This option exists in VP8, and it was rewritten in VP9 to support
skipping on different partition levels. After prediction is done,
we can check if the residuals in the partition block will be all
quantized to 0. If this is true, the skip flag is set, and only
prediction data are needed in reconstruction. Based on DCT's energy
conservation property, the skipping check can be estimated in
spatial domain.

The prediction error is calculated and compared to a threshold.
The threshold is determined by the dequant values, and also
adjusted by partition sizes. To be precise, the DC and AC parts
for Y, U, and V planes are checked to decide skipping or not.

Test showed that
1. derf set:
when static-thresh = 1, psnr loss is 0.666%;
when static-thresh = 500, psnr loss is 1.162%;
2. stdhd set:
when static-thresh = 1, psnr loss is 1.249%;
when static-thresh = 500, psnr loss is 1.668%;

For different clips, encoding speedup range is between several
percentage and 20+% when static-thresh <= 500. For example,
clip            bitrate  static-thresh psnr    time
akiyo(cif)       500        0          48.923  5.635s(50f)
akiyo            500        500        48.863  4.402s(50f)

parkjoy(1080p)   4000       0          30.380  77.54s(30f)
parkjoy          4000       500        30.384  69.59s(30f)

sunflower(1080p) 4000       0          44.461  85.2s(30f)
sunflower        4000       500        44.418  78.1s(30f)

Higher static-thresh values give larger speedup with larger
quality loss.

Change-Id: I857031ceb466ff314ab580ac5ec5d18542203c53

Functions: vp9_get_pred_context_switchable_interp,
           vp9_get_pred_context_intra_inter,
           vp9_get_pred_context_single_ref_p1,
           vp9_get_pred_context_single_ref_p2.

Change-Id: I3d6fb8aee23c9062270768e1e6da416dd9bb8f96

Change-Id: I4032dd0442043543954dcb3724df974b7cc7e515

Change-Id: I9a4df095732d561807de01a41dcb1a1960726a3c

We would skip the rectangular blocks for sub8x8 partitions because
we would conclude that PARTITION_NONE was better than PARTITION_SPLIT,
however, that conclusion was made before we actually really tested
PARTITION_SPLIT.

Change-Id: I8fa91e59894badc1d8cee3ba8a49e40ae4c4a489

Change-Id: Ic32acf3e2939c6d12d9c2bf192a5f5da59705fda

Change-Id: Ifd48f796fa70fe1dc9b87a6f2bdc715bc0ea5ad3

Change-Id: Ide58a74d31ff948319445a6337d2c05e98720e34

Change-Id: I96b8058f6dfecf8aa3e152cdcbfd7e10071fbbc9

This prevents a duplicate memcpy of a 128-byte struct every time
set_scale_factors() is called (which is a lot), thus leading to a
decrease from 3.7 MB to 1.85 MB of struct copying per 64x64 block
RD/partition loop.

Overall, this decreases encoding time of the first 50 frames of bus
@ 1500kbps (speed 0) from 1min5.9 to 1min4.9, i.e. about a 1.5%
overall speedup. We can likely get more gains by removing the copy
of the other struct (and replacing it with an indexing) as well.

Change-Id: I3dceb7e79f71e6fe911b11cc994cf89a869dde7a

This means we only do UV intra mode selection if we find any intra
mode to actually be useful at all; in addition, we only do UV intra
mode selection for the transform sizes that were selected, rather
than all sizes available in this partition.

First 50 frames of bus @ 1500kbps (speed 0) gains about 5% with this
change.

Change-Id: I7b461eb8b803247f57896c5a9505f745b55502b3

The break statement only breaks out of the nested loop, not the
top-level loop, so it doesn't always work as intended. Changing it
to a return statement does what's intended.

Change-Id: I585419823b39a04ec8826b1c8a216099b1728ba7

The same information already exists in union b_mode_info.

Change-Id: Iac5086b99a3c3cc270380138062bb693e58f9e6d

This could happen during golden overlay frame coding from a previous
alt-ref frame if the special overlay code was triggered.

Change-Id: I3056d0c547cd26903b260ef93c94026e96bd9868

Change-Id: Id5480a4fd56c184ad046c2192b30d190debb3de0

Change-Id: I1558fd969d9ad112bf6480bdd16ef87edd396ab5

Allow output of gas syntax assembly directly from obj_int_extract

Change-Id: I33a747e87ef1c590a8766dea17f8cb2497e54591

If count was greater than 1 the src pointer would be off on
the second loop.

Change-Id: I8e09037e68dc4ae92076a8067f7b6dacbbef8263

Change-Id: Id4f454831f3f11099f39c30246adeaa52857d08d

Make the use of mv_check_bounds consistent for mvs of both ref_frame[0]
and ref_frame[1].

Change-Id: I1ca24865cc7232ca9cbe5db566c53abad1592211

Change-Id: Ie692ed6e5fa1d2122e3a03573914d0fcce842f9e