[raymw]

@ray - the box reads the display capabilities from the HDMI port. If it doesn't get anything it will default to 720p. You can confirm this by logging on with PuTTY and typing:

cat /sys/class/amhdmitx/amhdmitx0/disp_cap

which will display what can be read from the HDMI port.

You should see something like this if it's working correctly, and you'd get to pick from these modes.

480i
480p
576i
576p
720p
1080i
1080p
720p50hz
1080i50hz*
1080p50hz


I have read that some HDMI cables don't work correctly and a cheap fix is to use an HDMI coupler.

I have also just spotted a commit that allows you to specify a disp_cap file in the userdata folder that will be read in preference to the HDMI device. This fix is to address exactly your issue so create a file called disp_cap with the entries above and see if it makes any difference.

EDIT: it looks as though this commit is not in 14.2 or even 15.0 so it would need to be patched into a custom build. Commit is here
https://github.com/pmos69/xbmc/commit/6c...a2c56a8bb1

Thank you so much Bobones for that. Yes I realised the HDMI does handshake of course as it si a two way comms link of course. And knew these days the KODI builds do default to 720p res if no handshaking is detected form the HDMI port which is sensible to endure a non full HD display will still get a signal it can read.

Shame about the commit not being in 14.2 or even the new 15.0 either so as I am not capable of producing a custom build this will then not be possible for now.

Strange thing is I took a brand new ATV1220 box (which I understand the basic hardware is the same as his troublesome ATV1200 box) and that had no problem at all reconfiguring to his new Samsung J6300 55" curved screen TV and we could easily and readily change resolution on that in the usual System|Settings|System area as normal. This ATV1220 has the same MX Linux build Helix 14.2 as the ATV1200 box too so very very baffling indeed. As I think I said this ATV1200 box will readily change resolution on his older (only last years model) Samsung 40" set. So I took his ATV1200 box home and had no problem with it working to my 4 year old but still excellent Samsung 46" Series 6, but anyway to be safe I completely reverted his box back to Android and re-flashed it anew to MX Linux Helix 14.2 compile of April 14th 2015 (same as it had before) and reconfigured it all for him . Took it back to his house and it still will not work with changing screen res on his new J6300 TV just greyed out with 720p mode. :-(

Have tried two standard el cheapo standard HDMI leads (the ones that come with the ATV1200/1220 boxes), which made no difference and yet both worked fine on his older 40" TV. Could try a better quality HDMI lead but not hopeful on that score. He may take one of the new ATV1220 boxes I set up for him for his new J6300 TV and use the older ATV1200 on his older 40" TV in his bedroom instead of the really old single core MyGica A11 box. I particularly want to get this right for him though as he is a local friend of mine and need to know where the problem lies in case I get this very unusual baffling problem again.

Getting another ATV1200 box in for upgrading next week so could quickly take it around to his house to test that to his J6300 TV to see if that one has this same problem with the same Linux Helix14.2 compile.