[linux-audio-dev] deconvolver for IR creation anyone?

Denis Sbragion d.sbragion at infotecna.it
Tue Dec 9 09:35:46 EST 2003


Hello,

At 10.17 09/12/2003 +0100, you wrote:
>Hello,
>
>Apostolos Dimitromanolakis wrote:
>>I would be interested in this project too. What I'm looking
>>for is actuallay an anti-reverb that will be able to cancel
>>reverbs in a listening room, well always in conjunction with
>>the listener position.
>
>Then I think DRC (digital room correction) is for you:
>   http://freshmeat.net/projects/drc/
>This works with bruteFIR
>   http://www.ludd.luth.se/~torger/brutefir.html
>But I must confess: I have not understand how to use the result
>of drc in bruteFIR.
>   For a reverb convolution I think only the first steps of the
>DRC process are necessary, but I haven't understand what to do
>there, too.

yep, you are right. To do the convolution between the measured sweep and 
the inverse filter to get the impulse response you can use brutefir (with a 
little trickery). I use it to do my own measurements with 45s log sweeps. 
The inverse filter is almost 2 millions taps, but brutefir eat it without 
esitation even with just 64 mb of RAM available. A truly wonderful piece of 
software!

>   And unfortunately the only DRC tutorial is for windows only
>:-((  And it doesn't explain the steps, it just shows them ...

Doing it under Linux is a bit more complicated. If you want I have some 
shell scripts that do all the steps needed to get the impulse response 
(sweep playing & recording + deconvolution). Anyway they are just a clumsy 
hack that I use myself for my measurements, don't expect any fancy 
interface. Despite this, thanks to the brutefir floating point accuracy and 
the long sweep used the results are state of the art (90+ dB of S/N even in 
a not so quiet environment with a dirty cheap panasonic WM-60A capsule and 
a DIY mic preamp).

>>The other useful thing would be a phase-filter to correct the
>>phases coming out from a two or three way loudspeaker to get
>>clarity in the sound similar to high-end speakers.
>
>As far as I understand what DRC does, this is one of the
>postprocessing steps.

Exactly, it tries also to compensate for the room acoustic (part of, no 
miracle can be performed here).

Bye,

--
	Denis Sbragion
	InfoTecna
	Tel: +39 0362 805396, Fax: +39 0362 805404
	URL: http://www.infotecna.it



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