Similar gains as the ssse3 version once again

Additional improvements by Clément Bœsch <u@pkh.me>.
Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Signed-off-by: Anton Khirnov <anton@khirnov.net>

Similar gains in performance as the SSSE3 version
Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Signed-off-by: Anton Khirnov <anton@khirnov.net>

The randomize_buffer() implementation assures that "most of the time",
we'll do a good mix of wide16/wide8/hev/regular/no filters for complete
code coverage. However, this is not mathematically assured because that
would make the code either much more complex, or much less random.

Some fixes and improvements by Rodger Combs <rodger.combs@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Fixes ffvp9_fails_where_libvpx.succeeds.webm.

Bug-Id: ffmpeg/3849.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

Palette format is always in RGBA.

This simplifies the code a bit, does not change output data in any way.

This is required for 10-bit surfaces.

A decoder may need this to be set correctly to output frames in the
right order.

This was not observed earlier because the only syntax element which
it normally misses with the current setup is slice_qp_delta, but that
is always going to be zero (in IDR frames QP isn't varied on the
slice) which will always exp-golomb code as a single 1 bit.  The
immediately following part is the byte alignment, which is always a 1
bit followed by 0s which are ignored, so as long as the bitstream is
never aligned at that point we will never notice because the only
difference is that an ignored bit is a 1 instead of a 0.

This was always too late; several fields related to it have been incorrectly
zero since the encoder was added.

It has been replaced by C11 stdatomic.h and is now unused.

Current code uses a plain int in a racy way, which is UB.

Adapted from the code by Rémi Denis-Courmont from VLC

Adapted from the code by Rémi Denis-Courmont from VLC

Adapted from the code by Rémi Denis-Courmont from VLC

Adapted from the code by Rémi Denis-Courmont from VLC

Adapted from the code by Rémi Denis-Courmont from VLC

Since this is a C11 feature, it requires -std=c11.

Not actually used for anything yet, that will be added in the following
commits.

Confirmed to work by checkasm.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Errors during decoding are currently considered non-fatal and do not
terminate transcoding, so even if parts of the data are corrupted, the
rest may be decodable.

However, that should apply only to the actual decoding calls, not to the
failures elsewhere (e.g. configuring filters).

The filtergraph's existence is used in several places to mean that the
filtergraph is fully configured. This causes problems if it's allocated,
but the initialization fails (e.g. if a non-existent filter is
specified).

Bug-Id: 966

The Intel binary iHD driver does not support the
VASurfaceAttribMemoryType, so surface allocation will fail when using
it.