A python project to test and evaluate different dsp algorithms
Execute the script src/main/start.py to generate pitch shifted audio. The output will be located on res/out/[song-name]_[shift]/. For each signal, the original, a reference and the results of the various pitch shift algorithm processors are stored there.
To change the number of half tones to shift, adjust the variable track_info.half_tone_steps_to_shift. To change the algorithms used, add or remove from the configs dict at the top of src/main/start.py
Add the test file to the folder res/test-data/ In main/start.py call the method pitch_shift_wav with the name of the test file
For comparison, each processed file is shifted using the rubberband audio library integrated with the pyrubberband wrapper and made available as reference track. Make sure to make the rubberband-cli available as env variable as described here bmcfee/pyrubberband#18 (comment)
| Name | Description | Status | Performance | Quality | Source |
|---|---|---|---|---|---|
| Phase Vocoder | Simple phase vocoder limited to horizontal phase propagation | Complete | Fast | acceptable for melodic, unusable for percussion | Based on DAFX Chapter 7.4.4 Block by block approach http://dafx.de/DAFX_Book_Page/index.html |
| Phase Locked Identity Vocoder | Advanced phase vocoder peak detection and horizontal / static vertical phase propagation | Complete | Med | Good results for percussion, has issue with broad harmonic envelopes | Based on Improved Phase Vocoder Time-Scale Modification of Audio Chapter III.C.2 Scaled Phase Locking https://ieeexplore.ieee.org/document/759041 |
| Phase Locked Scaled Vocoder | Advanced phase vocoder peak detection and horizontal / static vertical phase propagation | Complete | Med | Good results for percussion, has issue with broad harmonic envelopes | Based on Improved Phase Vocoder Time-Scale Modification of Audio Chapter III.C.2 Scaled Phase Locking https://ieeexplore.ieee.org/document/759041l |
| Phase Laminar Vocoder | Advanced phase vocoder with horizontal and adaptive vertical phase propagation | Complete | Slow (non-real-time) | Acceptable overall results, but lacks clairity | Based on Rubberband Source Code StretcherProcess.cpp Method: ModifyChunk https://breakfastquay.com/rubberband/ |
| Phase Locked Dynamic Vocoder | Advanced phase vocoder peak detection and horizontal / dynamic vertical phase propagation | Complete | Slow | Best overall results (except percussion). Only works for real-time with tolerance > 10**-4 | Based on Phase Vocoder Done Right pseudo code https://www.researchgate.net/publication/319503719_Phase_Vocoder_Done_Right |
Performs phase resets at percussive transients
Performs phase resets at high frequency transients
Mixes the above two detection methods. Provides the best over all results
Executes phase resets over the entire frequency range
Executes phase resets in the low and high frequency band, leaving the normal phase propagation for the mid frequency band. Provides the best over all results