---------------------------- Original Message ----------------------------

Subject: Re: [music-dsp] Real-time pitch shifting?

From: "Chris Cannam" <can...@all-day-breakfast.com>

Date: Mon, May 21, 2018 3:35 pm

To: music-dsp@music.columbia.edu



> On Mon, 21 May 2018, at 19:54, Matt Ingalls wrote:

>> "Rubber Band implements pitch-shifting using the standard technique of

>> resampling&hellip;

>> This method has the advantage of making the amount of pitch adjustment

>> extremely accurate and stable, even for small changes.&rdquo;
Rubber Band sounds pretty good to me and to my ears made of clay.� i thought, 
back in my day, that SPEED (SoundToys) sounded pretty good.

> It also means you only have to solve the auditory problem once -- if you can 
> keep the artifacts down for the time stretcher, then pitch-shifting is free.
unless you're gonna worry about formants, pitch shifting is just resampling 
applied to the output (or input) of a time
scaler.� i would do whichever operation increases the data first.� so pitch 
shifting up would be time-stretch first, then resample.� pitch shifting down 
would be resample first and then time-compress.

> Unfortunately it does create some complications in terms of managing the 
> proper frame timing and so on.
resetting the frame alignment whenever a transient is detected is a real pain 
in the ass.� but the idea to do that then let the phases drift (glitchlessly) 
after the transient is a
good idea.� doesn't seem to solve the phasiness problem for human voice when 
pitches change but no transient is detected (then phases can get outa alignment 
again).� i really don't know a clean way of keeping those phases well aligned.
> I assume this wouldn't work with your use-case as you want to keep the frames 
> synchronised so you can resynthesise everything in one go.
it would need more buffering, but you can do it real-time, even with the frames 
being reset and initially aligned with a transient.�
but it gets complicated and the throughput delay gets large.


r b-j� � � � � � � � � � � � �r...@audioimagination.com

"Imagination is more important than knowledge."

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