commit d7c8bc77c615a85bcc38aafeceb5230aaa162791
author hui su <huisu@google.com> Thu Nov 12 19:18:32 2015 -0800
committer hui su <huisu@google.com> Tue Dec 01 11:15:47 2015 -0800
tree 2419e91f4c1332a5fcac8253cdcfae46b40defec
parent d1486c38377a57b5c4e8bc796104e72e5a7298a5

Speed up angle search in intra mode selection

Estimate angle histogram using gradient analysis, then skip those
angles that are unlikely to be chosen.

On ext-intra experiment, turning off filter-intra modes:
for all-key-frame setting, computation overhead is reduced
by about 40%, coding gain dropped from +2.08% to +1.96% (derflr);
with kf-max-dist=150, computation overhead is reduced
by about 60%, coding gain dropped from +0.58% to +0.49% (derflr).

Change-Id: I36687410fb10561b8e1a8eebb1528cf17755bd5b