On Thu, May 1, 2008 at 9:39 AM, hard off hard.off@gmail.com wrote:
from this site, in the section titled 'group delay'
http://www.dspguru.com/info/terms/filtterm/index2.htm
i got an equation to calculate the 'group delay' of a linear FIR filter.
the equation is:
group delay = phase shift / -2pi
where phase shift is a value of radians / hz
can anyone please tell me how to calculate the phase shift with a basic FIR filter in pd?
You can take the FFT of the FIR impulse response. Then, phase = atan ( imag/real) where the real part != 0.
Then, just differentiate the result of atan with respect to f, and there's your group delay.
You can make the block size arbitrarily large to get a good enough approximation. If you have the coefficients, and you want something more exact... there's relevant theory in z-transforms, and probably a better way to do the calculations.
Chuck
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