[FFmpeg-devel] [PATCH 2/2] lavfi: reimplement MPlayer's af_pan filter for libavfilter.

[Stefano Sabatini]

On date Friday 2011-11-11 19:39:40 +0100, Nicolas George encoded:
> Le primidi 21 brumaire, an CCXX, Stefano Sabatini a écrit :
> > hard on my eyes, maybe easier:
> > pan=stereo:c0=0.4:0:0:0.4:0.2:0, c1=0:0.2:0.3:0.3:0.1:0.1
> > 
> > or even:
> > pan=stereo:FL=0.4:0:0:0.4:0.2:0,FR=0:0.2:0.3:0.3:0.1:0.1
> > 
> > anyway I think the spec for each channel specification should go
> > separated from the others.
> 
> This is not the same syntax as MPlayer's pan filter. But since FFmpeg and
> MPlayer are two distinct tools, I do not think we should feel obligated to
> keep the syntax.
> 
> If we go that way, then we can be more ambitious, for example:
> 
> pan=stereo:FL=0.6*FL+0.4*RL:FR=0.6*FR+0.4*RR
> 
> or even, with automatic removal of inexistent channels and normalization:
> 
> pan=stereo:FL=FL+0.6*RL/:FR=FR+0.6*RR/
> 
> (equivalent to FL=0.625*FL+0.375*RL or to just FL=FL, depending on whether
> RL exists or not; I could not come up with a better syntax than the trailing
> '/', but if someone has a better idea, I would like to see it)

I like this syntax, and I had a very similar idea but I didn't want to
force you to implement this extension, which seems complex enough.
But the idea is worthful, so if you can't/don't have time I could
give a try myself.

> 
> This above is quite easy to write. We could go for even more ambitious, with
> Turing-complete decision features, but I fear we would not finish anytime
> soon.
-- 
FFmpeg = Formidable and Forgiving Maxi Power Enhancing Guru