LUMA mapping with chroma scaling (LMCS) in video coding

A device for coding video data, the device comprising:

• memory configured to store the video data;
• and
• processing circuitry configured to:
• determine that chroma related syntax elements of the video data are present for luma mapping with chroma scaling (LMCS) for a first coding unit (CU) of the video data;
• code a first syntax element of the video data when the chroma related syntax elements are present for LMCS for the first CU, the first syntax element is indicative of a first value for determining a scaling parameter for chroma scaling in LMCS;
• code a chroma block of the first CU based on the scaling parameter for chroma scaling;
• code a second syntax element in a picture header for a picture that includes a second CU having a luma block, the second syntax element being an identification of an adaptation parameter set (APS);
• code a third value for a third syntax element for the luma block, the third syntax element specifying a number of bits used for representation of a fourth syntax element for LMCS, wherein the second syntax element is in the picture header and the third value of the third syntax element is within a range of 0 to a bit depth —2;
• and
• code the luma block using LMCS.

A non-transitory computer-readable storage medium storing instructions thereon that when executed cause one or more processors to:

• determine that chroma related syntax elements of the video data are present for luma mapping with chroma scaling (LMCS) for a first coding unit (CU) of the video data;
• code a first syntax element of the video data when the chroma related syntax elements are present for LMCS for the first CU, the first syntax element is indicative of a first value for determining a scaling parameter for chroma scaling in LMCS;
• code a chroma block of the first CU based on the scaling parameter for chroma scaling;
• code a second syntax element in a picture header for a picture that includes a second CU having a luma block, the second syntax element being an identification of an adaptation parameter set (APS);
• code a third value for a third syntax element for the luma block, the third syntax element specifying a number of bits used for representation of a fourth syntax element for LMCS, wherein the second syntax element is in the picture header and the third value of the third syntax element is within a range of 0 to a bit depth —2;
• and
• code the luma block using LMCS.

A device for coding video data, the device comprising:

• means for determining that chroma related syntax elements of the video data are present for luma mapping with chroma scaling (LMCS) for a first coding unit (CU) of the video data;
• means for coding a first syntax element of the video data when the chroma related syntax elements are present for LMCS for the first CU, the first syntax element is indicative of a first value for determining a scaling parameter for chroma scaling in LMCS;
• means for coding a chroma block of the first CU based on the scaling parameter for chroma scaling;
• means for coding a second syntax element in a picture header for a picture that includes a second CU having a luma block, the second syntax element being an identification of an adaptation parameter set (APS);
• means for coding a third value for a third syntax element for the luma block, the third syntax element specifying a number of bits used for representation of a fourth syntax element for LMCS, wherein the second syntax element is in the picture header and the third value of the third syntax element is within a range of 0 to a bit depth —2;
• and
• means for coding the luma block using LMCS.