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ffmpeg-loudnorm-helper ffmpeg-loudnorm-helper logo

License

Command line helper for performing audio loudness normalization with ffmpeg's loudnorm1 audio filter.

Performs the loudness scanning pass of the given file and outputs the string of desired loudnorm options to be included in ffmpeg arguments. This automates the two-pass workflow that is necessary for the loudnorm filter to apply a uniform linear normalization that is desirable for keeping the original audio dynamics intact.

This program is a simpler alternative to the ffmpeg-normalize Python script.

Requirements

The program relies on ffmpeg of version >= 3.1 for its functions and expects it to be accessible from the environment.

Output of the --resample option implies ffmpeg is compiled with the SOX resampler support (libsoxr), though it is only printed and never executed.

Usage

Summary: Perform a single pass with ffmpeg-lh input.wav or use command substitution to combine both passes.

ffmpeg-loudnorm-helper is designed to work using your shell's command substitution capability. It launches an ffmpeg instance to measure the original audio loudness and then outputs the properly formatted copy-pasteable audio filter string to perform the required normalization. If the requested loudness target is provably unattainable with linear normalization, the program will warn the user. However, loudnorm is a bit picky, so there's no guarantee it will not fall back onto dynamic normalization.

Full help available with the --help switch.

Bash example

ffmpeg -i input.mov -c:v copy -c:a libopus $(ffmpeg-lh input.mov) normalized.mkv

Windows CMD example

for /f "tokens=*" %i in ('ffmpeg-lh input.mov') do ffmpeg -i input.mov -c:v copy -c:a libopus %i normalized.mkv

How to build

Developed with stable Rust with the minimal number of direct dependencies (Serde and clap).

To build the program, go to the project directory and run:

$ cargo build --release

The executable will be located at target/release/ffmpeg-lh.

Contributing

The project is open for contributions. Open an issue for bugs, ideas and feature requests.

License

ffmpeg-loudnorm-helper is licensed under GNU General Public License version 3;

See LICENSE.md for full details.

Footnotes

  1. An informative description of the filter's inner-workings by its author, Kyle Swanson. ↩