FFmpeg

103591 Commits

37 Branches

400 Tags

483 MiB

Tag: Branch: Tree: 966fc3c070

Commit Graph

Author	SHA1	Message	Date
Lynne	033105a739	h274: remove optimization pragma This results in warnings on compilers which don't support it, objections were raised during the review process about it but went unnoticed, and the speed benefit is highly compiler and version specific, and also not very critical. We generally hand-write assembly to optimize loops like that, rather than use compiler magic, and for 40% best case scenario, it's simply not worth it. Plus, tree vectorization is still problematic with GCC and disabled by default for a good reason, so enabling it locally is sketchy.	3 years ago
Niklas Haas	6bc29a6b57	avcodec/h274: add film grain synthesis routine This could arguably also be a vf, but I decided to put it here since decoders are technically required to apply film grain during the output step, and I would rather want to avoid requiring users insert the correct film grain synthesis filter on their own. The code, while in C, is written in a way that unrolls/vectorizes fairly well under -O3, and is reasonably cache friendly. On my CPU, a single thread pushes about 400 FPS at 1080p. Apart from hand-written assembly, one possible avenue of improvement would be to change the access order to compute the grain row-by-row rather than in 8x8 blocks. This requires some redundant PRNG calls, but would make the algorithm more cache-oblivious. The implementation has been written to the wording of SMPTE RDD 5-2006 as faithfully as I can manage. However, apart from passing a visual inspection, no guarantee of correctness can be made due to the lack of any publicly available reference implementation against which to compare it. Signed-off-by: Niklas Haas <git@haasn.dev> Signed-off-by: James Almer <jamrial@gmail.com>	3 years ago

Author

SHA1

Message

Date

Lynne

033105a739

h274: remove optimization pragma

This results in warnings on compilers which don't support it,
objections were raised during the review process about it but went unnoticed,
and the speed benefit is highly compiler and version specific, and
also not very critical.

We generally hand-write assembly to optimize loops like that, rather
than use compiler magic, and for 40% best case scenario, it's simply
not worth it.

Plus, tree vectorization is still problematic with GCC and disabled by default
for a good reason, so enabling it locally is sketchy.

3 years ago

Niklas Haas

6bc29a6b57

avcodec/h274: add film grain synthesis routine

This could arguably also be a vf, but I decided to put it here since
decoders are technically required to apply film grain during the output
step, and I would rather want to avoid requiring users insert the
correct film grain synthesis filter on their own.

The code, while in C, is written in a way that unrolls/vectorizes fairly
well under -O3, and is reasonably cache friendly. On my CPU, a single
thread pushes about 400 FPS at 1080p.

Apart from hand-written assembly, one possible avenue of improvement
would be to change the access order to compute the grain row-by-row
rather than in 8x8 blocks. This requires some redundant PRNG calls, but
would make the algorithm more cache-oblivious.

The implementation has been written to the wording of SMPTE RDD 5-2006
as faithfully as I can manage. However, apart from passing a visual
inspection, no guarantee of correctness can be made due to the lack of
any publicly available reference implementation against which to
compare it.

Signed-off-by: Niklas Haas <git@haasn.dev>
Signed-off-by: James Almer <jamrial@gmail.com>

3 years ago

2 Commits (966fc3c070c1e5143537007fb26340c179cc02c5)