[FFmpeg-devel] [PATCH 6/6] avformat/av1dec: Disallow seeking by bytes

[Andreas Rheinhardt]

James Almer:
> On 8/22/2021 10:25 AM, Andreas Rheinhardt wrote:
>> The low overhead OBU format provides no means to resync after performing
>> a byte-based seek; in other words: Byte based seeking is just not
>> supported.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
>> ---
>> The reason I didn't disallow this earlier was that there is one scenario
>> where such a seek would work: When one  already knows the correct
>> position for the start of a frame. But otherwise it just doesn't work.
>>
>> Somehow ffplay tries byte based seeking even for formats with the
>> AVFMT_NO_BYTE_SEEK flag set. Line 2837 should probably be changed to no
>> longer do that.
>>
>>   libavformat/av1dec.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavformat/av1dec.c b/libavformat/av1dec.c
>> index 88a3c325e4..37f21483b9 100644
>> --- a/libavformat/av1dec.c
>> +++ b/libavformat/av1dec.c
>> @@ -428,7 +428,7 @@ const AVInputFormat ff_obu_demuxer = {
>>       .read_packet    = obu_read_packet,
>>       .read_close     = av1_read_close,
>>       .extensions     = "obu",
>> -    .flags          = AVFMT_GENERIC_INDEX,
>> +    .flags          = AVFMT_GENERIC_INDEX | AVFMT_NO_BYTE_SEEK,
>>       .priv_class     = &av1_demuxer_class,
>>   };
>>   #endif
> 
> LGTM.
> 
> Maybe also AVFMT_NOTIMESTAMPS could be added.

But isn't AV1 able to contain timestamps via its timing_info() and
metadata_timecode() structure?

- Andreas