fft
How to calculate a Fourier series in Numpy?
In the end, the most simple thing (calculating the coefficient with a riemann sum) was the most portable/efficient/robust way to solve my problem: import numpy as np def cn(n): c = y*np.exp(-1j*2*n*np.pi*time/period) return c.sum()/c.size def f(x, Nh): f = np.array([2*cn(i)*np.exp(1j*2*i*np.pi*x/period) for i in range(1,Nh+1)]) return f.sum() y2 = np.array([f(t,50).real for t in time]) plot(time, y) … Read more
Improving FFT performance in Python
You could certainly wrap whatever FFT implementation that you wanted to test using Cython or other like-minded tools that allow you to access external libraries. GPU-based If you’re going to test FFT implementations, you might also take a look at GPU-based codes (if you have access to the proper hardware). There are several: reikna.fft, scikits.cuda. … Read more
Cepstral Analysis for pitch detection
Okay, let’s go through one by one: I’m looking to extract pitches from a sound signal. Although I am not an expert and have had minimal formal training, I think I know the best answer to this problem. I’ve done a lot of searching, reading, and experimenting over the past few years. My consensus is … Read more
How to generate the audio spectrum using fft in C++? [closed]
There are quite a few similar/related questions on SO already which are well worth reading as the answers contain a lot of useful information and advice, but in essence you need to do this: Convert the audio data to the format required by FFT (e.g. int -> float, with separate L/R channels); Apply suitable window … Read more
What does the FFT data in the Web Audio API correspond to?
yes,getByteFrequencyData results in a normalized array of values between 0 and 255. (it copies the data to the array it gets passed-in). the frequency bands are split equally, so each element N of your array corresponds to: N * samplerate/fftSize so, the first bin is 0. and, assuming a samplerate of 44100 and a <analyzerNode>.fftSize … Read more
Graphing the pitch (frequency) of a sound
Frequency (an objective metric) is not the same as pitch (a subjective quantity). In general, pitch detection is a very tricky problem. Assuming you just want to graph the frequency response for now, you have little choice but to use the FFT, as it is THE method to obtain the frequency response of time-domain data. … Read more
FFT library in android Sdk [closed]
You can use this class, which is fast enough for real time audio analysis public class FFT { int n, m; // Lookup tables. Only need to recompute when size of FFT changes. double[] cos; double[] sin; public FFT(int n) { this.n = n; this.m = (int) (Math.log(n) / Math.log(2)); // Make sure n is … Read more