Re: Finding audio frequency
Re: Finding audio frequency
- Subject: Re: Finding audio frequency
- From: Brian Willoughby <email@hidden>
- Date: Tue, 26 Jan 2010 19:33:49 -0800
On Jan 26, 2010, at 06:46, Paul Bruneau wrote:
I am only concerned with the "base" or "foundation" frequency--that
is, I don't care about harmonics, I only care about how many times
per second the string is "vibrating" (for lack of a better term).
I think I could sort of brute-force my way through this by looking
at each sample and keeping track of where the "wave" crosses zero,
but I'm pretty sure there is some better "dsp" way to do this,
perhaps using some nice open source algorithms.
Be wary that, for a string, harmonics above the root can have a
higher amplitude than the fundamental, thus zero-crossings will often
false trigger an octave up. You've probably heard this happen in
many guitar effects, particularly synthesizers, where they track the
correct frequency for a while and then suddenly jump up an octave
(annoyingly).
Only part of your solution will involve CoreAudio. Another mailing
list that you might want to visit is PerfOptimization. The
Performance Optimization list deals with FFT, convolution, and other
API offered by OSX that you might find useful for your task.
Brian Willoughby
Sound Consulting
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