5.1 Audio from Stereo Sources

@XfinityAmandaB  Thanks for the reply. 

Yes, expanding stereo to 5.1 is a feature of many sound systems.   I guess the question is how Xfinity is doing the expansion.   Is it using a tool like ProLogic or Dolby Surround?  Is it duplicating the LR channels to the surrounds?  Or, is it sending the stereo signal in a 5.1 wrapper where the other channels are silent? 

Also, is there a way on the X1 to send stereo in stereo?  I can change the audio output to PCM, but doing that means genuine 5.1 and Atmos content is downmixed to stereo.  So, that's no good. 

@XfinityMartyR  Thanks.  I'm quite familiar with DD 5 1, ProLogic, and DD+, which you you didn't mention. ProLogic is a 2.0 output with the extra channels folded into the signal for extraction by the home audio processor.  It is used when the source content is multichannel.   But, with apps like Spotify and YouTube, the source content is only 2.0 to begin with, so how would ProLogic be used? 

Let's drill down a little more.  I asked which type of expansion to 5.1 the X1 is doing and your reply says i should be able to switch between DD 5.1 and PL depending on my set up and preferences.  I don't see a way to do that on my XG1v4 boxes or to even identify which format the X1 is applying.  As noted in my first post, Expert mode sends 5.1 PCM while Auto Detect sends 5.1 DD+.  So, my initial question remains, how is X1 expanding a 2.0 source into a 5.1 output. 

As for a setting to send the original stereo, my post and your reply both note that the current setting for that means actual multichannel content will be downmixed to 2.0, making that setting a non-starter.

Thanks again.