FFT Format for iTunes Plug-ins.
FFT Format for iTunes Plug-ins.
- Subject: FFT Format for iTunes Plug-ins.
- From: Justin Bakse <email@hidden>
- Date: Wed, 11 Jun 2003 15:49:51 -0500
Hello,
I am working on creating an iTunes visualizer plug in using the sdk.
From the tech-note describing the sdk, it is mentioned that the
provided array (visualPluginData->renderData.spectrumData) is a
512-point FFT of the sample data, but give very little additional
information beyond that. I am fairly new to FFT and have not been
able to confidently infer a few things. I would like to take the FFT
data and display a frequency/power display. Plotting the array
directly seems to be pretty close, but i want to make sure. (also it
doesn't quite match up the the display in the track display part of
iTunes)
So, some specific questions, hopefully someone can point me in the
right direction.
Is the FFT data already processed into frequency/power?
Are the real and imaginary parts in the array? Perhaps something like
RIRIRIRI... or RRRRiii
Since i tunes can play a variety of sample rates, is the fft
performed on data that is always the same rate (say 44.1 khz)
Is there sample code for finding the strength of a given frequency
(say 440hz) from the fft data provide by iTunes? I have seen similar
code for different FFT implementation, but it looks like i need to
know a little more about the format of what iTunes provides.
This might be slightly off topic for the list, if so please point me
to the right venue.
Thank you, -justin
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