commit 342a368fd489d4bb2fd2ef9189a933ff7b643d64
author Yunqing Wang <yunqingwang@google.com> Tue Feb 16 14:33:18 2016 -0800
committer Yunqing Wang <yunqingwang@google.com> Mon Feb 29 12:14:47 2016 -0800
tree cf3c05d987fcd595b552bc8d1dffcd14d3985b9f
parent db084506d8098feaec1aee0cb519cc8d207e734f

Do sub-pixel motion search in up-sampled reference frames

Up-sampled the reference frames to 8 times in each dimension using
the 8-tap interpolation filter. In sub-pixel motion search, use the
up-sampled reference frames to find the best matching blocks. This
largely improved the motion search precision, and thus, improved
the compression quality. There was no change in decoder side.

Borg test and speed test results:
1. On derflr set,
Overall PSNR gain: 1.306%, and SSIM gain: 1.512%.
Average speed loss on derf set was 6.0%.
2. On stdhd set,
Overall PSNR gain: 0.754%, and SSIM gain: 0.814%.
On hevchd set,
Overall PSNR gain: 0.465%, and SSIM gain: 0.527%.
Speed loss on HD clips was 3.5%.

Change-Id: I300ebaafff57e88914f3dedc8784cb21d316b04f