KR101215138B1 - Method for fast determining inter/intra mode of macroblock - Google Patents

Abstract

The present invention relates to a method of fast determining inter / intra mode of a macroblock for determining a macroblock mode of H.264 / AVC. According to the method of the present invention, the candidate mode is determined as the SKIP mode (mode 0) and the inter16 × 16 mode (mode 1), and the rate-distortion costs RDC0 and RDC1 of the mode 0 and the mode 1 are inter 8 ×. Compared with the rate-distortion cost RDC3 of the 16 modes (mode 3), the candidate mode is determined as the mode 0 and the mode 1, and the rate-distortion cost of the mode 3 and the inter16x8 mode (mode 2) By comparing the RDC3 and RDC2, a mode having a low rate-distortion cost is determined as a candidate mode, and whether or not to skip intra mode determination is determined according to an optimal mode of P8x8 (sub-macroblock).

Description

High-speed decision method of macro block inter / intra mode {METHOD FOR FAST DETERMINING INTER / INTRA MODE OF MACROBLOCK}

The present invention relates to a method for quickly determining an encoding mode of a macroblock, and more particularly, to an inter / intramode fast decision method for a macroblock for use in an H.264 / AVC system.

H.264 / AVC (Advanced Video Coding) is a digital video codec standard with a very high data compression rate. It is the Video Coding Experts Group (n VCEG) of the International Telecommunications Union-Telecommunication Standardization Sector (ITU-T). And the Moving Picture Experts Group (MPEG) of the International Standardization Organization / International Electro-technical Commision (ISO / IEC) jointly formed a joint video team (JVT) to standardize.

Such H.264 / AVC achieved about 60% efficient encoding at the same image quality compared to MPEG-2 and MPEG-4, which are the existing video encoding standards, and at about the same image quality compared to H.263. 30% bit savings.

In the intra-prediction encoding in the inter frame, the picture quality improved by about 3 to 4 dB over JPEG2000 and MPEG-4 at the same bit amount. However, despite this excellent coding efficiency, intra prediction coding in an inter frame has a disadvantage that the complexity of the encoder and the decoder is much higher than that of the previous video coding standard when compared to the existing video coding standard.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems, and an object thereof is to provide a fast method for determining inter / intra mode of a macroblock to reduce coding speed while maintaining coding efficiency in H.264 / AVC. .

In order to achieve the above object, the macroblock mode inter / intra-mode fast decision method of the present invention for determining the macroblock mode of H.264 / AVC, (a) the candidate mode and the SKIP mode (mode 0) and Determining an inter16x16 mode (mode 1); (b) The rate-distortion costs RDC0 and RDC1 of the mode 0 and the mode 1 are compared with the rate-distortion cost RDC3 of the inter 8x16 mode (mode 3), and a candidate mode is selected from the mode 0 and the mode. Determining to mode 1; (c) comparing the rate-distortion costs (the RDC3, RDC2) of the mode 3 and the inter16 × 8 mode (mode 2) to determine a mode having a small rate-distortion cost as a candidate mode; And (d) determining whether to skip intra mode determination according to an optimal mode of P8x8 (sub-macroblock).

In this case, step (a) may include: (e) determining the RDC0 and the RDC1 of the mode 0 and the mode 1, respectively; (f) The average value of the rate-distortion cost (RDCL) of the reference block in which the optimal mode among the reference blocks of the current frame and the previous frame is determined to be mode 0 or mode 1, and the optimal mode of the reference blocks of the current frame and the previous frame is mode 0. Or determining a rate-distortion cost average value RDCH of the reference block not determined to be mode 1; And (g) comparing the RDC0, the RDC1, the RDCL, and the RDCH to determine the mode 0 and the mode 1 as an optimal mode in certain cases, and the step (g) For the RDC0, the RDC1, the RDCL and the RDCH, the mode 0 and the mode 1 are optimal when the condition of {(RDCL <RDCH) & (RDC0 <RDCL) & (RDC1 <RDCL)} is satisfied. It is desirable to determine the mode.

In the step (b), the mode 0 and the mode 1 are optimal modes when the conditions of {(RDC0 <RDC3) & (RDC1 <RDC3)} are satisfied with respect to the RDC0, the RDC1, and the RDC3. It is preferable to determine.

On the other hand, (h) preferably further comprises the step of omitting the determination of the intra mode.

Step (c) compares (i) the average value of the rate-distortion cost of the mode 2 and the mode 3 with the weighted value of the rate-distortion cost of the mode 0, whereby P8 × 8 (sub-macroblock Omitting mode determination of; And (j) measuring an average bit rate AR of an optimal inter mode as an intra frame temporal correlation diagram and an average block boundary error ABE as an intra frame spatial correlation diagram, and omitting intra mode determination in certain cases. Preferably, (k) if the RDC2 is smaller than the RDC3, omitting the mode determination of the mode 3, and omitting the mode determination of the inter4x8 mode at P8x8 (sub-macroblock); And (l) if the RDC2 is not smaller than the RDC3, omitting the mode determination of the mode 2 and omitting the mode determination of the inter8 × 4 mode at P8 × 8 (sub-macroblock). It is desirable to.

} 조건을 만족하는 경우에, P8×8(서브-매크로블록)의 모드결정을 생략하는 것이 바람직하고, 상기 (j)단계는, AR<ABE인 경우 인트라모드 결정을 생략하는 것이 바람직하다.In this case, step (i) is performed by {

} When the condition is satisfied, it is preferable to omit the mode determination of P8x8 (sub-macroblock), and in step (j), it is preferable to omit the intra mode determination when AR <ABE.

Also, the step (d) may include: (m) omitting intra 4 × 4 mode determination when the optimal mode is two or more of four P8 × 8 (sub-macroblocks); And (n) in the case where the optimal mode among the four P8x8 (sub-macroblocks) is two or more 4x4, it is preferable to omit the intra16x16 mode determination.

In the present invention as described above, in order to determine the mode of the H.264 / AVC macroblock, the candidate mode is initially determined as the SKIP mode (mode 0) and the inter16 × 16 mode (mode 1), and based on the rate-distortion cost. By omitting the determination of the intra mode, the coding speed can be reduced while maintaining the coding efficiency.

FIG. 1A is an exemplary diagram for describing an intermode for visual prediction in H.264 / AVC.
1B is an exemplary view for explaining an intra mode for prediction in a spatial domain in H.264 / AVC.
FIG. 2A is an exemplary diagram for describing each prediction mode in detail in the intra16 × 16 mode of FIG. 1B.
FIG. 2B is an exemplary diagram for describing each prediction mode in detail in the intra 4 × 4 mode of FIG. 1B.
3A is an exemplary view for explaining blocks used in the inter / intra mode fast determination method of a macroblock according to the present invention.
FIG. 3B is an exemplary view for explaining a reference block of a current frame in FIG. 3A.
FIG. 3C is an exemplary diagram for describing a current macroblock in FIG. 3A.
FIG. 3D is an exemplary view for explaining a reference block of a previous frame in FIG. 3A.
4 is a flowchart illustrating a method of quickly determining an inter / intra mode of a macroblock according to the present invention.
FIG. 5 is a detailed flowchart of an embodiment for describing S71 of FIG. 4 in detail.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1A is an example diagram for describing an intermode for visual prediction in H.264 / AVC, and FIG. 1B is an example diagram for explaining an intra mode for prediction in a spatial domain in H.264 / AVC. to be.

The H.264 / AVC international video standard uses motion prediction and mode determination. The motion prediction and mode determination method is a motion compensation technique using a variable block, and uses a rate-distortion optimization technique after dividing the macroblock size from 16 × 16 to 4 × 4. Intra mode is set separately.

Referring to FIG. 1A, five inter modes are supported according to a unit size of a macroblock as a mode for visual prediction. That is, there are a skip (SKIP) mode, an inter16x16 mode, an inter8x16 mode, an inter16x8 mode, and an inter8x8 mode. 8 × 8 macroblocks included in the inter8 × 8 mode may be divided into sub-macroblocks having sizes of 8 × 8, 8 × 4, 4 × 8, and 4 × 4.

Referring to FIG. 1B, three intra modes are supported according to a unit size of a macroblock as a mode for prediction in a spatial domain. That is, there are intra16x16 mode (luminance), intra8x8 mode (color), and intra4x4 mode (luminance). Intra8x8 mode is provided only in the 'FRExt' profile, so I will explain it except intra8x8 mode.

In the intra16x16 mode, four prediction modes and directions are supported, and in the intra8x8 mode, eight directional modes and DC mode, which is an average prediction mode without directionality, are supported. Intra mode predicts the current macroblock using the boundary pixels of the previously encoded valid neighboring macroblocks (pixels on the left, top, top right or top left).

FIG. 2A is an exemplary diagram for describing each prediction mode in more detail in the intra16 × 16 mode of FIG. 1B, and FIG. 2B is an illustration for explaining each prediction mode in more detail in the intra4 × 4 mode of FIG. 1B. It is also.

2A and 2B, the intra mode predicts a pixel of a block to be currently encoded by using pixels of the base-encoded top, left, top right, or top left corners. Intra 16x16 mode predicts prediction mode 0 (vertical prediction) using the upper pixels, predicted mode 1 (horizontal prediction) using the left pixels, and predicts the average value using the pixels on the left and upper sides. Mode 2 (average value prediction), prediction mode 3 (average prediction) that predicts using the left and top pixels, and intra 4x4 mode has a total of nine prediction modes from prediction mode 0 to prediction mode 8.

H.264 / AVC calculates the rate-distortion cost of each of the various prediction modes as described above, and determines a mode having the minimum value as an optimal mode to encode. Since the mode is determined and the prediction coding on the granular block must be performed, it has a relatively high complexity compared to the intra16x16 mode.

If the change in the video signal is small in a general video such as a background, the pixel information of the current block (the current block to be encoded) and the neighboring block are similar. In addition, if the optimal prediction direction of the current block is the same as the prediction direction of the neighboring block in the intra 4x4 mode, the pixel information of the current block and the neighboring block is also likely to be similar. Therefore, when the similarity between blocks is high, rather than calculating the rate-distortion cost for each of the nine candidate modes in order to determine the optimal mode of the current block of intra4x4 mode, the current information is determined using the neighboring mode information that has already been determined. Determining the optimal mode of the block reduces the complexity.

Accordingly, the present invention can reduce the coding speed while maintaining the coding efficiency by determining the mode by using the reference blocks of the previous frame and the current frame. That is, H.264 / AVC provides five inter modes and two intra modes, among which are SKIP and inter 16 × 16 modes having relatively low complexity and number of bits. In the present invention, the SKIP mode and the inter16x16 mode are determined as the optimal mode early, so that mode determination for 8x8, 8x4, 4x8, and 4x4 is omitted.

FIG. 3A is an exemplary view for explaining blocks used in a method for quickly determining an inter / intra mode of a macroblock according to the present invention. FIG. 3B is an exemplary view for explaining a reference block of a current frame in FIG. 3A. FIG. 3C is an exemplary diagram for describing a current macroblock in FIG. 3A, and FIG. 3D is an exemplary diagram for explaining a reference block of a previous frame in FIG. 3A.

As shown in the figure, E is a current macroblock, A, B, C and D are reference blocks of the current frame, and F, G, H and I are reference blocks of the previous frame.

4 is a flowchart illustrating a method of quickly determining an inter / intra mode of a macroblock according to the present invention.

As shown in the figure, the inter / intra-mode fast decision method of the present invention provides a candidate mode for the early decision of the macroblock mode of H.264 / AVC. Mode 1) (S41), and calculates the rate-distortion cost RDC0 of the SKIP mode (mode 0) and the rate-distortion cost RDC1 of the inter16x16 mode (mode 1) (S43).

In the inter / intra-mode fast determination method of the present invention, the upper left side (A), the upper side (B), the upper right side (C), and the left side (D) which are reference blocks of the current frame are used, and the right side which is the reference block of the previous frame is used. (F), lower left side G, lower side H, and lower right side I are used. Here, the average value of the rate-distortion cost (RDCL) of the reference block determined as the optimal mode among the eight reference blocks in the SKIP mode (mode 0) or the inter16x16 mode (mode 1), and the optimal mode among the eight reference blocks are SKIP. After obtaining the average value of the rate-distortion cost (RDCH) of the reference blocks not determined as the mode (mode 0) or the inter16x16 mode (mode 1) (S45), the rate-distortion cost of the SKIP mode (mode 0) The rate-distortion cost RDC1 of the (RDC0) and the inter16x16 mode (mode 1) are compared. That is, when {(RDCL <RDCH) & (RDC0 <RDCL) & (RDC1 <RDCL)} is satisfied (S47), the optimum mode is determined as the SKIP mode (mode 0) and the inter16x16 mode (mode 1). (S49). In this case, intra mode determination is omitted (S51), and the rate-distortion cost for the activated mode is calculated (S53).

In S47, when {(RDCL <RDCH) & (RDC0 <RDCL) & (RDC1 <RDCL)} is not satisfied, the rate-distortion cost (RDC0) of the SKIP mode (mode 0) and the inter16x16 mode ( The rate-distortion cost RDC1 of mode 1) is compared with the rate-distortion cost RDC3 of inter 8x16 mode (mode 3). That is, when {(RDC0 <RDC3) & (RDC1 <RDC3)} is satisfied (S55), the optimum mode is determined as the SKIP mode (mode 0) and the inter16x16 mode (mode 1) (S49). Thereafter, intra mode determination is omitted (S51), and the rate-distortion cost for the activated mode is calculated (S53). The reason why RDC0 and RDC1 are not compared with RDC2 is that the accuracy and hit ratio HR of the inter8x16 mode (mode 3) are better than the inter16x8 (mode 2). .

}를 만족하는 경우(S57), P8×8(서브-매크로블록)의 모드결정을 생략하고(S59), 프레임간 시간상관도로서 최적인터모드의 평균 비트율(Average Rate; 이하, 'AR'이라 함)을 측정하고, 프레임내 공간상관도로서 평균 블록경계 에러(Average Boundary Error; 이하, 'ABE'라 함)를 측정하여(S61), AR<ABE를 만족하면(S63), 인트라모드 결정을 생략한다(S51). 만약 AR<ABE를 만족하지 않는 경우에는, 활성화된 모드에 대한 율-왜곡비용을 계산하는 것으로 마무리한다(S53).If, in S55, {(RDC0 <RDC3) & (RDC1 <RDC3)} is not satisfied, the ratio-distortion cost of the inter16x8 mode (mode 2) and the inter8x16 mode (mode 3) is determined. The average value is compared with the weighted value of the rate-distortion cost of the SKIP mode (mode 0) (S57). In other words, {

} Is satisfied (S57), mode determination of P8x8 (sub-macroblock) is omitted (S59), and the average bit rate of the optimal inter mode is hereinafter referred to as 'AR' as the time correlation between frames. The average block boundary error (hereinafter referred to as 'ABE') as an intraframe spatial correlation diagram (S61), and if AR <ABE is satisfied (S63), intra mode determination is performed. Omitted (S51). If AR <ABE is not satisfied, the process ends with calculating the rate-distortion cost for the activated mode (S53).

}를 만족하지 않는 경우에는, 인터16×8모드(모드2)의 율-왜곡비용(RDC2)과 인터8×16모드(모드3)의 율-왜곡비용(RDC3)을 계산하여, 율-왜곡비용의 값이 큰 모드를 후보모드에서 제외시킨다. 이를 상세하게 설명하면 다음과 같다.If, in S57, {

}, The rate-distortion cost RDC2 of the inter16x8 mode (mode 2) and the rate-distortion cost RDC3 of the inter8x16 mode (mode 3) are calculated, and the rate-distortion is performed. The mode with a high cost is excluded from the candidate mode. This will be described in detail as follows.

That is, when RDC2 <RDC3 is satisfied (S65), the mode decision of the inter8x16 mode (mode 3) is omitted, and the mode of the inter4x8 mode is determined by the mode determination of P8x8 (sub-macroblock). The determination is omitted (S67). If RDC2 <RDC3 is not satisfied (S65), the mode determination of the inter16x8 mode (mode 2) is omitted, and the inter8x4 mode is determined by the mode determination of P8x8 (sub-macroblock). Mode determination is omitted (S69).

Subsequently, in the inter / intra mode fast determination method of the macroblock of the present invention, the determination of the intra mode according to the optimum mode of the sub macroblock is omitted (S71). This will be described in detail with reference to the drawings.

FIG. 5 is a detailed flowchart of an embodiment for describing S71 of FIG. 4 in detail.

As shown in the figure, omitting the determination of the intra mode according to the optimum mode of the submacroblock (S71) first calculates the rate-distortion cost of P8x8 (sub-macroblock) and then calculates P8x8 ( The optimum mode of the sub-macroblock is determined (S73). In this case, when the optimal mode is determined as two 8 × 8 and two 4 × 4 P8 × 8 (sub-macroblocks) (S75), the intra 4 × 4 mode using the 4 × 4 square mask and the correlation between blocks is used. Determine (S77). As for the method of determining such an intra 4x4 mode, since it is already well known in the art to which the present invention belongs, the description thereof will be omitted.

If the optimal mode among the four P8 × 8 (sub-macroblocks) is not 8 × 8 2 and 4 × 4 2 (S75), that is, the optimal mode among the four P8 × 8 (sub-macroblocks) When all are determined to be 8x8 or the optimal mode is determined to be 2 or more and 8x8 among four P8x8 (sub-macroblocks) (S79), intra4x4 mode determination is omitted (S81). If the optimal mode among the four P8 × 8 (sub-macroblocks) is 4 × 4, or if two or more of the four P8 × 8 (sub-macroblocks) are 4 × 4 (S79), intra Determination of the 16x16 mode is omitted (S83).

 As described above, the inter / intra mode fast determination method of the present invention, in which the intra mode is omitted according to the optimal mode of the sub macroblock (S71), is then performed in the flow of the flowcharts S61, S63, S51, and S53. do. Since the detailed description is as shown above, it will be omitted.

Although embodiments according to the present invention have been described above, these are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments of the present invention are possible therefrom. Accordingly, the true scope of the present invention should be determined by the following claims.

Claims (10)

In the inter / intra mode fast decision method of macroblock, for macroblock mode determination of H.264 / AVC,
(a) determining the candidate mode as the SKIP mode (mode 0) and the inter16 × 16 mode (mode 1);
(b) The candidate mode is compared with the rate-distortion cost (RDC0) of the mode 0 and the rate-distortion cost (RDC1) of the mode 1 with the rate-distortion cost (RDC3) of the inter 8x16 mode (mode 3). Determining the mode 0 and the mode 1;
(c) comparing the rate-distortion cost (RDC3) of the mode 3 with the rate-distortion cost (RDC2) of the inter16x8 mode (mode 2), whereby the mode having the smallest rate-distortion cost is determined as the candidate mode. step; And
(d) determining whether to skip intra mode determination according to an optimal mode of 8x8 (sub-macroblock), wherein step (c) includes:
(i) By comparing the average value of the rate-distortion cost of the mode 2 and the mode 3 with the weighted value of the rate-distortion cost of the mode 0, mode determination of P8 × 8 (sub-macroblock) is omitted. step;
(j) measuring an average bit rate AR of an optimal inter mode as an intra frame temporal correlation diagram and an average block boundary error A BE as an intra frame spatial correlation diagram and omitting intra mode determination when AR <ABE;
(k) if the RDC2 is smaller than the RDC3, omitting the mode determination of the mode 3, and omitting the mode determination of the inter4x8 mode at P8x8 (sub-macroblock); And
(l) if the RDC2 is not smaller than the RDC3, skipping the mode determination of the mode 2 and omitting the mode determination of the inter8x4 mode at P8x8 (sub-macroblock) How to decide.
According to claim 1, wherein step (a),
(e) determining a rate-distortion cost (RDC0) of the mode 0 and a rate-distortion cost (RDC1) of the mode 1, respectively;
(f) The average value of the rate-distortion cost (RDCL) of the reference block in which the optimal mode among the reference blocks of the current frame and the previous frame is determined to be mode 0 or mode 1, and the optimal mode of the reference blocks of the current frame and the previous frame is mode 0. Or determining a rate-distortion cost average value RDCH of the reference block not determined to be mode 1; And
(g) The mode 0 and the mode when the conditions of {(RDCL <RDCH) & (RDC0 <RDCL) & (RDC1 <RDCL)} are satisfied by comparing the RDC0, the RDC1, the RDCL, and the RDCH). And determining 1 as the optimal mode.
delete The mode 0 and the mode of claim 1, wherein the step (b) is performed when the conditions of {(RDC0 <RDC3) & (RDC1 <RDC3)} are satisfied for the RDC0, the RDC1, and the RDC3. A fast decision method comprising determining 1 as an optimum mode.
The method according to any one of claims 1, 2, and 4,
(h) after step (d), further comprising the step of omitting the determination of the intra mode.
delete delete The method of claim 1, wherein step (i) comprises:

} When the condition is satisfied, the mode decision of P8x8 (sub-macroblock) is omitted.
delete The method of claim 1, wherein the step (d)
(m) omitting intra 4 × 4 mode determination if the optimal mode of the four P8 × 8 (sub-macroblocks) is two or more; And
and (n) skipping intra16x16 mode determination when the optimal mode is 4x4 or more among four P8x8 (sub-macroblocks).

Images