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I've got a large amount of .MKV video files which seem to all play at a very low volume - I end up having to turn the TV up all the way to hear them, which is really irritating when I switch to another channel and wake the dead because it's so loud.

What I'm looking for is a command-line method to increase the volume (so I can run it on all of them quickly) that would hopefully work regardless of the audio codec in use in the particular file. (I don't mind hard-coding the output audio though).

For reference, I'm using Ubuntu 9.04 on my server, and the files are being played back with Boxee on a Mac Mini, but the volume problem is the same on Windows too.

kinokijuf
  • 8,364
The How-To Geek
  • 6,212

2 Answers2

31

It isn't very well documented, but FFmpeg has a -vol switch which will allow you to increase volume output.

Example:

ffmpeg -i vid.mkv -vol 512 -vcodec copy output.mkv

Some things to take note of:

  • the -vol switch uses "byte percent", so you can't just specify a 200% volume increase, 100% = 256 so specifying 256 would leave the volume as is, 512 would double it and so on.
markostamcar
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14

The -vol switch is deprecated I've found this method to be useful currently:

ffmpeg -i input.mkv -vcodec copy -filter:a "volume=5.000000" output.louder.mkv

Adjust the number after volume= to suit your needs.

You can also use decibel measures. To increase the volume by 15dB: ffmpeg -i input.mkv -vcodec copy -filter:a "volume=15dB" output.louder.mkv

The -vcodec copy simply copies the video as is and -filter:a tells ffmpeg to filter the audio. Note that -vcodec can be shortened to -c:v

Sources:

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

Testing.

Elder Geek
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