bulk/batch convert mp4 and m4v files to webm via command line?

is it possible to convert mp4 and m4v to webm via command line?

I'd like to just in a bulk swoop convert my mp4 and m4v files to web so i can play them in firefox without any issues.

1 Answer

Yes, with ffmpeg and bash this is not only possible, but very easy.

Here is the command for variable bit-rate conversion for .mp4 -> .webm:

ffmpeg -i input.mp4 -c:v libvpx -b:v 1M -c:a libvorbis output.webm

You can then use the command in a bash script to batch covert your files. Here is an example of how you could do that:

#!/bin/bash
for FILE in *.mp4 ; do OUTNAME=`basename "$FILE" .mp4`.webm ffmpeg -i $FILE -c:v libvpx -b:v 1M -c:a libvorbis $OUTNAME
done

Keep in mind that depending on your computer, this may take a very long time.

And of course, this can be done for the m4v files as well. I won't guarantee everything will work since I don't have ffmpeg installed on this machine to test it, so you may need to modify the script and/or the conversion settings to suit your needs.

Documentation for the webm encoder can be found here: