid a large increase in the cost of calculation due to division.

In equations (4), (5) and (6), ">>" of a >> b represents an operator for arithmetic shift of an integer a to the right b bits. The "clip" function represents a trimming function to set the value of "()" to 0 when it is less than 0, and to set the value to 255 when it is greater than 255.

In this case, it is assumed that LY is the amount of displacement of a luminance signal, and LC is the amount of displacement of a color difference signal. Like these LY and LC offset values, values determined in advance between the video encoding apparatus and the video decoding apparatus are used. The video coding apparatus encodes the amounts of LY and LC offset, together with a table and encoded data, in a predetermined coding unit, for example, a frame, a change or a section, and transmits the resulting data to the apparatus of video decoding This allows the two devices to share the amounts of travel Ly and LC.

In this embodiment, tables of combinations of reference image numbers and predictive parameters are prepared as shown in FIG. 9 and 10 in the predictive parameter controller 203 of FIG. 2. Referring to FIG. 9 and 10, the index i corresponds to prediction images that can be selected for each block. In this case, four types of prediction images are present in correspondence with 0 to 3 of index i. The "reference image number" is, in other words, the number of a decoded local video signal used as the reference image.

"Indicator" is an indicator that indicates whether a predictive equation using a predictive parameter applies or not to a reference image number indicated by the index i. If the Indicator is "0", the motion compensation prediction is made using the decoded local video signal corresponding to the reference image number indicated by the index i without using any predictive parameter. If the Indicator is "1", a prediction image is generated according to equations (4), (5) and (6) using a decoded local video and a predictive parameter corresponding to the reference image number indicated by the index i, thus performing motion compensation prediction. This Indicator information is also encoded, together with a table and encoded data, using a predetermined value between the video encoding apparatus and the video decoding apparatus or in a predetermined encoding unit, for example, a frame, a field or a section, in the video coding apparatus. The resulting data is transmitted to the video decoding apparatus. This allows the two devices to share the Indicator information.

In these cases, a prediction image is generated using a predictive parameter when the index i = 0 with respect to a reference image number 105, and motion compensation prediction is performed without using any predictive parameter when i = 1. According to described above, there may be a plurality of predictive schemes for the same reference image number.

The table shown in FIG. 9 has predictive parameters D1 (i), D2 (i), E1 (i), E2 (i), F1 (i) and F2 (i) assigned to a luminance signal and two color difference signals corresponding to the equations (4), (5) and (6). FIG. 10 shows an example of a table in which predictive parameters are assigned only to luminance signals. In general, the number of bits of a color difference signal is not very large compared to the number of bits of a luminance signal. For this reason, in order to reduce the amount of calculation required to generate a prediction image and the number of bits transmitted in a table, a table is prepared, in which the predictive parameters for color difference signals are omitted according to is shown in FIG. 10 and the predictive parameters are assigned only to luminance signals. In this case, only equation (4) is used as a predictive equation.

Equations (7) to (12) are predictive equations in a case where a plurality (two in this case) of reference images is used.

LY −1

P () i = (D () i × R () i + 2) >> L + D () i

Y 1 YY 2

(7)

LC −1

P () i = (E () i × (R () i - 128) + 2) >> L + E () i + 128

Cb 1 Cb C 2

(8)

LC −1

P () i = (F () i × (R () i - 128) + 2) >> L + F () i + 128

Cr 1 Cr C 2

(9) Y = clip ((PY () i + PY () j + 1) >> 1)

(10) Cb = clip ((P () i + P () j + 1) >> 1)

Cb Cb

(11) Cr = clip ((P () i + P () j + 1) >> 1)

Cr Cr

(12)

The information fragments of the predictive parameters D1 (i), D2 (i), E1 (i), E2 (i), F1 (i), F2 (i), LY and LC and Indicator are values determined in advance between the video coding apparatus and the video or encoding decoding apparatus, together with encoded data, in an encoding unit such as a frame, a field or a section, and are transmitted from the video encoding apparatus to the decoding apparatus of video. This allows the two devices to share these pieces of information.

If an image to be decoded is an image that has a frame structure, a reference image used for motion compensation prediction is also treated as a frame regardless of whether a decoded image as a reference image has a structure. frame or field structure. A reference image number is assigned to this image. Similarly, if an image to be programmed is an image that has a field structure, a reference image used for motion compensation prediction is also treated as a field regardless of whether an image decoded as a reference image has a frame structure or a field structure. This image is assigned a reference image number.

(About index information syntax)

FIG. 11 shows an example of a syntax in a case where the index information is encoded in each block. First, the MODE mode information is present for each block. It is determined according to the MODE mode information whether or not the index information IDi indicating the index value i and the index information IDj indicating the index value j are encoded. The motion vector information information MVi for the index motion compensation prediction i and the motion vector information MVj for the predictive motion compensation of index j is added as a motion vector information for each block after the indexed information encoded.

(About the structure of coded bit stream data)

FIG. 12 shows a specific example of a bit stream encoded for each block when a prediction image is generated using a reference image. The IDi index information is set after the MODE mode information, and the motion vector information MVi is subsequently set. The motion vector information MVi is generally two-dimensional vector information. Depending on a motion compensation procedure in a block that is indicated by mode information, a plurality of two-dimensional vectors can be additionally sent.

FIG. 13 shows a specific example of a bit stream encoded for each block when a prediction image is generated using two reference images. The IDi index information and the IDj index information are set after the MODE mode information, and the motion vector information MVi and the motion vector information MVj are subsequently set. The motion vector information MVi and the motion vector information j are generally two-dimensional vector information. Depending on a motion compensation procedure in a block indicated by mode information, a plurality of two-dimensional vectors can be additionally sent.

Note that the previous structures of a syntax and a bit stream can also be applied to all embodiments.

[Fourth embodiment]

Next, the fourth embodiment of the present invention will be described with reference to FIG. 14 and 15. Since the overall configurations of a video coding apparatus and a video decoding apparatus in this embodiment are almost the same as those of the first embodiment, only the differences with respect to the forms will be described of first, second and third realization. In the third embodiment, the coding on a frame basis and the coding on a field basis are switched for each image. In the fourth embodiment, the coding on a frame basis and the coding on a field basis are switched for each macroblock.

When encoding on a frame basis and coding on a field basis are switched for each macroblock, the same reference image number indicates different images, even within the same image, depending on whether a macroblock is encoded on the basis. of plot or on the basis of field. For this reason, with the tables shown in FIG. 9 and 10 used in the third embodiment, an appropriate prediction image signal may not be generated.

In order to solve this problem, in this embodiment, the tables of combinations of reference image numbers and predictive parameters such as those shown in FIG. 14 and 15 are prepared in a predictive parameter controller 203 in FIG. 2. Assume that when a macroblock is to be encoded on the field basis, the same predictive parameter is used as that corresponding to a reference image number (reference frame index number) used when the macroblock is encoded on the frame base.

FIG. 14 shows a table used when the macroblock is encoded on a field basis and an image to be encoded is a higher field. The upper and lower rows of each field index column correspond to the upper and lower fields, respectively. As shown in FIG. 14, the frame index j and the field index k are related so that when k = 2j in the upper field, k = 2j + 1 in the lower field. The reference frame number m and the reference field number n are related so that when n = 2m in the upper field, n = 2m + 1 in the lower field.

FIG. 15 shows a table used when the macroblock is encoded on a field basis, and an image to be encoded is a lower field. As in the table shown in FIG. 14, the upper and lower rows of each field index column correspond to an upper field and the lower field, respectively. In the table of FIG. 15, the frame index j and the field index k are related so that when k = 2 + 1 in the upper field, k = 2j in the lower field. This makes it possible to assign a small value as field index k to a lower field in phase. The relationship between reference frame number m and reference field number n is the same as in the table of FIG. 14.

When the macroblock is to be encoded on a field basis, a frame index and a field index are encoded as index information using the tables shown in FIG. 14 and 15. When the macroblock is to be encoded on a frame basis, only the frame rate common to the tables in FIG. 14 and 15 is coded by index as index information.

In this embodiment, the predictive parameters are assigned to a frame and a field using a table. However, a table for frames and a table for fields for an image or section can be prepared separately.

Each embodiment described above has illustrated the coding scheme

5 tion / video decoding using orthogonal transformation on a block base. However, even if another transformation technique is used as a wave train transformation, the technique of the present invention described in the previous embodiments can be used.

The video encoding and decoding processing according to the present invention

10 can be implemented as hardware (device) or software using a computer. Some processing can be implemented by hardware, and other processing can be done by software. According to the present invention, a program can be provided to make a computer execute the previous video encoding or decoding of video or a storage medium that stores the program.

15 Industrial Applicability

As described above, the method and the video encoding / decoding apparatus according to the present invention are suitable for the field of image processing in which a luminance-changing video is encoded and decoded.

over time, such as a fade video or a dissolution video, in particular.

Claims (2)

1. A video coding method for performing predictive coding by motion compensation in an input video image that has luminance (Y) and two color differences (Cr, Cb) comprising: the selection of a combination from a plurality of indexed combinations of a reference image, a weighting factor prepared for each luminance and two color differences and a displacement prepared for each luminance and two color differences for a block to be encoded of the input video image; obtaining index information (215) indicating the selected indexed combination; the generation of a motion compensation prediction image (212) for the block to be encoded by adding the offset to the reference image multiplied by the weighting factor, according to a motion vector (214) for the block to be encoded; the generation of a prediction error signal for the block to be encoded calculating an error between the input video image and the prediction image of motion compensation; the quantified generation of an orthogonal transformation coefficient (210) for the block to be encoded by subjecting the prediction error signal to transformation orthogonal and quantification; Y the coding of the quantified orthogonal transformation coefficient, the motion vector information and the index information. 2. A video coding apparatus for performing predictive coding of motion compensation in an input video image having a luminance (Y) and two color differences (Cr, Cb) comprising: means for selecting a combination from a plurality of indexed combinations of a reference image, a weighting factor prepared for each luminance and two color differences and a displacement prepared for each luminance and two color differences for a block to be encoded of the input video image; means (203) for obtaining index information (215) indicating the combination in dexada selected; means (204) for generating a motion compensation prediction image for the block to be encoded by adding the offset to the reference image multiplied by the weighting factor, according to a motion vector (214) for the block to be encoded; means (101) for generating a prediction error signal for the block to be encoded by calculating an error between the input video image and the motion compensation prediction image; means (103, 104) for generating an orthogonal transformation coefficient quantified for the block to be encoded by subjecting the prediction error signal to orthogonal transformation and quantification; Y 10 means (111) for encoding the quantified orthogonal transformation coefficient, the motion vector information and the index information.