Gonna have to test this one tonight. It may very well be that I am thinking about it passing via digital, but will test to see.
Receivers typically can automatically select between digital and analog inputs, and can automatically select dts, dts-ES Discrete, dts-ES Matrix, Dolby Digital (DD) 5.1, 5.0, 4.0, etc., DD-EX, and when fed PCM, DD 2.0, or analog stereo, can apply whatever sound processing one has selected for it (e.g., DPL, DPL II, DPL IIx, none [i.e., stereo], etc.). And, when selecting dts or DD, automatically selects the proper decompression for the amount of compression applied (both dts and DD are somewhat variable in how much they can be compressed). So there are lots of things that can automatically be decoded or selected. All I am saying is that DPL cannot be "automatically" distinguished from stereo sources, as DPL is simply the decoder for the 2 channel result of "folding" 4 channels into 2 in a particular manner.
And, receivers can typically have different settings used on different inputs, so one could set up 2 channel sources from a CD player to be not processed (i.e., left as stereo), and one could set up 2 channel sources from a DVD player to be decoded as DPL (or DPL II or DPL IIx or whatever). But those things are selected by the user (or manufacturer, in the case of someone not changing the settings), they are not determined by whether or not a recording engineer encoded the signal as DPL.
