[FFmpeg-devel] [PATCH v1] lavf/mov: Fix timestamp rescale on sidx atom

[Jun Li]

On Thu, May 16, 2019 at 1:00 AM Jun Li <junli1026 at gmail.com> wrote:

>
>
> On Sun, May 12, 2019 at 7:44 PM Jun Li <junli1026 at gmail.com> wrote:
>
>>
>>
>> On Fri, May 10, 2019 at 7:25 PM Jun Li <junli1026 at gmail.com> wrote:
>>
>>>
>>> On Thu, May 9, 2019 at 2:08 AM Jun Li <junli1026 at gmail.com> wrote:
>>>
>>>> Fix #5090
>>>> Fix the timestamp rescale issue, from sidx timebase to
>>>> stream's timebase.
>>>> ---
>>>>  libavformat/mov.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>>>> index 78f692872b..d058855e6c 100644
>>>> --- a/libavformat/mov.c
>>>> +++ b/libavformat/mov.c
>>>> @@ -5017,7 +5017,7 @@ static int mov_read_sidx(MOVContext *c,
>>>> AVIOContext *pb, MOVAtom atom)
>>>>              return AVERROR_PATCHWELCOME;
>>>>          }
>>>>          avio_rb32(pb); // sap_flags
>>>> -        timestamp = av_rescale_q(pts, st->time_base, timescale);
>>>> +        timestamp = av_rescale_q(pts, timescale, st->time_base);
>>>>
>>>>          index = update_frag_index(c, offset);
>>>>          frag_stream_info = get_frag_stream_info(&c->frag_index, index,
>>>> track_id);
>>>> --
>>>> 2.17.1
>>>>
>>>
>>> Ping
>>>
>>
>> This change is for fix the issue of calculating sidx_pts.
>> Sidx box has "earliest_presentation_time", used as pts of  the referent
>> track, sidx also has timescale field.
>> So the operation should convert from sidx's timescale to track's
>> timescale, this patch is for addressing this, as well as fixing #5090.
>>
>> Of course this is based on my understanding, so please correct me if I am
>> wrong. Thanks !
>>
>>
> Ping.
> I believe this is a bug and triggered whenever sidx box's timescale is
> different from track's timescale.
> Created this kind of content and verified that ffplay couldn't play while
> VLC plays well.
> Then I checked VLC's implementation:
>
> https://github.com/videolan/vlc/blob/5609c1b41d6fbca6323103619c6139caf7bc9e6e/modules/demux/mp4/mp4.c#L4735
>
> Hope someone could help to have a review ? Thanks ! :)
>
> Best Regards,
> -Jun
>
>
>> Best Regards,
>> Jun
>>
>
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