I have a Samsung pn42b450 and it is like most 42" plasma's a 1024x768 widescreen. I'm wondering if anyone can share how they have adjusted for it. Have you found better success using the Nvidia DPI setting or the Xorg display size setting.
Also if you could share what DPIs or sizes you have used with which screen/display it might be helpful to have a little database for nonstandard TV's.
According to Amazon, it's a 720p set, so its maximum resolution should be 1280x720. I drive my 40" Sony (LCD, not plasma) at that resolution with the NVIDIA control application. (My TV supports 1920x1080, but my eyes don't!) I'd stick with using the NVIDIA app unless you like mucking around with xorg.conf.
That said, I have problems with the dot pitch when I use this TV and Kubuntu. After installation I have to add an
Options "DPI" "100x100"
line in the Monitor section of xorg.conf. Otherwise the text on my screen is miniscule. I'm guessing this is some type of handshake issue where the installer can't determine the proper display characteristics (even though the Sony has a valid EDID).
In the past when I had an NVIDIA 6600 with both VGA and DVI, I could drive the screen at 1280x720 using either method. Now I have a 9500GT which has only DVI, so I use a DVI<>HDMI cable. Works fine. It appears your TV only has HDMI connectors, so you'll be using the second approach.
Just a heads up on this, I ended up with an ATI chipset not an NV.
But I am not currently able to make DisplaySize work. Xdpyinfo picks up the changed settings both the correct calculated DPI and the entered screen size settings. But it does not seem to want to use them.
I looked up that set and it's native resolution is 1024x768 (which means it uses rectangular pixels). Most sets that say they are 720p just means that have a native vertical resolution of 720 or 768 pixels. They take 1280x720 as an input (and often 1920x1080i) but scale it down to its native res of 1024x768 (so you'll lose a little horizontal information in picture but it will look like 720p). My plasma has a native resolution of 1024x768, but I'm passing it 1280x720 (it should be fairly well optimized to take that resolution for TV signals, since that's what set top boxes will send it). I know I didn't set DPI in xorg - I have to look at nvidia settings - but as your are using ATI, I'm not sure how to help - I avoid ATI like the plague.
I'm using 1024x768 since it's native, but would like to have my hulu and other images not so stretched out.
I didn't like 1280x720 in windows but i could give it a try here and see if it looks any better. Also 1366x768 might be interesting too.
I would just love to have the DPI be set to something like 54x96 though...