High-Level Introduction

What does the program do?

The program takes one or more input files and, by default, writes them to a folder called normalized, using an .mkv container. The reason for choosing the MKV container is that it can handle almost any codec combination without any additional configuration.

All audio streams will be normalized so that they have the same (perceived) volume according to the EBU R128 standard. This is done by analyzing the audio streams and applying a filter to bring them to a target level. This ensures that multiple files normalized with this filter will have the same perceived loudness.

Under the hood, the ffmpeg-normalize program uses ffmpeg's loudnorm filter to do this; the filter was originally written by Kyle Swanson.

How do I specify the input?

Just give the program one or more input files as arguments. It works with most media files, including video files:

ffmpeg-normalize input1.mp3

This will create a file called normalized/input1.mkv in the current directory.

What codec is chosen?

The default audio encoding method is uncompressed PCM (pcm_s16le) to avoid introducing compression artifacts.

Note

This default keeps the quality high, but will result in a much higher bitrate than you might want, for example if your input files are MP3s, and now your output is much larger.

If you want to keep the file size down, use -c:a and specify an audio codec (e.g., -c:a aac for ffmpeg's built-in AAC encoder):

ffmpeg-normalize input1.mp3 -c:a aac

This will create a file called normalized/input1.mkv in the current directory, now using the AAC codec.

How do I specify the output file name or extension?

You don't have to specify an output file name (the default is normalized/<input>.mkv), but if you want to override it, you can specify one output file name for each input file with the -o option. In this case, the container format (e.g. .wav) will be inferred from the file name extension that you've given.

Example:

ffmpeg-normalize 1.wav 2.wav -o 1-normalized.wav 2-normalized.wav

Using the -ext option, you can supply a different output extension common to all output files, e.g. -ext m4a. Example:

ffmpeg-normalize input.mp3 -c:a aac -ext m4a

This will create a file called normalized/input.m4a.

Warning

You need to make sure that the container supports the codecs used for the output. For example, you cannot place AAC audio in a WAV container.

What will get normalized?

By default, all streams from the input file will be written to the output file. For example, if your input is a video with two language tracks and a subtitle track, both audio tracks will be normalized independently.

Any video and subtitle tracks will be copied over to the output file.