there are mobile audio "CD" players that will play DVD's
but they are specifically designed to do so and are technically
described as "Multi-media players"
a DVD is physically different from a DVD and a player not designed to read them cannot.
Most DVD players can play audio CD's Cd's loaded with mp3 files
(my car player (actually my changer) doesn't even require that the
discs be "finalized") and even DVD's loaded with mp3's, but CD players are far more limited.