| Subtest 2: Maximum palette predictor size
Tester: InterDigital, JCTVC-S0189
Crosschecker: Qualcomm (JCTVC-S0222)
Maximum palette predictor sizes of 96 and 128 were tested for the default palette size in SCM 2.0, relative to the current predictor size of 64. The palette predictor size was signalled in the PPS.
It was asked whether it is actually beneficial for the maximum palette size to be smaller than the maximum palette predictor size. That question was left open.
For lossless coding, there was some gain by increasing the palette predictor size – e.g., 1% for 96 entries, 2% for 128 entries for 1080p YUV text & graphics with motion (not so much for other classes of content). There is also a related contribution outside of this CE that relates to this.
Subtest 3: Combinations
Subtest 3.a: Max size 15 with predictor size 32
Subtest 3.b: Max size 15 with predictor size 48
Losses were observed in both cases, although somewhat less so with the latter combination.
Decision (Cleanup): When palette mode is enabled, send maximum palette size and maximum palette predictor size at SPS level as ue(v), and establish a profile constraint to disallow values greater than 31 and 64, respectively.
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