HDMI sound issues from PC to Yamaha RX-V777


Jan 18, 2016
Hi all.
I recently got myself a new AV receiver, and it sounds great!


First: My setup.
I am connected HTPC>receiver>tv all by brand new and tested HDMI 1.4 cables.
HTPC has an AMD R9 280 graphics card, capable of 7.1 over HDMI.
All drivers are up to date as of last night.
PowerDVD 15 is used for all blu-ray / MKV playback, and is set to HDMI and "non-decoded high-definition audio to external device".
Windows audio is set to 24 bits, 48khz, which is supported by the receiver.

Second: here's what I want.
All stereo material (netflix, prime video, spotify, nowtv etc) sent to the receiver as 2 channels, where the Receiver can either leave it alone, or upmix to 5.1/7.1 with pro logic II or neo6, which it can do.
All native 5.1/7.1 content (from blu-ray, dvd, or rips of these, whether DTS HD, DD HD, AAC 5.1, whatever) sent as bitstream so that the receiver can deal with it and send it out as true surround. The receiver supports all these formats and I have tested and confirmed this.

Third: here's what I'm getting!
When PC is set to stereo: all stereo sources can be successfully upmixed to neo 6 or prologic or whatever by the receiver. Receiver screen displays 5 speaker icons and Dolby PLII.
If i switch off Dolby PL or Neo6, the receiver displays PCM and only 2(.1) speaker icons. This is correct!

Blu-rays and uncompressed MKV's (at about 40gb) of movies play in surround, and the receiver displays the 5 speaker icons, and DD-HD or DTS-HD on the display panel.
However, compressed movies, often using VBR AAC 5.1 audio, will still play as stereo, upmixed to Dolby PLII, as displayed on the front of the receiver.

If I switch windows to 5.1 or 7.1 in the sound settings, then HD sound tracks still play as a bitstream (displaying DD-HD on the receiver) and AAC 5.1 soundtracks also play correctly. However 2 channel sources such as netflix don't play nicely. The receiver displays PCM, and 5 speaker icons, however sound will only come out of the two front channels. It will also not allow me to select and sort of upmixing, with PLII and Neo6 greyed out in the menu. It almost as if windows is sending 2 channelsbof PCM and 3(.1) channels of empty data, making the receiver think it's playing surround, and therefore not letting me use PLII or neo6, as this would be pointless downmixing for a surround sound track.

So - where do i go from here?! Hopefully I have provided enough information, even if rambling!

I look forward to your responses.