[mad-dev] question about left channel frequency information in stereo mode

Hi there:

I met with a new problem in the stereo mode: The two channels have different sound information and I only need to detect a tone with the specific frequency in the left channel. What changes shall I make for the following formula if I have two channels and each channel has 576 units pcm information.

Thank you!

shiming

1. I use mad library to get the pcm data of a marker tone, each frame

contain 576 samples. I turned each 16 bits integer samples into floating point by divided by 32768. And I put it into a floating point array pcm[576].

2. I tried to do fourier transformation to those pcm data:

Fk = sum (pcm[i] * cos(2*pi*k*i / N))

N = 576 i: from 0 to N k: from 0 to N / 2 F[288]: is a floating point array

Thank you!

shiming

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