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Topic: Default analyzer frequency mapping (Read 1896 times) previous topic - next topic
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Default analyzer frequency mapping

Hi!

It's been a while since I've used a forum, but here goes
I'm doing some Fourier-transform digging and as a sample project, I've implemented a small spectrum analyzer that uses audio data from the underlying sound card. The design goal is to replicate (possibly with a half-buffer delay) the results of foobar2000's integrated spectrum analyzer. Everything works pretty well, however I can't figure out the function used to map the FFT frequency bins to the bars.
On a sample (20Hz-20kHz sine wave), I've noticed that my exponential function (extrapolated from the frequency bins displayed for the 10/20/40 bar display) climbs faster on the low end, but slows down near the high end

Here's a screen shot of everything in action: http://img651.imageshack.us/img651/1808/analyzer.png

Oh, yeah, and I know the peaks are way off, but from what I can observe, foobar is cheating here as well as they all seem to fall off at constant speed after a timeout (however, given the overhead of processing a second's worth of spectrum data for peak analysis, I'd say it's an acceptable approximation for display)

Anyone got a clue as to how I can replicate the results?