JVET-P0077 CE8-1.3: Line-based CG Palette Mode [Y.-H. Chao, C.-H. Hung, W.-J. Chien, T. Hsieh, M. Karczewicz (Qualcomm)]
In this CE, a line-based CG palette mode, which reduces the buffer to store index values, index maps in HEVC palette mode, is tested. A palette mode coded CU is divided into multiple line segments (line coefficient group (CG)) of m samples based on the traverse scan mode, as shown in Figure 2. The coefficient parsing, i.e., parsing the index runs, palette index values, and quantized colors, are done sequentially for each line CG.
The parsing of the palette index run in each line CG is as follows: a context coded bin (index_flag) is parsed for each sample indicating if the sample is of the same run mode as the previously scanned sample, i.e., if the previous scanned sample and the current sample are both of run type COPY_ABOVE or if the previous scanned sample and the current sample are both of run type INDEX with the same index value. If the pixel and the previous sample are of different mode, a context coded bin is parsed indicating the run type, i.e., INDEX or COPY_ABOVE. Same as the HEVC palette, decoder doesn’t have to parse run type if the sample is in the first row (horizontal traverse scan) or in the first column (vertical traverse scan) since the INDEX mode is used by default. Also, decoder doesn’t have to parse run type if the previously parsed run type is COPY_ABOVE.
The index values (for index runs of INDEX mode) and quantized escape colors are bypass coded and grouped apart from encoding/parsing of context coded bins, i.e., index_flag and run_type, to improve throughput within each line CG.
Line CG segmentation for horizontal and vertical traverse scans
Non-CE Technology proposals
CE1 related – Reference picture resampling filters (13)
Contributions in this category were discussed Friday 4 Oct. 1430–1900 in Track B (chaired by GJS).