[FFmpeg-devel] [PATCH 5/5] avformat/movenc: add support for AV1 streams

[James Almer]

On 7/9/2018 7:23 PM, Baptiste Coudurier wrote:
> Hi James,
> 
> On Mon, Jul 9, 2018 at 11:26 AM, James Almer <jamrial at gmail.com> wrote:
> 
> [...]
> 
> 
>> @@ -5438,7 +5461,7 @@ int ff_mov_write_packet(AVFormatContext *s,
>> AVPacket *pkt)
>>          av_log(s, AV_LOG_WARNING, "pts has no value\n");
>>          pkt->pts = pkt->dts;
>>      }
>> -    if (pkt->dts != pkt->pts)
>> +    if (pkt->dts != pkt->pts && par->codec_id != AV_CODEC_ID_AV1)
>>          trk->flags |= MOV_TRACK_CTTS;
>>      trk->cluster[trk->entry].cts   = pkt->pts - pkt->dts;
>>      trk->cluster[trk->entry].flags = 0;
>>
> 
> [...]
> 
> Interesting, is there a spec document that would explicitly mention that
> AV1 forbids "ctts" atom ?
> 
> Thanks!


Yes, https://aomediacodec.github.io/av1-isobmff/#sampleformat

"Unlike many video standards, AV1 does not distinguish the display order
from the decoding order, but achieves similar effects by grouping
multiple frames within a sample. Therefore, composition offsets are not
used. In tracks using the AV1SampleEntry, the ctts box and composition
offsets in movie fragments SHALL NOT be used. Similarly, the is_leading
flag, if used, SHALL be set to 0 or 2."