tree 3501ac45c68dfb50c98702b2718bce8bec9a40f7
parent 106fa482329cffa9b85b2dc81f9957a56386ec2a
author Yunqing Wang <yunqingwang@google.com> 1533583644 -0700
committer Yunqing Wang <yunqingwang@google.com> 1533837948 +0000

Use the short filter in subpel motion search

While using accurate subpel search(sf->use_accurate_subpel_search=1), we
use 8-tap interplation filter, which brings high computational complexity.
This patch replaced it with 4-tap filter, and enabled it as a speed 1
feature. The borg test result showed
negligable coding performance change.
           avg_psnr  ovr_psnr   ssim
hdres set:  -0.010   -0.090    -0.001
midres set: -0.009   -0.015     0.015
lowres set:  0.021    0.046     0.005

The SIMD optimization of 4-tap filters will be added later that will give
encoder speedups. Also, the filter can be redesigned for this purpose.

STATS_CHANGED

Change-Id: I296c340a3c4977f43a623a9e7c826f6ea2bf18b8