ALAC

Lossless audio compression in format that Premiere Pro can open directly:

ffmpeg -i song.wav -c:a alac song.alac.m4a

The usual toALAC script.

On a sample of 56 random songs ALAC compressed audio is 66.67% the size of original wavs.

p.s. FLAC default comes out as 61.11%. FLAC file-by-file encoding is much slower than ALAC, taking 2m45s to finish, compared to ALACs 1m40s.