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Re: stretch time, keeping pitch
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Re: stretch time, keeping pitch


  • Subject: Re: stretch time, keeping pitch
  • From: Michael Hanna <email@hidden>
  • Date: Wed, 1 Dec 2004 10:26:44 -0500

Well that's really cool. Thanks for the heads-up.

Does the stream have to be uncompressed then? How does one transcode from compressed to uncompressed?

I've never coded in C++ really, just Java, C and Objective-C, is it really that hard? My project is in Cocoa Frameworks, can I easily incorporate C++ CoreAudio code into it?

If it's an AAC or MP3 file, maybe I can somehow transcode the file first, stretch the sound with SoundTouch, then with the output of that, make a playback callback with MTCoreAudio.

sound feasible?

Michael

On 30-Nov-04, at 12:09 PM, David M. Cotter wrote:

I'm using coreaudio to play my audio, rather than quicktime, this lets me get a shot at the uncompressed stream. try:
/Developer/Examples/CoreAudio/Services/PlayAudioFile/


Then, I'm using "SoundTouch" library to change tempo/pitch independently.
http://sky.prohosting.com/oparviai/soundtouch/


On Nov 30, 2004, at 3:37 AM, Michael Hanna wrote:

Hi, my app loads a sound via NSSound and manipulates it via Quicktime. I'd like to take a subregion of the sound/movie and play it back slowly, but keeping pitch like the original.

First of all, is it possible to get a 'subregion' or piece of the sound? I'd imagine that's a Quicktime call? From the light research I've done on this, does this sound have to have 1:1 frame/packet ratio(such as wav or aiff) in order to properly apply the dsp technique? Do I apply a FFT for this.. not sure where to start on this.

regards,
Michael

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