I have a 5.1 system from Logitech connected to a Macbook Pro through a Sound Blaster Omni Surround 5.1. The setup is correct because the audio test performed by the SB Omni control panel activates correctly each speaker individually. Same with the Audio MIDI Setup utility in Mac OS X: it is configured to output 5.1 sound and it activates correctly each speaker during the test. So far so good. The problem is that when I play a movie from a DVD or iTunes, that has 5.1 sound, I have only stereo output. This affects both DVD Player and iTunes in two machines, one under Snow Leopard and one under Yosemite. I tried to open the DVD with VLC and it says that the system audio is not configured for 5.1 sound and that I have to do this through Audio MIDI Setup. But this is already configured correctly, therefore, for some reason, the Mac OS X applications fail to see the setting. Of course if I enable SBX Pro Studio enhancements in the SB Omni control panel I have audio from all speakers but if I understand well, this is only an enhancement, a kind of simulated surround sound. At this point I ran out of ideas. Anyone with suggestions, solutions? Thanks!