How to plot spectrogram from fft magnitude spectrum ?

10 April 2020 0 9K Report

Hi,

I have been trying to plot a spectrogram(in c++) based on my self created Audio signal. So far by following tutorials, I have performed these operations programmatically :

1. window function (fairly trivial, e.g. Hanning)

2. FFT (FFTW would be a good choice but if licensing is an issue then go for Kiss FFT or similar)

3 .calculate log magnitude of frequency domain components (trivial: log(sqrt(re * re + im * im))

If I give my input signal to Audacity for spectrogram, I get the result as picture attached.

Now, If I want to plot spectrogram programmatically in C++ what should be the steps after calculating the log magnitude of frequency domain components.? How should I plot these log magnitude against time?

Regards,

Khubaib

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