A few comments: The Nyquist frequency is half the sampling rate. You are working with regularly sampled data, so you want a digital filter, not an analog filter. This means you should not use analog=True in the call to butter, and you should use scipy.signal.freqz (not freqs) to generate the frequency response. One goal of … Read more
I want to explain with picture from C3D. In a nutshell, convolutional direction & output shape is important! ↑↑↑↑↑ 1D Convolutions – Basic ↑↑↑↑↑ just 1-direction (time-axis) to calculate conv input = [W], filter = [k], output = [W] ex) input = [1,1,1,1,1], filter = [0.25,0.5,0.25], output = [1,1,1,1,1] output-shape is 1D array example) graph … Read more
This lets you give frequency, duration, and amplitude, and it is 100% .NET CLR code. No external DLL’s. It works by creating a WAV-formatted MemoryStream which is like creating a file in memory only, without storing it to disk. Then it plays that MemoryStream with System.Media.SoundPlayer. using System; using System.Collections.Generic; using System.IO; using System.Linq; using … Read more
This is challenging to explain in a single StackOverflow post. In general, the simplest beat-detection algorithms work by locating peaks in sound energy, which is easy to detect. More sophisticated methods use comb filters and other statistical/waveform methods. For a detailed explication including code samples, check this GameDev article out.
The guy that did AForge did a fairly good job but it’s not commercial quality. It’s great to learn from but you can tell he was learning too so he has some pretty serious mistakes like assuming the size of an image instead of using the correct bits per pixel. I’m not knocking the guy, … Read more
I prefer a Savitzky-Golay filter. It uses least squares to regress a small window of your data onto a polynomial, then uses the polynomial to estimate the point in the center of the window. Finally the window is shifted forward by one data point and the process repeats. This continues until every point has been … Read more
Robust peak detection algorithm (using z-scores) I came up with an algorithm that works very well for these types of datasets. It is based on the principle of dispersion: if a new datapoint is a given x number of standard deviations away from some moving mean, the algorithm signals (also called z-score). The algorithm is … Read more
I just got the FFT code working for an iPhone project: create a new project delete all the files except for main.m and xxx_info.plist going to project settings and search for pch and stop it from trying to load a .pch (seeing as we have just deleted it) copy paste the code example over whatever … Read more
The first bin in the FFT is DC (0 Hz), the second bin is Fs / N, where Fs is the sample rate and N is the size of the FFT. The next bin is 2 * Fs / N. To express this in general terms, the nth bin is n * Fs / N. … Read more