JP2003284090A - Intra-macroblock/inter-macroblock decision method in video coding, video coding apparatus, video coding program and storage medium for the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a deterioration in image quality by avoiding a color sticking phenomenon which occurs in such a case that a motion vector has not appropriately calculated in coding a video. <P>SOLUTION: For a macroblock to be coded which is decided to be an inter- macroblock by comparing the levels between a MAD (maximum absolute difference) of a luminance value Y and an SAD (sum of absolute difference) of the value Y, MAD and SAD in two color difference values U, V in the macroblock are further calculated by a color difference decision means 12 respectively. When a value obtained by subtracting the weighted coefficient from either of the SADs is larger than the MAD, a predicted error of the macroblock to be coded is considered to be large, and the macroblock is re-decided to be an intra-macroblock. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION In video coding, a macroblock to be coded is an intra macroblock without prediction from other macroblocks or an inter macroblock with prediction from other macroblocks. It is desirable to determine which is to be used for encoding after considering the effect on image quality.

The present invention relates to coding control of video coding, and in particular, it relates to a macroblock in video coding for determining whether a macroblock to be coded should be coded by an intra macroblock or an inter macroblock. The present invention relates to an intra / inter determination method in video encoding by color difference SAD, a video encoding device, a video encoding program, and a recording medium of the program.

[0003]

2. Description of the Related Art MPEG-an international standard for video coding
The verification model ver. 16 (VM1
In the encoding control of 6), in the intra / inter determination that determines which type (mode) of the macro block to be encoded in the P-VOP, the intra macro block or the inter macro block is encoded, As the predicted generated code amount when the target macroblock is encoded as an intra macroblock, the MAD of the luminance value Y of the pixel in the encoding target macroblock (the difference between the average value of the pixel values in the macroblock and each pixel value) Of the difference between the pixel value of the predicted image created by the motion vector calculated in advance and the pixel value of the original image as the predicted generated code amount when the image is coded as an inter macroblock. Using the sum of absolute values) and comparing the magnitudes of these values, the one with the smaller predicted code amount was adopted.

FIG. 4 is a diagram for explaining an example of a conventional intra / inter determination method. In the intra / inter determination unit 60 in the conventional video encoding, the brightness value determination means 11
The MAD of the luminance value Y of the pixel in the input P-VOP encoding target macroblock and the SAD of the luminance value Y are compared in size, and the MAD of the luminance value Y is higher than the SAD of the luminance value Y. When it takes a small value, specifically, the brightness value Y
MAD value A _y is the SAD value SAD of the luminance value Y
If it is smaller than the value obtained by subtracting a predetermined value 2 * N _B from _{inter, the} macroblock to be coded is determined to be an intra macroblock, otherwise it is determined to be an inter macroblock.

Incidentally, "MPEG-4", "VM16",
“P-VOP”, “macroblock”, “intra macroblock”, “inter macroblock”, “intra / inter determination”, “motion vector”, “MAD”,
"SAD" is described in the following documents 1 and 2. -Reference 1: "" All about MPEG-4 ", pp.37-
116, Koichi Miki, Industrial Research Committee ”. -Reference 2: "" ISO / IEC JTC1 / SC29 /
WG11: MPEG-4 Video Verica
section Model version 16.0 ",
Shigeru Fukunaga et al., Pp. 48-
50, March, 2000 ".

[0006]

In a general MPEG encoding system, a means for reducing color difference information by utilizing the fact that human beings are not sensitive to color is often used. MPE, which is one of the video encoding methods targeted by the present invention
In G-4, since the color difference information is reduced by half in the vertical direction and in the horizontal direction, the information amount of the color difference information is ¼ of the information amount of the luminance information. Therefore, it can be said that the information that has a large influence on the overall generated code amount is the luminance information.

In the conventional intra / inter determination of macroblocks, the mode is determined by comparing the magnitudes of the predicted generated codes when the macroblocks are coded as intra macroblocks and when the macroblocks are coded as inter macroblocks.
As described above, only the luminance value having a large amount of information is used for the prediction of the generated code amount.

Therefore, if intra / inter determination is performed by the conventional method as described with reference to FIG. 4, even if the error of the color difference value becomes large, this is not taken into consideration at all, and the determination based on only the luminance value information is performed. Inter-judgment was sometimes made, and there were many phenomena in which color sticking remained visually.

That is, as a problem of the determination method according to the prior art, for example, when the SAD of the luminance value Y becomes a smaller value when the motion vector is not properly calculated, the intra-interlace is used. In the determination, since it is determined as an inter macroblock, there is a phenomenon in which the difference between the two color difference values U and V actually remains in the screen as a sticky color. This is a phenomenon that often occurs in an image in which an object including many color difference values U and V in the screen moves around violently.

It is necessary to encode such a macroblock as an intra macroblock, but the conventional determination method avoids such a phenomenon because the determination is made using only the luminance value Y. I couldn't.

An object of the present invention is to encode a video in
The purpose is to perform intra / inter determination of macroblocks in order to suppress the phenomenon of color sticking.

[0012]

In order to solve the above problems, the present invention provides a MAD of a brightness value Y and an SA of a brightness value Y at the time of intra / inter determination of a macroblock to be encoded.
For the determination of D, MAD and SAD are calculated for the two color difference values U and V in the encoding target macroblock, and intra / inter determination processing is added again.

That is, in the conventional intra / inter determination, with respect to the encoding target macroblock determined to be an inter macroblock, MAD at the two color difference values U and V in the encoding target macroblock is further calculated.
The SADs are calculated and the magnitude comparison is performed. When the value obtained by subtracting the weighting coefficient from any of the SADs becomes a value larger than MAD, it is considered that the prediction error of the encoding target macroblock is large, and the re-determination processing is added to the intra macroblock. .

The conventional technique is the luminance value Y of a pixel in a macroblock for intra / inter determination of the macroblock.
In addition to the determination by the above, there is a large difference in that the two color difference values U and V are used for the determination.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a principle configuration of an embodiment of the present invention. Reference numeral 10 is an intra / inter judgment for determining whether a macroblock is coded as an intra macroblock or an inter macroblock in video coding. A determination unit, 11 is a brightness value determination unit, and 12 is a color difference value determination unit.

The brightness value judging means 11 is the same as the brightness value judging means 61 in the conventional intra / inter judging section 60 shown in FIG. 4, and the pixel value in the macroblock to be coded of the input P-VOP is determined. The magnitude comparison processing of the MAD of the luminance value Y and the SAD of the luminance value Y is performed.

When the MAD of the brightness value Y takes a value smaller than the SAD of the brightness value Y, specifically, the MAD value A _y of the brightness value Y is a predetermined value from the SAD value SAD _inter of the brightness value Y. 2 * If N less than minus _B is a the coding target macroblock is determined that the intra-macro block, and terminates the intra-inter judging process, in other cases, the color difference value determining means 12 And pass the process.

The color difference value determining means 12 compares the SAD of the color difference value U and the MAD of the color difference value U of the pixels in the encoding target macro block, and compares the SAD of the color difference value V with the MAD of the color difference value V. Perform processing. SAD value S of color difference value U
A value obtained by subtracting the weighting coefficient OM from AD _u is M of the color difference value U.
When the value is larger than the value A _{u of} AD, or when the value obtained by subtracting the weighting coefficient OM from the value SAD _v of the SAD of the color difference value V is larger than the value A _v of the MAD of the color difference value V. , The encoding target macroblock is determined to be an intra macroblock, otherwise it is determined to be an inter macroblock, and the intra / inter determination processing ends.

The above N _B and weighting coefficient OM
Should be decided in advance by experiments using various sample images. In the example above,
The relational expressions of the R, G, B signals and the luminance signal Y and the color difference signals U, V are as follows (ITU-R BTR
ec. 601).

Y = 0.299R + 0.587G + 0.114B U = R−Y = 0.701R−0.587G−0.11
4B V = B−Y = −0.299R−0.587G + 0.88
6B FIG. 2 is a block diagram of an MPEG-4 encoder to which the present invention is applied, and FIG. 3 is a processing flow chart thereof. Figure 2
, 10 is an intra / inter determination unit, 20 is D
A CT / quantization processing unit, 30 is an inverse quantization / IDCT processing unit, 40 is a frame memory storage unit, and 50 is a motion compensation processing unit.

An application example of the present invention will be described below with reference to FIGS. In step S1, it is determined whether the frame type of the input image is I-VOP. If the frame type is I-VOP, step S5
Then, the process proceeds to step S20, the intra macroblock coding process (DCT process, quantizing process) is performed by the DCT / quantization processing unit 20, and if the frame type is not I-VOP, step S
Go to 2.

In step S2, the frame type is P-
It is determined whether or not it is a VOP, and it is not P-VOP but B
If it is a VOP, go to step S4. If the frame type is P-VOP, the intra / inter determination unit 10 performs intra / inter determination processing in step S3. Here, if the intra / inter determination processing described in FIG. 1 is performed and the determination result is an inter macroblock, the inter macroblock encoding processing (D) by the DCT / quantization processing unit 20 is performed in step S4.
CT processing and quantization processing). If the determination result is an intra macroblock, DCT
Intra macroblock coding processing (DCT processing, quantization processing) by the quantization processing unit 20 is performed.

The coded data generated by each coding process is subjected to the dequantization process and the IDCT process by the dequantization / IDCT processing unit 30 in step S6, and the frame memory storage unit 40 is processed in step S7.
Is stored in the frame memory according to the above, and in step S8, the motion compensation processing unit 50 performs motion compensation processing and reuses it for the processing of the next frame and subsequent frames.

The above processing can be realized by a dedicated processor or hardware circuit, or can be realized by a general-purpose computer and a software program, which is a computer-readable portable medium memory, semiconductor memory, It can be stored in an appropriate recording medium such as a hard disk and read out from the recording medium to be executed by a computer. Further, the program can be downloaded from another computer via a communication line, and can be installed and executed.

[0025]

As described above, according to the present invention,
By the intra / inter determination processing using the two color difference values U and V of the pixels in the macroblock, it is possible to avoid the color sticking phenomenon that occurs when the motion vector is not correctly calculated, and the image quality is deteriorated. Can be greatly suppressed.

[Brief description of drawings]

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

FIG. 2 is a block diagram of an MPEG-4 encoder to which the present invention is applied.

FIG. 3 is a processing flow chart of an MPEG-4 encoder to which the present invention is applied.

FIG. 4 is a diagram illustrating an example of a conventional intra / inter determination method.

[Explanation of symbols]

10,60 Intra / inter judgment section 11,61 Luminance value determination means 12 Color difference value determination means 20 DCT / quantization processing unit 30 Dequantization / IDCT processing unit 40 frame memory storage 50 Motion compensation processing unit

Continued front page    (72) Inventor Naoki Ono             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Kumi Qinsenji             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Hiroyuki Tsuji             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Toru Sakata             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Yoshiyuki Yashima             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Naoki Kobayashi             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F-term (reference) 5C057 AA03 BA01 CA01 DA06 EA02                       EA07 EG01 EM04 EM09 EM16                 5C059 KK02 MA05 MA14 MA23 MC11                       NN01 PP05 PP06 PP07 PP16                       SS06 SS20 TA18 TB07 TC01                       TD13 UA02 UA33                 5J064 AA02 BA16 BC01 BC08 BC14                       BC16 BD03

Claims (4)

[Claims] 1. An intra discriminator for determining whether a macroblock is encoded as an intra macroblock or an inter macroblock in video encoding.
The inter determination method is an intra / inter determination based on the luminance value Y of the pixel in the macroblock to be encoded.
For a macroblock determined to be an inter-macroblock, SAD and MAD are respectively calculated for two color difference values U and V of pixels in the macroblock,
An image characterized by re-determining the macroblock as an intra macroblock when a value obtained by subtracting a predetermined weighting coefficient from any of the SADs becomes a value larger than the corresponding MAD of the color difference value. Intra / inter decision method in encoding. 2. An intra discriminator that determines whether a macroblock is encoded as an intra macroblock or an inter macroblock in video encoding.
In a video encoding device having an inter determination unit, the intra / inter determination unit includes a brightness value determination unit that performs an intra / inter determination based on a brightness value Y of a pixel in a macroblock to be encoded, and the brightness value determination unit. For a macroblock determined to be an inter-macroblock, SAD and MAD are calculated for the two color difference values U and V of the pixels in the macroblock, and a predetermined weighting coefficient is subtracted from either SAD. Value is
A video encoding device, comprising: a color difference value determining means for determining the macroblock as an intra macroblock when the value becomes larger than the corresponding color difference value MAD. 3. A program for determining by a computer whether to code a macroblock as an intra macroblock or an inter macroblock in video coding, which is a program for determining a pixel in a macroblock to be coded. Intra / inter determination based on the luminance value Y, and SAD for a macroblock determined to be an inter macroblock by the intra / inter determination, and for two color difference values U and V of pixels in the macroblock , MAD is calculated, and either SAD is calculated based on the calculation result.
When a value obtained by subtracting a predetermined weighting coefficient from the value becomes larger than the corresponding MAD of the color difference value, the computer is caused to execute a process of re-determining the macroblock as an intra macroblock. Video coding program. 4. A recording medium in which a program for determining by a computer whether a macroblock is coded as an intra macroblock or an intermacroblock in video coding is recorded, which is a macroblock to be coded. The process of performing intra / inter determination based on the luminance value Y of the pixel in the block, and the two color difference values U of the pixels in the macro block for the macro block determined to be the inter macro block by the intra / inter determination , V, SAD, MA
If the value obtained by subtracting a predetermined weighting coefficient from one of the SADs is larger than the corresponding MAD of the color difference value based on the processing for calculating D and the calculation result, the macroblock A recording medium for a video coding program, characterized in that a program for causing a computer to execute the process of re-determining as an intra macroblock is recorded.