Enable adaptive pred filter type for sub8x8

This commit enables an adaptive prediction filter type selection
for sub8x8 block sizes. In speed 1, it re-uses the filter type of
collocated 8x8 block if it is tested in the rate-distortion optimization
loop, for the sub8x8 blocks. Otherwise, it runs the normal test
over all the three filter types. In speed 2, it re-uses the 8x8
block's prediction filter type, if available. Otherwise, force it
to be EIGHTTAP.

Compression and speed performance wise:
speed 1
derf -0.266%
yt   -0.138%

bus at 2000 kbps: 33766ms -> 30451ms (10% speed-up)
football at 600 kbps: 48173ms -> 43786ms (9% speed-up)

speed 2
derf -0.026%
yt   +0.134%

bus at 2000 kbps: 18973ms -> 17698ms (6% speed-up)
football at 600 kbps: 26748ms -> 25096ms (6% speed-up)

Change-Id: I77e097533b969fd3472147225fa79fc98095d342

1 files changed, 1 insertions, 0 deletions

diff --git a/vp9/encoder/vp9_onyx_int.h b/vp9/encoder/vp9_onyx_int.h
index 13ab75330..8f2ffc989 100644
--- a/vp9/encoder/vp9_onyx_int.h
+++ b/vp9/encoder/vp9_onyx_int.h
@@ -270,6 +270,7 @@ typedef struct {
   int using_small_partition_info;
   // TODO(jingning): combine the related motion search speed features
   int adaptive_motion_search;
+  int adaptive_pred_filter_type;
 
   // Implements various heuristics to skip searching modes
   // The heuristics selected are based on  flags