Fixes an assertion failure in vdpau_get_buffer() when -hwaccel auto is
used, but hwaccel init fails.

Otherwise the expression will be evaluated as unsigned, which will break
when the result should be negative.
CC:libav-stable@libav.org

The table is MMX-specific and used nowhere else.

Based on a patch by Michael Niedermayer.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Certain instrumentation addons leads to a false positive in configure
and link failures at the end of the build phase.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Original decoder seems to always use 176x128 tiles anyway and this helps
avoiding lots of issues with odd tile sizes in fuzzed files.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

The field still remains in MpegEncContext because it is used by the
mpeg4 decoder.

It is only used in one place immediately after it is set.

That field is never set for encoding.

The field remains in MpegEncContext for use in the encoder.

The line setting it was mistakenly removed in
ecf442a5

This supplements the deprecated request_channels-based control of XCh decoding.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

The check for (prim_channels > 2) before calling dca_downmix made these
cases unreachable, but now 2.1 layouts will go through the downmix code.
Having dual mono, Lt/Rt and sum-difference layouts print errors when
regular Stereo doesn't seems pointless.
Signed-off-by: Anton Khirnov <anton@khirnov.net>