Android does not have great deal of control over the hdmi scaling. What I'd like to do is do "centered, fit width" scaling. So in other words, on 1920x1200 tablet top and bottom has 60 pixels cut which results in 1080p output with no scaling.
Or as an another example, ipad resolution tablet would be scaled to 1920p width with some 500 pixels dropped.
Either way, full TV screen is used. How android does it is by scaling image smaller until it will fit the target resolution. With the ipad resolution that adds up to quite big black borders. And with netflix it's even worse as you get more black borders on top of it which you'd see on the tablet screen. Not pretty.
Now my Chinese tablet has Intel chipset which has some hdmi scaling options but sadly nothing that'd result in what I'd like to see. I also have an old nexus 10 which is used for netflix / HBO nordic duty. Nexus has no hdmi settings at all.
So is there any utility or system setting to control the hdmi scaling? I have root so editing system files is no problem.
My current solution is using second screen which can scale the tablet display to a different resolution, 1920x1080 in this case. It even does automated profile switching on hdmi connect. Sadly however it does not play nice with some apps, most notably swiftkey. Nova launcher is not fond of resolution changes on the fly either. Most annoyingly top menus are difficult to reach as the "swipe from top" function is confused by the inactive screen area.
So it works but it could be better.