Originally Posted by bicker1
I recently was told that "matrix" is the wrong setting for 5.1... that the right setting is "stereo".
Of the four audio options available through the guide, only one setting applies to the digital output (both coax and optical), but not to digital sound over HDMI. That setting allows you to select either AC3 or PCM output. That must be set to AC3 to get 5.1 and Dolby sound to work.
All of the other options apply only to analog sound from the red and white jacks. The "matrix" setting is the equivalent of simulated surround sound. This works fairly well if your older model TV does not do its own simulated surround.
The "compression" sounds like a digital term, but it applies to analog only and means something like how wide the stereo field appears to be.
Digital output does not respond to the volume control of the Motorola boxes, so the volume is "fixed", regardless of the setting in the options. The digital output is, however, controlled by the "mute" function of the box.
For the HDMI output only, the digital sound responds to mute, but not to any settings in the guide options. To correctly set up HDMI sound, you must do so in the Motorola options, reached by turning off the box, then pressing Menu. There is an option for "Addiitonal HDMI" settings, where you must select "Auto" for sound format, otherwise 5.1 and Dolby will not work.