[Ffmpeg-devel] Validity of non-zero PTS (original) (raw)

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 matter.

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 I-frame.

-- M?ns Rullg?rd mru at inprovide.com

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