[FFmpeg-devel] [PATCH] lavfi: add asendcmd and sendcmd filters

Nicolas George nicolas.george at normalesup.org
Tue Sep 11 21:26:56 CEST 2012

Le sextidi 26 fructidor, an CCXX, Clément Bœsch a écrit :
> If you are working on editing, it's likely you want frame exact filtering,
> and not hope that the timestamp will match that exact frame.

You do not have to hope that the timestamp will match the exact frame, you
just have to give the correct timestamp.

> A typical editing FFmpeg application would provide a GUI with a user
> editable timeline frame based for the user, and the app would construct a
> sendcmd filtergraph to feed a ffmpeg.

The GUI adds a "pts" field to the data structure it uses to store the frames
and uses it to build the sendcmd script.

> Does that sound like a very specific case to you? IMO, even editing in
> command line, assuming you could get the frame id (through SMPTE timecode,
> or with a drawtext printing frame number in ffplay + the next frame
> feature like '.' in MPlayer), it could be pretty useful.

I do not know exactly what SMPTE timecode is supposed to do, but as for the
other example, you can as easily get drawtext to print the timestamp than
the frame number. Actually, MPlayer already does it: -osd-fractions 1.

> I'd say that frame accurate editing is quite common and justified (maybe
> nine times out of ten).

Yes, frame-*accurate* is necessary. But timestamps are microsecond-accurate:
even taking a large margin to guard against rounding errors, they still are
accurate enough to grant frame-accuracy.


  Nicolas George
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