New subject: [linux-audio-dev] Re: Software controller for homemade edrums

8 Jun 2005

...
  Message: 10
 Date: Wed, 08 Jun 2005 15:57:23 +0200
 From: Olivier Guilyardi &lt;ml(a)xung.org&gt;
 Subject: Re: [linux-audio-dev] Re: Software controller for homemade
         edrums
 To: "The Linux Audio Developers' Mailing List"
         &lt;linux-audio-dev(a)music.columbia.edu&gt;
 Message-ID: &lt;42A6F943.4080606(a)xung.org&gt;
 Content-Type: text/plain; charset=ISO-8859-1; format=flowed

 Hi Florian,

 Florian Schmidt wrote:
 For quick tests without libDSP you can tweak the
jack_convolve Makefile
a little:

uncomment the

#COMPILE_FLAGS += -DC_CMUL

line and remove "-ldsp" from the LINK_FLAGS line. This will use an
unoptimized C complex multiplication implementation. jack_convolve will
use around 10-20% more cpu than with the libDSP implementation.

 It did compile. I also needed to remove the #include <dsp/dspop.h> in
 convolve.c

 Okay, so I now have an idea of what convolution is. Your little piece of
 software is very nice, very easy to understand. I used three samples : a
 bassdrum, a snare drum, and a short guitar chord. I plugged the output
 of one of my pads into jack_convolve's input and its output into the
 alsa_pcm playback.

 Both the bassdrum and the chord sounded quite nice. But the snare drum
 sounded like very far away. I guess this comes from the silence at the
 end of this sample.

 What exactly happens with these "response files" ? Should I use very
 simple samples, like a sine wave with no silence ? Shouldn't convolving
 be coupled with trigerring ? I mean : hitting the pad would start the
 sample playback, and the convolving engine would use both this sample
 playback and the pad signal to produce its output. In this case,
 jack_convolve would then need one output and two inputs :
 - one for the pad signal,
 - and one for the "response signal", that is : the sample playback that
 started right when the pad got hit

 Is this possible, or do I misunderstand convolution here ? 
Olivier, I think the next step is to run jack_convolve, and connect the 
soundcard input directly into jack_convolve's input using qjackctl.  then 
connect the output of jack_convovle to the soundcard's outputs.  
(jack_convolve may already do this for you, I can't check just this moment)

Now when you hit a pad, it should be "convolved" with the response signal 
giving you something different than the simple "click" of the input signal.

I'm very interested to see how this works out (I suggested this path to 
Olivier, I hope it's not totally worthless :) ).  It could be a way to build 
a cheap, responsive electronic drum kit that preserves the nuances of the 
input signal.  I wonder if this is how the Korg Wavedrum worked?

-Ben

Re: [linux-audio-dev] Re: Software controller for homemade edrums