Palette run hiding in palette-based video coding

A method of encoding video data, the method comprising:

• determining palette indices of non-escape coded pixels of a first block of the video data, wherein, for each respective non-escape coded pixel of the first block, the palette index of the respective non-escape coded pixel indicates an entry in a first palette, wherein each respective entry in the first palette indicates a respective set of sample values;
• identifying a first series of runs in the first block, the first series of runs including two or more runs, each respective run of the first series of runs consisting of one pixel or two or more consecutive pixels of the first block, each pixel of each respective run of the first series of runs having a same palette sample mode;
• generating a first set of one or more palette run length syntax elements, wherein the first set of one or more palette run length syntax elements indicate lengths of one or more runs in the first series of runs;
• generating a first syntax element having a first value indicating the first set of palette run length syntax elements does not indicate a length of the first run of the first series of runs;
• determining palette indices of pixels of a second block of the video data, wherein, for each respective pixel of the second block, the palette index of the respective pixel indicates an entry in a second palette, wherein each respective entry in the second palette indicates a respective set of sample values;
• identifying a second series of runs, each respective run of the second series of runs consisting of one pixel or two or more consecutive pixels of the second block, each pixel of each respective run of the second series of runs having a same palette sample mode;
• generating a second set of one or more palette run length syntax elements, wherein the second set of palette run length syntax elements indicates lengths of one or more runs of the second series of runs;
• and
• generating a second syntax element, the second syntax element having a second value indicating the second set of palette run length syntax elements does not indicate a length of the last run of the second series of runs, the second value being different from the first value.

A device for decoding video data, the device comprising:

• a memory configured to store the video data;
• and
• one or more processors configured to:
• obtain a first syntax element from a bitstream that comprises an encoded representation of a first block of the video data, wherein the first block comprises a first series of runs, the first series of runs including two or more runs, each respective run of the first series of runs consisting of one pixel or two or more consecutive pixels of the first block, each pixel of each respective run of the first series of runs having a same palette sample mode;
• obtain, from the bitstream, a first set of one or more palette run length syntax elements, wherein the first set of one or more palette run length syntax elements indicate lengths of one or more runs in the first series of runs;
• determine, based on the first syntax element having a first value, that the first set of palette run length syntax elements does not indicate a length of the first run of the first series of runs;
• determine, based on the number of pixels in the first block and the lengths indicated by the first set of palette run syntax elements, the length of the first run of the first series of runs;
• determine, based on palette sample modes of non-escape coded pixels of the first block, palette indices of the non-escape coded pixels of the first block, wherein, for each respective non-escape coded pixel of the first block, the respective palette index of the respective non-escape coded pixel indicates an entry in a first palette, each respective entry in the first palette indicating a respective set of sample values;
• determine, based on the palette indices of the non-escape coded pixels of the first block, values of the non-escape coded pixels of the first block;
• obtain, from the bitstream, a second syntax element, wherein a second block of the video data comprises a second series of runs, the second series of runs including two or more runs, each respective run of the second series of runs consisting of one pixel or two or more consecutive pixels of the second block, each pixel of each respective run of the second series of runs having a same palette sample mode;
• obtain, from the bitstream, a second set of one or more palette run length syntax elements, wherein the second set of palette run length syntax elements indicates lengths of one or more runs of the second series of runs;
• determine, based on the second syntax element having a second value different from the first value, that the second set of palette run length syntax elements does not indicate a length of the last run of the second series of runs;
• determine, based on the number of pixels in the second block and the lengths indicated by the second set of palette run syntax elements, the length of the last run of the second series of runs;
• determine, based on palette sample modes of the pixels of the second block, palette indices of the pixels of the second block;
• and
• determine, based on the palette indices of the pixels of the second block, values of pixels of the second block.

A device for encoding video data, the device comprising:

• a memory configured to store the video data;
• and
• one or more processors configured to:
• determine palette indices of non-escape coded pixels of a first block of the video data, wherein, for each respective non-escape coded pixel of the first block, the palette index of the respective pixel indicates an entry in a first palette, wherein each respective entry in the first palette indicates a respective set of sample values;
• identify a first series of runs in the first block, the first series of runs including two or more runs, each respective run of the first series of runs consisting of one pixel or two or more consecutive pixels of the first block, each pixel of each respective run of the first series of runs having a same palette sample mode;
• generate a first set of one or more palette run length syntax elements, wherein the first set of one or more palette run length syntax elements indicate lengths of one or more runs in the first series of runs;
• generate a first syntax element having a first value indicating the first set of palette run length syntax elements does not indicate a length of the first run of the first series of runs;
• determine palette indices of pixels of a second block of the video data, wherein, for each respective pixel of the second block, the palette index of the respective pixel indicates an entry in a second palette, wherein each respective entry in the second palette indicates a respective set of sample values;
• identify a second series of runs, each respective run of the second series of runs consisting of one pixel or two or more consecutive pixels of the second block, each pixel of each respective run of the second series of runs having a same palette sample mode;
• generate a second set of one or more palette run length syntax elements, wherein the second set of palette run length syntax elements indicates lengths of one or more runs of the second series of runs;
• and
• generate a second syntax element, the second syntax element having a second value indicating the second set of palette run length syntax elements does not indicate a length of the last run of the second series of runs, the second value being different from the first value.