JVET-O1170 Bitstream conformance with a virtual IBC buffer concept [J. Xu, L. Zhang, K. Zhang, H. Liu, Y. Wang (Bytedance), J. Li, C.S. Lim (Panasonic), X. Xu, X. Li, S. Liu (Tencent)] [late]
Presented Wed 10 July afternoon Track B
During discussion of IBC conformance, it is agreed that it is better targeting a bitstream constraint without imposing a mandatory check at the decoder and a simple solution is preferred to define the IBC bitstream constrains. This document presents a simple design of bitstream constrains based on a virtual IBC buffer concept.
It is generally agreed that the concept goes into the right direction and largely simplifies the definition of the bitstream constraint. The current version still requires improvements, e.g.
- definition of variables
- it is inconsistent that the changing of the state of ibcbuf is part of the decoding process in clause 8.7.5.1, whereas it is not mandatory for a decoder. This should be clarified and better referred to the bitstream restriction in clause 8.6.2.1 (perhaps just adding notes)
It is noted that JVET-O1171 is identical.
Decision: Adopt JVET-O1170 – remaining issues to be sorted out with editor.
It is further noted that the improved text should also include one more restrictions on IBC that was agreed in context with JVET-O1161 discussion: Limit largest IBC luma CU size to 64x64.
Furthermore, the text already includes disabling IBC for chroma in case of dual tree (as adopted from JVET-O0258).