Who understands USB audio files?

In the car when I got it is an Alpine-- CDA105 -- tuner, with USB input, which I never tried until this morning.

Finally just tried it--copied some files to a USB stick, and................

Some files play, some don't. Now these are a mis--mash

Some are files converted to audio MP-3 with software---OK

Some are downloaded MP-3---MP-4 VIDEOS from Youtube

Some of these play fine, some don't. One, example, that works fine, is some Pink Floyd I downloaded in MP-4 but I have others that the thing does not recognize, so things seem to be pretty "hit and miss." These files are all in the root of the USB stick, no folders, so access should be "equal."

Thoughts, suggestions?