tree 60b75fc35c08eb69e5780c1ecd6bf9125fc177c9
parent 5b5b19fed541b8c47046d49b9f3732534d2ce3cd
author Cheng Chen <chengchen@google.com> 1574125503 -0800
committer Cheng Chen <chengchen@google.com> 1574354742 +0000

Use unfiltered frame to determine screen content type

BUG=aomedia:2516

Recent encoding results provided by Yunqing@ show that by turning off
"--enable_keyframe_filtering", encoding speed has a big improvement
on several clips.

Filename                                                    | Speedup
---------------------------------------------------------------------
Netflix_PierSeaside_1920x1080_60fps_8bit_420_60f.y4m        |  38.7%
Netflix_RollerCoaster_1280x720_60fps_8bit_420_60f.y4m       |  54.4%
Netflix_TunnelFlag_1920x1080_60fps_8bit_420_60f.y4m         |  48.3%
aspen_1080p_60f.y4m                                         |  48.9%

The reason is that the screen content type is determined by the
filtered keyframe. In the above clips, they are all falsely determined
as screen content type. Therefore more coding tools are evaluated,
which causes encoding speed slowdown.

This change uses the unfiltered source frame to determine screen
content type. Therefore mitigate the slowdown. Coding performance
is not expected to change much.

STATS_CHANGED

Change-Id: Iadee2bcb73959d9e7093335d395e9e1424c8bcf0