Comparison between xvid and HD?

[Graeme]

I have a HD-capable TV, but do not receive HD broadcasts (in the UK I'd have to pay a subscription fee).

I do, however, download TV programs which have been ripped from HD broadcasts then encoded with Xvid (an episode of, say, CSI, is a 350mb avi file) and the picture quality looks great to me.

I'm wondering how the picture quality of the avi file compares to the original HD broadcast. Can anyone advise?

Thanks.