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csteinmetz1 / pyloudnorm

Flexible audio loudness meter in Python with implementation of ITU-R BS.1770-4 loudness algorithm
https://www.christiansteinmetz.com/projects-blog/pyloudnorm
MIT License
650 stars 56 forks source link

(request) Meter and normalization for true-peak level #61

Open spencerwilson opened 8 months ago

spencerwilson commented 8 months ago

Hello! I'm using this library to prepare audio for broadcast. Distributors like Apple Music request the following:

To prevent such content-driven volume adjustments, we recommend that the audio signals are preconditioned so the overall loudness remains around -16 dB LKFS, with a +/- 1 dB tolerance, and that the true-peak value doesn’t exceed -1 dB FS. The LKFS and true-peak values are calculated according to the ITU-R BS.1770-4 recommendation. The preconditioning steps need to occur before the encoding process. We recommend this because audio compression algorithms typically don’t modify the loudness and might clip the signal if the recommended true-peak value is not respected.

My understanding is that pyloudnorm doesn't contain the functions to measure true-peak level, but it could be a natural addition to the library since it's also part of BS.1770.

spencerwilson commented 8 months ago

If true-peak metering isn't in scope of this package, users can consider the implementation in essentia: https://essentia.upf.edu/reference/std_TruePeakDetector.html