[gst-devel] gst-bad equalizer element

Stefan Kost ensonic at hora-obscura.de
Tue Feb 13 09:06:36 CET 2007


another thought for the equalizer. Using the g_param_spec_value_array  
for the band values is imho not so nice:
* one can't easily change single band values
* one can make the band values controllable

Two thoughts. First we can make it using GstChildProxy. That means it  
would need to have a minimal GType for the bandvalue.
Apps then can do:
* bands could be GstObjects and thus have names (center frequency)!
* band-values are controlable

Additionally we could add two more elements Equalizer3, Equalizer10 to  
the plugin. Those would have a fixed number of bands (yes, 3 and 10).  
These elements  target players that want to have a simple interface.  
The high end audio app, that needs a 32band eq, can use the ChildProxy  
based version.

I am only afraid that we can't name the children or den properties  
like '100Hz', '1KHz' as gobject names must begin with a alpha char :(


Quoting Christophe Dehais <christophe.dehais at gmail.com>:

> Hi !
> The equalizer element has been ported to 0.10 and is currently in gst-bad CVS
> I'm making a plugin for rhythmbox that uses this element, however I
> don't understand precisely what the properties mean:
> - num-bands seems to specify the partition of the spectrum but what is
> the min and max frequency ? And I guess that it's not regularly
> divided, so what  scheme is used ?
> - band-values holds values in [-1.0; 1.0]. Is this mappable to
> something in decibels ?
> I browsed rapidly through the code, and I thought I was not good
> enough in signal theory to answer this whithout further research, so I
> would appreciate any help from someone who knows (maybe the author of
> the element ?)
> thanks,
> Christophe
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