New subject: [linux-audio-user] changing speed without changing pitch

21 Oct 2002

Hi,

I *finally* got around to trying the csound method of changing the speed of
an audio file without changing the pitch, but it didn't work for me :(

I used the following "orc" file:

...
  sr        =         44100
 kr        =         4410
 ksmps     =         10
 nchnls    =         1

           instr     1
 	  kfreqscale	=	1
 	  ispecwp   =         0
 	  ktime     line      1, p3, 0
 	  apvl       pvoc      ktime, kfreqscale, "file.pvc", ispecwp
 out apvl	  
 endin 
and then the "sco" file:
...
  i1 0 12 
 e 
with a 6 second sample, so this should double the audio to 12 seconds. I did
the PV analysis like this:

...
  csound -U pvanal -n 1024 -w 4 file.wav file.pvc

and then ran csound via:

...
  csound -W -R -d file.orc file.sco -o slow.wav 
and then I waited for a little while :)

When csound was done, the ourput file was, well, interesting...
Basically the input file was 6 seconds of single-note guitar playing, and
the output was a weird (though not unpleasant :) whooshing-sweeping-phasing
sound for 2 seconds, then a faint LFO-type sound to the end of the file. No
sign of the original clip, slowed or otherwise.

Can anybody out there tell me what I (or csound :) did wrong?

Thanks in advance,

Stuart

RE: [linux-audio-user] changing speed without changing pitch