[linux-audio-user] jack_convolve-0.0.10, libconvolve-0.0.3 released

From: Florian Schmidt <mista.tapas@email-addr-hidden>
Date: Mon Jun 27 2005 - 14:57:34 EEST


i added an experimental feature to libconvolve/jack_convolve which might
be able to preserve some of those precious cpu cycles from being burnt.

jack_convolve now has commandline switches --min_bin=bin_no and
--max_bin=bin_no which can be used to specify which bins of the fourier
transformed signal and response to multiply. The range for both is
always 0..periodsize+1, but min_bin must always be < than max_bin..

An example:

assuming jack periodsize of 2048 and samplerate of 48khz:

jack_convolve response_file.wav --max_bin=1200

This leaves out the top 849 bins out of the multiplication and thus
reduces cpu load by ca. 2/5. The cost is that the high frequency
spectrum is cut off. And it's not even a really clean cutoff which

jack_convolve response_file.wav --max_bin=40

would show (you get crackles due to edge effects, etc).

This feature is probably most useful to get some preview with degraded
quality but less cpu consumption. Although at some samplerates it even
makes sense.

Assume a samplerate of 96khz, then there's quite a bit of signal which
doesn't need to be processed since it's far out of the range of human

the min_bin parameter is not really useful and only included for
completeness sake :) It cuts out low frequency bins out of the equation.
Due to the crackle effects when throwing away bins that are audible one
should not use these settings for filtering of the convolution in the
audible frequency range..

In one of the previous releases (which went unannounced i think) i also
added a gain argument which can be used to boost the level of the
convolution output.


jack_convolve response_file.wav --gain=4.0

to get a 300% increase in level..


P.S.: I am also currently working on a qt app which uses libconvolve,
but it might still take a while until initial release (due to my time
constraints induced by studying). Preliminary screenshot here:


Help would, of course, be appreciated :) Anyone know of waveform or vu
meter widgets for qt which are reusable?


Palimm Palimm!
Received on Thu Jul 7 16:15:29 2005

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