Adjust Audio Volume by Decibels with FFmpeg

This article explains how to use the FFmpeg volume filter to precisely adjust the audio levels of your media files using decibels (dB). You will learn the correct command-line syntax to both increase and decrease audio volume, while preserving the video quality of your files without unnecessary re-encoding.

To adjust audio volume using decibels in FFmpeg, you need to use the audio filter option, represented by -filter:a or the shorthand -af. The volume adjustment is specified by passing the desired decibel value followed by dB to the volume filter.

How to Increase Audio Volume

To increase the volume, specify a positive decibel value. For example, to boost the audio by 6 decibels, use the following command:

ffmpeg -i input.mp4 -filter:a "volume=6dB" -c:v copy output.mp4

How to Decrease Audio Volume

To lower the volume, use a negative decibel value. For example, to reduce the audio level by 10 decibels, run:

ffmpeg -i input.mp4 -filter:a "volume=-10dB" -c:v copy output.mp4

Command Breakdown

• -i input.mp4: Defines the path to your input video or audio file.
• -filter:a "volume=XdB": Applies the audio filter. Replace X with a positive or negative number to scale the decibels.
• -c:v copy: Instructs FFmpeg to stream copy the video. This prevents the video from being re-encoded, which saves processing time and preserves the original video quality.
• output.mp4: The name of the newly generated file with the adjusted audio levels.