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

[Hendrik Leppkes]

On Fri, Apr 13, 2018 at 11:54 AM, Paul B Mahol <onemda at gmail.com> wrote:
> On 4/13/18, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
>> 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).
>
> Please add { } brackets around new code.
>

Applied with that changed.

- Hendrik