How to scratch audio like a DJ?

I have to develop an iPhone app which is a DJ app. It includes everything right from playing song to scratching the a开发者_StackOverflowudio.

Is there a way I can scratch the audio? Are there any good frameworks which you can suggest? Which are best possible options?

I have referred to this links below but didn't help my cause

http://blog.glowinteractive.com/2011/01/vinyl-scratch-emulation-on-iphone/

Scratching Audio

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I'd start with reading Kjetil Falkenberg Hansen's recent PhD thesis: The Acoustics and Performance of DJ Scratching to get to grips with the nature of the problem. This should provide you with some effective parameters for your program.

I imagine you'll want to buffer a certain amount of the audio to be 'scratched' and simply advance through said buffer at varying speeds both forward and backwards.

Consider this link (and similar ones) for how to build a buffer.

If the iphone API doesn't provide a useful way to advance through the buffer at different speeds you might consider making your own temporary buffer, then using this to populate the buffer used by the iPhone based on some interpolating function.

BTW - the first link you posted looks very useful indeed! What's it missing?