Links to more digital TV information...

HDTV in the San Francisco Bay Area ... (a Yahoo discussion group)


The AVS Forum (best location I've found)


HDTV - High Definition Television FAQ, by Richard Gillmann
An excerpt from this page:
The 18 ATSC Digital TV Formats
Scan Lines Horizontal Pixels Aspect Ratio Frames/sec
1080 1920 16:9 60i, 30p, 24p
720 1280 16:9 60p, 30p, 24p
480 704 16:9 and 4:3 60p, 60i, 30p, 24p
480 640 4:3 60p, 60i, 30p, 24p

My notes about the table above...

60i means 60 interlaced fields per second, or 30 frames per second.
Two fields make a complete picture frame.  One contains the odd scan rows; the other contains the even rows.
Note that each pair of fields in a frame could have been recorded from the same moment in time, but are typically 1/60 of a second apart.
60p means 60 progressive frames per second.  Likewise with 24p and 30p.
All rows are scanned in one pass (row 1, 2, 3, 4, etc.) from top to bottom.  So the entire frame is  recorded at the same moment in time typically.