Sub-partition intra prediction

Abstract

Techniques are described for improving intra-subpartitioning (ISP) mode for splitting coding blocks into sub-blocks. In some cases, whether ISP mode is enabled for a coding block is based on size constraints pertaining to data units (e.g., VPDUs, transform blocks, among others). For instance, based on a size constraint related to a VPDU, the ISP mode can be disabled for coding blocks crossing VPDU boundaries. In some cases, whether to enable ISP mode may be based on comparison of the width and/or height of the coding block to size thresholds corresponding to one or more maximum transform block sizes. In some cases, where the ISP mode is enabled for a coding block, a value of a flag used for defining a type of split, horizontal or vertical, for the coding block, can be inferred based on the width and/or height of the coding block relative to one or more thresholds.

What is claimed is: 
     
         1 . An apparatus for encoding video data, the apparatus comprising:
 a memory; and   a processor implemented in circuitry and configured to:
 obtain a current block of a picture of video data; 
 determine whether at least one of a width of the current block of the picture is greater than a width size threshold and a height of the current block is greater than a height size threshold, the width size threshold corresponding to a width of a data unit and the height size threshold corresponding to a height of the data unit; 
 determine whether an intra-subpartitions mode flag is to be signaled for the current block based on whether at least one of the width of the current block is greater than the width size threshold and the height of the current block is greater than the height size threshold, wherein a value of the intra-subpartitions mode flag indicates whether the current block is partitioned into rectangular transform block subpartitions; and 
 generate, based on determining whether the intra-subpartitions mode flag is to be signaled for the current block, an encoded video bitstream including at least the current block. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the width size threshold is equal to the height size threshold. 
     
     
         3 . The apparatus of  claim 1 , wherein the width size threshold is different than the height size threshold. 
     
     
         4 . The apparatus of  claim 1 , wherein a value of the intra-subpartitions mode flag being equal to a first value specifies that the current block is partitioned into rectangular transform block subpartitions, and the value of the intra-subpartitions mode flag being equal to a second value specifies that the current block is not partitioned into rectangular transform block subpartitions. 
     
     
         5 . The apparatus of  claim 4 , wherein the processor is further configured to:
 determine the width of the current block is greater than the width size threshold or the height of the current block is greater than the height size threshold; and   based on the determination that the width of the current block is greater than the width size threshold or the height of the current block is greater than the height size threshold, determine the value of the intra-subpartitions mode flag for the current block to be equal to the second value.   
     
     
         6 . The apparatus of  claim 4 , wherein the processor is further configured to:
 determine the width of the current block is less than or equal to the width size threshold and the height of the current block is less than or equal to the height size threshold; and   based on the determination that the width of the current block is less than or equal to the width size threshold and the height of the current block is less than or equal to the height size threshold, determine to signal the intra-subpartitions mode flag for the current block.   
     
     
         7 . The apparatus of  claim 4 , wherein the processor is further configured to:
 determine the width of the current block is less than or equal to a size threshold and the height of the current block is less than or equal to the size threshold, the size threshold corresponding to a maximum transform block size; and   based on the determination that the width of the current block is less than or equal to the size threshold and the height of the current block is less than or equal to the size threshold, determine to signal the intra-subpartitions mode flag for the current block.   
     
     
         8 . The apparatus of  claim 4 , wherein the processor is further configured to:
 determine the width of the current block is less than or equal to a size threshold or the height of the current block is less than or equal to the size threshold, the size threshold corresponding to a maximum transform block size; and   based on the determination that the width of the current block is less than or equal to the size threshold or the height of the current block is less than or equal to the size threshold, determine that the value of the intra-subpartitions mode flag for the current block is the second value.   
     
     
         9 . The apparatus of  claim 4 , wherein the processor is further configured to:
 determine the intra-subpartitions mode flag is to be signaled for the current block; and   based on the determination that the intra-subpartitions mode flag is to be signaled for the current block, include the intra-subpartitions mode flag for the current block in the encoded video bitstream.   
     
     
         10 . The apparatus of  claim 1 , wherein the processor is further configured to:
 determine that at least one of a width and a height of the current block is greater than a size threshold corresponding to a maximum transform block size; and   based on the determination that the width or the height of the current block is greater than the size threshold corresponding to the maximum transform block size, determine a value for an intra-subpartitions split flag for the current block, the intra-subpartitions split flag specifying whether a type of split for partitioning the current block is horizontal or vertical.   
     
     
         11 . The apparatus of  claim 10 , wherein the processor is further configured to:
 determine the width of the current block is greater than the size threshold; and   based on the determination that the width of the current block is greater than the size threshold, determine a first split value for the intra-subpartitions split flag, the first split value corresponding to a vertical split type.   
     
     
         12 . The apparatus of  claim 10 , wherein the processor is further configured to:
 determine the height of the current block is greater than the size threshold; and   based on the determination that the height of the current block is greater than the size threshold, determine a second split value for the intra-subpartitions split flag, the second split value corresponding to a horizontal split type.   
     
     
         13 . The apparatus of  claim 10 , wherein the processor is further configured to:
 divide the current block vertically or horizontally into sub-partitions based on the value of the intra-subpartitions split flag for the current block.   
     
     
         14 . The apparatus of  claim 1 , wherein the current block is an intra-predicted block. 
     
     
         15 . The apparatus of  claim 1 , wherein the data unit is a Virtual Pipeline Data Unit (VPDU). 
     
     
         16 . The apparatus of  claim 1 , wherein the data unit is a transform block. 
     
     
         17 . The apparatus of  claim 16 , wherein the width size threshold and the height size threshold are equal to a maximum transform block size. 
     
     
         18 . A method of decoding video data, the method comprising:
 obtaining an encoded video bitstream including video data;   determining that an intra-subpartitions split flag is not present in the encoded video bitstream for a current block of video data, the intra-subpartitions split flag specifying whether a type of split for an intra-subpartitions mode used for the current block is horizontal or vertical;   determining that at least one of a width and a height of the current block is greater than a size threshold corresponding to a maximum transform block size; and   determining a value for the intra-subpartitions split flag for the current block based on whether the width or the height of the current block is greater than the size threshold.   
     
     
         19 . The method of  claim 18 , further comprising:
 determining an intra-subpartitions mode flag is enabled for the current block; and   determining that the intra-subpartitions split flag is not present in the encoded video bitstream based on the determination that the intra-subpartitions mode flag is enabled for the current block, wherein the current block is partitioned into rectangular transform block subpartitions using the intra-subpartitions mode based on the intra-subpartitions mode flag being enabled for the current block.   
     
     
         20 . The method of  claim 18 , further comprising:
 determining the width of the current block is greater than the size threshold; and   based on the determination that the width of the current block is greater than the size threshold, determining a first split value for the intra-subpartitions split flag, the first split value corresponding to a vertical split type.   
     
     
         21 . The method of  claim 20 , further comprising:
 splitting the current block into two or more sub-blocks using the vertical split type, wherein respective widths of each of the two or more sub-blocks are smaller than the width of the current block based on the vertical split type.   
     
     
         22 . The method of  claim 18 , further comprising:
 determining the height of the current block is greater than the size threshold; and   based on the determination that the height of the current block is greater than the size threshold, determining a second split value for the intra-subpartitions split flag, the second split value corresponding to a horizontal split type.   
     
     
         23 . The method of  claim 22 , further comprising:
 splitting the current block into two or more sub-blocks using the horizontal split type, wherein respective heights of each of the two or more sub-blocks are smaller than the height of the current block based on the horizontal split type.   
     
     
         24 . The method of  claim 18 , further comprising:
 determining that an intra-subpartitions mode flag for enabling the intra-subpartitions mode for a second block of the video data is not present in the encoded video bitstream; and   determining a mode value of the intra-subpartitions mode flag for the second block based on the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block.   
     
     
         25 . The method of  claim 24 , wherein the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block is indicative of at least one of a width of the second block being greater than a width size threshold or a height of the second block being greater than a height size threshold, the width size threshold corresponding to a width of a data unit and the height size threshold corresponding to a height of the data unit. 
     
     
         26 . The method of  claim 25 , wherein the width size threshold is equal to the height size threshold. 
     
     
         27 . The method of  claim 25 , wherein the width size threshold is not equal to the height size threshold. 
     
     
         28 . The method of  claim 25 , wherein the data unit is a Virtual Pipeline Data Unit (VPDU). 
     
     
         29 . The method of  claim 25 , wherein the data unit is a transform block. 
     
     
         30 . The method of  claim 29 , wherein the width size threshold and the height size threshold are equal to a maximum transform block size. 
     
     
         31 . The method of  claim 18 , wherein the current block is an intra-predicted block. 
     
     
         32 . The method of  claim 18 , further comprising:
 performing block-based partitioning of a block of video data to generate one or more coding blocks including the current block;   determining the intra-subpartitions mode is enabled for the current block; and   based on determining the intra-subpartitions mode is enabled for the current block, partitioning the current block into two or more sub-blocks using the intra-subpartitions mode.   
     
     
         33 . The method of  claim 32 , further comprising:
 reconstructing the two or more sub-blocks by applying respective two or more residual values to the two or more sub-blocks.   
     
     
         34 . An apparatus for decoding video data, the apparatus comprising:
 a memory; and   a processor implemented in circuitry and configured to:
 obtain an encoded video bitstream including video data; 
 determine that an intra-subpartitions split flag is not present in the encoded video bitstream for a current block of video data, the intra-subpartitions split flag specifying whether a type of split for an intra-subpartitions mode used for the current block is horizontal or vertical; 
 determine that at least one of a width and a height of the current block is greater than a size threshold corresponding to a maximum transform block size; and 
 determine a value for the intra-subpartitions split flag for the current block based on whether the width or the height of the current block is greater than the size threshold. 
   
     
     
         35 . The apparatus of  claim 34 , wherein the processor is further configured to:
 determine an intra-subpartitions mode flag is enabled for the current block; and   determine that the intra-subpartitions split flag is not present in the encoded video bitstream based on the determination that the intra-subpartitions mode flag is enabled for the current block, wherein the current block is partitioned into rectangular transform block subpartitions using the intra-subpartitions mode based on the intra-subpartitions mode flag being enabled for the current block.   
     
     
         36 . The apparatus of  claim 34 , wherein the processor is further configured to:
 determine the width of the current block is greater than the size threshold; and   based on the determination that the width of the current block is greater than the size threshold, determine a first split value for the intra-subpartitions split flag, the first split value corresponding to a vertical split type.   
     
     
         37 . The apparatus of  claim 36 , wherein the processor is further configured to:
 split the current block into two or more sub-blocks using the vertical split type, wherein respective widths of each of the two or more sub-blocks are smaller than the width of the current block based on the vertical split type.   
     
     
         38 . The apparatus of  claim 34 , wherein the processor is further configured to:
 determine the height of the current block is greater than the size threshold; and   based on the determination that the height of the current block is greater than the size threshold, determine a second split value for the intra-subpartitions split flag, the second split value corresponding to a horizontal split type.   
     
     
         39 . The apparatus of  claim 38 , wherein the processor is further configured to:
 split the current block into two or more sub-blocks using the horizontal split type, wherein respective heights of each of the two or more sub-blocks are smaller than the height of the current block based on the horizontal split type.   
     
     
         40 . The apparatus of  claim 34 , wherein the processor is further configured to:
 determine that an intra-subpartitions mode flag for enabling the intra-subpartitions mode for a second block of the video data is not present in the encoded video bitstream; and   determine a mode value of the intra-subpartitions mode flag for the second block based on the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block.   
     
     
         41 . The apparatus of  claim 40 , wherein the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block is indicative of at least one of a width of the second block being greater than a width size threshold or a height of the second block being greater than a height size threshold, the width size threshold corresponding to a width of a data unit and the height size threshold corresponding to a height of the data unit. 
     
     
         42 . The apparatus of  claim 41 , wherein the width size threshold is equal to the height size threshold. 
     
     
         43 . The apparatus of  claim 41 , wherein the width size threshold is not equal to the height size threshold. 
     
     
         44 . The apparatus of  claim 41 , wherein the data unit is a Virtual Pipeline Data Unit (VPDU). 
     
     
         45 . The apparatus of  claim 41 , wherein the data unit is a transform block. 
     
     
         46 . The apparatus of  claim 45 , wherein the width size threshold and the height size threshold are equal to a maximum transform block size. 
     
     
         47 . The apparatus of  claim 34 , wherein the current block is an intra-predicted block. 
     
     
         48 . The apparatus of  claim 34 , wherein the processor is further configured to:
 perform block-based partitioning of a block of video data to generate one or more coding blocks including the current block;   determine the intra-subpartitions mode is enabled for the current block; and   based on determining the intra-subpartitions mode is enabled for the current block, partition the current block into two or more sub-blocks using the intra-subpartitions mode.   
     
     
         49 . The apparatus of  claim 48 , wherein the processor is further configured to:
 reconstruct the two or more sub-blocks by applying respective two or more residual values to the two or more sub-blocks.   
     
     
         50 . The apparatus of  claim 34 , wherein the apparatus comprises a mobile device with a camera for capturing one or more pictures. 
     
     
         51 . The apparatus of  claim 34 , further comprising a display for displaying one or more pictures. 
     
     
         52 . A non-transitory computer-readable medium having stored thereon instructions that, when executed by one or more processors, cause the one or more processors to:
 obtain an encoded video bitstream including video data;   determine that an intra-subpartitions split flag is not present in the encoded video bitstream for a current block of video data, the intra-subpartitions split flag specifying whether a type of split for an intra-subpartitions mode used for the current block is horizontal or vertical;   determine that at least one of a width and a height of the current block is greater than a size threshold corresponding to a maximum transform block size; and   determine a value for the intra-subpartitions split flag for the current block based on whether the width or the height of the current block is greater than the size threshold.   
     
     
         53 . The non-transitory computer-readable medium of  claim 52 , wherein the instructions further cause the processor to:
 determine an intra-subpartitions mode flag is enabled for the current block; and   determine that the intra-subpartitions split flag is not present in the encoded video bitstream based on the determination that the intra-subpartitions mode flag is enabled for the current block, wherein the current block is partitioned into rectangular transform block subpartitions using the intra-subpartitions mode based on the intra-subpartitions mode flag being enabled for the current block.   
     
     
         54 . The non-transitory computer-readable medium of  claim 52 , wherein the instructions further cause the processor to:
 determine the width of the current block is greater than the size threshold; and   based on the determination that the width of the current block is greater than the size threshold, determine a first split value for the intra-subpartitions split flag, the first split value corresponding to a vertical split type; and   split the current block into two or more sub-blocks using the vertical split type, wherein respective widths of each of the two or more sub-blocks are smaller than the width of the current block based on the vertical split type.   
     
     
         55 . The non-transitory computer-readable medium of  claim 52 , wherein the instructions further cause the processor to:
 determine the height of the current block is greater than the size threshold; and   based on the determination that the height of the current block is greater than the size threshold, determine a second split value for the intra-subpartitions split flag, the second split value corresponding to a horizontal split type; and   split the current block into two or more sub-blocks using the horizontal split type, wherein respective heights of each of the two or more sub-blocks are smaller than the height of the current block based on the horizontal split type.   
     
     
         56 . The non-transitory computer-readable medium of  claim 52 , wherein the instructions further cause the processor to:
 determine that an intra-subpartitions mode flag for enabling the intra-subpartitions mode for a second block of the video data is not present in the encoded video bitstream; and   determine a mode value of the intra-subpartitions mode flag for the second block based on the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block.   
     
     
         57 . The non-transitory computer-readable medium of  claim 56 , wherein the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block is indicative of at least one of a width of the second block being greater than a width size threshold or a height of the second block being greater than a height size threshold, the width size threshold corresponding to a width of a data unit and the height size threshold corresponding to a height of the data unit. 
     
     
         58 . The non-transitory computer-readable medium of  claim 57 , wherein the width size threshold is equal to the height size threshold. 
     
     
         59 . The non-transitory computer-readable medium of  claim 57 , wherein the width size threshold is not equal to the height size threshold. 
     
     
         60 . The non-transitory computer-readable medium of  claim 57 , wherein the data unit is a Virtual Pipeline Data Unit (VPDU). 
     
     
         61 . The non-transitory computer-readable medium of  claim 57 , wherein the data unit is a transform block. 
     
     
         62 . The non-transitory computer-readable medium of  claim 57 , wherein the width size threshold and the height size threshold are equal to a maximum transform block size. 
     
     
         63 . The non-transitory computer-readable medium of  claim 52 , wherein the current block is an intra-predicted block. 
     
     
         64 . An apparatus for decoding video data, the apparatus comprising:
 means for obtaining an encoded video bitstream including video data;   means for determining that an intra-subpartitions split flag is not present in the encoded video bitstream for a current block of video data, the intra-subpartitions split flag specifying whether a type of split for an intra-subpartitions mode used for the current block is horizontal or vertical;   means for determining that at least one of a width and a height of the current block is greater than a size threshold corresponding to a maximum transform block size; and   means for determining a value for the intra-subpartitions split flag for the current block based on whether the width or the height of the current block is greater than the size threshold.   
     
     
         65 . The apparatus of  claim 64 , further comprising:
 means for determining that an intra-subpartitions mode flag for enabling the intra-subpartitions mode for a second block of the video data is not present in the encoded video bitstream; and   means for determining a mode value of the intra-subpartitions mode flag for the second block based on the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block.   
     
     
         66 . The apparatus of  claim 65 , wherein the intra-subpartitions mode flag not being present in the encoded video bitstream for the second block is indicative of at least one of a width of the second block being greater than a width size threshold or a height of the second block being greater than a height size threshold, the width size threshold corresponding to a width of a data unit and the height size threshold corresponding to a height of the data unit. 
     
     
         67 . The apparatus of  claim 66 , wherein the data unit is a Virtual Pipeline Data Unit (VPDU). 
     
     
         68 . The apparatus of  claim 66 , wherein the data unit is a transform block. 
     
     
         69 . The apparatus of  claim 68 , wherein the width size threshold and the height size threshold are equal to a maximum transform block size.