Adjust Audio Volume with FFmpeg Volume Filter

This article explains how to use the FFmpeg volume filter to modify the audio levels of your media files. You will learn how to increase or decrease volume using multiplier values, adjust volume precisely using decibels (dB), and apply these filters to video or standalone audio files with quick command-line examples.

To adjust volume in FFmpeg, you use the audio filter flag, written as -filter:a or abbreviated as -af, followed by the volume filter and your desired value.

Adjusting Volume with Multipliers

You can scale the audio volume by multiplying the original signal.

• Halve the volume (50% of original): Use a multiplier of 0.5.

  ffmpeg -i input.mp3 -filter:a "volume=0.5" output.mp3

• Double the volume (200% of original): Use a multiplier of 2.0.

  ffmpeg -i input.mp3 -filter:a "volume=2.0" output.mp3

Adjusting Volume with Decibels (dB)

For more precise logarithmic control, you can specify the change in decibels (dB).

• Increase volume by 6 dB:

  ffmpeg -i input.mp3 -filter:a "volume=6dB" output.mp3

• Decrease volume by 10 dB:

  ffmpeg -i input.mp3 -filter:a "volume=-10dB" output.mp3

Adjusting Audio Inside a Video File

When adjusting the audio of a video file, you can copy the video stream directly without re-encoding it. This saves processing time and preserves the original video quality. Use the -c:v copy option to achieve this:

ffmpeg -i input.mp4 -filter:a "volume=1.5" -c:v copy output.mp4