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filtersignal-processingfrequencyxaudio2

XAudio2 filter radian frequency

In the documentation for the XAudio2 filter parameters it mentions

Filter radian frequency calculated as (2 * sin(pi * (desired filter cutoff frequency) / sampleRate))

Can someone explain to me where that formula comes from? Because the only source of frequency conversion that would make sense to me would come from sin(f * t) and cosine(f * t) vs sin(2*pi*f * t) and cosine(2*pi*f * t) where f is a "frequency" and t is time.

Solution 
  • (2 * sin(pi * (desired filter cutoff frequency) / sampleRate))

    This value will go monotonically from 0 to 2.0 as the filter cut-off frequency goes from DC to half the sample rate.

    Digital filters scale relative to the sample rate, and your other offered options don't.