[Ffmpeg-devel] Validity of non-zero PTS

Måns Rullgård mru
Wed Feb 1 11:25:43 CET 2006

Andy Parkins said:
> Hello,
> Quick question: is it valid to purposefully create a stream with a non-zero
> PTS as the first frame?

You've been talking about MPEG (TS) previously, so I'll assume this is what
you are thinking of here.  In MPEG1 system streams and MPEG2 PS/TS the rule
is that the first frame must have *some* PTS.  The exact value does not

> I'm thinking, for example, if you were to extract the middle of a stream - do
> you have to adjust all the PTS values so that zero is at the beginning?

No change required.  The only thing you might need to do is add a timestamp to
the first frame.  Figuring out the proper value might be a little tricky.  You
could of course cut the stream at a time stamp, but that might not be at an

M?ns Rullg?rd
mru at inprovide.com

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