When you open those .m4a or .mp4 files (never heard of .mp4a) in QuickTime Player and take a look at the Inspector window (CMD+I), what does it say there?
It's m4a. Sorry for the typo.
It says Apple Lossless, stereo.
But I don't understand, I guess it shold be ALAC file. 😕
It is an ALAC file, as ALAC stands for Apple Lossless Audio Codec. .m4a is just the container it is embedded in.
![]()
from http://en.wikipedia.org/wiki/Apple_Lossless found via search for "ALAC"
I use XLD.
Let's me do 16 conversions simultaneously.
... It looks like you're using old versions which used still the .mp4" extensions, now it is m4a.
It's m4a. ...
xACT does exactly what you want (with batch processing support).
ALAC (Apple Lossless) -> AIFF -> iTunes -> Apple Lossless.