Increase Volume of an MKV Video from Linux Terminal

Question

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.

Answer 1

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 -acodec copy output.mkv

Some things to take note of:

• specifying copy in for -acodec will copy the raw codec data from the original file, if you wish to use another audio codec you must change that.
• 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.