Question for Mike Knapp

In the "Please Help a Moron" thread you mentioned that HDTV and DTV are different. Could you explain the difference?

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Istagi *Feather Head*
Moderator of the Now Playing Forum
DDS-351

Currently the plans are to broadcast Digital Television in 720p or 1080I, While this falls within the prescribed guidelines of HDTV it is NOT the best that is achievable.

The current spec allows for 1020p. The broadcasters are splitting the bandwidth and giving us a lower resolution image than is possible so that they may use the remaining bandwith for advertising or a seperate standard channel.

So, while it is technically HDTV it is barely HDTV. It will still blow your socks off but you will always know it could be better.

To me it is like buying a Lexus with handcranked windows and cloth seats......it is good but it isnt using all of its potential. (BTW, I dont even think you can buy a Lexus with those options)

Mike

[This message has been edited by Mike Knapp (edited 08-11-1999).]

I understand now. I have seen some HDTV demos and yea it blew my socks off but to think it could be even better....... damn.

Thanks for the clarification

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Istagi *Feather Head*
Moderator of the Now Playing Forum
DDS-351

I realize that this is completely off the topic but.....Geez Knapp. You have as much time on your hands as I do. How many of these forums am I going to find you in?

John O from Lancaster PA

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Everyone is entitled to their opinion no matter how wrong it is

[Chromy]

DTV is a standard that encompases SDTV and HDTV. Not everyone will have a HDTV at the time of the switchover. Some stations/shows will not be good enough to qualify for HDTV.

There will be a lower quality digital television SDTV (the "S" stands for standard) that will also be used.

SDTV sets are 4:3 and 16:9 while HDTV sets are only 16:9

I think...

Not sure about the resolutions of SDTV.

Chromy

[1138]

Doesn't DTV (Digital Television) just mean that the signal is delivered digitally while HDTV (High Definition Television) means it has higher resolutions than today's standard television? For instance, Japan has for a while now had HDTV, but it is analog. Granted, all new HDTV in the U.S. is going to be digital (seem to remember that being the specs set for the format in the U.S.), but digital does not necessarily mean higher resolutions than todays TV's. Tell me if I'm completely off on this please. Thanks.

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Floyd is pink.
http://www.geocities.com/Hollywood/Lot/3924/

Mike,

You are right in stating that there is a higher resolution specification than the HDTV that we see demoed in the stores, but it's 1920 X 1080p/60Hz.

The broadcasters are not being cheap by giving us 720p or 1080i.
The bandwidth of 1080i is 19.3Mhz, and the standard TV channel bandwidth is 6Mhz (about the same as DVD).

The current compression technologies can squeeze the 19.3Mhz into the 6Mhz space, but not double that amount necessary for 1080p.

There may be a future possibility of local 1080i to 1080p line doublers, or local circuitry that takes the 1080p/24Hz HDTV film material and buffers the frames 1 to 3 to produce 1080p/72Hz.

But the projectors would have to have a horizontal scan rate of over 64Khz to make it work, as opposed to 480p SDTV (31.5Khz), 1080i HDTV (34Khz), and 720p HDTV (48Khz).

The programming information that you are talking about relates to data that can be transferred during scenes that have a low bit rates like a static logo on a black field. During those moments, the broadcasters can utilize the extra bandwidth for special services. The resulting quality should not be affected, unless the broadcaster purposly increases the compression to steal the bandwidth.

This is the same thing as MPEG2 compresion on DVDs. The discs with the best source, and highest bitrate look better, so it's a fine line for the broadcasters to walk, and they won't be able to sell HDTV if it doesn't look visibly better than DVD/DSS does.

All,

There are 18 ATSC DTV resolution standards.
DTV refers to the whole family of digital broadcasting standard resolutions and refresh rates. DTV display classification requires a HD decoder that is able to take any one of the resolutions and convert it to the display's native resolution.

HDTV refers to the top three DTV resolutions that must display over 1 million pixels, 720p, 1080i, and 1080p. Even though 1080p is not currently feasible within the 6Mhz bandwidth, it is included in the ATSC DTV standards so there is room to grow, and so the standard is not obsolete right away.

Both Japanese and European high definition broadcasts (which have been active in those countries for years) are of course true HDTV resolutions, but for discussion simplicity we only talk about the ATSC digital HD resolutions because those are the only HD standards in the U.S.

With the advent of violet-light lasers, and their massive data storage/thruput capabilities, there has been mention of a coming UDTV 3500 X 2000 resolution standard. But unless there is a similar breakthrough in display technologies, it probably won't be available as a consumer product in the forseeable future.

-Dean.

Dean,
Thanks for the info. But I liked thinking of my local affiliate as a cheap SOB that is trying to deprive me of the finer things available.

I need an enemy! I guess I will just continue to hate them for taking awat my DSS signal. hahaha

Mike

[1138]

Thanks Dean. VERY informative. Excellent.

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Floyd is pink.
http://www.geocities.com/Hollywood/Lot/3924/

[Dennis Nicholls]

In case any of you didn't know this, the ATSC has posted all of their standards in .pdf format for free downloading at

www.atsc.org

The specs are rather dense, but all the info you could ever want are there.

I'm impressed because you usually have to pay big bucks to get the real technical details about systems.