I assume then, that input source selection is made by the ARM by controlling the input souce to the DSP, either by a DSP input selection, or by controlling input selection to a single multiple-input pre-amp (which has pre-set input gains for each input, such as the radio - again under ARM control?)?

If this is the case, then when the user selects input source on the menu, the ARM must actively set the input channel for the DSP, and then de-activate the visuals, presumably since the MP3 player is paused when the input source changes.

Can the visuals not be left active (even though they no longer have an activity stimulus from the MP3 player) when the select takes place, even if the MP3 player is no longer active as input source to the DSP?