[linux-audio-user] Resampling loop libraries

[Frank Barknecht]

Hallo,
Mark Knecht hat gesagt: // Mark Knecht wrote:

>    Sox looks interesting. Quite a lot of capabilities there also.
> 
>    Maybe I need to do something to take advantage of the 'Acidized'
> feature of the loops also? Acid loops have tempo and root note info in
> the files. It would be nice to somehow be able to use that to get a
> better result.

In my understanding (which may well be much out of date) the Acid-info
is just meta-data to let Acid show things like bpm and such quckly.
So it's useless for time stretching or shifting (I use these terms
interchangably, which is technically not correct, I guess)

Normally stretching is done in one of these ways: 

a) Resampling by changing the sample rate. This also changes pitch and
   has artifacts, unless you do counter measures. Vinyl DJs do it a
   lot in the analog realm.

b) rotating-tapehead delay pitch shifting. I think, Steve made a
   plugin that works this way. You might use it for example with 
   ecasound. This is an old-fashioned effect and can be heard. Itself,
   it only changes pitch and thus can undo the resampling
   side-effects.
   
c) FFT-based pitch shifting. I think, Steve also made a plugin with
   this approach (of course ;) It gives good results.

d) Granular resynthesis. This is used increasingly in commercial
   software, for example Ableton Live is somehow a granular sample
   player. The SndObj-library has a cool granulator called syncgrain
   that I ported to a Pd external. As usual with granular synthesis,
   you need to control a lot of paramenters, which can be difficult.
   But simple loop-speed changing is rather easy with that.

ciao
-- 
 Frank Barknecht                               _ ______footils.org__