[FFmpeg-devel] mpegtsenc: add option to define a timestamp offset

Harald Axmann harald.axmann at hotmail.com
Sun Mar 24 16:03:31 CET 2013

Am 18.03.2013 22:22, schrieb Harald Axmann:
> On 17.03.2013 21:44, Nicolas George wrote:
>> [...]
>> IMHO, adding an option is not a correct solution. I understand you 
>> doing it
>> if you need a result urgently, but for integration, understanding 
>> what is
>> going on is necessary.
>> [...]
> Sounds reasonable of course. However I fear that I do not have the 
> time for a deeper investigation now. If I find out something, I'll 
> report.
> [...]

I did a little debugging on this issue. As far as I understand it, the 
mpegts encoder will always create its own time base from the picture 
number. So the original timestamp and every offset added to it in some 
filter get lost anyway. Furthermore setpts is a video only filter 
(intended for changing the speed), so it cannot be used to shift streams 
containing video and audio.

Hence AFAIK current ffmpeg doesn't provide a solution for mpegts 
timestamp shifting. From that point of view the option seems like a good 
idea to me again. Of course it is specific to mpegts. But is timestamp 
shifting necessary for all encoders? If we want to implement it for all 
formats, a change in every single encoder might be necessary, because 
they all can have some specialties (like PCR in TS). On the other hand 
the provided solution is small, local and free of side effects. It just 
adds a feature to mpegts, where it is obviously currently needed.

I'm looking forwards to your comments.
   Harald Axmann

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