I have some albums that were ripped in wma form (yes a shame I know) and have since lost the original CDs. I wanted them converted into mp3 so my collection remains consistent and they also could work in my car.
So this would be a command to run in a folder filled with .wma files. This keeps the names but not the tags so be sure to use something like easytag to fill them after.
for i in *.wma ; do mplayer -vo null -vc dummy -af resample=44100 -ao pcm:waveheader "$i" && lame -m j -h -vbr-new -b 320 audiodump.wav -o "`basename "$i" .wma`.mp3"; done; rm -f audiodump.wav
Reencoding from a lossy to another lossy format is a bad idea. Only use it if no other option remains.