tree 9c2f718e780f9d402f00bbff74e32a61b231aab0
parent 49404055f830881785cc02d4b124ab750f1edefd
author Yunqing Wang <yunqingwang@google.com> 1510622007 -0800
committer Yunqing Wang <yunqingwang@google.com> 1510960465 +0000

Reuse neighbor's warped motion parameters

If a block's motion_mode is WARPED_CAUSAL and its mode is NEARESTMV, search
its immediate above and left neighbors to get the set of neighbor blocks
using WARPED_CAUSAL motion mode, pick the one with largest block size, and
use that neighbor's warped motion parameters directly for the current block.
If none of the neighbors uses WARPED_CAUSAL motion mode, we estimate the
current block's warped motion parameters.

Before this patch, for every block, we estimate its warped motion parameters.
With this patch, we reduce the number of blocks doing parameter estimation.
Here are results by testing on clips with camera motions.
                    WARPED_CAUSAL blocks   blocks reusing parameters
station2_240p(30f):     3857                    1678
netflix_arieal(30f):     692                     223

No noticable changes in coding gain. Borg test result showed a PSNR
change of +0.006% on cam_lowres set, and -0.014% on lowres set.

Change-Id: If12387ad0ca8a1996ea4c3f1bedcb269ebf78c6c