python-convert-m4a-to-mp3

Since my car's entertainment system only supports .mp3 files for audio, and a decent portion of my music collection is .m4a files, I created this repo for batch converting audio files.

For DRM-protected .m4p files that I purchased through iTunes, I created playlists of them, burned those to CDs, and then re-imported them as .m4a files.

Converting a .m4a file to a .mp3 file can be done easily with ffmpeg (e.g. ffmpeg -i "$m4a_file" -codec:a libmp3lame -qscale:a 1 "$mp3_file"), but this does not transfer the metadata (artist, album, song, etc.). See the bash-convert-m4a-to-mp3-NO-METADATA.sh file in this repo for an example.

Create working copy of the music files

As I would prefer not to create extraneous copies in my main music collection, I copied all of the .mp3 and .m4a files to a separate directory for processing:

SOURCE_DIR="$HOME/Music/iTunes/iTunes Media/Music"
TARGET_DIR="$HOME/Music/tmp/convert-m4a-to-mp3"
mkdir -p $TARGET_DIR
rsync -av \
  --include '*/' \
  --include '*.mp3' \
  --include '*.m4a' \
  --exclude '*' \
  "$SOURCE_DIR/" \
  "$TARGET_DIR"

Setup

Install dependencies:

Note: On my Mac, I've installed python3 with Homebrew and it is located earlier in $PATH than the system version. This means I do not have to use sudo or a python virtual environment to install packages.

python3 -m pip install pydub mutagen

Run

python3 python-convert-m4a-to-mp3.py path/to/directory/to/convert path/to/logfile.log

Depending on the size of your music collection this could take quite some time, so after it is completed, you can check for errors (adjust log file if updated above):

grep -A1 -B1 'PROBLEM WITH CONVERTING' /path/to/logfile.log