Why is interlaced still around?

[jmann]

I know there must be a good explanation, so I hope someone could fill me in: NTSC(30i) is interlaced, because it is a 70 year old legacy standard, and there was origionally a good reason for interlaced video. However when HD and digital standards were developed, why was it included in the new standards? With video being viewed now on native progressive displays (LCD, Plasma, etc.), it seems to me that interlacing and then having to de-interlace everything is stupid. But The people who develop these stands are smart, so there must be a good reason- what is it?

[edDV]

In this order.

Cost
Bandwidth
Compatibility

Moving to progressive was left as an option in ATSC.

720x480p/60 (EDTV) *
1280x720p/60 (ABC, ESPN and FOX went this way)
1920x1080p/24 **

* 480p is possible but almost nobody is broadcasting it. Most all SD is 480i

** possible to broadcast this but 19Mb/s is barely adequate. Broadcasters would rather do 1080i plus one or two SD channels. 1920x1080p/24 could only be used for movies. It isn't adequate for live action.

There will be a second generation of ATSC standards based on MPeg4. Only then will all progressive broadcasting at 1920x1080p/60 become practical.

[uxbridge]

DTV and HDTV standards are quite old in design.
They were therefore developed to be viewed on interlaced CRT display, since at the time there was no real idea of what is the current invasion and inflation of plasma and LCD digital displays.