Converting WMA Files to MP3

During the pandemic lockdown in France, my son’s German teacher has been sending out listening exercises in the WMA format. WMA stands for Windows Media Audio and in our household we don’t have any Windows devices that can natively play this proprietary format. At least they are not encumbered with any digit rights management (DRM) crap. Yet I still had to come up with a means for my son to be able to listen to these files to do his assignments. He does have an iPhone, so ideally he will be able to use it and not my personal laptop while figuring out what Christina is saying in German.

As one might expect, macOS and iOS do not natively know what to do with a WMA file. My son even went so far as installing GarageBand on his phone to try and play the file as an instrument. I did a quick search and found that the most popular solution was mplayer. After installing via Homebrew, I was indeed able to play the file using

% mplayer Christina.mp3

But that was not going to do much good for him and his iPhone. But I already had a solution to recording audio from the system output: I fired up the excellent Audio Hijack application, and started an ad-hoc recording session just to record the output of mplayer. A bit heavy-handed to get a conversion, it nonetheless did what I needed to give my son a playable audio file.

A further search revealed a command-line solution using the excellent FFmpeg toolkit. I already had FFmpeg installed (again via the lovely Homebrew macOS package manager) for another project, so it took little effort to recreate the solution. Here is the Bash/Zsh script I came up with to do the work:


BIT_RATE=$(ffprobe -v error -show_entries format=bit_rate -of default=noprint_wrappers=1:nokey=1 "${INPUT}")
ffmpeg -i "${INPUT}" -vn -ar 44100 -ac 2 -ab "${BIT_RATE}" -f mp3 "${OUTPUT}"

First, we use ffprobe to identify the bit rate of the WMA file. Then we use the bit rate as an option to the ffmpeg command to convert from WMA to MP3. A WMA input file of foo/bar.wma be converted into an MP3 file named foo/bar.mp3. Short and sweet. The only remaining step is sending the file to my son via SMS or email or Apple’s quite handy AirDrop.

Alles ist gut.