General 120hz and dvd question - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 13 Old 11-06-2007, 10:05 AM - Thread Starter
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I see all this hype about the 120hz LCD tv and I read that it's supposed to help with judder and what not. Isn't the way things work on a regular tv(when watching a DVD) is mpeg2 has a flag whether the material is a movie or a video and the dvd player from there knows whether to perform 3:2 pulldown or 2:2 pulldown. Assuming that is true and the output is 30 fps no matter what material is being watched then even having a 120hz tv does not eliminate the processing done by the dvd player and in result renders itself somewhat pointless?
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post #2 of 13 Old 11-06-2007, 01:29 PM
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You need a HD DVD player or an HD TV program shot and sent out in 24 fps. This is displayed without any pulldown at the player or the display on a 120 Hz display. Although 24 fps is part of the HDTV broadcast standard I have never seen this in the wild.

24 fps material displayed on a 120 fps scan rate display could provide a display of film with less jitter. The advertisements I have seen that claim that a 120 fps display provides a picture with less jitter with source material shot live at 60 fps is pure false advertising. It is the response time of the display that makes a difference with fast moving material, not the display's scan rate.

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post #3 of 13 Old 11-06-2007, 01:49 PM - Thread Starter
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Thanks for the response, I just wasn't clear on whether some DVD players actually display 24 frames. So in result the only benefit is watching DVD/BR/HDDVD movies and having both tv and source capable of 24fps, otherwise it doesn't matter?
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post #4 of 13 Old 11-06-2007, 07:44 PM - Thread Starter
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Thanks for the reply Joe,
I am aware of what happens during the 3:2 pulldown I just wasn't sure whether it happens in the dvd player or the tv. Or what dvd players are capable of bypassing 3:2 and instead just output 24 fps.
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post #5 of 13 Old 11-07-2007, 07:11 PM
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Interesting information. Does anyone know, however, with a regular DVD player and a CRT TV what the player is outputting what the TV does with that information? I'm thinking the player sends out a 480i signal in 3:2 "telecine" format (is that the right term?) at 60hz and the t.v. then displays that information by interlacing the information to form 30 images per second. It sounds like that's the set up for the judder that everyone is now trying to get rid of, because the DVD player has to combine two separate frames film for every third or fourth frame of data output in order to convert 24 fps to the 60hz the TV can accept. I think in the old days, (i.e., 10 years ago) televisions did not do any of the conversion work, they could only accept the 480i, 60hz signal they were designed to accept. A separate device like a DVD player had to do the conversions. Now the TV's are designed to do the conversion as well. Thus, the judder that one sees on a CRT tv would not be seen if one was watching the movie in a theatre (it seems like I've read elsewhere that some people like the judder because it seems more "natural" like the film was "intended" to be viewed).
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post #6 of 13 Old 11-07-2007, 10:36 PM - Thread Starter
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swimmer,
from what I know the CRT tvs have no changed, they still take 60 half frames per second and display them as such, a progressive tv is able to accept 30 frames a second and display them but no conversion happens in the CRT tv to my knowledge.
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post #7 of 13 Old 11-08-2007, 03:04 PM
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Does the interlacing necessary to convert 24fps to 480i/60hz happen within the DVD player or does a standard DVD have information that has already been interlaced at 480i/60hz? Do upconverting DVD players then "convert" this native 480i/60hz information on the disk to a different type of data, like 720p/60hz? If a new TV is able to convert a signal to its native resolution why is an upconverting DVD player an advantage--do the DVD players just do a better job of converting? Thanks for your answers.
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post #8 of 13 Old 11-08-2007, 08:56 PM
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All DVDs are, at most, 720x480 interlaced and anamorphic.
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post #9 of 13 Old 11-08-2007, 10:55 PM
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So what sort of output do you get with a regular DVD player and what sort with an upconverting player?
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post #10 of 13 Old 11-09-2007, 10:52 AM - Thread Starter
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Quote:
Originally Posted by swimmer_sf View Post

So what sort of output do you get with a regular DVD player and what sort with an upconverting player?

Regular: 720x480i=480i=60 interlaced frames per second
Progressive:720x480p=30 noninterlaced frames per second.

These are for NTSC/US
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post #11 of 13 Old 11-09-2007, 11:27 AM
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Thanks Calcvictim. My regular DVD player says it is progressive scan, but since I have a CRT TV I can't take advantage of that feature I assume. Do you know what is different then about an upconverting DVD player that supposedly creates HD output from a regular DVD? Does an upconverting player try to interpolate lines of information from what's around it and then provide pseudo 1080 or 768 or 720 resolution information to an HD flat-panel tv? Do you know if the tv could do that on it's own without an upconverting player, and whether one could do it better than another? Thanks.
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post #12 of 13 Old 11-09-2007, 03:22 PM
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Thanks, these threads look very helpful.
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post #13 of 13 Old 11-11-2007, 08:39 AM
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Regular DVD's may have material either as 480i or as 24 fps 480p.

All regular DVD players currently decode all disks initially yielding interlaced video. Those which are progressive have a second stage to create 480p including the 24 fps variety.

I don't think any 120 Hz TV's do a correct 5:5 pulldown when the incoming source is 60 fps or 480i. (They end up doing 6-4 pulldown, over which is added various blending techniques used to reduce motion blur inherent to LCD.)

No TV really displays 24 fps at any time.

You do not unconditionally need an upconverting or progressive DVD player to go with your HDTV. The TV will do any and all of the necessary conversions.

Some CRT HDTV's display DVD as 960i instead of 1080i. This is not an inherent disadvantage. You may still see a difference in quality (either way; try both) depending on whether the DVD player is sending out 480i or 480p. Some CRT HDTV's have a 1080i/540p selection that also changes 960i (if present) to 480p at the expense of making thin black gaps appear between scan lines. Try this too if you wish, but put it back to 1080i before viewing HD broadcasts.

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