Earlier we were only testing for bit_pos == LBITS. But this is not
sufficient,
as bit_pos can jump from < LBITS to > LBITS.
This was resulting in some bit-stream truncation errors not being
caught.
Note: Not a security bug though, as br->pos wasn't incremented in such
cases
and so we weren't reading beyond the buffer.
Change-Id: Idadcdcbc6a5713f8fac3470f907fa37a63074836
kLevelsFromDelta[sharpness][delta] is an inverse look-up table
that tells the minimum filtering strength needed to trigger the
filtering of a step with amplitude 'delta'. We use this table
in various situations:
a) when computing the initial (/global) filtering
strength for each segment. We look at the quantization
step and deduce the proper filtering strength needed
to result this quantization noise (talking the -f option
into account).
b) during intra16 calculation, when a block ends up
very empty (only DC coeffs are non-zero, all ACs have
vanished). We'll rely on the in-loop filtering to
restore the smoothness (if the source was gradient-like
smooth. That's why we look at the distortion too before
triggering the filtering).
Step b) goes _in addition_ to a), potentially raising
the filtering strength if blockiness is likely.
Change-Id: Icaeca93ef21da195b079e6587a44d9edfc8e9efa
Earlier "f = f->next_" was executing for both inner and outer loop, thus
skipping validation of some frames.
Change-Id: Ice5cdb4ff5da78384aa0573addd3a5e5efa0b10c
-> helps debanding (sky, gradients, etc.)
This dithering can only be triggered when using -preset photo
or -pre 2 (as a preprocessing). Everything is unchanged otherwise.
Note that this change is likely to make the perceived PSNR/SSIM drop
since we're altering the input internally.
Change-Id: Id8d4326245d9b828141de162c94ba381b1fa5813
method 1 grouping: [parse + reconstruction] // [filtering + output]
method 2 grouping: [parse] // [reconstruction+filtering + output]
Depending on some heuristics (see VP8ThreadMethod()), we
can pick one of the other when -mt flag (or option.use_threads)
is selected.
Conservatively, we always use method #2 for now until the heuristic
is refined (so, timing should be the same the before this patch)
+ replace 'use_threads' by 'mt_method'
+ define MIN_WIDTH_FOR_THREADS constant
+ fix comment alignment
Change-Id: I11a756dea9070d6e21b1a9481d357a1e8aa0663e
Mostly visible for large images.
Reconstruction+filtering is now done in parallel to bitstream-parsing.
Change-Id: I4cc4483d803b255f4d97a2fcd9158b1c291dd900
Specifically:
- Merge OptimizeAndEncodeFrame with WebPFrameCacheAddFrame: they use the same
if-else structure.
- Move maintenance of 'prev_canvas' and 'curr_canvas' to util.
- Move ReduceTransparency() and FlattenPixels() calls to SetFrame(): This is in
preparation for the next patch: which will try try lossless encoding for
each frame, even when '-lossy' option is given.
- Make most methods static inside util.
No changes to output expected.
Change-Id: I1f65af25246665508cb20f0f6e338f9aaba9367b
broken since:
a5c297c swig/java: reduce wrapper function code duplication
this was a part of v0.3.1, but not v0.3.0.
Change-Id: I001d4bd0a7a1aa1b2d267bc63bc1d8226bff00c1
Needs more memory but allows for future parallelization.
Noticeably faster on ARM, slightly faster on x86
also: remove dec->filter_row_ unnecessary field
Change-Id: I044a808839b4e000c838a477e3e8688820436d9a
quite rarely, it gives a different output
then without the HINT, but that's often for
a smaller size (tested with default -m and -m 6)
Change-Id: I51d221ab61f8e007983325031345728e8d80b241
helps during lossless compression.
10% average saving, but that's mostly on what was previously
'difficult' cases, where the gain is ~30-50% actually.
Non-difficult cases are mostly unchanged.
Tested over ~7k random web gifs.
Change-Id: I09db4560e4ab09105d1cad28e6dbf83842eda8e9
happens surprisingly often at low quality, so we might
as well hard-code a simplified TransformWHT() directly.
Change-Id: Ib7a858ef74e8f334bd59d6512bf5bd3e455c5459
We reduce transparency by turning some transparent pixels into
corresponding RGB values from previous canvas.
This improves compression by about 23%.
Change-Id: I02d70a43a1d0906ac09a7e2dc510be3b2d38f593
