FFT blues

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rouncer 104 Sep 22, 2008 at 23:55

is there another algorythm apart from the fft for doing frequency work, because the fft packs phase information with the amplitude and it makes it useless to use.

but is there a way to get the average phase in each bin as well as the average amplitude separately? cause thats exactly what i want.

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Reedbeta 168 Sep 22, 2008 at 23:59

The FFT should return an array of complex values, where the magnitude/phase of each complex number are the amplitude/phase of the associated wave.

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rouncer 104 Sep 23, 2008 at 00:25

amplitude/phase?!?

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Reedbeta 168 Sep 23, 2008 at 03:10

The magnitudes of the complex numbers are the amplitudes of the waves, and the phases of the complex numbers are the phases of the waves.

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rouncer 104 Sep 23, 2008 at 23:24

but a number is only one number… it only has an amplitude! i dont understand - what does phase mean? the differences between the adjacent bins? that doesnt make sense to me

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Reedbeta 168 Sep 24, 2008 at 00:10

No, the output of the FFT should be a complex number for each bin. As such it has two components, real and imaginary. If you think of this as a 2D vector, its length is the amplitude and its angle from the x-axis is the phase.

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rouncer 104 Sep 27, 2008 at 05:13

oh- thankyou. now i understand.

im coding a phase vocoder by the way, and its going pretty well.

im doing the filter bin approach, but now i might try the fft.