I have a fairly large music collection, which is 9.9 GB in size. It's mainly made up of MP3 files, with some OGG Vorbis files and a handful of WAV and WMA files. I would like to convert the entire library to AAC (or a better format, if there is one) in order to reduce the size of my collection by a considerable amount.
My library is organised using this folder structure:
~/Music/{Artist}/{Album}/{Track}
Can anyone recommend a GUI tool or shellscript which would recursively convert the files, map across the metadata, and dump the files into a different folder with the same directory structure?
EDIT: I have used a script to convert everything to Opus. Problem solved, just working out the kinks now.
Converting from one lossy codec another isn't generally recommended, plus you aren't likely to save that much disk space by converting to AAC.
10 GB is actually pretty small for a local music collection, quite honestly. If I were you, I would try to expand your storage capacity instead of wasting time, and potentially audio quality, by transcoding.
If I were you, I would stick to streaming in that case.
However, if you're dead set on storing files locally and there's no other option but to transcode, then use 128kbps Opus instead of AAC - assuming that iPhones support it (I haven't checked). It's a lot more efficient.
A good converter program to use is fre:ac but don't ask me for an iOS only app because I'm not an Apple guy at all.
Edit: I agree with other commenters, that it's a bad idea to convert from one lossy codec to another one! If you want to do it anyway (and your files are at least encoded with high bitrates >192k), I'd recommend this:
The best lossy audio codec by far is opus (best perceived quality vs. small file size), which also has the benefit that it's free and has got a great open source reference implementation that is also integrated in ffmpeg. So the conversion can be done with ffmpeg. I would personally use fd-find for multithreaded batch processing (using the -x option).
On Windows, nothing beats foobar for playback, tagging, and conversion support. I use Deadbeef which is like the Foobar of Linux. It has a similar user interface and a playlist format conversion tool as well. VLC also converted audio if I remember correctly?
If you are a Mac users (which I am assuming yes based on your preference toward AAC), the program Pine Player does an excellent job with batch conversion. Otherwise FFMPEG is probably acceptable as well.
If you have access to a Mac, use the Apple AAC encoder. It will give you better results than libfdk_aac, which itself is much better than the ffmpeg built-in aac encoder.