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

[Clément Bœsch]

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:
> > TIME+FRAME_COUNT
> > FRAME_COUNT+TIME
> > 
> > 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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