DanielRudrich / SimpleCompressor

Code and theory of a look-ahead compressor / limiter.

SimpleCompressor

Code and theory of a look-ahead compressor/limiter.

Purpose

The purpose of this project to demonstrate and describe, how a look-ahead limiter works and how to implement it. About 95%¹ of all the sources (books, internet articles and forum threads) recommend a very easy way to implement the look-ahead feature, but unfortunately, 100%² of those applications will lose their ability to limit the signal's level.

With this, I want to shed a little light on the mystery of look-ahead limiters 😉

What's in the box?

Clicking the following links brings you directly to the docs.

This repository includes:

• C++ classes
  • computation of the gain reduction from a given side-chain signal
  • look-ahead processing of the gain reduction samples
• JUCE class: a compressor class which wraps the gain reduction class into a JUCE audio processor
• JUCE example projects
  • SimpleCompressor: making use of the wrapper, implementing a compressor without look-ahead
  • LookAheadCompressor: compressor / limiter with look-ahead feature
• thirdpary classes for multi-channel samples-delays and visualization of the compressor characteristic
• a tutorial: How to implement look-ahead limiters

References

The compressor class is mainly based on this presentation:

• http://c4dm.eecs.qmul.ac.uk/audioengineering/compressors/documents/Reiss-Tutorialondynamicrangecompression.pdf

The sample delay class and visualization class is taken from the IEM Plug-in Suite

• website: https://plugins.iem.at
• source-code: https://git.iem.at/audioplugins/IEMPluginSuite

Screenshot of the LookAheadCompressor plug-in

¹ not based on scientific data, but estimated rather subjectively.

² yeah, all of them.