Constraint of minimum quaternary tree size
An apparatus for video encoding includes processing circuitry that is configured to decode partition information from a coded video bitstream. The partition information is indicative of a minimum allowed QT leaf node size for a I slice. The minimum allowed QT leaf node size for the I slice is constrained by a threshold that is lower than a CTU size. The processing circuitry is configured to determine, based on an override enabling flag, the minimum allowed QT leaf node size according to one of a first syntax element in an SPS or a second syntax element in a PH included in the partition information. The processing circuitry is configured to partition a coding tree block in the I slice into coding blocks based on the determined minimum allowed QT leaf node size. The processing circuitry is configured to reconstruct the coding blocks respectively from the coded video bitstream.
1. A method for video decoding in a decoder, comprising:
decoding, by processing circuitry, partition information from a coded video bitstream, the partition information being indicative of a minimum allowed quaternary tree (QT) leaf node size for an intra coded (I) slice, the minimum allowed QT leaf node size for the I slice being constrained by a threshold that is lower than a coding tree unit (CTU) size;
determining, by the processing circuitry based on an override enabling flag, the minimum allowed QT leaf node size according to one of a first syntax element in a sequence parameter set (SPS) or a second syntax element in a picture head (PH) included in the partition information;
partitioning, by the processing circuitry, a coding tree block in the I slice into coding blocks based on the determined minimum allowed QT leaf node size, wherein a base 2 logarithm of the minimum allowed QT leaf node size is less than a base 2 logarithm of the CTU size; and
reconstructing, by the processing circuitry, the coding blocks respectively from the coded video bitstream.
2. The method of claim 1 , wherein the partition information is indicative of a minimum allowed QT leaf node size for a luma component.
3. The method of claim 2 , wherein the minimum allowed QT leaf node size for the I slice, as indicated by the partition information, is constrained by the threshold when a dual tree partition is used for the I slice.
4. The method of claim 2 , further comprising determining the threshold based on an implicit QT split requirement.
5. The method of claim 1 , wherein the partition information is indicative of a minimum allowed QT leaf node size for chroma components.
6. The method of claim 1 , wherein the threshold is determined based on (i) the base 2 logarithm of the CTU size and (ii) a dual tree partition being applied to the intra coded I slice.
7. The method of claim 1 , wherein the determining the minimum allowed QT leaf node size further comprises:
based on (i) the base 2 logarithm of the CTU size and (ii) a dual tree partition being applied to the intra coded I slice,
determining that the minimum allowed QT leaf node size is between a base 2 logarithm of a minimum coding block size in the CTU and the base 2 logarithm of the CTU size minus 1.
8. The method of claim 1 , further comprising:
applying QT splits to partition the coding tree block into QT leaf nodes that satisfy a requirement of the minimum allowed QT leaf node size, before applying a binary tree (BT) split or a ternary tree (TT) split.
9. The method of claim 1 , wherein the base 2 logarithm of the minimum allowed QT leaf node size for the I slice, as indicated by the partition information, is smaller than the base 2 logarithm of the CTU size by 1.
10. An apparatus for video encoding, comprising:
processing circuitry configured to:
determine partition information being indicative of a minimum allowed quaternary tree (QT) leaf node size for an intra coded (I) slice, the minimum allowed QT leaf node size for the I slice being constrained by a threshold that is lower than a coding tree unit (CTU) size;
encoding one of a first syntax element in a sequence parameter set (SPS) or a second syntax element in a picture head (PH) included in the partition information based on an override enabling flag indicating the minimum allowed QT leaf node size;
partition a coding tree block in the I slice into coding blocks based on the determined minimum allowed QT leaf node size, wherein a base 2 logarithm of the minimum allowed QT leaf node size is less than a base 2 logarithm of the CTU size; and
encoding the partitioned coding blocks in a bitstream.
11. The apparatus of claim 10 , wherein the partition information is indicative of a minimum allowed QT leaf node size for a luma component.
12. The apparatus of claim 11 , wherein the minimum allowed QT leaf node size for the I slice, as indicated by the partition information, is constrained by the threshold when a dual tree partition is used for the I slice.
13. The apparatus of claim 11 , wherein the processing circuitry is further configured to determine the threshold based on an implicit QT split requirement.
14. The apparatus of claim 10 , wherein the partition information is indicative of a minimum allowed QT leaf node size for chroma components.
15. The apparatus of claim 10 , wherein the threshold is determined based on (i) the base 2 logarithm of the CTU size and (ii) a dual tree partition being applied to the intra coded I slice.
16. The apparatus of claim 10 , wherein the processing circuitry is further configured to:
based on (i) the base 2 logarithm of the CTU size and (ii) a dual tree partition being applied to the intra coded I slice,
determine that the minimum allowed QT leaf node size is between a base 2 logarithm of a minimum coding block size in the CTU and the base 2 logarithm of the CTU size minus 1.
17. The apparatus of claim 10 , wherein the processing circuitry is further configured to:
apply QT splits to partition the coding tree block into QT leaf nodes that satisfy a requirement of the minimum allowed QT leaf node size, before applying a binary tree (BT) split or a ternary tree (TT) split.
18. The apparatus of claim 10 , wherein the base 2 logarithm of the minimum allowed QT leaf node size for the I slice, as indicated by the partition information, is smaller than the base 2 logarithm of the CTU size by 1.
19. A method of processing visual media data, the method comprising:
processing a bitstream that includes the visual media data according to a format rule, wherein
the bitstream includes partition information from a coded video bitstream, the partition information being indicative of a minimum allowed quaternary tree (QT) leaf node size for an intra coded (I) slice, the minimum allowed QT leaf node size for the I slice being constrained by a threshold that is lower than a coding tree unit (CTU) size; and
the format rule specifies that
based on an override enabling flag, the minimum allowed QT leaf node size is determined according to one of a first syntax element in a sequence parameter set (SPS) or a second syntax element in a picture head (PH) included in the partition information,
a coding tree block in the I slice is partitioned into coding blocks based on the determined minimum allowed QT leaf node size, wherein a base 2 logarithm of the minimum allowed QT leaf node size is less than a base 2 logarithm of the CTU size; and
the coding blocks are respectively reconstructed from the coded video bitstream.
20. The method of claim 19 , wherein the partition information is indicative of a minimum allowed QT leaf node size for a luma component.