In summary, this commit encompasses a series of changes in attempt to
improve the 8x8 transform based coding to help overall compression
quality, please refer to the detailed commit history below for what
are the rationale underly the series of changes:

a. A frame level flag to indicate if 8x8 transform is used at all.
b. 8x8 transform is not used for key frames and small image size.
c. On inter coded frame, macroblocks using modes B_PRED, SPLIT_MV
and I8X8_PRED are forced to using 4x4 transform based coding, the
rest uses 8x8 transform based coding.
d. Encoder and decoder has the same assumption on the relationship
between prediction modes and transform size, therefore no signaling
is encoded in bitstream.
e. Mode decision process now calculate the rate and distortion scores
using their respective transforms.

Overall test results:
1. HD set
http://www.corp.google.com/~yaowu/no_crawl/t8x8/HD_t8x8_20120206.html
(avg psnr: 3.09% glb psnr: 3.22%, ssim: 3.90%)
2. Cif set:
http://www.corp.google.com/~yaowu/no_crawl/t8x8/cif_t8x8_20120206.html
(avg psnr: -0.03%, glb psnr: -0.02%, ssim: -0.04%)
It should be noted here, as 8x8 transform coding itself is disabled
for cif size clips, the 0.03% loss is purely from the 1 bit/frame
flag overhead on if 8x8 transform is used or not for the frame.

---patch history for future reference---
Patch 1:
this commit tries to select transform size based on macroblock
prediction mode. If the size of a prediction mode is 16x16, then
the macroblock is forced to use 8x8 transform. If the prediction
mode is B_PRED, SPLITMV or I8X8_PRED, then the macroblock is forced
to use 4x4 transform. Tests on the following HD clips showed mixed
results: (all hd clips only used first 100 frames in the test)

http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdmodebased8x8.html
http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdmodebased8x8_log.html

while the results are mixed and overall negative, it is interesting to
see 8x8 helped a few of the clips.

Patch 2:
this patch tries to hard-wire selection of transform size based on
prediction modes without using segmentation to signal the transform size.
encoder and decoder both takes the same assumption that all macroblocks
use 8x8 transform except when prediciton mode is B_PRED, I8X8_PRED or
SPLITMV. Test results are as follows:

http://www.corp.google.com/~yaowu/no_crawl/t8x8/cifmodebase8x8_0125.html
http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdmodebased8x8_0125log.html

Interestingly, by removing the overhead or coding the segmentation, the
results on this limited HD set have turn positive on average.

Patch 3:
this patch disabled the usage of 8x8 transform on key frames, and kept the
logic from patch 2 for inter frames only. test results on HD set turned
decidedly positive with 8x8 transform enabled on inter frame with 16x16
prediction modes: (avg psnr: .81% glb psnr: .82 ssim: .55%)

http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdintermode8x8_0125.html
results on cif set still negative overall

Patch 4:
continued from last patch, but now in mode decision process, the rate and
distortion estimates are computed based on 8x8 transform results for MBs
with modes associated with 8x8 transform. This patch also fixed a problem
related to segment based eob coding when 8x8 transform is used. The patch
significantly improved the results on HD clips:

http://www.corp.google.com/~yaowu/no_crawl/t8x8/hd8x8RDintermode.html
(avg psnr: 2.70% glb psnr: 2.76% ssim: 3.34%)
results on cif also improved, though they are still negative compared to
baseline that uses 4x4 transform only:
http://www.corp.google.com/~yaowu/no_crawl/t8x8/cif8x8RDintermode.html
(avg psnr: -.78% glb psnr: -.86% ssim: -.19%)

Patch 5:
This patch does 3 things:
a. a bunch of decoder bug fixes, encodings and decodings were verified
to have matched recon buffer on a number of encodes on cif size mobile and
hd version of _pedestrian.
b. the patch further improved the rate distortion calculation of MBS that
use 8x8 transform. This provided some further gain on compression.
c. the patch also got the experimental work SEG_LVL_EOB to work with 8x8
transformed macroblock, test results indicates it improves the cif set
but hurt the HD set slightly.

Tests results on HD clips:
http://www.corp.google.com/~yaowu/no_crawl/t8x8/HD_t8x8_20120201.html
(avg psnr: 3.19% glb psnr: 3.30% ssim: 3.93%)

Test results on cif clips:
http://www.corp.google.com/~yaowu/no_crawl/t8x8/cif_t8x8_20120201.html
(avg psnr: -.47% glb psnr: -.51% ssim: +.28%)

Patch 6:
Added a frame level flag to indicate if 8x8 transform is allowed at all.
temporarily the decision is based on frame size, can be optimized later
one. This get the cif results to basically unchanged, with one bit per
frame overhead on both cif and hd clips.

Patch 8:
Rebase and Merge to head by PGW.
Fixed some suspect 4s that look like hey should be 64s in regard
to segmented EOB. Perhaps #defines would be bette.
Bulit and tested without T8x8 enabled and produces unchanged
output.

Patch 9:
Corrected misalligned code/decode of "txfm_mode" bit.
Limited testing for correct encode and decode with
T8x8 configured on derf clips.

Change-Id: I156e1405d25f81579d579dff8ab9af53944ec49c

Change-Id: Idb328dd29ebcd360e39886abe48694f90f2e1140

Change-Id: Ieaaa07c50eae41118596197f6a4d848135946e41

This commit only involves the removal of placeholder comments
//#if CONFIG_SEGFEATURES.

Change-Id: I94b350daaf998ee0cfdde5aa25b1d3b0522ab816

Merge the extended Q experiment as indicated by the

Change-Id: I02d9e654fff9998cc7e9e2f1f5cd838dad8fb431

Merged in most of the current common prediction changes
that were under the #if CONFIG_COMPRED option.

Change-Id: If4e6f61dbe7b86dd449f6effbe93b5eb7e893885

Further changes to make experiments with the context
used for coding the dual pred flag easier.

Current best performing method tested on derf is a two
element context based on reference frame. I also tried
various combinations of mode and reference frame as
shown in commented out case using up to 6 contexts.

Derf +0.26 overall psnr +0.15% ssim vs original method.

Change-Id: I64c21ddec0abbb27feaaeaa1da2e9f164ebaca03

Further use of common prediction functions and experiments
with alternate contexts based on mode and reference frame.

For the Derf set using reference frame as basis of context
gives +0.18% Overall Psnr and +0.08 SSIM

Change-Id: Ie7eb76f329f74c9c698614f01ece31de0b6bfc9e

We should only change the dual prediction mode if we actually entered
the recode branch. Else, it may potentially undo beneficial changes
to the dual prediction mode in the first encode iteration.

Change-Id: I79fc53e5fd0bb551092ed422c797619f1566f002

Change-Id: Icf7a6749ca2f8ad6a032f86c34540d1c5880cf68

Some conditions were conditional under a threshold, whereas they should
always execute. Also, some conditions were testing an array instead of
the values within it.

Change-Id: Ia6892945cfbbe07322e6af6be42cd864bf9479c1

The existing code updated the reference frame probabilities before
the test to evaluate the impact of using updated probabilities
in vp8_estimate_entropy_savings().

The estimate of cost and savings is still basic and does not reflect
the new prediction code but this would require per MB costings
and the benefit is probably marginal, as this is really just used for
rate estimation in the loop.

Change-Id: Id6ba88ae6e11c273b3159deff70980363ccd8ea1

This commit merges the NEWNEAR experiment such that it
is effectively always on.

The fact that there were changes in the threading code again
highlights the need to strip out such features during the
bitstream development phase as trying to maintain this code
(especially as it is not being tested) slows the development cycle.

Change-Id: I8b34950a1333231ced9928aa11cd6d6459984b65

Initial modifications to make limited use of common prediction
functions.

The only functional change thus far is that updates to the probabilities are
no longer "damped". This was a testing convenience but in fact seems to
help by a little over 0.1% over the derf set.

Change-Id: I8b82907d9d6b6a4a075728b60b31ce93392a5f2e

Moved the prob_dualpred[] sturcture to common.
Created common prediction entry for Dual flag.

Change-Id: I9ac3d128bae6114f09e5c18216d4b95cf36453d5

Trial of a modified prediction function that ranks each possible
reference frame based on a combination of local usage and
frame level probability. The code is a bit cleaner and simpler.

In direct comparison with old unpredicted method with segment level
coding turned off for mode,ref & EOB the prediction gives a gain on derf
of around 0.4%. There is some further gain from bug fixes over earlier code.

With segment coding on the prediction method is slightly -ve on some very
easy clips (at low rates) due to slightly higher overheads, but better on harder
clips. Overall neutral on derf in direct comparison on latest code base, but
compared to earlier code without bug fixes about +0.7% overall psnr
+0.3% SSIM.

Change-Id: I5b8474658b208134d352d24f6517f25795490789

Extended prediction and coding of reference frame where
a subset of options are flagged as available at the segment level.

Updated copyright notices.

Switch to SAD in mbgraph code as SATD problematic for the
foreground and background separation as it can ignore large DC shifts.

Change-Id: I661dbbb2f94f3ec0f96bb928c1655e5e415a7de1

As a precursor to encoding 32x32 blocks this cl adds the
ability to encode the frame superblock (=32x32 block) at
a time. Within a SB the 4 indiviual MBs are encoded in
raster-order (NW,NE,SW,SE).

This functionality is added as an experiment which can be
enabled by ispecifying --enable-superblocks in the
command line specified to configure (CONFIG_SUPERBLOCKS
macro in the code).

To make this work I had to disable the two intra
prediction modes that use data from the top-right of the
MB.

On the tests that I have run the results produce
almost exactly the same PSNRs & SSIMs with a very
slightly higher average data rate (and slightly higher
data rate than just disabling the two intra modes in
the original code).

NOTE: This will also break the multi-threaded code.

This replaces the abandoned change:
Iebebe0d1a50ce8c15c79862c537b765a2f67e162

Change-Id: I1bc1a00f236abc1a373c7210d756e25f970fcad8

Commented out changes from earlier checking:

"Change Iab7f1eff: vpnext use segref segmentation filter"

Which in its current state breaks the decoder.

Change-Id: I9185098aeda8ce65310f338c4c9375f4a39005d3

The bug was introduced by the commit that added I8X8 intra prediction
mode for inter frames, the decoder was not update to accept the additional
probability update from encoder. This causes the decoder typicall to crash
when encoder sends intra mode probability update.

Change-Id: Ib7dc42dc77a51178aa9ece41e081829818a25016

Please see the following for details:
https://gerrit.chromium.org/gerrit/#change,10925

Change-Id: Ie692261c255c58d7762df22eeca566a7d13adcba

Please see the following public commit for details:
https://gerrit.chromium.org/gerrit/#change,7608

Change-Id: I589eed0b6078e2c5c9c74e942886e503bd02b273

This line of code incorrectly set maxq = maxq rather than
capping minqtarget.

Change-Id: Ifbc86df8b0ff2779e7b2a5f7349724d04a18bd62

This check in uses the common prediction interface functions
to code reference frame.

Some updates made regarding the impact of the new code in rd loop
but there remain TODOs in this regard.

Change-Id: I9da3ed5dfdaa489e0903ab33258b0767a585567f

This does not change any functionality just modifies the code to
use the common prediction module interface for coding
the segment data.

Change-Id: Ifd43e9153573365619774a4f5572215e44fb5aa3

This function adds the common prediction modules,  some data structures
and a config option but does not use them.

It also corrects a bug in clearing down  the MODE_INFO border and introduces
a new element that indicates if an entry corresponds to an "in image" macro block
or is part of the border.

Change-Id: Ib69eec0876173ebe9d1de9df9537d0b2447702e0

Encoder side changes

Change-Id: I8921800e4fccec5e5a9e4755b80cbd472623107b

In this commit only the decoder side was updated.

Change-Id: Ia9bd58da07d1a943f028e330f0489344e62b0d02

Moved some segmentation data structures into VP8_COMMON

Change-Id: I59c6e2edf7a0176e35319936eea450027aeb3b39

Fixes a rounding issue with the 8-tap filters, which allows us to
use sharper filters that before with a little better performance.
Results on derf (0verall gain 0.76):
http://www.corp.google.com/~debargha/vp8_results/enhinterp.html
Results on a 720P set (Overall gain 0.61):
http://www.corp.google.com/~debargha/vp8_results/enhinterp_hd.html

Change-Id: I4cd7bdf3583db974dc5589fa64857bc31ac861fa

Goes through set of ref frames used by each macroblock and
sets seg_lvl_ref_frame flags accordingly..

http://www.corp.google.com/~jimbankoski/no_crawl/segref.html

Change-Id: Iab7f1effd75a839b34eb310d7168692c8f105411

Picks a per segment loopfilter.  Adapts the algorithm to search for
a loopfilter value for each separate segment.  Further todo fix the
bias

Improvements .06 % ov psnr, .11% ssim
http://www.corp.google.com/~jimbankoski/no_crawl/segmentedpicklpf.html

Change-Id: Ic6a571c16fcd6ec0139f4de1f8061f87c6515a10

changed the token cost for 8x8 transformed macroblock used in trellisquant
from those derived from 4x4 transform coefficient distribution to those
derived from 8x8 transform coefficient distribution. Test results show
this fix help 8x8 transform based compression consistently on cif and hd
sets:

http://www.corp.google.com/~yaowu/no_crawl/t8x8/cif_cost8x8only.html
(avg psnr:.14% glb psnr: .17% ssim: .20%)
http://www.corp.google.com/~yaowu/no_crawl/t8x8/hd_cost8x8only.html
(avg psnr:.17% glb psnr: .18% ssim: .58%)

Note: To test the effect of this change, 8x8 transform was forced to be used
only on 16x16 predicted macroblocks on inter frames, the effect would be
bigger had all macroblocks been forcd to use 8x8 transform.

Change-Id: If9b7868b75357c66541f511e5ee78e4d2d4929a4

using an 8-tap filter.

The results with 3 different 8-tap filters on the derf set are in:
http://www.corp.google.com/~debargha/vp8_results/enhinterp.html
The one that gives the most gain achieves an overall gain of about
0.6%. The results for a set of 12 hd (720p) videos are in:
http://www.corp.google.com/~debargha/vp8_results/enhinterp_hd.html
with max gain of 0.55% with the same filter. The best filter apparently
achieves the best trade-off between pass band ripple and stop band
attenuation.

Change-Id: I919e28ae245c0493147fa0864f8c9d048a9dd530

This introduces base functions for introducing implicit segmentation.
The code that actually stores the results to the segment map isn't
here yet.   This just prints out the segmentation map results
if you call it.

Uses connected component labeling technique on mbmi info so that only
if 2 mbs are horizontally or vertically touching do they get the same
segment.

vp8next - plumbing for rotation

code to produce taps for rotation ( tapify. py ),  code
for predicting using rotation ( predict_rotated.c ) ,  code
for finding the best rotation find_rotation.c.

didn't checkin code that uses this in the codec.   still work
in progress.

Fixed copyright notice

Change-Id: I450c13cfa41ab2fcb699f3897760370b4935fdf8

This commit added a set of loop filter functions for macroblocks
using 8x8 transform. First we turned off the regular loop filtering
on 4x4 block boundaries that do not exist in macroblocks using 8x8
transform. Second, we change to use the same loop filter(mask and
7 tap filter) that used for macroblock edge filtering.

Change-Id: I3a00460b7674ced116917d86812ffc32578c1d3a

This fixed a conflict introduced by the change of adding 8x8 intra
prediction modes. The 8x8 intra prediction mode code assumed the
use of 4x4 transform, and causes encoder crashes when the codec is
configured with --enable-t8x8.

Change-Id: I00cc94df63e9725377ffba9eb51be6b77fe3fcf9