Real time pitch detection

Question

I'm trying to do real time pitch detection of a users singing, but I'm running into alot of problems. I've tried lots of methods, including FFT (FFT Problem (Returns random results)) and autocorrelation (Autocorrelation pitch detection returns random results with mic input), but I can't seem to get any methods to give a good result. Can anyone suggest a method for real-time pitch tracking or how to improve on a method I already have? I can't seem to find any good C / C++ methods for real time pitch detection.

Thanks,

Niall.

Edit: Just to note, i've checked that the mic input data is correct, and that when using a sine wave the results are more or less the correct pitch.

Edit: Sorry this is late, but at the moment, im visualizing the autocolleration by taking the values out of the results array, and each index, and plotting the index on the X axis and the value on the Y axis (both are divided by 100000 or something, and im using OpenGL), plugging the data into a VST host and using VST plugins isn't an option to me. At the moment, it just looks like some random dots. Am i doing it correctly, or can you please point me torwards some code for doing it or help me understand how to visualize the raw audio data and autocorrelation data.

Answer 1

Taking a step back... To get this working you MUST figure out a way to plot intermediate steps of this process. What you're trying to do is not particularly hard, but it is error prone and fiddly. Clipping, windowing, bad wiring, aliasing, DC offsets, reading the wrong channels, the weird FFT frequency axis, impedance mismatches, frame size errors... who knows. But if you can plot the raw data, and then plot the FFT, all will become clear.

Answer 2

I found several open source implementations of real-time pitch tracking

• dywapitchtrack uses a wavelet-based algorithm

• "Realtime C# Pitch Tracker" uses a modified autocorrelation approach now removed from Codeplex - try searching on GitHub

• aubio (mentioned by piem; several algorithms are available)

There are also some pitch trackers out there which might not be designed for real-time, but may be usable that way for all I know, and could also be useful as a reference to compare your real-time tracker to:

• Praat is an open source package sometimes used for pitch extraction by linguists and you can find the algorithm documented at http://www.fon.hum.uva.nl/paul/praat.html

• Snack and WaveSurfer also contain a pitch extractor