# HDTV question



## oscar madison (Aug 14, 2007)

I am not sure where to put this thread, so I apologize if it doesn't belong here.

I am looking to buy an HDTV and wonder if the 120hz is worth the extra 200 bones?

I can afford it, but just like anything, if I don't need it, why bother.

I have never owned an HDTV before.

Thanks


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## veryoldschool (Dec 10, 2006)

Should you want to play Blu-ray disk that are 1080p/24 at the 24 frames/sec, then a TV that supports 1080p/24 [120 Hz] would be "nice".
My HDTV is 1080p, but "only" 1080p/60, so a Blu-ray player must up-convert 1080p/24 to 1080p/60.
Some new DirecTV VOD is/will be in 1080p/24. I can watch it but need to in 1080i [which still looks great].
There is very little 1080p anything so far.
So "if I were you": I'm not sure. :lol: 
Part of me "thinks" if it's within my price range, then sure.
Part of me "thinks" if there is a TV that looks better/has features I like more, and doesn't have 1080p/24, then this would be a better choice.


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## RACJ2 (Aug 2, 2008)

This was discussed recently in the link below. Hope it helps.

http://www.dbstalk.com/showthread.php?t=145828&highlight=120hz


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## oscar madison (Aug 14, 2007)

veryoldschool said:


> Should you want to play Blu-ray disk that are 1080p/24 at the 24 frames/sec, then a TV that supports 1080p/24 [120 Hz] would be "nice".
> My HDTV is 1080p, but "only" 1080p/60, so a Blu-ray player must up-convert 1080p/24 to 1080p/60.
> Some new DirecTV VOD is/will be in 1080p/24. I can watch it but need to in 1080i [which still looks great].
> There is very little 1080p anything so far.
> ...


So the way to tell whether a TV supports 1080p/24 is it must be 120Hz?

Thanks. I'm looking at the Vizio 47" XVT 120


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## davring (Jan 13, 2007)

Not all 120 hz TV's will display 1080P24, but a set that can can display 1080P24 will most certainly be 120 hz.


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## oscar madison (Aug 14, 2007)

davring said:


> Not all 120 hz TV's will display 1080P24, but a set that can can display 1080P24 will most certainly be 120 hz.


I've went thru this whole user's manual for the 47" Vizio
http://www.vizio.com/assets/0/92/94/118/de070116-91ba-4d18-b436-f3c168e03b53.pdf and I can't tell if it will display 1080p24. What are the magic words I'm looking for?


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## davring (Jan 13, 2007)

As I understand it, many sets can accept a 1080P24 signal but convert it to 1080i to display it. At this point only a very few, usually higher end, sets can accept and properly display a true 24 fps signal.


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## oscar madison (Aug 14, 2007)

davring said:


> As I understand it, many sets can accept a 1080P24 signal but convert it to 1080i to display it. At this point only a very few, usually higher end, sets can accept and properly display a true 24 fps signal.


So, what I'm hearing is, don't waste money on 120hz b/c it most likely can't accept and properly display 1080p/24?


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## BattleZone (Nov 13, 2007)

davring said:


> Not all 120 hz TV's will display 1080P24, but a set that can can display 1080P24 will most certainly be 120 hz.


Not quite correct.

TVs in the US have always had fixed 60 Hz refresh rates. Film uses 24 frames per second, which has always required a conversion to be used on TV, and not a perfect one at that. The conversion is done by repeating the first film frame 3 times, repeating the second frame twice, the third frame 3 times, the fourth frame twice, and so on. So, of the 24 film frames, the 12 odd-numbered frames are repeated 3 times (36) and the even-numbered frames are repeated twice (24). 36+24=60. This is called a 3:2 cadence.

The problem is that you can see the timing problems when there is motion, and modern technology, with bigger, higher resolution screens and new display technologies like LCD and Plasma make it even more noticable. This problem is called "judder".

The solution would be to have the TV offer an alternate refresh rate; something that was evenly divisable by 24. And as of 2007, the first such TVs became available, and quite a few more 2008 models have this feature. This thread at Blu-Ray.com lists all TV models that are confirmed to support 24 frame content (i.e., anything shot on film) with a proper refresh rate.

But different display technologies do this at different resolutions. There are currently TVs that offer panel refresh rates of 48, 72, 96, and 120 Hz, in addition to the standard 60 Hz. All of those are multiples of 24, and, when the TV is configured properly, the TV will duplicate the film frames at the same multiple as the refresh rate. So...

48 Hz panels will refresh 24p content with a 2:2 cadence.
72 Hz panels use a 3:3 cadence
96 Hz panels use a 4:4 cadence
120 Hz panels use 5:5 cadence

But the result is the same (if properly implemented): each film frame gets displayed for 1/24th of a second, as originally intended. Judder is eliminated and motion looks smoother and more natural.

Virtually all HD transfers of film-based content are mastered at 1080/24p. This includes Blu-Ray movies and the "1080p" VoD content from DirecTV and Dish, and likely any other vendor who eventually offers 1080p content. Of course, video-based sources are shot at 60i or 60p, so sports and other live TV (i.e., anything shot on video instead of film), as well as video games and computer displays use 60 Hz refresh rates.

There are other benefits from these high-refresh-rate TVs, like Sony's MotionFlow (which, BTW, must be DISabled for 1080/24p to work right), but that's another thread.


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## veryoldschool (Dec 10, 2006)

oscar madison said:


> So, what I'm hearing is, don't waste money on 120hz b/c it most likely can't accept and properly display 1080p/24?


While you may not want to "waste your money" [I understand], the 120 Hz panel is kind of pointing to the TV being able to handle 1080p/24 & 1080p/60. Vizio isn't very clear in their manual.


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## BattleZone (Nov 13, 2007)

oscar madison said:


> So, what I'm hearing is, don't waste money on 120hz b/c it most likely can't accept and properly display 1080p/24?


You're getting confused.

As far as 1080/24p support is concerned, there are 3 categories of TVs:

1. Fixed 60 Hz refresh TVs that DON'T support 24p input signals; these TVs require the source device to convert the content to 60i (a signal the TV can understand) in order to display it. 24p content is displayed with a 3:2 cadence.

2. Fixed 60 Hz refresh TVs that DO support 24p input signals; these TVs can understand 24p input signals, but cannot display the frames at 1/24th of a second due to the 60 Hz panel, so the TV must convert these signals to 60i internally. Obviously, you can have the source device do the conversion instead, just like TVs in the first category. The result is the same: 24p content is displayed with a 3:2 cadence.

3. Variable-refresh TVs that support 24p input signals AND have a refresh mode that is a multiple of 24. These TVs can display 24p content at the proper cadence, displaying each frame for 1/24th of a second. These TVs offer the full benefit of digital HD film encoding - it's the closest thing to a real theater.

There ARE a handful of TVs that SHOULD be in the third category, because they have variable-refresh panels, but due to poor design/implementation, they don't actually display 24p content properly. Research carefully.


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## BattleZone (Nov 13, 2007)

oscar madison said:


> I've went thru this whole user's manual for the 47" Vizio
> http://www.vizio.com/assets/0/92/94/118/de070116-91ba-4d18-b436-f3c168e03b53.pdf and I can't tell if it will display 1080p24. What are the magic words I'm looking for?


This is a good example of a TV that SHOULD properly support 1080/24p, given that money was spent giving it a 120 Hz panel, but in fact does NOT refresh 24p content at a multiple of 24, nor does it appear to even accept 1080/24p input signals.

120 Hz refresh unfortunately cannot be used to guarentee proper 1080/24p support.


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## oscar madison (Aug 14, 2007)

IIP said:


> This is a good example of a TV that SHOULD properly support 1080/24p, given that money was spent giving it a 120 Hz panel, but in fact does NOT refresh 24p content at a multiple of 24, nor does it appear to even accept 1080/24p input signals.
> 
> 120 Hz refresh unfortunately cannot be used to guarentee proper 1080/24p support.


So, the words I am looking for in my research are refreshes 24p content at a multiple of 24? I didn't see that in the user's manual.

Amazon has a Sony Bravia S-Series KDL-46S4100 46-Inch 1080p LCD HDTV and a
Samsung LN46A550 46-Inch 1080p LCD HDTV which are not sold as 120 hz, but would they be comparable to the VIZIO that claims 120 hz but can't deliver b/c they are Samsung and Sony names?

Thanks so much. I am okay with paying, but if it doesn't even accept 1080p/24p input signals, why bother?


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## oscar madison (Aug 14, 2007)

IIP said:


> You're getting confused.
> 
> As far as 1080/24p support is concerned, there are 3 categories of TVs:
> 
> ...


You bet I am.


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## BattleZone (Nov 13, 2007)

oscar madison said:


> So, the words I am looking for in my research are refreshes 24p content at a multiple of 24? I didn't see that in the user's manual.
> 
> Amazon has a Sony Bravia S-Series KDL-46S4100 46-Inch 1080p LCD HDTV and a
> Samsung LN46A550 46-Inch 1080p LCD HDTV which are not sold as 120 hz, but would they be comparable to the VIZIO that claims 120 hz but can't deliver b/c they are Samsung and Sony names?


Both of these TVs are "Category 2" in my list; they accept 1080/24p signals, but have fixed 60Hz panels and have to convert the signal anyway.

To get a Category 3 TV (one that displays 24p content at a multiple of 24), you need to buy a W-series or higher Sony, or a 630 or higher Samsung.

Again, here is the definitive list:

http://forum.blu-ray.com/showthread.php?t=5155


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## TomCat (Aug 31, 2002)

IIP said:


> ...2. Fixed 60 Hz refresh TVs that DO support 24p input signals; these TVs can understand 24p input signals, but cannot display the frames at 1/24th of a second due to the 60 Hz panel, so *the TV must convert these signals to 60i internally.* ...The result is the same: 24p content is displayed with a 3:2 cadence...


Your post seemed to be the most accurate and informative one here, but I think I must take issue with the part I added my own emphasis to above. While such a TV must indeed display the frames with 3:2 pulldown (which does add judder) there is no reason for it to interlace the content. 1080p24 is progressive content, and a 1080p TV displays progressively. The addition of pulldown is the only thing needed to get from 24 fps to 60 fps, and there should be no reason to need to go to an intermediate interlaced mode to do that, or to display progressive content on a progressive display. Conversion to "60i" also implies the addition of interlace error, which I think would also not be the case, since I don't think such a conversion happens.


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## oscar madison (Aug 14, 2007)

IIP said:


> Both of these TVs are "Category 2" in my list; they accept 1080/24p signals, but have fixed 60Hz panels and have to convert the signal anyway.
> 
> To get a Category 3 TV (one that displays 24p content at a multiple of 24), you need to buy a W-series or higher Sony, or a 630 or higher Samsung.
> 
> ...


Thank you, Amazon has the W-series for 1400 and the 650 for 1555 with a free Blue-ray player. Wow, this is tempting. Taking away the taxes I'd have to pay at Sam's for the Vizio, I'm under a $25 difference with the SONY.

Thank you so much.


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## BattleZone (Nov 13, 2007)

TomCat said:


> Your post seemed to be the most accurate and informative one here, but I think I must take issue with the part I added my own emphasis to above. While such a TV must indeed display the frames with 3:2 pulldown (which does add judder) there is no reason for it to interlace the content. 1080p24 is progressive content, and a 1080p TV displays progressively. The addition of pulldown is the only thing needed to get from 24 fps to 60 fps, and there should be no reason to need to go to an intermediate interlaced mode to do that, or to display progressive content on a progressive display. Conversion to "60i" also implies the addition of interlace error, which I think would also not be the case, since I don't think such a conversion happens.


I know exactly what you mean, and though I didn't elaborate, having read over a hundred reviews from multiple sources (usually linked from AVSForum), many TVs actually DO convert to 60i, THEN convert that to 60p, instead of doing the conversion directly. It doesn't make sense to me either.

Not all TVs do this; Sony and Samsung in particular seem to be leading the way in eliminating these "not so smart" engineering choices, but other manufacturers seem to be following along. Do I need to point out that the "value brands" often take these kinds of shortcuts? Though it's hard to blame them when the big names did it first, even when they quickly correct those errors on newer models.


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