Re: [LAD] Paul's Extreme Sound Stretch

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To: Patrick Shirkey <pshirkey@...>
Cc: Linux Audio Developers <linux-audio-dev@...>
Date: Thursday, September 30, 2010 - 10:47 am

On 09/30/10 09:40, Patrick Shirkey wrote:

Are you sure? Where did you get that info from?

Just skimming over Stretch.cpp gives me the impression that it's based
on Fourier analysis and re-sythesis.
http://en.wikipedia.org/wiki/Fourier_analysis

The process() loop looks like:
{
apply_window();
smp2freq(); // Fourier Analysis
process_spectrum();
freq2smp(); // Fourier Synth
}

In layman terms:

There's a smart French guy by the name of Joseph F. sitting inside it:
If you play him some audio: He thinks: "Hey, this is actually just a few
simple sine-waves added together (superpositioned)", he quickly
calculates their frequencies and amplitudes and asks "Now, you want to
change the duration?" easy: "I'll generate some new sine-waves with
these frequencies and amplitudes, how long did you say you want?"

(The smart thing about this French guy is that he actually speaks fluent
English - Sorry I could not resist :)

>

Yes, but its implementation is not very well done.

> Otherwise yes, he has designed it so that adding jack support would be

Indeed, to change the integrated player to output to JACK would be
trivial. It currently uses the PortAudio's StreamCallback which is very
similar to JACK's process callback.

Using it to do "live" timestreching with JACK (jack-in -> jack-out) is
AFAICT impossible because:

If you feed it N samples (or seconds) of audio you end up with M samples
(or seconds) with M > N.

One could do a kludge:
eg. for a 1:10 time stretch with continuous output:
- read 1 sec of audio from the input
- ignore 9 secs of the input
but I don't think this will be useful.

best,
robin
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Messages in current thread:
[LAD] Paul's Extreme Sound Stretch, Louigi Verona, (Thu Sep 30, 7:01 am)
Re: [LAD] Paul's Extreme Sound Stretch, Philipp Überbacher, (Thu Sep 30, 6:52 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Thu Sep 30, 7:21 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Philipp Überbacher, (Thu Sep 30, 8:25 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Louigi Verona, (Thu Sep 30, 6:56 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Philipp Überbacher, (Thu Sep 30, 8:28 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Chris Cannam, (Thu Sep 30, 9:10 am)
Re: [LAD] Paul's Extreme Sound Stretch, Patrick Shirkey, (Thu Sep 30, 7:40 am)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Thu Sep 30, 10:47 am)
Re: [LAD] Paul's Extreme Sound Stretch, Patrick Shirkey, (Thu Sep 30, 2:01 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Dave Phillips, (Thu Sep 30, 11:15 am)
Re: [LAD] Paul's Extreme Sound Stretch, torbenh, (Thu Sep 30, 12:18 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Thu Sep 30, 11:53 am)
Re: [LAD] Paul's Extreme Sound Stretch, , (Thu Sep 30, 12:29 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Camilo Polymeris, (Fri Oct 1, 12:32 am)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Fri Oct 1, 1:25 am)
Re: [LAD] Paul's Extreme Sound Stretch, Renato, (Sat Oct 2, 1:40 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Philipp Überbacher, (Thu Sep 30, 6:49 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Thu Sep 30, 7:23 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Jens M Andreasen, (Fri Oct 1, 7:37 am)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Fri Oct 1, 1:02 am)
Re: [LAD] Paul's Extreme Sound Stretch, Arnold Krille, (Thu Sep 30, 10:28 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Louigi Verona, (Thu Sep 30, 11:35 am)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Thu Sep 30, 2:21 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Philipp Überbacher, (Thu Sep 30, 8:41 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Robin Gareus, (Thu Sep 30, 10:45 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Folderol, (Thu Sep 30, 10:09 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Erik de Castro Lopo, (Thu Sep 30, 11:51 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Folderol, (Fri Oct 1, 4:43 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Erik de Castro Lopo, (Sat Oct 2, 12:08 am)
Re: [LAD] Paul's Extreme Sound Stretch, gene heskett, (Fri Oct 1, 8:07 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Philipp Überbacher, (Fri Oct 1, 9:03 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Ray Rashif, (Fri Oct 1, 10:17 pm)
Re: [LAD] Paul's Extreme Sound Stretch, gene heskett, (Fri Oct 1, 9:17 pm)
Re: [LAD] Paul's Extreme Sound Stretch, Ralf Mardorf, (Sat Oct 2, 5:54 am)