Comments on: Time Stretching And Pitch Shifting of Audio Signals – An Overview

By: Murugesh

Murugesh — Wed, 17 Feb 2010 07:18:41 +0000

Thanks for the material!!! very informative…..expect some more on “Wavelets”!!!

Thanks in advance…

By: mg

mg — Thu, 17 Dec 2009 06:41:28 +0000

Many commercial multi-trackers have the ability to play video alongside audio. Things like Ableton Live, Logic, Cubase (I’m not sure which ones have that functionality at this point). Most of said audio editors allow you to change the speed of an audio file without changing the pitch (one method is to chop it into slices and adjust the time between the slices). They may allow you to change the speed of the video along with it (changing video speed is easier because there is no such thing as “pitch” in video).

By: michal

michal — Tue, 24 Nov 2009 21:12:29 +0000

Thanks for this great tutorials, but I would like to ask if is it possible to do some explanation also on time-stretching and TD-PSOLA algorithm. I try to search on internet but I only found your page with some useful and easy understanding explanation

By: Daniel Burakowski

Daniel Burakowski — Wed, 29 Jul 2009 22:03:32 +0000

I am a guitar student studying from instructional DVDs. Is it possible to change the tempo of both the audio and video portions without changing the pitch of the music. Also can anyone suggest how to search for such a program.

By: madmik3

madmik3 — Fri, 17 Apr 2009 18:49:45 +0000

Here is a C# version of v1.0 of the code:
http://sites.google.com/site/mikescoderama/pitch-shifting

By: Taj

Taj — Mon, 09 Feb 2009 20:50:54 +0000

It’s in table 2: http://www.dspdimension.com/admin/pitch-shifting-using-the-ft/

By: Jim

Jim — Mon, 09 Feb 2009 19:37:39 +0000

Is the link of the article in this specific page, cause I am not that familiar with the website yet. I am currently using the pVoc code found here: http://www.daimi.au.dk/~pmn/sound/pVoc/index.html, of Steffen Brandorff. But I have some problems with it and I still haven’t been able to implement the LFO. My other choice till now was the PSOLA code that I have found in the DAFX book.
Again, thank you very much for your immediate response.

By: Taj

Taj — Mon, 09 Feb 2009 17:45:48 +0000

I would recommend you check out the time stretching using the fourier transform article, it comes with pitch shifting source code that helped me a lot. Many people are using it, even in the professional realm (Celemony’s Melodyne apparently uses it as well).

By: Jim

Jim — Mon, 09 Feb 2009 17:01:38 +0000

Trully, an excellent overview over pitch shifting and time stretching. I am a final year project and I am working on pitch shifting in order to use it as an audio effect. The main idea behind my project is to not only try to implement the pitch shifting technique, but introduce an LFO or any other signal source to drive the pitch shifting. The LFO will vary the pitch factor that is applied to the signal. Theoretically, the outcome will be similar to the vibrato but done in a different way. I have some questions over the topic.
Since I am aiming to create a sound effect, mostly to apply it on the guitar, what is the best code to use in order to deal with polyphonic signals (like chords etc.) of this nature? PSOLA or the Phase Vocoder?
I have the real-time application in my mind as well but it is not the first priority for now. Furthermore, I am not really sure where in the code to introduce the LFO for the pitch shifting variation. I have a lot of experience with the theoretical aspect of sound effects but I really lack in software. I will be using Matlab for all the above.
Thank you very much for your time. I will really appreciate it if anybody just give me a couple of ideas or hints
Regards Jim

By: Bernsee

Bernsee — Fri, 30 Jan 2009 07:12:27 +0000

I have contacted Andrew DeTorres and hopefully he will email me with a working link to his Java implementation soon.

–smb

By: Alan P

Alan P — Fri, 30 Jan 2009 02:41:32 +0000

Looking for a java version of smbPitchShift(). Tried the link from the previous post, but it no longer works. Any idea where else this may be available.

http://www.adetorres.com/keychanger/KeyChangerReadme.html

Thanks!

By: Taj

Taj — Sun, 04 Jan 2009 09:17:25 +0000

You need an overlap of at least 3 in order to prevent modulation. Taking the sqr of the window will distort its frequency response so it’s generally not a good idea to do.

By: Dave H

Dave H — Sat, 03 Jan 2009 23:34:14 +0000

Regarding ’smvPuitchShift,’ I’ve found that applying a square root to the window array removes the tremolo effect. I guess because it is applied twice to the same data in the code…

By: Bernsee

Bernsee — Wed, 30 Apr 2008 14:06:49 +0000

Thank you, I’m glad you like it.

As a matter of fact, there is a Java version of smbPitchShift() available from the following web site: http://www.adetorres.com/keychanger/KeyChangerReadme.html

I don’t know why this link didn’t make it on our news page, it must have been lost during the site redesign. Sorry for that.

HTH,
–smb

By: Richard Martin

Richard Martin — Wed, 30 Apr 2008 13:54:29 +0000

An excellent overview. However, rather than implement this from scratch myself (fun though that would be), I have been trying to find an open-source java library that will handle realtime pit shifting and time stretching. It seems there arn’t any which, given the public availability of the algorithms, I find very strange. Is there some fundamental limitation in the JavaSound API (the lack of an accurate enough clock maybe) that is preventing this being implemented in Java?

Does anyone know of an (open-source) Java implementation of realtime pitch-shifting and time-stretching?

By: J Allen

J Allen — Thu, 14 Feb 2008 09:38:15 +0000

Excellent tutorials–these are the easiest to understand, ergo the best I’ve seen…this was about the fortieth site I visited, but the first to actually provide the answer I was looking for.

By: Bernsee

Bernsee — Wed, 06 Feb 2008 11:42:33 +0000

Thank you for your interest in our web site. May we suggest you post this question to our forum at http://www.surroundsfx.com/forum as there are a lof of pro sound engineers there who can help you with this kind of question in a more appropriate manner than it would be possible for us to do in just a reply to your comment here… Thanks!

By: Shawn Below

Shawn Below — Wed, 06 Feb 2008 08:52:06 +0000

Hi,

I´m planning to process an old tape recorded song digitally to slow it a bit, and to pitch it down a bit. I also want to remaster it. I work with protools audiosuite TCE and Pitch shift plug ins. I´m wondering;

* The protools user manual says about normalize the audio before processing. Would it be better to master it and normalize and then pitch shifting it?

* My source material is the tracks from a CD. Would it be better for the processing to work in a session with a higher sample rate and bit depth?

By: Bernsee

Bernsee — Thu, 06 Dec 2007 09:50:43 +0000

There are quite a few. ONe example is Prosoniq’s TimeFactory, you can find more information at

http://products.prosoniq.com/cgi-bin/register?service=showdetail&refno=40

Regards
–smb

By: Ag

Ag — Thu, 06 Dec 2007 09:13:23 +0000

is there any software out there that focus on time stretching and pitch control ?

thanks this site was helpful