Commit Graph

6 Commits

Author SHA1 Message Date
Deb Mukherjee
fd18d5dffe Modeling default coef probs with distribution
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
2013-03-25 23:43:38 -07:00
Deb Mukherjee
a28139c849 Continued experiment with nonzero count
Adds probability updates for extra bits for the nzcs, code for
getting nzc stats, plus some minor cleanups and fixes.

Change-Id: If2814e7f04fb52f5025ad9f400f3e6c50a00b543
2013-03-08 16:37:08 -08:00
Deb Mukherjee
eb6ef2417f Coding con-zero count rather than EOB for coeffs
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
2013-03-07 07:20:30 -08:00
Dmitry Kovalev
7f99c3c59a Code cleanup.
Removing redundant 'extern' keywords, fixing formatting and #include order,
code simplification.

Change-Id: I0e5fdc8009010f3f885f13b5d76859b9da511758
2013-03-05 14:12:16 -08:00
Ronald S. Bultje
4cca47b538 Use standard integer types for pixel values and coefficients.
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
2012-12-18 15:31:19 -08:00
John Koleszar
fcccbcbb39 Add vp9_ prefix to all vp9 files
Support for gyp which doesn't support multiple objects in the same
static library having the same basename.

Change-Id: Ib947eefbaf68f8b177a796d23f875ccdfa6bc9dc
2012-11-27 14:12:30 -08:00