Re: [FFmpeg-devel] [PATCH] avcodec/hevc_sei: Fix check for SEI end

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Andreas Rheinhardt:
> The intention behind the current check seems to be to check for
> the rbsp_trailing_bits() syntax structure which is always 0x80
> for valid SEI messages. Yet this is wrong: These trailing bits
> are not part of the GetBitContext -- they have already been
> stripped in ff_h2645_packet_split(). And it is harmful, as
> 0x80 is a legal SEI message payload type (namely for
> Structure of pictures information SEI messages). We ignore this
> type of SEI, but because of this bug we also ignored every
> SEI message in the same NALU following it.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
>  libavcodec/hevc_sei.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/libavcodec/hevc_sei.c b/libavcodec/hevc_sei.c
> index a5c7df34b0..953633f4bd 100644
> --- a/libavcodec/hevc_sei.c
> +++ b/libavcodec/hevc_sei.c
> @@ -549,12 +549,6 @@ static int decode_nal_sei_message(GetByteContext *gb, void *logctx, HEVCSEI *s,
>      }
>  }
>  
> -static int more_rbsp_data(GetByteContext *gb)
> -{
> -    return bytestream2_get_bytes_left(gb) > 0 &&
> -           bytestream2_peek_byteu(gb) != 0x80;
> -}
> -
>  int ff_hevc_decode_nal_sei(GetBitContext *gb, void *logctx, HEVCSEI *s,
>                             const HEVCParamSets *ps, int type)
>  {
> @@ -569,7 +563,7 @@ int ff_hevc_decode_nal_sei(GetBitContext *gb, void *logctx, HEVCSEI *s,
>          ret = decode_nal_sei_message(&gbyte, logctx, s, ps, type);
>          if (ret < 0)
>              return ret;
> -    } while (more_rbsp_data(&gbyte));
> +    } while (bytestream2_get_bytes_left(&gbyte) > 0);
>      return 1;
>  }
>  

Will apply this tonight unless there are objections.

- Andreas
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