6by9 wrote: ↑
Tue Dec 10, 2019 11:31 am
Overscan support wasn't available in the kernle until July. Raspbian is a moderate chunk behind the bleeding edge as stability is the key.
When had you updated previously so that we can gauge what you've updated from?
And what are you using to play back videos?
You can use xrandr to configure overscan - it's the margins parameters. That should apply to any layer that is composed using KMS. If your app uses MMAL, IL, or DispmanX to put additional layers on the screen, then those aren't through KMS, and will be using the overscan values configured in the firmware. (The firmware attempts to set the KMS margins based on the fw settings via the kernel command line).
My install was based on 2019-09-26-raspbian-buster and updated this week. I've tried several options:
1. full RPD desktop with overscan off so on 4K TV, the screen is full and proper until I use screen configuration to change to 1080p.
2. Raspbian lite with X, Mate, lightdm. Same as #1
3. Raspbian lite with X, Openbox and xinit. xrandr was used to set the screen to 1080p. Since I don't have a desktop I can't say for sure what happens, but my application GUI and video play look proper on the screen when running. in this case it's Mythtv frontend.
I can use #3, but a full RPD system is more convenient and it doesn't get in my way. I've done all this since August, but last week some update changed the desktop so that changing the screen size for 4K to 1080p pushes the desktop off the screen a few characters so the menu is not readable. The 4K UHD TV and the RP4 has some compatibility issue that makes the default 3840x2160 /30 and that really messes with video playback and since all the videos are 1080i or 720p, reducing the screensize should make the performance better.