Low-delay checking process is required for TMVP derivation. The process is carried out by comparing the POC values of current picture and its reference pictures.

In HEVC text, the low-delay checking process is specified in the section of TMVP derivation (i.e. 8.5.3.2.8 Derivation process for collocated motion vectors), which means the low-delay checking process is done at block-level.

However the low-delay checking process is performed at slice-level in HM reference software, where a low-delay flag is firstly determined at slice-level and then used in TMVP derivation.

It seems the low-delay checking at block-level specified in HEVC text is not reasonable for practical design, since the low-delay checking process is only based on POC values, instead of any block-level information, and meanwhile the block-level low-delay checking increase complexity. Hence alignment with HM reference software is suggested for consideration.