Help with HDMI output on an older TV

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ginjabunny
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Help with HDMI output on an older TV

Post by ginjabunny » Sat Oct 22, 2016 11:21 am

Hi,

For a friend I recently set up Mint 18 Cinnamon 64bit on an old mini PC that I had behind my TV for 6 years (running XP), it's a bit slow but has an nVidia GeForce 9200 video card so works fine with video in HD, to cut down on overheads I installed LXDE and got it all working fine on my TV after initial problems fixed by changing the TV to underscan and used xrandr to set the resolution to 1280x720 (1920x1080 is too small to read from the sofa).

So I took the PC to my friends who has an old Toshiba LCD TV, it booted up straight to the desktop and there was a problem, the desktop is bigger than the display by about 20 pixels all round, so I can only just see the top the the bottom panel and the menu button is off the screen, when windows are opened full screen the title bar and controls are also off the screen, I did xrandr and it said it supports 1920x1080i and 1280x720 (and a few lower resolutions) so I tried changing it to 1080 and got a black screen, so I thought I'll login to cinnamon to see if I can tweak it, but MDM is also 1080 so I get a black screen. I checked the TV's manual and hunted through the settings and nothing about setting underscan on HDMI or amything like that.
I bodged it and put icons on the desktop so my friend could use it and left it at that for the moment.

My questions are

1) can I use xrandr (or something similar) to shrink the desktop so it actually displays smaller, like it had a 20 pixel black border round it so it appears to fit on the screen, I had a look at xrandr and don't understand the terminology it seems very complicated and can't figure out if I need to use panning or transform or something like that, I did spot something about setting xrandr to underscan as well but would that work, all very confusing.
2) can I force MDM to do 1280x720 as at the moment it seems to pick up that the TV reports it can do 1080 but obviously can't so I can't use the login screen to choose the cinnamon session.
3) if I installed the nVidia drivers could that fix my issues (I'm assuming it's the TV that's the problem).

Any input would be gratefully accepted.

deepakdeshp
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Re: Help with HDMI output on an older TV

Post by deepakdeshp » Sun Oct 23, 2016 7:21 am

Hello.
Display setings can be changed by going to syatem settings-- Display where you can change the resolution.
If I have helped you solve a problem, please add [SOLVED] to your first post title, it helps other users looking for help, and keeps the forum clean.
Regards,
Deepak

I am using Mint 19.2 Cinnamon 64 bit with AMD A8/7410 processor . Memory 8GB

rene
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Re: Help with HDMI output on an older TV

Post by rene » Sun Oct 23, 2016 7:54 am

Does the following help?

https://www.techwalla.com/articles/how- ... shiba-hdtv

If not, also try changing HDMI ports; it appears some Toshiba TVs have or had only one HDMI port configured to not overscan; HDMI1, probably.

ginjabunny
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Re: Help with HDMI output on an older TV

Post by ginjabunny » Sun Oct 23, 2016 11:12 am

@Rene thanks, but I tried all the picture settings in both HDMI ports, I have the user manual and there is nothing in the settings about enabling underscan.
Unfortunately my friend lives a long way from me so I can't easily do any testing so was trying to find someone who may have had a similar issue. I think xrandr is the way to go but can't figure out if it does what I want it too, which is output at 1280x720 but make the desktop have a 20 pixel black border so only 1240x680 usable area so we could see it properly on the screen, or something like that, not sure if it's possible. Will try to do more tests on mine.

rene
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Re: Help with HDMI output on an older TV

Post by rene » Sun Oct 23, 2016 2:27 pm

You may need to get your friend to type/test since what works on one TV generally says little about another. And I for example cannot seem to test anything locally, what with my own TV blanking on basically anything.

One I wanted to suggest though, since you may overlook it otherwise: you could try, for the relevant value of HDMI-0,

Code: Select all

xrandr --output HDMI-0 --set audio force-dvi
A TV overscans to hide edge-garbage in TV-like input but quirky as it may seem, some gladly take the above hint to give it a rest already. To consider the input computer-like.

Failing that, you may be able to get something going with, e.g.,

Code: Select all

xrandr --output HDMI-0 --size 1280x720 --fb 1240x680 --transform 1,0,-20,0,1,-20,0,0,1
if, as expected, a simple

Code: Select all

xrandr --output HDMI-0 --set underscan on
is not available. Or by installing XP on the thing again, of course. If nothing else helps, you'd need to look into generating a custom modeline (through the "cvt" command) to add to xorg.conf or by means of xrandr --newmode.

ginjabunny
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Re: Help with HDMI output on an older TV

Post by ginjabunny » Sun Oct 23, 2016 3:40 pm

@Rene thanks, these were the sorts of things I was looking into, but didn't have the time to research it while I was there and I found it pretty confusing.
Unfortunately my friend is completely non-technical, so I will try some testing here, and build up a list of stuff to try next time I'm go round (maybe in a few weeks), it's not the end of the world if it doesn't work, just annoying, it is usable as it is as they use if to watch films etc full-screen so as I left it working it's not a problem, would be nice to get it to work properly so it can be used as a PC.

WinXp is not an option any more as lots of things don't support it any more (like Google Chrome) and new stuff is never going to be developed (like streaming h264 in HTML5), this is why I put Mint on it, everything works fine, but the TV is old tech! (this shows as all the supported VGA modes are 4:3, so it must be a very early model before widescreen laptops and monitors)

trapperjohn
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Re: Help with HDMI output on an older TV

Post by trapperjohn » Sun Oct 23, 2016 5:20 pm

I had this same problem with a friend's old Sharp TV. I eventually hacked the right screen size with the xrandr --transform option using successive approximations. Yup, the manpage is a bit obtuse on the transform option. Here is an example of one of my trials (in this case an HDMI connection):
xrandr --output DVI-I-1 --transform 1.0,0,+1,0,1.0,+2,0,0,1

A similar allusion to this hack appears in answer 1 at http://askubuntu.com/questions/508358/o ... l-graphics

ginjabunny
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Re: Help with HDMI output on an older TV

Post by ginjabunny » Sun Oct 23, 2016 5:30 pm

@trapperjohn cheers, I'll give it a go :)

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