H.265 Codec: Motion estimation Settings

Motion search range

The default is derived from the default CTU size (64) minus the luma interpolation half-length (4) minus maximum subpel distance (2) minus one extra pixel just in case the hex search method is used. If the search range were any larger than this, another CTU row of latency would be required for reference frames.
Default 57

Motion search method

Generally, the higher the number the harder the ME method will try to find an optimal match.
Diamond search is the simplest. Hexagon search is a little better.

Subpel Refinement

Amount of subpel refinement to perform.
The higher the number the more subpel iterations and steps are performed.
Default 2

Max Merge

Maximum number of neighbor (spatial and temporal) candidate blocks that the encoder may consider for merging motion predictions. If a merge candidate results in no residual, it is immediately selected as a “skip”. Otherwise the merge candidates are tested as part of motion estimation when searching for the least cost inter option. The max candidate number is encoded in the SPS and determines the bit cost of signaling merge CUs.
Default 2

Enable temporal motion vector predictors in P and B slices

This enables the use of the motion vector from the collocated block in the previous frame to be used as a predictor.
Default is enabled

Enable weighted prediction in P slices

This enables weighting analysis in the lookahead, which influences slice decisions, and enables weighting analysis in the main encoder which allows P reference samples to have a weight function applied to them prior to using them for motion compensation. In video which has lighting changes, it can give a large improvement in compression efficiency.
Default is enabled

Enable weighted prediction in B slices

Default disabled

Analyze SRC Pics

Enable motion estimation with source frame pixels, in this mode, motion estimation can be computed independently.
Default disabled.