Sometimes, the reference SSIM is significantly higher than the
SSIM level expected for the test. This is the case when the source format
has a much lower bit depth than the destination format. In this case, the fact
that legacy swscale does not accurately preserve the source dither pattern
gives it an unfair advantage in a direct comparison, leading to false
positives.
For example, conversion like rgb4 -> rgb565 should be lossless, but swscale
low passes / downscales the input chroma, throwing away massive amounts of
detail. This gives it a higher SSIM score since the lowpassed result removes
some of the dither noise that was present in the source.
We can calculate with some confidence the theoretical expected SSIM
from an "ideal" conversion, by computing the reference SSIM level
for an image dithered with uniformly distributed quatization noise.
This gives us an additional safety net to check for regressions even in
the absence of a reference to compare against.
And bias it towards Y. This is much better at ignoring errors due to differing
dither patterns, and rewards algorithms that lower luma noise at the cost of
higher chroma noise.
The (0.8, 0.1, 0.1) weights for YCbCr are taken from the paper:
"Understanding SSIM" by Jim Nilsson and Tomas Akenine-Möller
(https://arxiv.org/abs/2006.13846)
Instead of the lossy yuva420p. This does change the results compared to the
status quo, but is more reflective of the actual strength of a conversion,
since it will faithfully measure the round-trip error from subsampling and
upsampling.
I need this to be able to test the new unscaled conversion code more quickly.
We re-order the flags order to make 0 the first entry, so we don't set any
flags when performing unscaled tests.
The field width in a %s directive gives the amount of characters
to read from the input and not the size of the receiving buffer;
the latter must be of course also have space for the trailing \0
which has been forgotten here. The commit adds it (and fixes a
-Wfortify-source warning from Clang).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
We only parse 12 values, so this check always failed. Regression caused by
a change to the print format.
Fixes: 59c39a79ca
Signed-off-by: Niklas Haas <git@haasn.dev>
Sponsored-by: Sovereign Tech Fund
With the ability to set the thread count as well. This benchmark includes
the constant overhead of context initialization.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
This rewrite cleans up the code to use AVFrames and the new swscale API. The
log format has also been simplified and expanded to account for the new
options. (Not yet implemented)
The self testing code path has also been expanded to test the new swscale
implementation against the old one, to serve as an unchanging reference. This
does not accomplish much yet, but serves as a framework for future work.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
And preserve the public SwsContext as separate name. The motivation here
is that I want to turn SwsContext into a public struct, while keeping the
internal implementation hidden. Additionally, I also want to be able to
use multiple internal implementations, e.g. for GPU devices.
This commit does not include any functional changes. For the most part, it is
a simple rename. The only complications arise from the public facing API
functions, which preserve their current type (and hence require an additional
unwrapping step internally), and the checkasm test framework, which directly
accesses SwsInternal.
For consistency, the affected functions that need to maintain a distionction
have generally been changed to refer to the SwsContext as *sws, and the
SwsInternal as *c.
In an upcoming commit, I will provide a backing definition for the public
SwsContext, and update `sws_internal()` to dereference the internal struct
instead of merely casting it.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
changes since v1:
- made into fate test
- fixed c90 warnings
- tests more intermediate formats
- tested on BE mips too
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
In libswcale/tests/swcale.c, the function fileTest() calls sscanf in
an argument of "%12s" on character srcStr[] and dstStr[], which are
only 12 bytes. So, if the input string is 12 characters, a
terminating null byte can be written past the end of these arrays.
This bug was found by cppcheck.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
