I have a webm video on my Linode VPS (Ubuntu 12.04). I prefer to convert it online rather than do it on my computer and then upload it.
For the license reason, libfaac is not supported in repository and if you don’t want to compile ffmpeg and then reinstall it, just use aac for the audio codec instead.
You must add ‘-strict experimental’ argument after the source file name.
ffmpeg -i src.webm -strict experimental -vcodec libx264 -b 250k -bt 50k -acodec aac dest.mp4