[FFmpeg-devel] [PATCH] avcodec/aac_ac3_parser: account for data already in the parsing buffer

[Hendrik Leppkes]

On Wed, Apr 11, 2018 at 1:40 PM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
> If a frame starts very close to a packet boundary, the start code may
> already have been added to the parsing buffer, indicated by a small
> negative value of "i", while the header is still being tracked in the
> "state" variable.
>
> Reduce the remaining size accordingly, otherwise trying to find the next
> frame could skip over the frame header and lump two frames together as
> one.
> ---
>  libavcodec/aac_ac3_parser.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/libavcodec/aac_ac3_parser.c b/libavcodec/aac_ac3_parser.c
> index 019074b0dd..7f20626285 100644
> --- a/libavcodec/aac_ac3_parser.c
> +++ b/libavcodec/aac_ac3_parser.c
> @@ -60,6 +60,8 @@ get_next:
>                      s->remaining_size += i;
>                      goto get_next;
>                  }
> +                else if (i < 0)
> +                    s->remaining_size += i;
>              }
>          }
>      }
> --
> 2.16.1.windows.4
>

Ping.
Note that this is somewhat of a regression in AC3 parsing since the
recent AC3+EAC3 combined stream support (the bug existed before, but
that change exposed it).

- Hendrik