Hi,
For comparison, two HD resolutions are "1080", which is 1920 x 1080 pixels, and "720", which is 1280 x 720 pixels. These are both 16:9, though. The centre 4:3 section of these two comes out as 1440 x 1080 and 960 x 720 respectively.
The resolution I'm running my MythTV system for 819-line is 1152 x 738, as covered in
this thread.
That falls neatly in between the two HD formats. So 819-line is HD. Case closed?
Cheers, Kat