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Discussion Starter · #1 ·
All,


I give up. I have tried so many different configurations and I just cannot get 24hz 1920x1080 working. I give up. I have spent hours, if not weeks trying to get this darn thing to work.


No matter what I do i get "sticking" @ 24hz. THe film is just not as smooth. So to those of you out there with an Nvidia 8700 or better with smooth 24 fps, enjoy.


The only thing at 24hz consistently right now is the fan the rope is tied to.
 

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Perfectly happy at 60hz here. Suggest joining my camp and just enjoying a movie or two. Careful with that noose.
 

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Quote:
Originally Posted by mkedda /forum/post/15525508


all,


i give up. I have tried so many different configurations and i just cannot get 24hz 1920x1080 working. I give up. I have spent hours, if not weeks trying to get this darn thing to work.


No matter what i do i get "sticking" @ 24hz. The film is just not as smooth. So to those of you out there with an nvidia 8700 or better with smooth 24 fps, enjoy.


The only thing at 24hz consistently right now is the fan the rope is tied to.


23.976
 

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Th only way to get smooth 24fps video is with a 120Hz display that will detect the 24fps inpout and then will use 5:5 pulldown to dislay each of the frames in the 24fps source 5 times so that all of the frames in the 24fos source are displayed for the same amout of time otherwise you get judder since with a 60fps display some of the frames have to displayed 3 time and other 2 times to so that they all get displayed in one second.
 

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Quote:
Originally Posted by walford /forum/post/15527138


Th only way to get smooth 24fps video is with a 120Hz display that will detect the 24fps inpout and then will use 5:5 pulldown to dislay each of the frames in the 24fps source 5 times so that all of the frames in the 24fos source are displayed for the same amout of time otherwise you get judder since with a 60fps display some of the frames have to displayed 3 time and other 2 times to so that they all get displayed in one second.

You are assuming that the display is not capable of supporting 24p natively, which is not necassarily true. IF your display supports 24p playback natively (which lots do nowadays), 24p playback is silky smooth with a 24fps source.
 

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Discussion Starter · #9 ·
kapone, i do have a 24fps capable receive, projector and video card. so, what can i do. what is wrong. short of scraping my 8700m and getting a whole new machine

Quote:
Originally Posted by kapone /forum/post/15527350


You are assuming that the display is not capable of supporting 24p natively, which is not necassarily true. IF your display supports 24p playback natively (which lots do nowadays), 24p playback is silky smooth with a 24fps source.
 

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Quote:
Originally Posted by walford /forum/post/15527138


Th only way to get smooth 24fps video is with a 120Hz display that will detect the 24fps inpout and then will use 5:5 pulldown to dislay each of the frames in the 24fps source 5 times so that all of the frames in the 24fos source are displayed for the same amout of time otherwise you get judder since with a 60fps display some of the frames have to displayed 3 time and other 2 times to so that they all get displayed in one second.

Walford this is becoming a habit.


You need 23.976Hz not 24Hz. 2:2 , 3:3 , 5:5 pulldown is irrelevant.


24hz will judder , 23.976 will be smooth.


Just as 59.94 will be somewhat smoother than 60Hz as I often point out to the people who think they are seeing 3:2 pulldown when their PCs are doing 60Hz.
 

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Mr. D I totally disagree with your analysis. Please explain your mathematical anaslysis or a web link that explains how you can display 24 fps in one second with each frame being displayed for the same amount of time so that no judder occurs. If using a dislay that refreshes at a 60fps rate that would require that each of the the 24 frames would have to be displayed 2.5 times which is obviously impossible.

The reason for 23.976 instead of 24 AFAIK is stictly to allow time for audio to be also be transmitted over an HDMI interface.
 

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First off, as Mr. D says you need to run at 23.976 or 59.94 to eliminate judder due to the audio and video clocks being different.


To save typing, I'll just use 24 (and its multiples) instead of 23.976 from now.


When you are displaying a 24 fps film on a 60 Hz display you don't show half frames, you show frames in a 3:2 cadence. I.e. one frame gets shown 3 times, the next frame gets shown twice, etc. If you have a 48/72/96/120 Hz display then you show the same frame 2/3/4/5 times sequentially.


Where most people get tripped up is they believe that when they set their video card to 23.976 that it actually runs at EXACTLY that speed. That is a false assumption. Since the reference clocks on the video cards have tolerances it is virtually guaranteed that your refresh rate will NOT be what you set it to.


The only way I know to completely eliminate judder in a PC is to use Reclock to measure the resfresh rate and then fine tune the video card timing so that the measured rate is as close to 23.976 (or a multiple or 59.94) as possible.
 

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Using 3:2 pull down with interlaced will eliminate motion blur by creating a pure 3:2 cadence data stream which is the cause of judder or slight jerkiness with 60 fps displays

For 24fps content the elimination of judder by displaying all frames the same number of which can only ge accompliushed whose display rate is = to or a multiple of 24. 120Hz can do this with 5:5 pulldown.


The following link describes the issue very well.

http://www.hdtvprimer.com/ISSUES/what_is_ATSC.html
 

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I'm not debating the fact that for a 24fps source that you need to have an integer multiple refresh rate to get the smoothest playback.


The point I was trying to make is that for an HTPC there is a second source of judder which is audio related.
 

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Quote:
Originally Posted by walford /forum/post/15532469


Using 3:2 pull down with interlaced will eliminate motion blur by creating a pure 3:2 cadence data stream which is the cause of judder or slight jerkiness with 60 fps displays

For 24fps content the elimination of judder by displaying all frames the same number of which can only ge accompliushed whose display rate is = to or a multiple of 24. 120Hz can do this with 5:5 pulldown.


The following link describes the issue very well.

http://www.hdtvprimer.com/ISSUES/what_is_ATSC.html

Here we go again. You are mixing up several different issues. That article varies between badly worded and downright incorrect.


24p runs at 23.976. It runs at 23.976 regardless of whether it's natively progressive or deinterlaced correctly for 60i (59.94) 3:2 pulldown.


To get this to run smoothly you need to display using a refresh rate that is an exact multiple of 23.976 not 24 (reclocking aside).


Vector based frame interpolation which that article poorly explains is a totally different subject but even that would ideally need to be displayed at a multiple of 23.976.


Those of us with displays limited to 60hz would be best advised to use a refresh rate of 59.94. You will still have 3:2 repeat frame judder (assuming it's correctly deinterlaced) but at least you won't have additional irregular frame repeats forced by the incorrect refresh rate to contend with.
 

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I agree with what you say. The point I have been trying to make and you have confirmed is that you will get judder unless you can do 5:5 pulldown with a 120Hz display that accepts 24 hz or as you point out should actually be sent at 23.976 hz.

I agree with you that what I like to call pixel adaptive de-interlacing is not described well.
 

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Quote:
Originally Posted by walford /forum/post/15535878


I agree with what you say. The point I have been trying to make and you have confirmed is that you will get judder unless you can do 5:5 pulldown with a 120Hz display that accepts 24 hz or as you point out should actually be sent at 23.976 hz.

I agree with you that what I like to call pixel adaptive de-interlacing is not described well.

I'm not sure we do agree.


Two issues here:


24p runs at 23.976 and you need to match that refresh rate or mulitples thereof otherwise you will get judder.


5:5 pulldown is just frame repeats: each frame repeated 5 times for a refresh rate of 119.88. What your link is suggesting is interpolating extra frames to smooth out motion presentation not merely frame repeats.


The whole notion of interpolating additional frames is a completely different issue ( and one I find completely distasteful) and is not particularly relevant to the original poster's problem. Even if you were interpolating additional frames you would still need to refresh at multiples of the original 23.976 rate otherwise you would get irregular motion presentation and you would still introduce judder. (I speak from experience)
 

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No I am not suggesting interpoloating extra frames. A 120Hz display is also capable of doing that with 60Hz source but that is separate 120Hz mode from 5:5 pulldown mode which is available on some 120Hz units and which is used with 24hz source and which repeats each frame 5 times so that each origional frame is displayed for 1/24 of a second. If the actual time to display each frame 24 times per second is less then a second since they are being sent at 23.976 I believe that that would never be noticed.
 

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Quote:
Originally Posted by walford /forum/post/15537017


No I am not suggesting interpoloating extra frames. A 120Hz display is also capable of doing that with 60Hz source but that is separate 120Hz mode from 5:5 pulldown mode which is available on some 120Hz units and which is used with 24hz source and which repeats each frame 5 times so that each origional frame is displayed for 1/24 of a second. If the actual time to display each frame 24 times per second is less then a second since they are being sent at 23.976 I believe that that would never be noticed.

I'm not entirely sure what you mean here.


If I ask you a question it might help to clarify things.


What do you think is improved by showing the same frame multiple times before moving on to the next one?


Flicker or smoothness?


Its still running at multiples of 23.976, this is the key.


My JVC HD1 frame doubles the input to 47.952 it then displays at 95.904


23.976 material takes longer than 1 sec to display 24 frames not less.


My panasonic 42PHD8 takes 23.976 and then I'm not sure how it displays it , the desktop is quite flickery but video playback looks rock solid . I doubt its using frame repeats.


If I use 24Hz as the refresh rate I get judder because every so often the graphics card has to remove a frame at irregular intervals to maintain audio sync. This is very objectionable more so than running at 59.94 with regular 3:2 pulldown repeat frames because at least with the 59.94 technique the repeat frames are in a regular pattern.


If you run at 23.976 or multiples thereof you will get smooth playback (assuming your kit is not dropping frames for other reasons and your display can accept 23.976).


The other alternative is to use Reclock and speed up the 23.976 to 24.

I don't really see the point of this when its a lot easier on the hardware to just get 23.976 correct in the first place but Reclock can sync your clocks more reliably (although EVR is supposed to do this anyway).
 

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Quote:
Originally Posted by walford /forum/post/15527138


Th only way to get smooth 24fps video is with a 120Hz display that will detect the 24fps inpout and then will use 5:5 pulldown to dislay each of the frames in the 24fps source 5 times so that all of the frames in the 24fos source are displayed for the same amout of time otherwise you get judder since with a 60fps display some of the frames have to displayed 3 time and other 2 times to so that they all get displayed in one second.

No - that is ONE way of achieving smooth 24fps (*) video not the ONLY way.


There are other displays with 48i, 48p, 72p (and I think 96p) (*) native support that use 2:2 interlaced, 2:2 progressive, 3:3 progressive or 4:4 progressive to achieve smooth replay - 120Hz is not the ONLY way.


(*) and for 24Hz and multiples there-of please read 23.976Hz and mulitples thereof - as this is also vital to avoid dropped/repeated frames every few seconds.


Broadcast TV, DVDs and Blu-ray discs use 59.94/23.976Hz refresh rates because of the frame rate changed introduced with the colour subcarrier for NTSC broadcasts in the 50s. To avoid the subcarrier (which is locked to line and field/frame rates) interfering with the sound carrier on NTSC-M broadcasts AND to avoid changing the number of lines per field or the sound subcarrier frequency (both of which would have been tricky to do compatibly) they instead changed the field/frame rate slightly - which did not cause compatibility problems.


However displaying 23.978 or 59.94 content at 24 or 60 will cause issues (though these take a bit longer to see as they are more separated in time) - however these are not the same issues caused by 3:2 cadence judder, which is constant and very obvious.
 
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