CN112714314B - Multi-type tree structure block partition mode decision-making early termination method - Google Patents

Multi-type tree structure block partition mode decision-making early termination method Download PDF

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CN112714314B
CN112714314B CN202011586141.8A CN202011586141A CN112714314B CN 112714314 B CN112714314 B CN 112714314B CN 202011586141 A CN202011586141 A CN 202011586141A CN 112714314 B CN112714314 B CN 112714314B
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CN112714314A (en
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姚英彪
王娇娇
杜晨杰
徐欣
冯维
许晓荣
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Hangzhou Dianzi University
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    • H—ELECTRICITY
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    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/136—Incoming video signal characteristics or properties
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    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
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    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/119—Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
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    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
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Abstract

The invention discloses a method for deciding and terminating a multi-type tree structure block partition mode in advance, which comprises the following steps: s1, obtaining an optimal decision threshold by taking a first frame in the image group as a key frame; s2, initializing all selectable partition modes of the current CU; s3, selecting the ith mode from all the selectable dividing modes S as the dividing mode of the current CU; s4, according to the selected mode, carrying out corresponding judgment for horizontal division or vertical division to carry out quick partition decision; and S5, correspondingly judging whether the selected mode is binary tree division or ternary tree division so as to carry out quick partition decision. According to the invention, the threshold value is controlled through the first frame of the image group, so that the threshold value is more suitable for the current image frame, unnecessary partition mode prediction is avoided by utilizing the spatial texture information of the image, the calculation complexity of a coding algorithm can be effectively reduced on the premise of ensuring the coding effect, the coding time is greatly saved, and the performance loss of coding is negligible.

Description

Multi-type tree structure block partition mode decision-making early termination method
Technical Field
The invention belongs to the technical field of video compression, and particularly relates to a multi-type tree structure block partition mode decision early termination method.
Background
The advent of ultra-high resolution video, such as high definition, ultra-high definition, and 4K video, on the one hand, means that a larger bandwidth is required to transmit video data, and on the other hand, means that a larger storage space is required to store video data. In order to alleviate the resource requirements of video transmission and storage, video coding standards are used as a common effective means of video compression technology, and the aim is to improve the video compression ratio to the greatest extent possible without reducing the video quality after video decoding. In the development process of video coding standards, new breakthroughs such as MPEG-1, MPEG-2, MPEG-4, H.261, H.263, H.264, H.265 and the like are always sought in the search for innovation. Currently, the latest version of video is the H.266/VVC (scalable video coding) standard.
In VVC, a nested multi-type tree mtt (multiple partitioning units) and a quadtree qt (quaternary tree) using Binary Tree (BT) and Ternary Tree (TT) structures, and combining a partition mode (as shown in fig. 1) replace the quadtree partition structure of hevc (high efficiency video coding). The multi-type tree structure comprises four division modes, namely vertical ternary tree division (SPLIT _ TT _ VER), vertical binary tree division (SPLIT _ BT _ VER), horizontal ternary tree division (SPLIT _ TT _ HOR), horizontal binary tree division (SPLIT _ BT _ HOR) and the like. VVC eliminates the difference between cu (coding unit), pu (prediction unit), and tu (transform unit) of HEVC. The MTT structure provides greater flexibility for CU partitioning schemes, but also greatly increases encoder time complexity. Therefore, an effective method is urgently needed to be found to solve the problem of extremely high time complexity in the decision process of the multi-type tree structure block division mode of the VTM.
Disclosure of Invention
In order to solve the problem of extremely high time complexity in the multi-type tree structure block partitioning mode decision process of the VTM, the invention discloses an H.266/VVC multi-type tree structure block partitioning mode decision early termination method. The method can effectively reduce the computational complexity of the coding algorithm on the premise of ensuring the coding effect.
The invention adopts the following technical scheme: a multi-type tree structure block partition mode choice early termination method comprises the following steps:
s1, taking the first frame in the image group as a key frame to obtain an optimal decision threshold;
s2, initializing all optional partition MODEs S of the current CU, where all optional partition MODEs S include 4 optional multi-tree block partition MODEs and 1 quad-tree partition MODE, and setting the number MT _ NUM _ MODE of the optional multi-tree block partition MODEs to 4, setting a FAST block partition ENABLE flag bit FAST _ ENABLE of a multi-tree structure to True, where the current CU is a CU in a frame number other than a first frame in the group of pictures;
s3, selecting the ith mode from all the selectable dividing modes S as the dividing mode of the current CU;
s4, judging whether the current CU partition mode is a quadtree partition mode, if so, partitioning by an H.266/VVC reference block partition method, then deleting the current partition mode from all the optional partition modes S, returning to the step S3, and if not, executing the step S5;
s5, determining FAST _ ENABLE to be tube or False, if FAST _ ENABLE is False, setting MT _ NUM _ MODE to MT _ NUM _ MODE-1, and partitioning by h.266/VVC reference block partitioning method, then deleting the current partitioning MODE from all selectable partitioning MODEs S, and returning to step S3, if not, performing step S6;
s6, when MT _ NUM _ MODE is 4, executing step S7, and when MT _ NUM _ MODE is 2, executing step S8;
s7, calculating the first characteristic F of the current CU block 1 And according to F 1 Judging whether preset termination conditions are met with the optimal decision threshold, if yes, skipping the current partitioning MODE, deleting the current partitioning MODE from all the selectable partitioning MODEs S and setting MT _ NUM _ MODE to be 2, then returning to the step S3, if not, setting FAST _ ENABLE to be False and MT _ NUM _ MODE to be 3, partitioning by an H.266/VVC reference block partitioning method, then deleting the current partitioning MODE from all the selectable partitioning MODEs S, and returning to the step S3;
s8, setting FAST _ ENABLE to False, MT _ NUM _ MODE to 1, and determining the current partitioning MODE, if the MODE is a horizontal binary tree partitioning MODE or a horizontal ternary tree partitioning MODE, performing step S9, and if the MODE is a vertical binary tree partitioning MODE or a vertical ternary tree partitioning MODE, performing step S10;
s9, calculating a second characteristic F of the current CU block 2 And according to F 2 Judging whether the current partition mode meets the preset termination condition with the optimal decision threshold, if so, skipping the current partition mode and dividing the current partition modeDeleting the mode from all the optional division modes S and returning to the step S3, if not, dividing by an H.266/VVC reference block division method, then deleting the current division mode from all the optional division modes S and returning to the step S3;
s10, calculating a third feature F of the current CU block 3 And according to F 3 And judging whether the preset termination condition is met or not according to the optimal decision threshold, if so, skipping the current division mode, deleting the current division mode from all the optional division modes S, returning to the step S3, if not, dividing by using an H.266/VVC reference block division method, then deleting the current division mode from all the optional division modes S, and returning to the step S3.
Preferably, in step S2, the 4 selectable multi-way tree block division modes are: SPLIT _ TT _ VER, SPLIT _ BT _ VER, SPLIT _ TT _ HOR and SPLIT _ BT _ HOR, wherein SPLIT _ TT _ VER is a vertical ternary tree division mode, SPLIT _ BT _ VER is a vertical binary tree division mode, SPLIT _ TT _ HOR is a horizontal ternary tree division mode, and SPLIT _ BT _ HOR is a horizontal binary tree division mode.
Preferably, in step S1, the taking the first frame in the image group as a key frame to obtain the optimal decision threshold specifically includes the following steps:
s1.1, dividing all CUs in the key frame by an H.266/VVC reference block dividing method;
s1.2, judging which division mode all CUs in the key frame are finally divided into, and if the division mode is SPLIT _ TT _ HOR, calculating the characteristic F 1 And F 2 And respectively stored in corresponding lists T12_ buf and T21_ buf; if the partition mode is SPLIT _ BT _ HOR, the feature F is calculated 1 And F 2 And respectively stored in the lists T12_ buf and T22_ buf; if the partition mode is SPLIT _ TT _ VER, the feature F is calculated 1 And F 3 And respectively stored in the lists T11_ buf and T31_ buf; if the partition mode is SPLIT _ BT _ VER, calculating the characteristic F 1 And F 3 And respectively stored in the lists T11_ buf and T32_ buf;
s1.3, setting an optimal decision threshold T according to the following formula i1 、T i2 ，i＝1,2,3：
T ij ＝(TH_T ij _buf_High+TH_T ij _buf_Low)/2，
Wherein, TH _ T ij Buf _ High and TH _ T ij Buf _ Low is the maximum and minimum values of the list Tij _ buf, respectively.
Preferably, in step S7, the first feature F is calculated according to the spatial feature FsobelX and the spatial feature FsobelY of the current CU block 1 The calculation formulas of the spatial feature FsobelX and the spatial feature FsobelY are as follows:
Figure BDA0002866096740000041
Figure BDA0002866096740000042
where f (i, j) represents the pixel value at location (i, j), and H and W are the height and width of the CU;
first feature F 1 The calculation formula of (c) is as follows:
F 1 ＝F sobelX /F sobelY 。
preferably, in step S7, the method is according to F 1 And judging whether the preset termination condition is met with the optimal decision threshold, and specifically comprising the following steps of:
s7.1, judging a current partitioning mode, performing the step S7.2 when the current partitioning mode is a horizontal partitioning mode, and performing the step S7.3 when the current partitioning mode is a vertical partitioning mode, wherein the horizontal partitioning mode comprises a horizontal binary tree partitioning mode and a horizontal ternary tree partitioning mode, and the vertical partitioning mode comprises a vertical binary tree partitioning mode and a vertical ternary tree partitioning mode;
s7.2, judgment F 1 ＞T 11 If the result is true, the preset termination condition is met, and if the result is false, the preset termination condition is not met;
s7.3, judging F 1 ＜T 12 And if the condition is not met, the preset termination condition is met, and if the condition is not met, the preset termination condition is not met.
Preferably, in step S9, the spatial features F are divided according to a horizontal binary tree of the current CU block BH And spatial features F of horizontal treelet partitioning TH Calculating a second feature F 2 Wherein:
spatial feature F of horizontal binary tree partitioning of current CU block BH The calculation method of (A) is as follows: dividing a luminance CU with the size of H multiplied by W into two horizontal sub-blocks with the area ratio of 1:1, and then calculating the spatial characteristics F of the horizontal binary tree division of the current luminance CU block according to the following formula BH ：
Figure BDA0002866096740000051
Spatial feature F of horizontal treelet partitioning of current CU block TH The calculation method is as follows: dividing a luminance CU with the size of H multiplied by W into three horizontal sub-blocks with the area ratio of 1:2:1, and then calculating the spatial characteristics F of the horizontal treelet division of the current luminance CU block according to the following formula TH ：
Figure BDA0002866096740000052
Where f (i, j) represents the pixel value at location (i, j), and H and W are the height and width of the CU;
second characteristic F 2 The calculation formula of (c) is: f 2 ＝F BH /F TH 。
Preferably, in step S9, the method is according to F 2 And judging whether the preset termination condition is met with the optimal decision threshold, and specifically comprising the following steps of:
s9.1, judging a current partitioning mode, and performing the step S9.2 when the current partitioning mode is a horizontal binary tree partitioning mode, and performing the step S10.3 when the current partitioning mode is a horizontal ternary tree partitioning mode;
s9.2, judgment F 2 ＞T 21 If the result is true, the preset termination condition is met, and if the result is false, the preset termination condition is not met;
s9.3, judgment F 2 ＜T 22 Whether or not it is establishedIf yes, the preset termination condition is met, and if not, the preset termination condition is not met.
Preferably, in step S10, the spatial feature F is divided according to a vertical binary tree of the current CU block BV And spatial features F of vertical treelet partitioning TV Calculating a third feature F 3 Wherein:
spatial feature F of vertical binary tree partitioning of current CU block BV The calculation method of (A) is as follows: dividing a luminance CU with the size of H multiplied by W into two vertical sub-blocks with the area ratio of 1:1, and then calculating the vertical binary tree division spatial feature F of the luminance CU block according to the following formula BV ：
Figure BDA0002866096740000061
Spatial feature F of vertical treeing partition of current CU block TV The calculation method is as follows: dividing a luminance CU with the size of H multiplied by W into three vertical sub-blocks with the area ratio of 1:2:1, and then calculating the vertical treelet division spatial feature F of the luminance CU block according to the following formula TV ：
Figure BDA0002866096740000062
Where f (i, j) represents the pixel value at position (i, j), and H and W are the height and width of the luminance CU.
Preferably, in step S10, the third feature F 3 The formula of (c) is as follows: f 3 ＝F BV /F TV 。
Preferably, in step S10, the method is according to F 3 And judging whether the preset termination condition is met with the optimal decision threshold, and specifically comprising the following steps of:
s10.1, judging a current partitioning mode, and performing the step S10.2 when the partitioning mode is a vertical binary tree partitioning mode, and performing the step S10.3 when the partitioning mode is a vertical ternary tree partitioning mode;
s10.2, judgment F 3 ＞T 31 If yes, the preset terminal is metStopping the condition, if not, not meeting the condition;
s10.3, judgment F 3 ＜T 32 And if the condition is not met, the preset termination condition is met, and if the condition is not met, the preset termination condition is not met.
The invention has the beneficial effects that: the first part makes corresponding judgment for horizontal division or vertical division according to the selected mode so as to make a quick partition decision. The second part makes corresponding judgment according to whether the selected mode is binary tree division or ternary tree division so as to make quick partition decision. Threshold control is performed through the first frame of the GOP, so that the threshold is more suitable for the current image frame. By utilizing the spatial texture information of the image, unnecessary partition mode prediction is avoided, the coding time is greatly saved, and the performance loss of coding is negligible.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a flow chart of a multi-type tree structure block partition mode decision early termination method;
FIG. 2 is a schematic diagram of a VVC block partitioning method;
FIG. 3 is a schematic diagram of the alternation of a threshold calculation phase and a fast partitioning phase;
FIG. 4 is a schematic diagram of horizontal spatial feature partitioning;
FIG. 5 is a schematic diagram of a vertical spatial feature partitioning approach;
Detailed Description
The following description is provided for illustrative purposes and is not intended to limit the invention to the particular embodiments disclosed. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
Referring to fig. 2, 5 CU block partition structures of h.266/VVC are shown, and are composed of 1 quadtree, 2 binary trees, and 2 ternary trees, where the 2 binary trees and the 2 ternary trees are the multiple-branch tree partition modes to be selected according to the present invention. The 4 selectable multi-way tree block division modes are respectively as follows: SPLIT _ TT _ VER, SPLIT _ BT _ VER, SPLIT _ TT _ HOR and SPLIT _ BT _ HOR, wherein SPLIT _ TT _ VER is a vertical ternary tree division mode, SPLIT _ BT _ VER is a vertical binary tree division mode, SPLIT _ TT _ HOR is a horizontal ternary tree division mode, and SPLIT _ BT _ HOR is a horizontal binary tree division mode. The quadtree partitioning pattern is SPLIT _ QT.
Referring to fig. 1, the present embodiment provides a method for deciding and terminating in advance for a multi-type tree structure block partition mode, which includes the steps of:
s1, taking the first frame in the image group as a key frame to obtain an optimal decision threshold;
s2, initializing all optional partition MODEs S of the current CU, where all optional partition MODEs S include 4 optional multi-tree block partition MODEs and 1 quad-tree partition MODE, and setting the number MT _ NUM _ MODE of the optional multi-tree block partition MODEs to 4, setting a FAST block partition ENABLE flag bit FAST _ ENABLE of a multi-tree structure to True, where the current CU is a CU in a frame number other than a first frame in the group of pictures;
s3, selecting the ith mode from all the selectable dividing modes S as the dividing mode of the current CU;
s4, judging whether the current CU partition mode is a quadtree partition mode, if so, partitioning by an H.266/VVC reference block partition method, then deleting the current partition mode from all the optional partition modes S, returning to the step S3, and if not, executing the step S5;
s5, determining FAST _ ENABLE as tube or False, if FAST _ ENABLE is False, setting MT _ NUM _ MODE as MT _ NUM _ MODE-1, and partitioning by h.266/VVC reference block partitioning method, then deleting the current partitioning MODE from all selectable partitioning MODEs S, and returning to step S3, if not, executing step S6;
s6, when MT _ NUM _ MODE is 4, step S7 is executed, and when MT _ NUM _ MODE is 2, step S8 is executed;
s7, calculating the first characteristic F of the current CU block 1 And according to F 1 Judging whether preset termination conditions are met with the optimal decision threshold, if yes, skipping the current partitioning MODE, deleting the current partitioning MODE from all the selectable partitioning MODEs S and setting MT _ NUM _ MODE to be 2, then returning to the step S3, if not, setting FAST _ ENABLE to be False and MT _ NUM _ MODE to be 3, partitioning by an H.266/VVC reference block partitioning method, then deleting the current partitioning MODE from all the selectable partitioning MODEs S, and returning to the step S3;
s8, setting FAST _ ENABLE to False, MT _ NUM _ MODE to 1, and determining the current partitioning MODE, if the MODE is a horizontal binary tree partitioning MODE or a horizontal ternary tree partitioning MODE, performing step S9, and if the MODE is a vertical binary tree partitioning MODE or a vertical ternary tree partitioning MODE, performing step S10;
s9, calculating a second characteristic F of the current CU block 2 And according to F 2 Judging whether the preset termination condition is met with the optimal decision threshold, if yes, skipping the current division mode, deleting the current division mode from all the selectable division modes S, returning to the step S3, if not, dividing by using an H.266/VVC reference block division method, then deleting the current division mode from all the selectable division modes S, and returning to the step S3;
s10, calculating a third feature F of the current CU block 3 And according to F 3 And judging whether the preset termination condition is met or not according to the optimal decision threshold, if so, skipping the current division mode, deleting the current division mode from all the optional division modes S, returning to the step S3, if not, dividing by using an H.266/VVC reference block division method, then deleting the current division mode from all the optional division modes S, and returning to the step S3.
Specifically, the method comprises the following steps:
referring to fig. 3, in step S1, the step of using the first frame in the image group as a key frame to obtain the optimal decision threshold specifically includes the following steps:
s1.1, dividing all CUs in the key frame by an H.266/VVC reference block dividing method;
s1.2, judging which division mode all CUs in the key frame are finally divided into, and if the division mode is SPLIT _ TT _ HOR, calculating the characteristic F 1 And F 2 And respectively stored in corresponding lists T12_ buf and T21_ buf; if the partition mode is SPLIT _ BT _ HOR, the feature F is calculated 1 And F 2 And respectively stored in the lists T12_ buf and T22_ buf; if the partition mode is SPLIT _ TT _ VER, the feature F is calculated 1 And F 3 And respectively stored in the lists T11_ buf and T31_ buf; if the partition mode is SPLIT _ BT _ VER, the feature F is calculated 1 And F 3 And stored in the lists T11_ buf and T32_ buf, respectively, as shown in table 1 below:
TABLE 1 partitioning method selected by CU and F i Correspondence table of calculation and buffer area
Block partitioning mode Computing features Correspondence list Computing features Correspondence list
SPLIT_TT_HOR F 1 T 12 _buf F 2 T 21 _buf
SPLIT_BT_HOR F 1 T 12 _buf F 2 T 22 _buf
SPLIT_TT_VER F 1 T 11 _buf F 3 T 31 _buf
SPLIT_BT_VER F 1 T 11 _buf F 3 T 32 _buf
S1.3, setting an optimal decision threshold T according to the following formula i1 、T i2 ，i＝1,2,3：
T ij ＝(TH_T ij _buf_High+TH_T ij _buf_Low)/2，
Wherein TH _ T ij Buf _ High and TH _ T ij Buf _ Low is the maximum and minimum of the list Tij _ buf, respectively.
Specifically, the threshold value T 11 、T 12 、T 21 、T 22 、T 31 、T 32 The calculation method of (c) is as follows:
T 11 ＝(TH_T 11 _buf_High+TH_T 11 _buf_Low)/2
T 12 ＝(TH_T 12 _buf_High+TH_T 12 _buf_Low)/2
T 21 ＝(TH_T 21 _buf_High+TH_T 21 _buf_Low)/2
T 22 ＝(TH_T 22 _buf_High+TH_T 22 _buf_Low)/2
T 31 ＝(TH_T 31 _buf_High+TH_T 31 _buf_Low)/2
T 32 ＝(TH_T 32 _buf_High+TH_T 32 _buf_Low)/2。
in step S7, a first feature F is calculated according to the spatial feature FsobelX and the spatial feature FsobelY of the current CU block 1 The calculation formulas of the spatial feature FsobelX and the spatial feature FsobelY are as follows:
Figure BDA0002866096740000111
Figure BDA0002866096740000112
where f (i, j) represents the pixel value at location (i, j), and H and W are the height and width of the CU;
first characteristic F 1 The calculation formula of (a) is as follows:
F 1 ＝F sobelX /F sobelY 。
in step S7, the method is according to F 1 And judging whether the preset termination condition is met with the optimal decision threshold, and specifically comprising the following steps of:
s7.1, judging a current partitioning mode, performing the step S7.2 when the current partitioning mode is a horizontal partitioning mode, and performing the step S7.3 when the current partitioning mode is a vertical partitioning mode, wherein the horizontal partitioning mode comprises a horizontal binary tree partitioning mode and a horizontal ternary tree partitioning mode, and the vertical partitioning mode comprises a vertical binary tree partitioning mode and a vertical ternary tree partitioning mode;
s7.2, judgment F 1 ＞T 11 If yes, meeting a preset termination condition, and if not, not meeting the preset termination condition;
s7.3, judging F 1 ＜T 12 Whether it is true, if so, thenIf the preset termination condition is met, the terminal does not meet the preset termination condition.
In step S9, the spatial characteristics F are divided according to the horizontal binary tree of the current CU block BH And spatial features F of horizontal treelet partitioning TH Calculating a second feature F 2 Wherein:
spatial feature F of horizontal binary tree partitioning of current CU block BH The calculation method of (A) is as follows: the luminance CU of size H × W is divided into two horizontal sub-blocks with an area ratio of 1:1 (see fig. 4 (a)), and then the spatial feature F of the horizontal binary tree division of the current luminance CU block is calculated as follows BH ：
Figure BDA0002866096740000121
Spatial feature F of horizontal treeing partition of current CU block TH The calculation method is as follows: the luminance CU of size H × W is divided into three horizontal sub-blocks of an area ratio of 1:2:1 (see fig. 4 (b)), and then the spatial feature F of horizontal treelet division of the current luminance CU block is calculated as follows TH ：
Figure BDA0002866096740000122
Where f (i, j) represents the pixel value at location (i, j), and H and W are the height and width of the CU;
second characteristic F 2 The calculation formula of (2) is as follows: f 2 ＝F BH /F TH 。
In step S9, the method according to F 2 And the optimal decision threshold value is used for judging whether the preset termination condition is met, and the method specifically comprises the following steps:
s9.1, judging a current partitioning mode, and performing the step S9.2 when the current partitioning mode is a horizontal binary tree partitioning mode, and performing the step S10.3 when the current partitioning mode is a horizontal ternary tree partitioning mode;
s9.2, judgment F 2 ＞T 21 If the result is true, the preset termination condition is met, and if the result is false, the preset termination condition is not met;
s9.3, judgment F 2 ＜T 22 And if the condition is satisfied, the preset termination condition is met, and if the condition is not satisfied, the preset termination condition is not met.
In step S10, the spatial features F are divided according to the vertical binary tree of the current CU block BV And spatial features F of vertical treble partitioning TV Calculating a third feature F 3 Wherein:
spatial feature F of vertical binary tree partitioning of current CU block BV The calculation method of (A) is as follows: dividing the luminance CU with size H × W into two vertical sub-blocks with area ratio of 1:1 (see fig. 5 (a)), and then calculating the vertical binary tree partition spatial feature F of the luminance CU block according to the following formula BV ：
Figure BDA0002866096740000131
Spatial feature F of vertical treeing partition of current CU block TV The calculation method of (A) is as follows: dividing a luminance CU with size H × W into three vertical sub-blocks with area ratio of 1:2:1 (see fig. 5 (b)), and then calculating a vertical treble partition spatial feature F of the luminance CU block according to the following formula TV ：
Figure BDA0002866096740000132
Where f (i, j) represents the pixel value at position (i, j), and H and W are the height and width of the luminance CU.
Third feature F 3 The calculation formula of (2) is as follows: f 3 ＝F BV /F TV 。
In step S10, the method according to F 3 And judging whether the preset termination condition is met with the optimal decision threshold, and specifically comprising the following steps of:
s10.1, judging a current partitioning mode, and performing the step S10.2 when the current partitioning mode is a vertical binary tree partitioning mode, and performing the step S10.3 when the current partitioning mode is a vertical ternary tree partitioning mode;
s10.2, judgment F 3 ＞T 31 If the result is true, the preset termination condition is met, and if the result is false, the preset termination condition is not met;
s10.3, judgment F 3 ＜T 32 And if the condition is not met, the preset termination condition is met, and if the condition is not met, the preset termination condition is not met.
The experimental result shows that compared with the VTM5.0 (a VVC reference model), the coding time of the algorithm provided by the invention is greatly shortened (about 45% on average), the coding bit Rate BD-Rate is only slightly increased (about 1.3% on average), and the computational complexity of the coding algorithm can be effectively reduced on the premise of ensuring the coding effect.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention by those skilled in the art should fall within the protection scope of the present invention without departing from the design spirit of the present invention.

Claims (1)

1. A multi-type tree structure block partition mode decision early termination method is characterized by comprising the following steps:
s1, taking the first frame in the image group as a key frame to obtain an optimal decision threshold;
s2, initializing all optional partition MODEs S of the current CU, where all optional partition MODEs S include 4 optional multi-tree block partition MODEs and 1 quad-tree partition MODE, and setting the number MT _ NUM _ MODE of the optional multi-tree block partition MODEs to 4, setting a FAST block partition ENABLE flag bit FAST _ ENABLE of a multi-tree structure to True, where the current CU is a CU in a frame number other than a first frame in the group of pictures;
s3, selecting the ith mode from all the selectable dividing modes S as the dividing mode of the current CU;
s4, judging whether the current CU partition mode is a quadtree partition mode, if so, partitioning by an H.266/VVC reference block partition method, then deleting the current partition mode from all the optional partition modes S, returning to the step S3, and if not, executing the step S5;
s5, determining FAST _ ENABLE as tube or False, if FAST _ ENABLE is False, setting MT _ NUM _ MODE as MT _ NUM _ MODE-1, and partitioning by h.266/VVC reference block partitioning method, then deleting the current partitioning MODE from all selectable partitioning MODEs S, and returning to step S3, if not, executing step S6;
s6, when MT _ NUM _ MODE is 4, executing step S7, and when MT _ NUM _ MODE is 2, executing step S8;
s7, calculating the first characteristic F of the current CU block 1 And according to F 1 Judging whether preset termination conditions are met with the optimal decision threshold, if so, skipping the current partitioning MODE, deleting the current partitioning MODE from all the selectable partitioning MODEs S and setting MT _ NUM _ MODE to be 2, then returning to the step S3, if not, setting FAST _ ENABLE to be False and MT _ NUM _ MODE to be 3, partitioning through an H.266/VVC reference block partitioning method, then deleting the current partitioning MODE from all the selectable partitioning MODEs S, and returning to the step S3;
s8, setting FAST _ ENABLE to False, MT _ NUM _ MODE to 1, and determining the current partitioning MODE, if the MODE is a horizontal binary tree partitioning MODE or a horizontal ternary tree partitioning MODE, performing step S9, and if the MODE is a vertical binary tree partitioning MODE or a vertical ternary tree partitioning MODE, performing step S10;
s9, calculating a second characteristic F of the current CU block 2 And according to F 2 Judging whether the preset termination condition is met with the optimal decision threshold, if yes, skipping the current division mode, deleting the current division mode from all the selectable division modes S, returning to the step S3, if not, dividing by using an H.266/VVC reference block division method, then deleting the current division mode from all the selectable division modes S, and returning to the step S3;
s10, calculating a third characteristic F of the current CU block 3 And according to F 3 Judging whether the preset termination condition is met with the optimal decision threshold, if yes, skipping the current division mode, deleting the current division mode from all the selectable division modes S, returning to the step S3, if not, dividing by using an H.266/VVC reference block division method, then deleting the current division mode from all the selectable division modes S, and returning to the step S3;
in step S2, the 4 optional multi-way treeblock partition modes are: SPLIT _ TT _ VER, SPLIT _ BT _ VER, SPLIT _ TT _ HOR and SPLIT _ BT _ HOR, wherein SPLIT _ TT _ VER is a vertical ternary tree division mode, SPLIT _ BT _ VER is a vertical binary tree division mode, SPLIT _ TT _ HOR is a horizontal ternary tree division mode, and SPLIT _ BT _ HOR is a horizontal binary tree division mode;
in step S1, the method for obtaining an optimal decision threshold by using the first frame in the image group as a key frame specifically includes the following steps:
s1.1, dividing all CUs in the key frame by an H.266/VVC reference block dividing method;
s1.2, judging the division mode into which all CUs in the key frame are finally divided, and if the division mode is SPLIT _ TT _ HOR, calculating the characteristic F 1 And F 2 And respectively stored in corresponding lists T12_ buf and T21_ buf; if the partition mode is SPLIT _ BT _ HOR, the feature F is calculated 1 And F 2 And respectively stored in the lists T12_ buf and T22_ buf; if the partition mode is SPLIT _ TT _ VER, the feature F is calculated 1 And F 3 And respectively stored in the lists T11_ buf and T31_ buf; if the partition mode is SPLIT _ BT _ VER, the feature F is calculated 1 And F 3 And respectively stored in the lists T11_ buf and T32_ buf;
s1.3, setting an optimal decision threshold T according to the following formula i1 、T i2 ，i＝1,2,3：
T ij ＝(TH_T ij _buf_High+TH_T ij _buf_Low)/2，
Wherein, TH _ T ij Buf _ High and TH _ T ij Buf _ Low is respectively the maximum value and the minimum value of the Tij _ buf list;
in step S7, the spatial characteristics F according to the current CU block sobelX And spatial feature F sobelY Calculating a first feature F 1 Wherein the spatial feature F sobelX And spatial feature F sobelY The calculation formula of (c) is as follows:
Figure FDA0003642795490000031
Figure FDA0003642795490000032
where f (i, j) represents the pixel value at location (i, j), and H and W are the height and width of the CU;
first feature F 1 The calculation formula of (a) is as follows:
F 1 ＝F sobelX /F sobelY ；
in step S7, according to F 1 And the optimal decision threshold value is used for judging whether the preset termination condition is met, and the method specifically comprises the following steps:
s7.1, judging a current division mode, and performing the step S7.2 when the current division mode is a horizontal division mode, and performing the step S7.3 when the current division mode is a vertical division mode, wherein the horizontal division mode comprises a horizontal binary tree division mode and a horizontal ternary tree division mode, and the vertical division mode comprises a vertical binary tree division mode and a vertical ternary tree division mode;
s7.2, judgment F 1 ＞T 11 If the result is true, the preset termination condition is met, and if the result is false, the preset termination condition is not met;
s7.3, judgment F 1 ＜T 12 If the result is true, the preset termination condition is met, and if the result is false, the preset termination condition is not met;
in step S9, the spatial characteristics F are divided according to the horizontal binary tree of the current CU block BH And spatial features F of horizontal treelet partitioning TH Calculating a second feature F 2 Wherein:
spatial feature F of horizontal binary tree partitioning of current CU block BH The calculation method of (A) is as follows: dividing a luminance CU with the size of H multiplied by W into two horizontal sub-blocks with the area ratio of 1:1, and then calculating the spatial characteristics F of the horizontal binary tree division of the current luminance CU block according to the following formula BH ：
Figure FDA0003642795490000041
Horizontal trigeminal of current CU blockSpatial features of tree partitioning F TH The calculation method is as follows: dividing a luminance CU with the size of H multiplied by W into three horizontal sub-blocks with the area ratio of 1:2:1, and then calculating the spatial characteristics F of the horizontal ternary tree division of the current luminance CU block according to the following formula TH ：
Figure FDA0003642795490000042
Where f (i, j) represents the pixel value at location (i, j), and H and W are the height and width of the CU;
second characteristic F 2 The calculation formula of (c) is: f 2 ＝F BH /F TH ；
In step S9, according to F 2 And judging whether the preset termination condition is met with the optimal decision threshold, and specifically comprising the following steps of:
s9.1, judging a current partitioning mode, and performing the step S9.2 when the current partitioning mode is a horizontal binary tree partitioning mode, and performing the step S10.3 when the current partitioning mode is a horizontal ternary tree partitioning mode;
s9.2, judgment F 2 ＞T 21 If the result is true, the preset termination condition is met, and if the result is false, the preset termination condition is not met;
s9.3, judgment F 2 ＜T 22 If yes, meeting a preset termination condition, and if not, not meeting the preset termination condition;
in step S10, the spatial characteristics F are divided according to the vertical binary tree of the current CU block BV And spatial features F of vertical treble partitioning TV Calculating a third feature F 3 Wherein:
spatial feature F of vertical binary tree partitioning of current CU block BV The calculation method of (A) is as follows: dividing a luminance CU with the size of H multiplied by W into two vertical sub-blocks with the area ratio of 1:1, and then calculating the vertical binary tree division space characteristic F of the luminance CU block according to the following formula BV ：
Figure FDA0003642795490000051
Spatial feature F of vertical treeing partition of current CU block TV The calculation method of (A) is as follows: dividing a luminance CU with the size of H multiplied by W into three vertical sub-blocks with the area ratio of 1:2:1, and then calculating the vertical ternary tree division spatial feature F of the luminance CU block according to the following formula TV ：
Figure FDA0003642795490000052
Where f (i, j) represents the pixel value at position (i, j), and H and W are the height and width of the luminance CU;
in step S10, the third feature F 3 The formula of (c) is as follows: f 3 ＝F BV /F TV ；
In step S10, according to F 3 And the optimal decision threshold value is used for judging whether the preset termination condition is met, and the method specifically comprises the following steps:
s10.1, judging a current partitioning mode, and performing the step S10.2 when the current partitioning mode is a vertical binary tree partitioning mode, and performing the step S10.3 when the current partitioning mode is a vertical ternary tree partitioning mode;
s10.2, judgment F 3 ＞T 31 If yes, meeting a preset termination condition, and if not, not meeting the preset termination condition;
s10.3, judgment F 3 ＜T 32 And if the condition is not met, the preset termination condition is met, and if the condition is not met, the preset termination condition is not met.
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