FreeLCS Free Loudness Correction Server
[FAQ] [Features]
[User Manual]
[Downloads]
[Changelog]
[Config Editor]
FreeLCS stands for Free Loudness Correction Server.
FreeLCS lets you automatically correct audio files to EBU R128 target
loudness level -23 LUFS. Beginning from version 3.6 it is also possible to
change the target loudness in range of -31 LUFS to -12 LUFS.
The software lets you easily set up a server that shares one of it's folders
to the network. Users of your network can then drop audio files to the
server for automatic loudness correction. For each processed file the server
also creates a loudness history graphics file which shows loudness
variations inside the file.
The software is very fast even on modest hardware giving 15 times faster
than realtime processing (16 bit stereo files, TruePeak measurement turned
on) on a server with one Intel Core 2 Duo processor, 4 GB Ram, 3 internal
Sata disks in software RAID 0.
FreeLCS uses other open source programs to get the job done (Linux,
libebur128, gnuplot, FFmpeg, sox, mediainfo). All software is free and Open
Source.
More detailed information can be found in FAQ,
Features and User
Manual.
Latest news:
2026.06.19 FreeLCS 4.1 released.
- As an afterthought I added links to the Config Editor in the documentation so that the user can start it up right there while reading the docs. Added link also to the FreeLCS homepage on Sourceforge.
2026.06.18 FreeLCS 4.0 released.
- FreeLCS is now installed and run inside the Docker environment. Installation on top of bare Ubuntu or Debian is now longer supported. This is quite a big change and completely changes how FreeLCS is configured, installed and maintained. In my opinion this makes installation and maintenance quite a bit easier.
- FreeLCS 4.0 requires installing the Docker environment.
- FreeLCS 4.0 has the same capabilities as the 3.x version of it.
- Configration is now edited and saved with a web browser. You can run it here: Config Editor
- As all configuration files and apps are stored in one directory outside Docker containers it is easy to duplicate or move FreeLCS and its configuration onto other computers.
- During installation the Ubuntu LTS Docker - image is downloaded and FreeLCS images are built upon that.
- A maintenance script is included that is able to backup FreeLCS Docker - images, delete the current ones and rebuild them with the latest Ubuntu LTS Docker - image and security updates. This script is also able to update the Docker host computer operating system if it is Ubuntu LTS. Instructions are provided how to setup periodic FreeLCS image backup and recreation with security updates.
- The preferred (and supported) operating system for the Docker host - computer is Ubuntu 26.04 LTS but it may be possible to use any other Linux distro since FreeLCS Docker images will contain all dependencies FreeLCS needs. For example I have successfully installed FreeLCS 4.0 into the Docker environment on a Arch - Linux machine.
- As it is no longer necessary to support both Debian and Ubuntu LTS distros separately, FreeLCS release cycle will change from a yearly to once every two years. The next release will be at 2028 when the next Ubuntu LTS Docker image is released (if no bugs will need attention before that).
2025.10.28 FreeLCS 3.12 released.
- This release supports Debian 13, Ubuntu 24.04.
- FFmpeg has a built in lookahead limiter (called alimiter)
and since Ubuntu 24.04 it supports channel counts more than two.
FreeLCS 3.12 uses alimiter and 4 x oversampling for TruePeak limiting
where needed. It gives a much better than before protection against
distortion when using target loudness higher than -23 LUFS (for
example -16 LUFS for social media).
- FFmpeg is now always installed since it is required for Truepeak
limiting.
- Configfile format changed from pickle to json. This makes it kind of
human readable.
Older news can be found here.
- Automatically loudness corrects audio files to conform with EBU R128
loudness recommendation.
- Very easy to use, just drop in your file and copy back the loudness
corrected version.
- Creates loudness history graphics that allows the user to see how
loudness varies inside a file (example picture below).
- Supports channel counts from mono to 5.1.
- Supports EBU TruePeak measurement.
- Uses a protective TruePeak limiter to keep peaks in the allowed range
where needed.
- Takes advantage of multiple processor cores to run calculations
simultaneously.
- User is able to define how many audio files are processed at the same
time, limited only by available cpu processing power and hard disk
bandwidth.
- Supports writing loudness measurement results to a machine readable
file.
- Modest hardware requirements, runs fine with only 6 GB of ram.
- Runs inside the Docker environment, no need to install onto a bare operating system.
- Fast processing. On typical hardware you can expect processing to be
10 - 20 faster than realtime.
- It is possible to change target loudness in the range of -31 LUFS to
-12 LUFS making it possible to adjust loudness to a level that is more
compatible with social media sites (Youtube, Spotify, etc) and mobile
devices.
- Cleans up automatically by deleting all files after a set time delay.
- Sends possible error messages to the admin by email.
- The wide range of FFmpeg supported formats can be processed.
- Support for multistream files, all audio streams are extracted and
processed individually.
- Extract audio from wrappers containing both video and audio.
- Remix audio from MXF files to required mixes before loudness
processing.
- All software is free and Open Source. Install on as many computers as
you like.
- Runs on the free Linux operating system, no need to pay for
proprietary os installation.
- Easy to integrate in many workflows.
- Written in Python 3.
- More specific information can be found in the FAQ.
Click here to go
to the download page (User manual is included in the download)
Click here to go to the User manual.
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