So HDMI output on TV looks terrible on my custom-built rig. It's a GTX770, drivers are fully updated, and the HDMI wire is known to work. I'm using a Samsung P2370HD-1 television as my main display.
The colours are just bad. It looks like anti-aliasing is disabled universally, and the colours have terrible contrast. I've already tried the Windows colour calibration to no avail (it helped a bit, but didn't solve my problems).
When I watch a youtube video in fullscreen, however, it looks just fine. It's my windows desktop and the programs that run in that look terrible. In fact, even when I put Google Chrome into full screen mode, it looks noticeably better.
I updated windows and even installed the drivers provided by Samsung onto my computer. It's really not working out well.
I stuck a laptop with HDMI into this monitor, and it was still bad. I put the laptop into another TV and the picture came back regular! In addition, I've tired a VGA - DVI connection (it's my previous configuration), and it works out fine!
If you have a 3.5mm sound input jack on the TV, you can use DVI since the TV has that option. Then just run your sound output to the input jack with a audio cable. The DVI signal is the same digital video as HDMI.
If you are using a DVI input on the TV, it will be digital, just the same as HDMI. But...
If you are using a VGA adapter in the card's DVI-I port and running a VGA cable to the VGA port on the TV, you are using a converted analog signal. Analog display is slightly lower quality that digital, but probably not noticeable unless you had them side by side and knew what to look for.
The gfx card produces a digital signal. It uses an digital to analog converter to produce an analog (VGA) signal on the 4 extra pins of the DVI-I port. The adapter uses those signal pins. At the HDTV, the signal is once again converted back from analog to digital to produce the display on the flat panel digital TV. This double conversion can introduce some signal loss and noise to the image.