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This patch changes the default with the modecoefprob expt
to use mode-based forward updates with one-node pegged
modeling.

The maximum difference with fully trained tables is now
less that 0.1%.

Change-Id: I06b44322e10c6703f93f3c1d48d973b1136a0618

The patch adds the flexibility to use standard EOB based coding
on smaller block sizes and nzc based coding on larger blocksizes.
The tx-sizes that use nzc based coding and those that use EOB based
coding are controlled by a function get_nzc_used().
By default, this function uses nzc based coding for 16x16 and 32x32
transform blocks, which seem to bridge the performance gap
substantially.

All sets are now lower by 0.5% to 0.7%, as opposed to ~1.8% before.

Change-Id: I06abed3df57b52d241ea1f51b0d571c71e38fd0b

This fixes uninitialized reads in the trellis, and probably makes the
trellis do something again.

Change-Id: Ifac8dae9aa77574bde0954a71d4571c5c556df3c

This gains about 0.2% on derf, 0.1% on hd and 0.4% on stdhd. I can put
this under an experimental flag if wanted, just trying to get my patch
queue in shape.

Change-Id: Ibe1a30fe0e0b07bec4802e0f3ff0ba22e505f576

These are mostly just for experimental purposes. I saw small gains (in
the 0.1% range) when playing with this on derf.

Change-Id: Ib21eed477bbb46bddcd73b21c5c708a5b46abedc

Now that the first AC coefficient in both directions use the same DC
as their context, there no longer is a purpose in letting both have
their own band. Merging these two bands allows us to split bands for
some of the very high-frequency AC bands.

In addition, I'm redoing the banding for the 1D-ADST col/row scans. I
don't think the old banding made any sense at all (it merged the last
coefficient of the first row/col in the same band as the first two of
the second row/col), which was clearly an oversight from the band being
applied in scan-order (rather than in their actual position). Now,
coefficients at the same position will be in the same band, regardless
what scan order is used. I think this makes most sense for the purpose
of banding, which is basically "predict energy for this coefficient
depending on the energy of context coefficients" (i.e. pt).

After full re-training, together with previous patch, derf gains about
1.2-1.3%, and hd/stdhd gain about 0.9-1.0%.

Change-Id: I7a0cc12ba724e88b278034113cb4adaaebf87e0c

Pearson correlation for above or left is significantly higher than for
previous-in-scan-order (absolute values depend on position in scan, but
in general, we gain about 0.1-0.2 by using either above or left; using
both basically just makes this even better). For eob branch skipping,
we continue to use the previous token in scan order.

This helps about 0.9% on derf after re-training on a limited data set.
Full re-training and results on larger-resolution clips are pending.

Note that this commit breaks trellis, so we can probably get further
gains out of it by fixing trellis at some later point.

Change-Id: Iead68e296fc3a105cca746b5e3da9555d6010cfe

Replaces the default tables for single coefficient magnitudes with
those obtained from an appropriate distribution. The EOB node
is left unchanged. The model is represeted as a 256-size codebook
where the index corresponds to the probability of the Zero or the
One node. Two variations are implemented corresponding to whether
the Zero node or the One-node is used as the peg. The main advantage
is that the default prob tables will become considerably smaller and
manageable. Besides there is substantially less risk of over-fitting
for a training set.

Various distributions are tried and the one that gives the best
results is the family of Generalized Gaussian distributions with
shape parameter 0.75. The results are within about 0.2% of fully
trained tables for the Zero peg variant, and within 0.1% of the
One peg variant.

The forward updates are optionally (controlled by a macro)
model-based, i.e. restricted to only convey probabilities from the
codebook. Backward updates can also be optionally (controlled by
another macro) model-based, but is turned off by default. Currently
model-based forward updates work about the same as unconstrained
updates, but there is a drop in performance with backward-updates
being model based.

The model based approach also allows the probabilities for the key
frames to be adjusted from the defaults based on the base_qindex of
the frame. Currently the adjustment function is a placeholder that
adjusts the prob of EOB and Zero node from the nominal one at higher
quality (lower qindex) or lower quality (higher qindex) ends of the
range. The rest of the probabilities are then derived based on the
model from the adjusted prob of zero.

Change-Id: Iae050f3cbcc6d8b3f204e8dc395ae47b3b2192c9

The automatic merge result was incomplete.

Change-Id: I8976318bfc346d867660a013a302c80edb25fc29

The previous implementation visited each node in the tree multiple times
because it used each symbol's encoding to revisit the branches taken and
increment its count. Instead, we can traverse the tree depth first and
calculate the probabilities and branch counts as we walk back up. The
complexity goes from somewhere between O(nlogn) and O(n^2) (depending on
how balanced the tree is) to O(n).

Only tested one clip (256kbps, CIF), saw 13% decoding perf improvement.

Note that this optimization should port trivially to VP8 as well. In VP8,
the decoder doesn't use this function, but it does routinely show up
on the profile for realtime encoding.

Change-Id: I4f2848e4f41dc9a7694f73f3e75034bce08d1b12

Adds probability updates for extra bits for the nzcs, code for
getting nzc stats, plus some minor cleanups and fixes.

Change-Id: If2814e7f04fb52f5025ad9f400f3e6c50a00b543

This patch revamps the entropy coding of coefficients to code first
a non-zero count per coded block and correspondingly remove the EOB
token from the token set.

STATUS:
Main encode/decode code achieving encode/decode sync - done.
Forward and backward probability updates to the nzcs - done.
Rd costing updates for nzcs - done.
Note: The dynamic progrmaming apporach used in trellis quantization
is not exactly compatible with nzcs. A suboptimal approach has been
used instead where branch costs are updated to account for changes
in the nzcs.

TODO:
Training the default probs/counts for nzcs

Change-Id: I951bc1e22f47885077a7453a09b0493daa77883d

Split macroblock and superblock tokenization and detokenization
functions and coefficient-related data structs so that the bitstream
layout and related code of superblock coefficients looks less like it's
a hack to fit macroblocks in superblocks.

In addition, unify chroma transform size selection from luma transform
size (i.e. always use the same size, as long as it fits the predictor);
in practice, this means 32x32 and 64x64 superblocks using the 16x16 luma
transform will now use the 16x16 (instead of the 8x8) chroma transform,
and 64x64 superblocks using the 32x32 luma transform will now use the
32x32 (instead of the 16x16) chroma transform.

Lastly, add a trellis optimize function for 32x32 transform blocks.

HD gains about 0.3%, STDHD about 0.15% and derf about 0.1%. There's
a few negative points here and there that I might want to analyze
a little closer.

Change-Id: Ibad7c3ddfe1acfc52771dfc27c03e9783e054430

Change-Id: I5416455f8f129ca0f450d00e48358d2012605072

This patch alters the balance of context between the
coefficient bands (reflecting the position of coefficients
within a transform blocks) and the energy of the previous
token (or tokens) within a block.

In this case the number of coefficient bands is reduced
but more previous token energy bands are supported.

Some initial rebalancing of the default tables has been
by running multiple derf clips at multiple data rates using
the ENTOPY_STATS macro. Further balancing needs to be
done using larger image formatsd especially in regard to
the bigger transform sizes which are not as well represented
in encodings of smaller image formats.

Change-Id: If9736e95c391e711b04aef6393d26f60f36e1f8a

Change-Id: I7a5314daca993d46b8666ba1ec2ff3766c1e5042

allowing the compiler to inline.

Change-Id: I66e5caf5e7fefa68a223ff0603aa3f9e11e35dbb

This patch abstracts the selection of the coefficient band
context into a function as a precursor to further experiments
with the coefficient context.

It also removes the large per TX size coefficient band structures
and uses a single matrix for all block sizes within the test function.

This may have an impact on quality (results to follow) but is only an
intermediate step in the process of redefining the context. Also the
quality impact will be larger initially because the default tables will
be out of step with the new banding.

In particular the 4x4 will in this case only use 7 bands. If needed we
can add back block size dependency localized within the function, but
this can follow on after the other changes to the definition of the
context.

Change-Id: Id7009c2f4f9bb1d02b861af85fd8223d4285bde5

This is an initial step to facilitate experimentation
with changes to the prior token context used to code
coefficients to take better account of the energy of
preceding tokens.

This patch merely abstracts the selection of context into
two functions and does not alter the output.

Change-Id: I117fff0b49c61da83aed641e36620442f86def86

Removal of the  NEWCOEFCONTEXT experiment to
reduce code clutter and make it easier to experiment with
some other changes to the coefficient coding context.

Change-Id: Icd17b421384c354df6117cc714747647c5eb7e98

Removal of experiment to simplify code base for other
changes.

Change-Id: If0a33952504558511926ad212bc311fc2bffb19a

Fixes some scaling issues. Adds an option to only compute the
dct on the low-low subband for 32x32 and 64x64 blocks using
only a single 16x16 dct after 1 and 2 wavelet decomposition
levels respectively. Also adds an option to use a 8x8 dct
as building block.

Currenlty with the 2/6 filter and with a single 16x16 dct on
the low low band, the reuslts compared to full 32x32 dct is
as follows:
derf: -0.15%
yt: -0.29%
std-hd: -0.18%
hd: -0.6%
These are my current recommended settings, since the 2/6 filter
is very simple.

Results with 8x8 dct are about 0.3% worse.

Change-Id: I00100cdc96e32deced591985785ef0d06f325e44

Change-Id: I615651e4c7b09e576a341ad425cf80c393637833

This is to add to the 64x64 transform experiment as an alternative to
a 64x64 DCT.
Two levels of wavelet decomposition is used on a 64x64 block, followed
by 16x16 DCT on the four lowest subbands. The highest three subbands
are left untransformed after the first level DWT.

Change-Id: I3d48d5800468d655191933894df6b46e15adca56

Change-Id: I0df99742029834a85c4933652b0587cf5b6b2587

Adds an experiment to derive the previous context of a coefficient
not just from the previous coefficient in the scan order but from a
combination of several neighboring coefficients previously encountered
in scan order.  A precomputed table of neighbors for each location
for each scan type and block size is used. Currently 5 neighbors are
used.

Results are about 0.2% positive using a strategy where the max coef
magnitude from the 5 neigbors is used to derive the context.

Change-Id: Ie708b54d8e1898af742846ce2d1e2b0d89fd4ad5

For coefficients, use int16_t (instead of short); for pixel values in
16-bit intermediates, use uint16_t (instead of unsigned short); for all
others, use uint8_t (instead of unsigned char).

Change-Id: I3619cd9abf106c3742eccc2e2f5e89a62774f7da

This matches the names of tables for all other transform sizes.

Change-Id: Ia7681b7f8d34c97c27b0eb0e34d490cd0f8d02c6

Change-Id: I9548891d7b8ff672a31579bcdce74e4cea529883

Modifies the scanning pattern and uses a floating point 16x16
dct implementation for now to handle scaling better.
Also experiments are in progress with 2/6 and 9/7 wavelets.

Results have improved to within ~0.25% of 32x32 dct for std-hd
and about 0.03% for derf. This difference can probably be bridged by
re-optimizing the entropy stats for these transforms. Currently
the stats used are common between 32x32 dct and dwt/dct.

Experiments are in progress with various scan pattern - wavelet
combinations.

Ideally the subbands should be tokenized separately, and an
experiment will be condcuted next on that.

Change-Id: Ia9cbfc2d63cb7a47e562b2cd9341caf962bcc110

Add a function clip_pixel() to clip a pixel value to the [0,255] range
of allowed values, and use this where-ever appropriate (e.g. prediction,
reconstruction). Likewise, consistently use the recently added function
clip_prob(), which calculates a binary probability in the [1,255] range.
If possible, try to use get_prob() or its sister get_binary_prob() to
calculate binary probabilities, for consistency.

Since in some places, this means that binary probability calculations
are changed (we use {255,256}*count0/(total) in a range of places,
and all of these are now changed to use 256*count0+(total>>1)/total),
this changes the encoding result, so this patch warrants some extensive
testing.

Change-Id: Ibeeff8d886496839b8e0c0ace9ccc552351f7628

Use these, instead of the 4/5-dimensional arrays, to hold statistics,
counts, accumulations and probabilities for coefficient tokens. This
commit also re-allows ENTROPY_STATS to compile.

Change-Id: If441ffac936f52a3af91d8f2922ea8a0ceabdaa5

This adds Debargha's DCT/DWT hybrid and a regular 32x32 DCT, and adds
code all over the place to wrap that in the bitstream/encoder/decoder/RD.

Some implementation notes (these probably need careful review):
- token range is extended by 1 bit, since the value range out of this
  transform is [-16384,16383].
- the coefficients coming out of the FDCT are manually scaled back by
  1 bit, or else they won't fit in int16_t (they are 17 bits). Because
  of this, the RD error scoring does not right-shift the MSE score by
  two (unlike for 4x4/8x8/16x16).
- to compensate for this loss in precision, the quantizer is halved
  also. This is currently a little hacky.
- FDCT and IDCT is double-only right now. Needs a fixed-point impl.
- There are no default probabilities for the 32x32 transform yet; I'm
  simply using the 16x16 luma ones. A future commit will add newly
  generated probabilities for all transforms.
- No ADST version. I don't think we'll add one for this level; if an
  ADST is desired, transform-size selection can scale back to 16x16
  or lower, and use an ADST at that level.

Additional notes specific to Debargha's DWT/DCT hybrid:
- coefficient scale is different for the top/left 16x16 (DCT-over-DWT)
  block than for the rest (DWT pixel differences) of the block. Therefore,
  RD error scoring isn't easily scalable between coefficient and pixel
  domain. Thus, unfortunately, we need to compute the RD distortion in
  the pixel domain until we figure out how to scale these appropriately.

Change-Id: I00386f20f35d7fabb19aba94c8162f8aee64ef2b

Change-Id: Ia1cce221f8511561b9cbd8edb7726fbc286ff243

Support for gyp which doesn't support multiple objects in the same
static library having the same basename.

Change-Id: Ib947eefbaf68f8b177a796d23f875ccdfa6bc9dc

Change-Id: Ic084c475844b24092a433ab88138cf58af3abbe4

For non-static functions, change the prefix to vp9_. For static functions,
remove the prefix. Also fix some comments, remove unused code or unused
function prototypes.

Change-Id: I1f8be05362f66060fe421c3d4c9a906fdf835de5

This change encompasses VP8_PTR, VP8_COMP, VP8D_COMP, VP8_COMMON,
VP8Decompressor and VP8Common.

Change-Id: I514ef4ad4e682370f36d656af1c09ee20da216ad

For local symbols, make them static instead.

Change-Id: I13d60947a46f711bc8991e16100cea2a13e3a22e

Change-Id: Ic5a5f60e1ff9d9ccae4174160d36529466eeb509