lavfi/lut3d: avoid overread.
lavfi/mp: try to pass interlaced & tff flags

This makes mp=softpulldown actually useful.

Signed-off-by: Paul B Mahol <onemda@gmail.com>
avformat/utils: Keep internal and external av_read_frame() packets in sync.

Otherwise, during error conditions, the caller will be left with
dangling pointers to a destructed packet => boom.

BUG=242786
TEST=ffmpeg_regression_tests

Commit slightly simplified by commiter
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>