[Kdenlive-devel] Questions about audio effects

Dan Dennedy dan at dennedy.org
Thu Jun 3 16:40:25 UTC 2010

2010/5/30 Hugh Tebby <hugh.tebby at gmail.com>:
> Hi everyone,
> I thought would look into the effects list in order to give more detailed
> information about the effects and maybe reorganize things a little, see what
> effects work, which ones don't etc.

Can I in interest you in raising this activity up a notch at the MLT
level? Don't be intimidated; this will not require a massive amount of
coding, but there will be some and you will need to read a lot of it.
MLT has a metadata system for formally documenting and describing
effects (actually services). However, there is not enough documented.
This metadata partially overlaps with the kdenlive effects XML, and
IMO ought to replace it eventually.


This is the part that will require a lot of code reading and obviously
yaml-tiny writing.

> I went through all the SOX and LADSPA audio effects, and here are a few
> conclusions :

The MLT frei0r module provides MLT metadata programmatically via the
frei0r plugin info API, and Kdenlive uses this unless an effects XML
document overrides it. I recommend we try to do the same for Sox and
LADSPA. This is the part that will require a fair amount of coding.

> - Many effects have either no effect or clearly don't work correctly

And you will answer many of these questions yourself along the way.

> - There are duplicates betwwen SOX, LADSPA and 'native' effects
> So here are a few questions :
> - If we remove the duplicate effects, which should be kept ? LADSPA or SOX ?

I think it should be considered on a case-by-case basis. One thing to
keep in mind is that both are actually optional modules in MLT;
however, sox is almost always available in the distro packages whereas
users may not have installed the optional LADSPA plugins.

> - Should all effects that don't seem to work correctly be disabled ?


> Should the xml file actually be removed or put into a "not_working" folder ?

I vote for moved.

> Cheers,
> Hugh

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