Need HDTV some fundamentals (1 Viewer)

[Perry Herndon]

Hello all,
It's been a while since I've posted here. I got out of the Home Theater Stuff since I went back to school and moved into an apartment, but graduation is upon me. I once again will be a wage earner and I need a little help in spending those wages effectively
I (and some friends - and they'll be asking me since I'm the engineer) will be buying new TVs. I'm looking at rear view projectors 60" and up that are either already have an HTDV tuner or are capable of accepting the input from one later.
I've given myself the google.com refesher course - reading everything I can find. I understand the differences between progressive and interlaced scanning, and know of the multitude of resolution/framerate combinations.
My best efforts at figuring out my next question via the internet have failed.
Is the capability to display 720p a function of the TV itself or of the tuner/set top box or both?
(Same question for 1080i.)
How does an external tuner connect to the TV? Through proprietary manufacturer specific connections or through standard component inputs or computer type VGA?
I have yet to find any sets that advertise that they display 720p so I'm guessing that it is more expensive to build a set to do this and it is a function of the TV itself. So what happens if you want to watch HDTV on ABC which I'm told broadcasts in 720p on a 1080i set? Is converted and then interlaced by the TV or by the tuner/add on box?
Are there any native 720p RP sets out there? Any that do both? I'm trying to future proof (or indecisive industry proof) my purchase.
Lastly, I understand that frame rates for any of the HDTV resolutions can be 24 or 30 or 60. If the manufacturer claims 1080i capability, for instance, does that mean it will display all three framerates?
Thanks for reading!

 

[Jack Briggs]

* 720p or 1080i capability is part of the TV's duty; it must scan at the appropriate rates to be able to show either format natively. Princeton Graphics and Sampo make sets that are 720p-capable (along with 10801 and 480p). All set-top boxes are capable of receiving 1080i and 720p signals, but most sets convert a 720p signal to 1080i--not good, from a purist's point of view.

* Most digital tuners connect to the display via wideband component inputs; sometimes they connect through RGB inputs.

* Please rephrase your question about frame rates. Are you asking about 2:3 pulldown compensation?

 

[Perry Herndon]

Thanks for the reply Jack.

I may not know enough to rephrase my question intelligently.

As I understand it there are 3 different possible frame rates for each resolution. Seems like the fastest frame rate (60fps) would require the most difficult and expensive equipment to display and to trasmit (as well as use up more of the frequency spectrum).

Are the networks standardizing on one framerate for their broadcasts or are they limited by their frequency allocation? If not and they transmit programs at differing framerates how does the TV handle this?

All of the spec sheets I've seen list resolution capabilities (if you're lucky enough to find one that detailed.) There is no information regarding frame rates in a given resolution. If a manufacturer says their TV displays 1080i - does that mean that it displays 1080i at 24, 30, or 60 fps - or does it down/up convert it to the framerate capability of the television.

Hope that is clear enough, but if not bear with me. I'm not up to speed on this stuff yet, but I'll get there.

BTW - you mentioned the Sampo and Princeton Graphics sets doing 720p natively, but those are direct view sets - correct? I'm looking for something in the 60" range so I've got to go RPTV. Are there any RPTVs out there that do 720p?

Again, thanks for helping me out.

-Perry

 

[Stephen Tu]

All set-top boxes are capable of receiving 1080i and 720p signals, but most sets convert a 720p signal to 1080i--not good, from a purist's point of view

More precisely, most CRT RPTVs on the market accept 1080i signals, but not 720p. It is the set-top box that does the conversion, not the TV, in most cases (some displays will do the conversion)

Most fixed-pixel technologies (DLP, LCD, plasma) will accept 720p; they are usually natively 720p or 768p on the HD models. 1080i will be displayed at the native resolution on these sets. Again, sometimes the set-top box does the conversion, but for these displays more often the display can convert.

Re frame rates -- the 24/30/60 only refers to the signal being transmitted over the air. The set-top will always convert to 60 fields/frames per second; otherwise there would be horrible flickering on any sort of raster-scan device, like all CRTs. (A 1080i CRT RPTV is displaying 1080i, 60 fields per second) The transmission can be 24p to save bandwidth, using more bits for better PQ rather than for sending redundant fields.

 

[Marc Rochkind]

There is a distinction between:

1. What inputs a TV accepts, and

2. What it actually displays.

For instance, there are TVs that can display 1080i and take it as input, but also take 720p input, which they upconvert. Some do it better than others.

Or, the reverse... a TV that can display 720p and downconverts 1080i.

Ditto for 480p, or 480i.

Any HDTV-ready or HDTV with a tuner MUST accept both 1080i and 720p, since these are the two HDTV resolutions. All also accept 480i, which is NTSC. Most accept 480p (input from a progressive-scan DVD player).

But, what such TVs actually display is all over the map... varies with the TV.