METHOD FOR APPARATUS FOR DERIVING MAXIMUM SUB-BLOCK TRANSFORM SIZE

1 .- 20 . (canceled)

21 . A method of decoding a bitstream to output one or more pictures for a video sequence, the method comprising:

decoding the bitstream;

determining, based on the decoded bitstream, a maximum transform size in luma samples; and

determining whether subblock transform (SBT) is allowed for a CU of the video sequence,

wherein the determining of whether the SBT is allowed for the CU is based on a comparison of a size of the CU to the maximum transform size in luma samples.

22 . The method according to claim 21 , wherein:

decoding the bitstream comprises decoding a flag associated with the video sequence; and

determining the maximum transform size in luma samples comprises determining the maximum transform size in luma samples based on a value of the flag.

23 . The method according to claim 22 , wherein the flag is signaled in a sequence parameter set (SPS) of the bitstream.

24 . The method according to claim 22 , wherein the flag is sps_max_luma_transform_size_64_flag.

25 . The method according to claim 22 , further comprising:

in response to a value of the flag being 1, determining the maximum transform size in luma samples to be equal to 64; or

in response to the value of the flag being 0, determining the maximum transform size in luma samples to be equal to 32.

26 . The method according to claim 22 , further comprising:

in response to the flag having a first value, determining the maximum transform size in luma samples to be equal to a second value; or

in response to the flag having a third value, determining the maximum transform size in luma samples to be equal to a fourth value.

27 . The method according to claim 21 , wherein the comparison of the size of the CU to the maximum transform size in luma samples comprises at least one of:

a comparison of a width of the CU to the maximum transform size in luma samples, or

a comparison of a height of the CU to the maximum transform size in luma samples.

28 . The method according to claim 21 , further comprising:

determining a maximum CU size that allows the SBT to be equal to the maximum transform size in luma samples.

29 . A method of encoding a video sequence into a bitstream, the method comprising:

determining, for the video sequence, a maximum transform size in luma samples;

determining whether to use subblock transform (SBT) for a coding unit of the video sequence,

wherein the determining of whether to use the SBT for the CU is based on a comparison of a size of the CU to the maximum transform size in luma samples.

30 . The method according to claim 29 , further comprising:

encoding a flag indicating the maximum transform size in luma samples.

31 . The method according to claim 30 , encoding the flag in a sequence parameter set (SPS) of a bitstream associated with the video sequence.

32 . The method according to claim 30 , wherein the flag is sps_max_luma_transform_size_64_flag.

33 . The method according to claim 30 , further comprising:

in response to the maximum transform size in luma samples being determined to be equal to 64, setting a value of the flag to be 1; or

in response to the maximum transform size in luma samples being determined to be equal to 32, setting the value of the flag to be 0.

34 . The method according to claim 30 , further comprising:

in response to the maximum transform size in luma samples being determined to be equal to a first value, setting the flag to have a second value; or

in response to the maximum transform size in luma samples being determined to be equal to a third value, setting the flag to have a fourth value.

35 . The method according to claim 29 , wherein the comparison of the size of the CU to the maximum transform size in luma samples comprises at least one of:

a comparison of a width of the CU to the maximum transform size in luma samples, or

a comparison of a height of the CU to the maximum transform size in luma samples.

36 . A non-transitory computer readable storage medium storing a bitstream associated with a video sequence, wherein the bitstream is decodable by:

determining, for the video sequence, a maximum transform size in luma samples; and

determining whether subblock transform (SBT) is allowed for a CU of the video sequence,

wherein the determining of whether the SBT is allowed for the CU is based on a comparison of a size of the CU to the maximum transform size in luma samples.

37 . The non-transitory computer readable storage medium according to claim 36 , wherein the bitstream comprises:

a flag indicating the maximum transform size in luma samples.

38 . The non-transitory computer readable storage medium according to claim 37 , wherein the bitstream comprises:

a sequence parameter set (SPS) associated with the video sequence, the flag being signaled in the SPS.

39 . The non-transitory computer readable storage medium according to claim 37 , wherein the bitstream is decodable by:

in response to a value of the flag being 1, determining the maximum transform size in luma samples to be equal to 64; or

in response to the value of the flag being 0, determining the maximum transform size in luma samples to be equal to 32.

40 . The non-transitory computer readable storage medium according to claim 37 , wherein the bitstream is decodable by:

in response to the flag having a first value, determining the maximum transform size in luma samples to be equal to a second value; or

in response to the flag having a third value, determining the maximum transform size in luma samples to be equal to a fourth value.