I’m ditching streaming services and just going with local music. However all my CDs are converted to either flac or 320kbps mp3 files on my PC and thus far too large for the limited storage I have on my phone.
I was hoping there might be an app that would automatically downconvert to something like 128kbps and then copy over to the Music directory on my phone. A bit like how Calibre can automatically convert eBook files (e.g. mobi to epub) and then send them to your ereader?
If your device supports it, you might want to encode to Opus instead. Opus produces much higher quality files at much smaller file sizes than MP3.
For example, Opus at 128kbps is considered transparent when compared to the source file. You can probably go down to 64-96kbps when its just for playback in your car.
https://wiki.xiph.org/Opus_Recommended_Settings
As for transcoding them, you might want to check out ffmpegfs: https://github.com/nschlia/ffmpegfs
It can create a “virtual” drive based on your source files and automatically transcodes them when you drag & drop files from there onto your device.