Hi all. So, this has been bugging me since I had gotten the PS4 two weeks ago.
My setup - Onkyo TX NR818. PS4 and all devices connected via HDMI to Onkyo and HDMI to the TV.
PS4 Audio setting to Bitstream DTS.
First game - NBA 2K.
Audio only out of the two fronts and two surrounds in Bitstream mode. (DTS or Dolby)
Sporadic but frequent audio drop to the point where it is very annoying.
Onkyo is not showing PCM, which makes sense as it's the device doing the decoding in this case.
If I play with the different sound modes, of course I can get the center channel to work, but it's the Onkyo blending the mix into the center channel.
Albeit NBA2k box says Dolby Digital and DTS, there is no indication of 5.1 or other sound formats. This leads me to believe that the mix does not use center channel.
If I place a blue-ray movie into the PS4, once I kick off the movie I go to the options from the controller and within that sub-menu change the audio options (sorry, don't have the exact steps) but am able to get DTS HD Master sound. Again, using the same config as I mentioned above allowing my Onkyo to manage the sound.
Second game.. inFamous: Second Son - same config as above and this game uses the center channel.
All this is observation. I am no expert, nor claim to be, and may have used some improper terminology but I think my analysis is somewhat sound.
Hope this helps somebody.