[Ffmpeg-devel] Frame rates and time_base

Rich Felker dalias
Sat May 7 07:04:58 CEST 2005

On Sat, May 07, 2005 at 12:00:46AM +0200, M?ns Rullg?rd wrote:
> Bill May <wmay at cisco.com> writes:
> > M?ns Rullg?rd wrote:
> >> OK, I'll try to rephrase it.  Where does libavcodec get the values it
> >> puts in AVFrame.pts?  If the demuxer supplies a pts with a frame, I'd
> >> like that pts to appear in the corresponding AVFrame.  How do I tell
> >> libavcodec about the pts of the encoded frames I'm feeding it?
> >
> > I'd like to know if:
> >
> > for the encoder, if it is possible to put a DTS, then get the PTS
> > of the returned frame ?  (x264 has this).
> >
> > for the decoder, pass in a PTS, and get a DTS from the decoded frame.
> If PTS and DTS are different for an encoded frame, there is no way to
> determine one from the other.  While decoding a sequence of frames, it
> is of course possible to determine any PTS, given the PTS of one of
> the frames.

Huh? Given a sequence of frames and their order, it's possible (and
easy -- see the NUT spec) to convert PTS to DTS. On the other hand
it's impossible to convert DTS to PTS without knowing specifics of the
codec.. :(

The situation would be reversed if you store frames in display order
rather than decode order, but that's just stupid..


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