Sky Stream - PCM from iPlayer etc received via passthrough as a Dolby signal?

[POckelford]

I have the Sky Stream in passthrough mode to a capable Denon AVR. Streaming live TV it sends a 2 channel PCM signal which I can apply DTS Neural X to and it sounds great. Streaming from iPlayer, Channel4 (or any app without 5.1+) it sends a 2 channel PCM signal that mh AVR will only let me listen to in Stereo, Dolby Surround, or Multi-Channel Stereo. Even in Pure Direct mode which cuts all processing it still plays the 2 channel PCM as a Dolby Surround upmiced 5.1 - which sounds awful as the dialogue bleeds into the surround channels.

Does Sky add some sort of Dolby wrapper to the apps' PCM? Other devices output pure PCM that can have Neural X applied (and it's so much better). 

Oddly, setting the Stream to DD+ allows my receiver to use Neural X - but I'm guessing that's because the Stream has already decided the audio - rather defeating the purpose of the receiver. 

It's very frustrating!

[POckelford]

decided should read decoded. Does this forum not allow edits?

[CoffeeDrinker]

Will check this evening and see if I get the same result with my Denon X3500H AVR with Stream & iPlayer.

The PCM format dates from the early 80s at the latest; there is nothing in the specification that allows a Dolby wrapper or similar. With a PCM stereo feed over HDMI or optical/coaxial and direct mode on the AVR, playback should only happen via the front L & R speakers as you'd expect if you hooked up a CD player. Alternatively you should be able to manually select either Dolby Surround (the newer version that upmixes to 5.1/7.1/above, not the original pre Pro-:Logic Dolby Surround) or DTS Neural X (which does DTS' equivalent of the Dolby Surround upmixer).