Low memory design for multiple reference line selection scheme
Methods, apparatus, and computer readable storage medium for multiple reference line intra prediction in video decoding. The method includes receiving, by a device, a coded video bitstream for a current block. The device includes a memory storing instructions and a processor in communication with the memory. The method also includes extracting, by the device, a parameter from the coded video bitstream, the parameter indicating a reference line for intra predication in the current block; partitioning, by the device, the current block to obtain a plurality of sub-blocks; and in response to a sub-block in the plurality of sub-blocks being located at a boundary of the current block, using, by the device, a top adjacent reference line as values for all top non-adjacent reference lines for the sub-block.
1. A method for video decoding, the method comprising:
receiving, by a device comprising a memory storing instructions and a processor in communication with the memory, a coded video bitstream for a current block;
determining that a multiple reference line selection is applied for the current block;
extracting, by the device, a parameter from the coded video bitstream, the parameter indicating a non-adjacent reference line index for intra predication in the current block;
partitioning, by the device, the current block to obtain a plurality of sub-blocks; and
when a first sub-block in the plurality of sub-blocks is located at a top boundary of the current block and the multiple reference line selection is applied for the current block, using, by the device, top-left values corresponding to an adjacent reference line to substitute values for top-left values of a non-adjacent reference line corresponding to the non-adjacent reference line index for the first sub-block.
2. The method according to claim 1 , further comprising:
using, by the device, a left adjacent reference line for the first sub-block.
3. The method according to claim 1 , wherein:
the current block comprises at least one of: a super block, a largest coding block, a coding tree block (CTB), a largest coding unit (LCU), or a predefined block with a predefined size.
4. The method according to claim 1 , wherein:
the first sub-block is located at a left boundary and the top boundary of the current block.
5. The method according to claim 1 , further comprising:
copying samples from the adjacent reference line to a non-adjacent reference line corresponding to the non-adjacent reference line index.
6. The method according to claim 1 , further comprising:
partitioning, by the device, the first sub-block to obtain a plurality of transform blocks.
7. The method according to claim 6 , further comprising:
when a first transform block in the plurality of transform blocks is located at a top boundary of the first sub-block, using, by the device, the adjacent reference line as values for all top non-adjacent reference lines for the first transform block; and
when the first transform block in the plurality of transform blocks is not located at the top boundary of the first sub-block, using, by the device, a reference line indicated by the parameter for the first transform block.
8. A method for video encoding, the method comprising:
receiving video data that comprises a plurality of blocks, including a current block;
determining that a multiple reference line selection is applied for the current block;
determining a non-adjacent reference line index for intra predication in the current block;
partitioning the current block to obtain a plurality of sub-blocks;
when a first sub-block in the plurality of sub-blocks is located at a top boundary of the current block and the multiple reference line selection is applied for the current block, encoding the first sub-block in accordance with top-left values corresponding to an adjacent reference line substituted for top-left values of a non-adjacent reference line corresponding to the non-adjacent reference line index for the first sub-block; and
signaling the encoded first sub-block and the non-adjacent reference line index in a video bitstream.
9. The method of claim 8 , further comprising using a left adjacent reference line for encoding the first sub-block.
10. The method of claim 8 , wherein the current block comprises at least one of: a super block, a largest coding block, a coding tree block (CTB), a largest coding unit (LCU), or a predefined block with a predefined size.
11. The method of claim 8 , wherein the first sub-block is located at a left boundary and the top boundary of the current block.
12. The method of claim 8 , further comprising copying samples from the adjacent reference line to a non-adjacent reference line corresponding to the non-adjacent reference line index.
13. The method of claim 8 , further comprising partitioning the first sub-block to obtain a plurality of transform blocks.
14. The method of claim 13 , further comprising:
when a first transform block in the plurality of transform blocks is located at a top boundary of the first sub-block, using a top adjacent reference line as values for all top non-adjacent reference lines for the first transform block; and
when the first transform block is not located at the top boundary of the first sub-block, using a reference line indicated by the non-adjacent reference line index for the first transform block.
15. A method of processing visual media data, the method comprising:
obtaining a source video sequence;
performing a conversion between the source video sequence and a bitstream of visual media data, wherein the bitstream comprises:
a plurality of encoded blocks, including a current block comprising a plurality of encoded sub-blocks;
an indicator for a non-adjacent reference line index for intra predication in the current block;
wherein the plurality of encoded sub-blocks include a first sub-block located at a top boundary of the current block; and
wherein the first sub-block is encoded in accordance with top-left values corresponding to an adjacent reference line substituted for top-left values of a non-adjacent reference line corresponding to the non-adjacent reference line index for the first sub-block.
16. The method of claim 15 , wherein the first sub-block is encoded using a left adjacent reference line.
17. The method of claim 15 , wherein the current block comprises at least one of: a super block, a largest coding block, a coding tree block (CTB), a largest coding unit (LCU), or a predefined block with a predefined size.
18. The method of claim 15 , wherein the first sub-block is located at a left boundary and the top boundary of the current block.
19. The method of claim 15 , wherein the first sub-block is encoded in accordance with samples from the adjacent reference line substituted for non-adjacent reference line values corresponding to the non-adjacent reference line index.