[FFmpeg-devel] Discussion about Color and light correction tools in libavfilter

Stefano Sabatini stefano.sabatini-lala
Tue Jul 14 00:19:01 CEST 2009

On date Monday 2009-07-13 10:53:24 +0200, Jean-Michel Pour? encoded:
> Hello,
> I just discovered libavfilter from Soc2007+soc2009.
> It seems to be oriented toward running filters, like 'watermark'.
> IMHO, the most important needs are in color and light correction.
> To understand user needs, it is interesting to study a photography
> correction tool. Of course Gimp, but it has too many features. 
> Showfo, which is part of Digikam for KDE4, is much more interesting,
> because it shows-up only the required material for color/light
> correction AND it is linked to libcv a high-quality and fast processing
> library, useful for video also.
> To install showfo, you only need to:
> apt-get install showfoto in Debian SID.
> From the interface, we discover that user needs are:
> * Display a multichannel color graph
> Then from the color menu
> * Curves adjust
> * Levels adjust
> * Channel mixer
> * Color effects
> * Auto correction
> * Brightness, contrast, gamma
> * Hue, saturation, lightness
> * Invest, black&white
> * Color management
> And enhance :
> * sharpen
> * blur
> * noise reduction
> I consider these tools a priority for any video editor.
> Why not fetch Showfoto basic code and adapt it to libavfilter Soc? 
> This would avoid a long and tedious work. Showfoto is linked to libcv.
> This would be the only requirement.

Usually in FFmpeg there is the tendency to avoid external
dependancies, also the basic filters in lavfi should not require
external libraries.

Also I don't think there are problems into implementing filters which
uses external libraries, maybe it would be even possible to write a
filter wrapper around a library (the same way as vf_scale.c is a
wrapper of libswscale), for example vf_gimp.c or vf_showfo.c.
Also note that in the medium / long term it would be a good idea to
implement a plugin system for filters, to make easy extend lavfi
without patching/recompilation.

> What are your plan for FFmpeg in term of color and light correction? I
> am very interested and could participate in writing some code, but I
> would like to hear your plans.

libavfilter is planned to replace libmpcodecs, so when it will be
ready (C) we plan to port all / most libmpcodecs filters. Most of what
you mentioned is likely already implemented in libmpcodecs.

Also as I already said, while it's a not useless exercise implement /
port filters, the priority now is to get libavfilter fully integrated
into the main repo, at that point all the people will run and scream
and post patches for getting their favorite filter into lavfi ;-).

> Kind regards,

FFmpeg = Frightening and Foolish Miracolous Pure Evil Gadget

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