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FFMPEG - Change Audio Level In Video

Today a colleague sent me a screen-capture tutorial on using a new system. Unfortunately their microphone was way too quiet for me to hear anything so I needed to find a way to boost the audio level of the video without wanting to reduce the quality of the video.

Using ffmpeg we can re-encode just the audio to increase/decrease the audio level without re-encoding the video, which means that we won't lose video quality, and the process will be really quick. Here are the commands to do so:

Increase Audio Level

ffmpeg -i [input file] \
-vcodec copy -af "volume=10dB" \
[output file]

Decrease Audio Level

Exactly the same as before, just use a - sign.

ffmpeg -i [input file] \
-vcodec copy -af "volume=-10dB" \
[output file]

Obviously you can change 10dB to be any integer, such as 20dB, depending on your needs.