I ripped a CD to mp3 files and tried to play them using Universal Media Streamer to my Yummyha CRX-N560D stereo, but it kept coming up with “unknown format” on the stereo display.  Oddly, other mp3 files were just fine.

Solution?  My stereo only plays mp3 with a bitrate of up to 256kb/s and these files were ripped at 320kb/s.  So how to change that?  Convert them using avconv and liblame to reduce the sampling frequency. Noice!

First install the Linux libav tools thus..

sudo apt-get install libav-tools

Now convert. This command resamples the songs, e.g. song-name.mp3 to song-name-out.mp3 at 256k and then moves song-name-out.mp3 to song-name.mp3 thus overwriting the original.

for f in ./*.mp3; do avconv -i "$f" -c:a libmp3lame -b:a 256k "${f%.*}-out.mp3" && mv "${f%.*}-out.mp3" "${f%.*}.mp3"; done

The finished result is that all the files are there but now sampled at 256kb/s and play perfectly on my stereo. Sweet.