Modified HEVC transform tree syntax
A method, apparatus, article of manufacture, and a memory structure for performing transform tree processing in advanced coding schemes is disclosed. Logical statements having two operands that can result in negative flag indexes have been replaced with conditional multiple logical statements with single operands.
1. In a processing device for decoding a sequence of a plurality of pictures, each of the pictures partitionable into one or more coding units, each coding unit coded at least in part according to at least one transform unit as specified in a transform tree, a method of processing the sequence, comprising:
receiving a bitstream comprising the sequence of the plurality of pictures;
partitioning each of the pictures into one or more coding units;
determining, by the processing device, if a size of the transform unit is greater than a minimum transform unit size;
if the transform unit size is greater than the minimum transform unit size:
determining, by the processing device, if the transform unit is at a same hierarchical depth as the coding unit associated with the transform unit;
if the transform unit is at the same hierarchical depth as the associated coding unit, reading, in a first logical statement executed by the processing device, a flag indicating whether a first chroma transform block has any non-zero coefficients;
if the transform unit is not at the same hierarchical depth as the associated coding unit, determining, by the processing device, if a second chroma transform block hierarchically above the first chroma transform block has any non-zero coefficients; and
if the second chroma transform block hierarchically above the first chroma transform block has any non-zero coefficients, reading, in a second logical statement executed by the processing device, the flag indicating whether the second chroma transform block has any non-zero coefficients; and
decoding a sign of any non-zero coefficients indicated by the flag.
2. The method of claim 1 , wherein:
the second chroma transform block comprises a Cb transform block describing a first set of chroma coefficients;
the flag is a flag describing whether any coefficients of the Cb transform unit are non-zero.
3. The method of claim 1 , wherein:
the second chroma transform block comprises a Cr transform block describing a second set of chroma coefficients; and
the flag is a flag describing whether any coefficients of the Cr transform block are non-zero.
4. The method of claim 1 , further comprising:
determining, from the transform tree syntax, if the transform unit is at the same hierarchical depth as the coding unit associated with the transform unit;
if the transform unit is at the same hierarchical depth as the associated coding unit, reading, in a third logical statement, another flag indicating whether a third chroma transform block has any non-zero coefficients;
if the transform unit is not at the same hierarchical depth as the associated coding unit, determining, from the transform tree syntax, if a fourth chroma transform block hierarchically above the third chroma transform block has any non-zero coefficients; and
if the fourth chroma transform block hierarchically above the third chroma transform block has any non-zero coefficients, reading, in a second logical statement, the another flag indicating whether the fourth chroma transform block has any non-zero coefficients.
5. The method of claim 4 , wherein:
the flag is a cbf_cb flag; and
the another flag is a cbf_cr flag.
6. The method of claim 1 , wherein:
the determining if the transform is at a same hierarchical depth as the coding unit associated with the transform unit is performed in a third logical statement; and
the determining if the second chroma transform block hierarchically above the first chroma transform block has any non-zero coefficients is performed in a fourth logical statement.
7. The method of claim 6 , wherein:
the third logical statement is an if statement with a single operand; and
the fourth logical statement is an else statement with a single operand.
8. The method of claim 1 , wherein:
the transform unit is determined to be at a same hierarchical depth as the coding unit associated with the transform unit according to a variable of the transform tree syntax; and
the second chroma transform block of hierarchically above the first chroma transform block is determined from an decremented index based on the variable of the transform tree syntax.
9. An apparatus for decoding a sequence of a plurality of pictures, each of the pictures partitionable into one or more coding units, each coding unit coded at least in part according to at least one transform unit as specified in a transform tree, the apparatus comprising:
a processor;
a memory, communicatively coupled to the processor, the memory storing instructions comprising instructions for:
receiving a bitstream comprising the sequence of the plurality of pictures;
partitioning each of the pictures into one or more coding units;
determining, by the processing device, if a size of the transform unit is greater than a minimum transform unit size;
if the transform unit size is greater than the minimum transform unit size:
determining, by the processing device, if the transform unit is at a same hierarchical depth as the coding unit associated with the transform unit;
if the transform unit is at the same hierarchical depth as the associated coding unit, reading, in a first logical statement executed by the processing device, a flag indicating whether a first chroma transform block has any non-zero coefficients;
if the transform unit is not at the same hierarchical depth as the associated coding unit, determining, by the processing device, determining if a second chroma transform block hierarchically above the first chroma transform block has any non-zero coefficients; and
if the second chroma transform block hierarchically above the first chroma transform block has any non-zero coefficients, reading, in a second logical statement executed by the processing device, the flag indicating whether the second chroma transform block has any non-zero coefficients; and
decoding a sign of any non-zero coefficients indicated by the flag.
10. The apparatus of claim 9 , wherein:
the second chroma transform block comprises a Cb transform block describing a first set of chroma coefficients;
the flag is a flag describing whether any coefficients of the Cb transform unit are non-zero.
11. The apparatus of claim 9 , wherein:
the second chroma transform block comprises a Cr transform block describing a second set of chroma coefficients; and
the flag is a flag describing whether any coefficients of the Cr transform block are non-zero.
12. The apparatus of claim 9 , further comprising:
determining, from the transform tree syntax, if the transform unit is at the same hierarchical depth as the coding unit associated with the transform unit;
if the transform unit is at the same hierarchical depth as the associated coding unit, reading, in a third logical statement, another flag indicating whether a third chroma transform block has any non-zero coefficients;
if the transform unit is not at the same hierarchical depth as the associated coding unit, determining, from the transform tree syntax, if a fourth chroma transform block hierarchically above the third chroma transform block has any non-zero coefficients; and
if the fourth chroma transform block hierarchically above the third chroma transform block has any non-zero coefficients, reading, in a second logical statement, the another flag indicating whether the fourth chroma transform block has any non-zero coefficients.
13. The apparatus of claim 12 , wherein:
the flag is a cbf_cb flag; and
the another flag is a cbf_cr flag.
14. The apparatus of claim 9 , wherein:
the determining if the transform is at a same hierarchical depth as the coding unit associated with the transform unit is performed in a third logical statement; and
the determining if the second chroma transform block of hierarchically above the first chroma transform block has any non-zero coefficients is performed in a fourth logical statement.
15. The apparatus of claim 14 , wherein:
the third logical statement is an if statement with a single operand; and
the fourth logical statement is an else statement with a single operand.
16. The method of claim 9 , wherein:
the transform unit is determined to be at a same hierarchical depth as the coding unit associated with the transform unit according to a variable of the transform tree syntax; and
the second chroma transform block of hierarchically above the first chroma transform block is determined from an decremented index based on the variable of the transform tree syntax.
17. An apparatus for decoding a sequence of a plurality of pictures, each of the pictures partitionable into one or more coding units, each coding unit coded at least in part according to at least one transform unit as specified in a transform tree, the apparatus comprising:
means for receiving a bitstream comprising the sequence of the plurality of pictures;
partitioning each of the pictures into one or more coding units;
means for determining if a size of the transform unit is greater than a minimum transform unit size;
means for determining if the transform unit is at a same hierarchical depth as the coding unit associated with the transform unit if the transform unit size is greater than the minimum transform unit size;
means for reading, in a first logical statement, a flag indicating whether a first chroma transform block has any non-zero coefficients if the size of the transform unit is greater than a minimum transform unit size and if the transform unit is at the same hierarchical depth as the associated coding unit;
means for determining if a second chroma transform block hierarchically above the first chroma transform block has any non-zero coefficients if the size of the transform unit is greater than a minimum transform unit size and if the transform unit is not at the same hierarchical depth as the associated coding unit; and
means for reading, in a second logical statement executed by the processing device, the flag indicating whether the first chroma transform block has any non-zero coefficients if the size of the transform unit is greater than a minimum transform unit size and if the second chroma transform block hierarchically above the second transform block has any non-zero coefficients; and
means for decoding a sign of any non-zero coefficients indicated by the flag.
18. The apparatus of claim 17 , wherein:
the second chroma transform block comprises a Cb transform block describing a first set of chroma coefficients;
the flag is a flag describing whether any coefficients of the Cb transform unit are non-zero.
19. The apparatus of claim 17 , wherein:
the second chroma transform block comprises a Cr transform block describing a second set of chroma coefficients; and
the flag is a flag describing whether any coefficients of the Cr transform block are non-zero.
20. The apparatus of claim 17 , wherein:
the transform unit is determined to be at a same hierarchical depth as the coding unit associated with the transform unit according to a variable of the transform tree syntax; and
the second chroma transform block hierarchically above than the first chroma transform block is determined from an decremented index based on the variable of the transform tree syntax.