[LAD] Rubber Band v1.0 - an audio time-stretching and pitch-shifting library and utility

[Tim Goetze]

[Chris Cannam]

>Rubber Band is an audio time-stretching and pitch-shifting library and
>utility designed for musical applications.
>
>  http://www.breakfastquay.com/rubberband/
>
>It includes a library that supports a sample-accurate multithreaded
>offline mode and a real-time lock-free streaming mode; a command-line
>utility program; and a LADSPA pitch-shifter plugin.  Rubber Band is
>Free Software under the GNU GPL.

I've just tried it at crispness levels 2 and 4 stretching 'Vesoul' by 
Brel to 2x duration and I have to say it does a wonderful job on 
the note onsets, who survive largely unsmeared (a bit better at 
crispness level 4, which also goes for the overall sound impression, 
as subjective as that may be).

  That's where it really outdoes the stretch utility I wrote some time 
ago (where the actual work is done by a Dolson phase vocoder from the 
CARL suite, cf. http://quitte.de/dsp/pvoc.html#stretch).  

  Unfortunately it also has to be noted that after the onset, the 
voice body in rubberband's output is not sounding quite as good as 
with 'stretch' -- there's a faint chorus/aliasing effect, not very 
strong but irritating.

  Is the engine capable of smoothly changing the stretch factor in 
realtime?  I've been pondering a simple looping & stretching playback 
solution for transcription work but the 'stretch' engine isn't 
flexible enough out of the box, it'd only allow a number of switchable 
stretch factor presets unless I put in some really serious work.

Cheers, Tim