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Discussion Starter · #1 ·
First of all this post is not intended to pick apart the differences of 720p and 1080i pq.


What I want to know is: Why did ABC choose to broadcast 720p over 1080i. Or this question can be read as: Why did CBS and NBC choose to broadcast 1080i over 720p? Does one format cost more over the other to broadcast therefore affecting the network's decision?


The reason I'm asking is because my Panny STB downconverts 720p to 480p, and my TV only does 480p/1080i. So I am out of luck catching any ABC programs in HD.I wanted to clarify which network(s)is being cheap here. IMO, everthing boils down to money and it'll anger me if ABC, chose this format to save a few bucks if indeed, 720p costs less to broadcast.


Furthermore, why doesn't my TV show 720p? Infact, most TV's I've encountered advertise 1080i, so why not just broadcast in 1080i ABC? I am grateful for ABC's efforts for the other forum members that can enjoy the HD programming but at my house, we'll be at CBS...still.


Thanks







[This message has been edited by Vettster (edited 09-09-2001).]
 

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That's an interestion question with some reasonable answers. Anyway, lets get to it...


As for why ABC chose 720p, I can't answer that. Many here will say that 720p is preferable to 1080i. In many ways, they are correct. But disagree and they'll berate you, insult your equipment, or even your vision to make their point. But when it comes to perceivable resolution... I personally prefer 1080i over 720p even with my 7-inch CRT equipped HDTV.


The reason most sets cannot do 720p is because 720p, even with a lower overall resolution, requires more bandwidth and higher performance CRTs.


If I recall my numbers correctly (I may be slightly off here)...


960i requires the same bandwidth as 480p (around 31khz?)

1080i requires the same bandwidth as 540p (around 36khz?)

1440i requires the same bandwidth as 720p (around 45khz?)

2160i requires the same bandwidth as 1080p (don't know, but lots)


Now, from what I understand, 2160i and 1440i are not in the ATSC standard. The two tops are 1080i and 1080p.


Now, since I know my ballpark numbers are close to accurate, they easily explain why most sets cannot sync to 720p. 720p just requires much more bandwidth than 1080i.


Now, ABC probably didn't know that the vast majority of manufacturers would take the cheap route in the beginning to get everybody hooked. So they settled on 720p for whatever reason.


This doesn't explain why Panasonic decided to drop 720p from this year's models... you'd think the costs would have come down.


-- Robert
 

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The reason why ABC choose 720P is that Panasonic made them a deal that they couldn't refuse on the equipment necessary to deal with HDTV at the broadcasting station(s).


If you look at the topic concerning 720P a bit further down on the this Forum, I duscussed the "format war" that when on when HDTV was developed in the mid 1970's by the Japanese...specifically Sony versus Mashustia (parent of Panasonic).


Lee

 

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For an explanation of "Why 720P", read this:
http://www.alvyray.com/DigitalTV/default.htm


Alvy Ray Smith is one of the fathers of computer graphics. He invented a number of the techniques used in every 2D and 3D program, and co-founded Pixar. His software company Altamira was bought by Microsoft and he beat the drum for adoption of 720P on behalf of the computer industry.
 

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Chris,


Great link. Answers a lot of questions for me.

I'm glad my projector does 720p.


------------------

Stephen Couch
 

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Not to knock 1080i (I vastly prefer it to 720p) but the 1080i broadcast of the US open had shimmering in the lines. I have also noticed it in other broadcasts. PBS' smart traveler is among the best 1080i but it has flicker.


------------------


 

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As you increase resolution, interlace flicker gets harder to see.


Some of us see interlace artifacts on 1080i broadcasts all the time, especially video-sourced broadcasts. As many of you develop a more critical eye, you will see them as well.


I still propose that many high-action sports would look better in 60fps 480p than in 1080i. When I do, people assume that 60fps 480p has to look like 480p DVD, which typically only contains 24 unique frames of visual information and is more compressed. Then I get flamed. http://www.avsforum.com/ubb/smile.gif
 

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You get flamed becuase its a stupid suggestoin. The only thing I maybe would agree with is that 720p is better for sports. But i would for sure rather have 1080i then 480p!
 

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Do I understand this data properly than to conclude that if I purchase a Panny STB (TU-20) that I will NOT be able to see ABC in HI DEF? I have seen it mentioned that the Panny will output 720p? I am a little confused http://www.avsforum.com/ubb/frown.gif


[This message has been edited by ********* (edited 09-09-2001).]
 

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Quote:
Originally posted by *********:
Do I understand this data properly than to conclude that if I purchase a Panny STB (TU-20) that I will NOT be able to see ABC in HI DEF? I have seen it mentioned that the Panny will output 720p? I am a little confused http://www.avsforum.com/ubb/frown.gif


[This message has been edited by ********* (edited 09-09-2001).]
The TU-HDS20 will convert from any format to any format but you will need to get up to change it at the box. It will convert 720p to 1080i. I believe you can also set it to automatically convert 480i to 480p and upconvert everything else to 1080i like the other current STBs.


Tony
 

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Chris,

I had to laugh when I saw the pictures on that link...talk about MISLEADING. You would think that a 1080i picture shimmers and dances to beat the band. In fact, most good 1080i broadcasts have little or no observable interlaced artifacts visible. This argument always bugs me because the progressive camp always uses our ancient NTSC interlaced standard as a means of making people believe that interlaced 1080i is ridden with the same type and degree of interlaced artifacts. In fact, our interlaced NTSC system IS ridden with artifacts but this is certainly not the case with 1080i. When the link went on to say that 480p looks "better" than 1080i, they lost me. I left the website.


[This message has been edited by Ken Ross (edited 09-09-2001).]
 

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Quote:
Originally posted by Tony Chick:
The TU-HDS20 will convert from any format to any format but you will need to get up to change it at the box. It will convert 720p to 1080i.

Tony


Thank You. I don't like the getting up part, but glad to see it can be done http://www.avsforum.com/ubb/smile.gif




[This message has been edited by ********* (edited 09-09-2001).]
 

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ABC broadcasts an approved ATSC signal. All digital receivers that accept ATSC signals accept all signals. They output what your set can receive. I have a Mitsubishi WS-55805 HDTV upgradable set. It accepts 480p and 1080i. My Echostar 6000 receiver with 8VSB module processes the ABC 720p ATSC signal it receives OTA and outputs it as 1080i to my receiver. The 720p is downconverted to 1080i. Both 720p and 1080i are classified by ATSC as HDTV.


You just have to make sure you set the receiver software to match the signal that your HDTV monitor can display.


------------------

Mike aka Hot


[This message has been edited by Hot (edited 09-10-2001).]
 

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Quote:
Originally posted by Ken Ross:
Chris,

I had to laugh when I saw the pictures on that link...talk about MISLEADING. You would think that a 1080i picture shimmers and dances to beat the band. In fact, most good 1080i broadcasts have little or no observable interlaced artifacts visible.
I just returned from CEDIA, and as displays have improved, the flaws of 1080i have become more objectionable. How can you can tell that a display is actually resolving 1080i? When you can see the interlace artifacts. The tennis match showed nasty aliasing.


Just so you know, Alvy invented quite a bit of the technology involved in anti-aliasing.

Quote:


This argument always bugs me because the progressive camp always uses our ancient NTSC interlaced standard as a means of making people believe that interlaced 1080i is ridden with the same type and degree of interlaced artifacts. In fact, our interlaced NTSC system IS ridden with artifacts but this is certainly not the case with 1080i. When the link went on to say that 480p looks "better" than 1080i, they lost me. I left the website.
Consider cooling off and re-reading it later. Also, consider the age of the article. Current 1080i displays function a lot better than the first generation.


But it is an indisputable fact that most set manufacturers prefered 1080i over 720p because they didn't have to make their sets that much better. 720p display requires a lot more from a display device.
 

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Quote:
I just returned from CEDIA, and as displays have improved, the flaws of 1080i have become more objectionable. How can you can tell that a display is actually resolving 1080i? When you can see the interlace artifacts. The tennis match showed nasty aliasing.
The same thing happened with NTSC display devices. Once I got a Wega flat screen CRT and set it up properly, I started to notice terrible tearing artifacts I had never noticed before (even on sets that were pretty good).


Interlace artifacts on 1080i are easier to see on a Viewsonic P815 than on a typical RPTV, and will be a lot easier to see on future devices as they roll out...unless they start filtering everything, reducing effective resolution. A lose-lose proposition.
 

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Quote:
Originally posted by Michael St. Clair:

The same thing happened with NTSC display devices. Once I got a Wega flat screen CRT and set it up properly, I started to notice terrible tearing artifacts I had never noticed before (even on sets that were pretty good).
Exactly. Consider how much better a progressive scan DVD player looks than a non-progressive one on the same display. I think everyone here can agree that this is the case.


But in this case, the number of pixels is exactly the same. 480 x 720 progressive dvd lights up exactly the same number of pixels as a 480 x 720 interlaced dvd display. The ONLY difference is that one is progressive and the other is not.


Alvy's point is exactly this. You you "go by the numbers" 1080i would appear at first approximation to have advantages over 720p. But the advantages of virtually any progressive display over virtually any interlaced display especially if you consider the increased frame rate and the temporal resolution increase, then yes, 480P can look better than 1080i.


At CEDIA, we saw all sorts of scalers taking 480p DVD sources and scaling them up. In every case, except Sony's misbegotten 960i system, they were converting to a higher progressive resolution. Nobody converts to 1080i if it's possible to avoid doing so. If the advantages of progressive weren't so great, they'd be happy converting to interlaced.

Quote:


Interlace artifacts on 1080i are easier to see on a Viewsonic P815 than on a typical RPTV, and will be a lot easier to see on future devices as they roll out...unless they start filtering everything, reducing effective resolution. A lose-lose proposition.
Right. When the networks made their decision to go with 1080i, there were virtually no displays that could show the flaws of 1080i. Alvy was evaluating 480p, 720p and 1080i on computer displays, which have always been ahead of consumer electronics in resolution.
 

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I read a Gary Merson article in "The Perfect Vision" that discussed 720p vs 1080i. You can easily tell his bias when he refers to "downconverting 720p to 1080i".


But, he had some formula (rule of thumb?) for the number of viewable lines in an interlaced display. It was something like .6 or .7 of the total lines.


In the Quotes section of the link provided above, there is a similar statement:


SMPTE, 3/81 Research and development on HDTV in Japan: "Picture quality with 2:1 interlacing is almost equivalent to that of progressive scanning with 60% of the number of scanning lines."



Even though my TV supports 720p, my DTC-100 converts everything to 1080i. I'm waiting for the new Zenith STB to come out so I can finally view true 720p.
 

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The thing that just baffles the heck out of me is why some sets with naturally progressive display technologies (like the Mitsubishi DLP -- with 720p native resolution) would only accept 1080i. Doesnt' that just seem goofy? The JVC D'Ahlia is the same way. I've yet to be able to figure out whether the Panasonic DLP accepts 720p input. http://www.avsforum.com/ubb/confused.gif


------------------

Mike Kobb

(Formerly "ReplayMike", but no longer affiliated with the company; these opinions are mine alone.)
 
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