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

The original sample was generated with invalid software.

Signed-off-by: Martin Storsjö <martin@martin.st>

And simplify and explain the expression.

Fault introduced in f3fdef10

It is always equal to nb_slice_ctx.

This is more correct and avoids wasting space when frame threading is
used.

This limit is now unnecessary, we can easily support an arbitrary number
of threads.

Those should already be set to the correct values.

In such a case, decode the MBs in parallel without the loop filter, then
execute the filter serially.

The ref2frm array was previously moved to H264SliceContext. That was
incorrect, since it applies to all the slices and should properly be in
H264Context (it did not actually break decoding, since this distinction
only becomes relevant with slice threading and deblocking_filter=1,
which was not implemented before this commit). The ref2frm array is thus
moved back to H264Context.

It is not used for anything internally, just exported in the output
frames. So remove the indirection and set it directly in frame_start().

It is no longer called from outside the h264 decoder.

It is always unconditionally initialized in decode_postinit() and then
immediately used in one place further below. All the other places where
it is accessed are just useless fluff.

This comment used to apply to code that was removed.

It is very fragile against fields being moved and hides what is actually
being copied. Copy all the fields explicitly instead.

This will allow decoupling the parser from the decoder.

Make the SEI parsing independent of the H264Context, to allow
decoupling the parser from the decoder.

This will allow decoupling the parser from the decoder.

Make the SPS/PPS parsing independent of the H264Context, to allow
decoupling the parser from the decoder. The change is modelled after the
one done earlier for HEVC.

Move the dequant buffers to the PPS to avoid complex checks whether they
changed and an expensive copy for frame threads.

It is no longer needed for anything.

This will allow decoupling the parser from the decoder.

It is no longer necessary after 741b494f

It has nothing to do with the reference count and so does not belong in
this function.

Remove now unused ff_h264_decode_nal().

Just pass through the bitstream as is. This is the same as what is done
for HEVC already.

Add a flag which applies here, which had been missed.
Signed-off-by: Martin Storsjö <martin@martin.st>