[FFmpeg-devel] [PATCH 3/5] avcodec/mpeg4videode: Eliminate out of loop VOP startcode reading for studio profile

[Kieran Kunhya]

On Sun, 29 Apr 2018 at 20:20 Michael Niedermayer <michael at niedermayer.cc>
wrote:

> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/mpeg4videodec.c | 4 ----
>  1 file changed, 4 deletions(-)
>
> diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
> index 9ee2f37c69..9318d7bd4e 100644
> --- a/libavcodec/mpeg4videodec.c
> +++ b/libavcodec/mpeg4videodec.c
> @@ -2931,9 +2931,6 @@ static int decode_studio_vop_header(Mpeg4DecContext
> *ctx, GetBitContext *gb)
>      if (get_bits_left(gb) <= 32)
>          return 0;
>
> -    if (get_bits_long(gb, 32) != VOP_STARTCODE)
> -        return AVERROR_INVALIDDATA;
> -
>      s->decode_mb = mpeg4_decode_studio_mb;
>
>      decode_smpte_tc(ctx, gb);
> @@ -3183,7 +3180,6 @@ int ff_mpeg4_decode_picture_header(Mpeg4DecContext
> *ctx, GetBitContext *gb)
>              if (s->studio_profile) {
>                  if ((ret = decode_studio_vol_header(ctx, gb)) < 0)
>                      return ret;
> -                break;
>              } else {
>                  if ((ret = decode_vol_header(ctx, gb)) < 0)
>                      return ret;
> --
> 2.17.0
>
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I appreciate you are going to ram this through as "maintainer" but many of
these changes do not reflect the intentions of the specification and build
on bad design decisions in mpeg4videodec from 10-15 years ago.

Kieran