Rules for intra-picture prediction modes when wavefront parallel processing is enabled

One or more non-transitory computer-readable media having stored thereon computer-executable instructions for causing one or more processing units, when programmed thereby, to perform operations comprising:

• determining that wavefront parallel processing (“WPP”) is enabled;
• outputting, as part of encoded data in a bitstream, a flag that indicates whether or not WPP is enabled, the flag being part of a picture parameter set syntax structure or sequence parameter set syntax structure in the bitstream;
• encoding a picture with WPP enabled, wherein the encoding produces encoded data for the picture, including, for a palette coding mode, predicting a palette for an initial unit in a current WPP row of the picture using previous palette data from a previous unit in a previous WPP row of the picture, wherein the previous palette data from the previous unit in the previous WPP row includes, for each of C colors, one or more color component values, and wherein C is limited by a threshold count for the previous palette data from the previous unit in the previous WPP row;
• and
• outputting the encoded data for the picture as part of the encoded data in the bitstream.

In a computer system, a method comprising:

• receiving encoded data in a bitstream, the encoded data including a flag that indicates whether or not wavefront parallel processing (“WPP”) is enabled, the flag being part of a picture parameter set syntax structure or sequence parameter set syntax structure in the bitstream, and the encoded data further including encoded data for a picture;
• and
• storing the encoded data, wherein the encoded data is usable to cause a computer-implemented video decoder, when processing the encoded data, to perform operations comprising:
• determining, based on the flag, that WPP is enabled;
• and
• decoding the encoded data for the picture with WPP enabled to reconstruct the picture, including, for a palette decoding mode, predicting a palette for an initial unit in a current WPP row of the picture using previous palette data from a previous unit in a previous WPP row of the picture, wherein the previous palette data from the previous unit in the previous WPP row includes, for each of C colors, one or more color component values, and wherein C is limited by a threshold count for the previous palette data from the previous unit in the previous WPP row.