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## Real Time Pitch Tracking

Posted on 2021-05-23 12:00

## Notes

### Yin

I'm a long-time Yin user, but the algorithm seems to have some serious limitations  for realtime use in an embedded enviroment:

* The algorithm is block-based and inherently latent
* The fast version of the algorithm requires an FFT on every block
* In my experiments the algorthm slows to a crawl with a large tau_max, so detecting pitches lower than ~70-80hz seems to have a pretty big impact on performance.

### Extended Complex Kalman Filter

=> https://ccrma.stanford.edu/~orchi/Documents/ekf_dafx_updated.pdf 2017 dafx paper

Das Orchisama, Chris Chafe and JOS to the rescue maybe?

* This algorithm is designed for low-latency real time use, and computes a pitch estimate on every sample instead of every frame like Yin.
* It still requires an FFT on every block, although there is a note about some mitigations in the paper...
* Seems to perform much better than Yin: much more stable and tracks fast moment more easily

### Bell Labs Hardware Implementation

=> https://ieeexplore.ieee.org/abstract/document/1162765 1976 IEEE paper: J Dubnowski, R Schafer, L Rabiner. Real-time digital hardware pitch detector

Is this something? They call this "high-quality" but that's in 1976. Maybe it's just a basic autocorrelation approach? (EG what Yin attempts to improve on...)

I'll have to track down access, I'm curious...

### MPM / Tartini

=> https://www.cs.otago.ac.nz/tartini/A_Smarter_Way_to_Find_Pitch.pdf 200? paper: Philip McLeod & Geoff Wyvill. A Smarter Way To Find Pitch

* The "clarity" param is interesting.
* Also requires an FFT.
* Is optimized to use small block sizes though, so latency should be lower... but then you're doing that many more FFTs a second...

=> https://www.cs.otago.ac.nz/students/postgrads/tartini/papers/Philip_McLeod_PhD.pdf The primary author's PhD thesis (1980) looks like a fantastic introduction to the literature (also discussions of wavelet analysis & LPC!)

## Reading Notes

### Comparison of Pitch Trackers for Real Time Guitar Effects

=> http://dafx10.iem.at/papers/VonDemKnesebeckZoelzer_DAFx10_P102.pdf 2010 dafx paper
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