diff --git a/docs/waveform_transforms/time_stretch.md b/docs/waveform_transforms/time_stretch.md index 8833e224..092ee877 100644 --- a/docs/waveform_transforms/time_stretch.md +++ b/docs/waveform_transforms/time_stretch.md @@ -5,6 +5,19 @@ _Added in v0.2.0_ Change the speed or duration of the signal without changing the pitch. This transform employs `librosa.effects.time_stretch` under the hood to achieve the effect. +Under the hood this uses phase vocoding. Note that phase vocoding can degrade audio +quality by "smearing" transient sounds, altering the timbre of harmonic sounds, and +distorting pitch modulations. This may result in a loss of sharpness, clarity, or +naturalness in the transformed audio, especially when the rate is set to an extreme +value. + +If you need a higher quality time stretch method, consider the following alternatives: + +* [atempo in ffmpeg](https://ffmpeg.org//ffmpeg-all.html#atempo) +* [Rubber Band library](https://breakfastquay.com/rubberband/) +* [https://github.com/KAIST-MACLab/PyTSMod](https://github.com/KAIST-MACLab/PyTSMod) +* [https://github.com/vinusankars/ESOLA](https://github.com/vinusankars/ESOLA) + ## Input-output example In this example we speed up a sound by 25%. This corresponds to a rate of 1.25.