Ubuntu – Ubuntu 18.04 Overscan/Underscan Issues


I am using an older flatscreen as a monitor. The issue is, it is an old enough TV that it does not have 1 to 1 pixel, or overscan/underscan options on any port except for the old VGA/PC Port, and I am connecting via HDMI from an AMD Radeon R9 290x. When I enable underscan in the settings, it makes it so the entire picture can be seen, but underscans it too much, causing the screen to be tiny, and also puts lines through the image, causing everything to look low quality, and for text to be hard to read. In addition, my TV is an old RCA L26WD26D, which supports a max resolution of 1368×768, which is also the resolution the TV manual recommends for PC connections (which Ubuntu for some reason wont let me set in the settings, without manually adding using xrandr).

So, I did the following in the terminal instead:

cvt 1366 768
    # 1368x768 59.88 Hz (CVT) hsync: 47.79 kHz; pclk: 85.25 MHz
    Modeline "1368x768_60.00"   85.25  1368 1440 1576 1784  768 771 781 798 -hsync +vsync

xrandr --newmode 1368x768_60.00 85.25  1368 1440 1576 1784  768 771 781 798 -hsync +vsync

xrandr --addmode HDMI-0 1368x768_60.00

I then went into the settings and selected the new resolution. However, it was still overscanning, and turning on underscan in the settings presented the same issue as before, so I ran the following command:

xrandr --output HDMI-0 --set underscan on

This fixed it underscanning too much, and the picture now matches the screen size exactly. However, it is still having issues with lines in the picture, making text hard to read, and all graphical elements and images look very bad. These are horizontal lines, not vertical, and I cannot find a way to make them go away, other than disabling underscanning, which makes the image too large for the screen again.

This is not an issue when I boot into Windows on the same machine, even though I am using underscanning to make the picture fit in Windows as well (however, underscanning is way more straight forward to get working right in Windows).

At this point, I would connect via VGA or DVI to get a resolution on this issue, but while my TV supports VGA, my graphics card does not, and my TV doesn't have a dedicated DVI input. I tried using a DVI to HDMI adapter on the TV, but the issue still persists. I have also tried using the amdgpu-pro drivers to see if they handle it any better than the open source drivers, but after installing, I get no image on boot, and I have to boot into recovery and issue the command "amdgpu-pro-uninstall" in the root terminal to get video working again, so that isn't an option. Any help would be greatly appreciated.