| JCTVC-M0333 AhG8: Residue rotation and significance map context for screen content coding [J. Sole, R. Joshi, M. Karczewicz (Qualcomm)]
Contributions JCTVC-J0069 and JCTVC-J0093 proposed a rotation of the residue for non-transformed coefficients (transform skip and lossless) and the usage of a constant context for the significance map. This contribution tests these methods in HEVC Range Extensions, targeting visually lossless improvements for screen content. Lossy and lossless results for the combination are provided. For screen content on the lossy high-tier setting, bit-rate savings are reportedly 2.5% for intra, 1.7% for random access and 1.8% for low delay B. The bit-rate savings for lossless are 1.9% for intra, 0.8% for random access and 0.9% for low delay B.
This affects 4x4 only (since TS only operates for 4x4).
It was remarked that this technique had been studied before and was well known to be beneficial, but had not been included in version 1 due to stability concerns while that was being finalized. It was remarked that the modification is simple.
Further study in CE with other entropy-coding-related modifications.
It was suggested to also consider K0294, which was somewhat similar. J0202/J0212/J0313 all proposed another technique. J0468 may have been the same as K0294.
Side activity was encouraged to identify which specific methods should be tested in the CE.
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