HDTV DTT specifications - can SD DTT decoder decode HD signals?

[jumpjack]

Where can I find HDTV DTT specifications?
I'd like to understand if an SD DTT receiver could be, at least theoretically, capable of decoding an HD signal: my Samsung TV with integrated SD DTT decoder is able to identify an HD stream and to play its audio, but it says "HD not supported" and it whos a black screen, so I wonder if it could actually just be reprogrammed with a different codec!

[jagabo]

Is that an SD TV or an HD TV? Market segmentation can sometimes lead to a cheaper TV and a more expensive TV sharing the same hardware, but the cheaper TV has some features disabled in the firmware. In such a case it may be possible to enable the disabled features. But you may end up with a brick if you don't do it properly. On the other hand, the cheaper TV may simply have less powerful hardware that isn't capable of handling the more sophisticated features. Basically, unless you know what your are doing (or can find someone who does), you're playing with fire.

[jumpjack]

it's an HD TV (1280x720). When I bought it, HD DTT didn't yet exist in italy.