How to using ffmpeg to change audio file's volume

 

How to using FFmpeg to change the audio file's volume: 

Changing volume

To change the audio volume, you may use FFmpeg's ​volume audio filter.

If we want our volume to be half of the input volume:

ffmpeg -i input.wav -filter:a "volume=0.5" output.wav

150% of current volume:

ffmpeg -i input.wav -filter:a "volume=1.5" output.wav

You can also use decibel measures. To increase the volume by 10dB:

ffmpeg -i input.wav -filter:a "volume=10dB" output.wav

To reduce the volume, use a negative value:

ffmpeg -i input.wav -filter:a "volume=-5dB" output.wav

Note that the volume filter only adjusts the volume. It does not set the volume. To set or otherwise normalize the volume of a stream, see the sections below.

Peak and RMS Normalization

To normalize the volume to a given peak or RMS level, the file first has to be analyzed using the volumedetect filter:

ffmpeg -i input.wav -filter:a volumedetect -f null /dev/null

Read the output values from the command line log:

[Parsed_volumedetect_0 @ 0x7f8ba1c121a0] mean_volume: -16.0 dB
[Parsed_volumedetect_0 @ 0x7f8ba1c121a0] max_volume: -5.0 dB
...

... then calculate the required offset, and use the volume filter as shown above.

Loudness Normalization

If you want to normalize the (perceived) loudness of the file, use the ​loudnorm filter, which implements the EBU R128 algorithm:

ffmpeg -i input.wav -filter:a loudnorm output.wav

This is recommended for most applications, as it will lead to a more uniform loudness level compared to simple peak-based normalization. However, it is recommended to run the normalization with two passes, extracting the measured values from the first run, then using the values in a second run with linear normalization enabled. See the loudnorm filter documentation for more.

Automatization with ffmpeg-normalize

To automate the normalization processes with ffmpeg without having to manually perform two passes, and run normalization on multiple files (including video), you can also use the ​ffmpeg-normalize Python program via pip install ffmpeg-normalize.

The script defaults to EBU R128 normalization with two passes, but peak and RMS normalization are also supported.

For details, run ffmpeg-normalize -h or see the README file.

Reference: https://trac.ffmpeg.org/wiki/AudioVolume