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

Clément Bœsch ubitux at gmail.com
Tue Sep 11 19:24:14 CEST 2012

On Tue, Sep 04, 2012 at 06:26:44PM +0200, Nicolas George wrote:
> Le nonidi 19 fructidor, an CCXX, Stefano Sabatini a écrit :
> > Yes. Of course anything which works with framecount won't be accurate
> > when seeking is performed.
> > 
> > Other variants:
> > 
> > suffer of the same problem (but should be possible otherwise).
> IMHO, we should really not encourage anything based on frame count: nine
> time out of ten¹, people use frame counts because they believe it is more
> accurate than the same information expressed in timestamp with a simple
> multiplication and do not realize that variable frame rate is in fact very
> common. Allowing frame counts will cause more fragile scripts on the loose.

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.

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.

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

Clément B.
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