unable to play aac song

I have 2 files in my ‘media’ folder; song.aac and airBag.mp4. I can successfully play airBag.mp4 using the VLC media player using this URI :rtsp://127.0.0.1:5544/vod/airBag.mp4 When I attempt to listen to the song.aac using rtsp://127.0.0.1:5544/vod/song.aac I get the error "Your input can’t be opened: VLC is unable to open the MRL ‘rtsp://127.0.0.1:5544/vod/song.aac’. How come it will stream one and not the other. Both files will play if I double click on them. Thanks again