TECHNICAL FIELD

This patent document relates to video coding/decoding techniques, devices and systems.

BACKGROUND

In spite of the advances in video compression, digital video still accounts for the largest bandwidth use on the internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, it is expected that the bandwidth demand for digital video usage will continue to grow.

SUMMARY

The present document describes various embodiments and techniques in which video coding or decoding is performed using sub-block based motion vector refinement. In one example aspect, a method of visual media processing is disclosed. The method includes determining whether to use an affine adaptive motion vector resolution (AMVR) technique on visual media data relying on a control information related to the affine AMVR technique in a bitstream representation of the visual media data, wherein the control information is included or excluded from the bitstream representation based on a rule; and performing a conversion between the visual media data and the bitstream representation of the visual media data.

In another example aspect, another method of visual media processing is disclosed. The method includes making a determination of whether or not subblock-based temporal motion vector prediction (sbTMVP) technique is applied to visual media data; in response to the determination, generating a sub-block merge candidate list for a current video block included in the visual media data; and performing a conversion between the current video block and a bitstream representation of the current video block, using the sub-block merge candidate list.

In yet another example aspect, another method of visual media processing is disclosed. The method includes appending, during a conversion between a current video block and a bitstream representation, one or more default merge candidates to a sub-block merge candidate list for the conversion; and performing the conversion using the sub-block merge candidate list with appended one or more default merge candidates.

In yet another example aspect, another method of visual media processing is disclosed. The method includes determining, during a conversion between a current video block of a video and a bitstream representation, applicability of subblock-based temporal motion vector prediction (sbTMVP) to the conversion wherein one or more bits in the bitstream representation correspond to the determining; and performing the conversion based on the determining.

In yet another example aspect, another method of visual media processing is disclosed. The method includes building a sub-block merge candidate list selectively based on a condition associated with a temporal motion vector prediction (TMVP) step or a subblock-based temporal motion vector prediction (sbTMVP) step; and performing a conversion between a current video block and a bitstream representation of the current video block based on the sub-block merge candidate list.

In yet another example aspect, another method of visual media processing is disclosed. The method includes during a conversion between a visual media data and a bitstream representation of the visual media data, determining an information related to a collocated reference picture associated with the visual media data, wherein the information is included or excluded in the bitstream representation based on whether a coding mode accessing temporal motion information is enabled; determining the collocated reference picture according to the indication; and performing, based on the collocated reference picture, the conversion between the visual media data and the bitstream representation of the visual media data.

In yet another example aspect, another method of visual media processing is disclosed. The method includes performing a conversion between a video block of a visual media data and a bitstream representation of the visual media data; and during the conversion, determining whether to apply a predictive refinement using optical flow (PROF) relying on a control information, which is included or excluded in the bitstream representation based on a rule.

In yet another example aspect, a video encoding and/or decoding apparatus comprising a processor configured to implement an above described method is disclosed.

In yet another example aspect, a computer readable medium is disclosed. The computer readable medium stores processor executable code embodying one of the above described method.

These, and other, aspect are further described in the present document.

