[FFmpeg-devel] [PATCH] Don't adjust start time for MP3 files; packets are not adjusted.

[Dale Curtis]

Any comments on this? Thanks.

- dale

On Thu, Apr 30, 2020 at 12:42 PM Dale Curtis <dalecurtis at chromium.org>
wrote:

> Ping for this patch. Thanks
>
> - dale
>
> On Thu, Apr 23, 2020 at 4:33 PM Dale Curtis <dalecurtis at chromium.org>
> wrote:
>
>> This is a patch Chromium has carried for a while, we forgot to send it
>> upstream. 7546ac2fee4 made it so that the start_time for mp3 files is
>> adjusted for skip_samples. However, this appears incorrect because
>> subsequent packet timestamps are not adjusted and skip_samples are
>> applied by deleting data from a packet without changing the timestamp.
>>
>> E.g., we are told the start_time is ~25ms and we get a packet with a
>> timestamp of 0 that has had the skip_samples discarded from it. As such
>> rendering engines may incorrectly discard everything prior to the
>> 25ms thinking that is where playback should officially start. Since the
>> samples were deleted without adjusting timestamps though, the true
>> start_time is still 0.
>>
>> Other formats like MP4 with edit lists will adjust both the start
>> time and the timestamps of subsequent packets to avoid this issue.
>>
>> Signed-off-by: Dale Curtis <dalecurtis at chromium.org>
>>
>