[FFmpeg-user] Using -filter_complex instead of lavfi with amerge hangs.

Nicolas George nicolas.george at normalesup.org
Tue Jun 26 13:47:59 CEST 2012

Le nonidi 9 messidor, an CCXX, Tim Nicholson a écrit :
> I do not understand that, as I thought that
> "amovie=LTA01631701.mxf:si=1, aconvert=s16:mono:planar [a1]"
> defined an input and assigned it to pad a1.

It is a source, not an input. An input is a link not connected to anything,
that ffmpeg will feed by itself.

>					      Having extra sources in a
> filtergraph is not uncommon, take the overlay filter for example, so
> expecting the use of amovie to define a source is not unreasonable in
> this circumstance, although possibly not the best way to do it.
> > input-driven (this needs to be fixed, but this is not urgent), your filter
> > graph does not fit its scheduling.
> >
> > Rule of thumb: do not use (a)movie with -filter_complex, use the ffmpeg -i
> > option instead (and second rule of thumb: do not use the same inputs several
> > times).
> >
> Just to clarify, with -vf it usual to add extra inputs (whether audio or
> video) using (a)movie, but with -filter_complex you just use multiple -i
> options and then pick the streams with the usual [file:stream] syntax?

That is exactly that. IMHO, using the (a)movie source should be considered
only a workaround for when ffmpeg was not able to deal with complex or audio
filters. Now that it can, it should not be used.

> something like, but use ":" not "." in the mappings...;)

My bad.

> Would using "join" with the mapping option be more appropriate for this
> operation?

join is Nit Invented Here version of amerge from libav. I did not look into
it in details, but at first glanced its design seemed botched.


  Nicolas George
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