I have a Marantz AV7704, which is up to date firmware wise. I was testing the upmixing capabilities of my new 4 height channels. For source material I was using Xfinity and Avengers Ultron, and then Deadpool 2. Both I believe are Dolby 5.1, at least off of Xfinity. My test was to find action scenes and try DTS-X and Dolby, turning off the 7 floor standing speakers and only listening to the height channels. In both of the content I could see (under info) that it was upmixing from 5.1 to 7.1.4. Unfortunately there was no sound coming out of the height speakers on DTS-X, but there was a low volume of some sound effects coming from the height speakers when Dolby was selected. In doing some research I found a bunch of articles from May & June of 2018 where Dolby was choosing to restrict non-native upmixing. Did this ever go into effect? Would the latest Marantz Firmware update have enabled this "feature?" Is there a reasonable hack to get around it? Perhaps having the cable box or Blu Ray player decode the Dolby and send it to the AV7704 decoded. Who in the Dolby Labs marketing department needs to be convinced of the stupidity of this decision and ill-will this causes? I will search my limited Blu-ray collection for some DTS material and see whether these will work with DTS-X upmixing as well.