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Discussion Starter · #1 ·
This really drives me insane to the point that over the years I have been slowly replacing my NTSC disks with PAL disks. I've often wondered do you HTPC guys across the pond not notice the judder or is there a way to eliminate it on a PC?


Using Theatertek 2.4 and Reclock, when I play a NTSC DVD I set my display to 48Hz and they usually play perfectly smoothly. For Pal I just set to 50Hz and all is still rosie.


I have some HD material (Gladiator and I Robot) and it also plays perfectly smooth at 48hz. But the problem is that some HD material seems to be confused as to whether it's 24fps or 29.97fps. I understand the whole process of getting 24fps to fit to 29.97, that's not the issue. I don't know why some material is seen by reclock as 24fps and other material at 29.97. The whole telecine process should have reclock seeing it all at 29.97.


Let's take a NTSC DVD for instance. For it to play smoothly on your TVs from a standard DVD player, it must have a frame rate of 29.97 (something close to half 60Hz). When I set my projector to 60Hz and feed it a NTSC DVD from a standard dvd player I get telecine stutter. This means that somebody in the mix (projector or DVD player) is not doing the 3:2 reverse pulldown thing. The only way I can get perfectly smooth playback is feed the projector 48Hz from a PC. But how the hell does that give smooth playback when the DVD should be converted to 29.97fps? Do most people using standard DVD players just put up with the microstutter or am I missing something here?


Also, what is the frame rate of HD-DVD? At either 60hz or 48hz I get very bad microstutter with PowerDVD 7.2 ultra.


So, what am I asking here?

1. Is there any way with my setup to get smooth playback of NTSC material at 60Hz? or is this as good as it gets?

2. How do I get smooth playback on HD material that is flagged at 29.97fps. I don't believe that anyone could find acceptable, the kind of judder I'm seing on this stuff


My setup is listed below.


HS60 (51A) projector

Core 2 Duo 2.4GHz

1 GB DDR2 RAM (One stick)

XFX GeForce 7900GS 525M 256MB GDDR3

Theatertek 2.4

Reclock

PowerDVD 7.2



Thanks in advance
 

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probably a result of the years of conditioning watching movies on TV all those years growing up....

 

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For the purposes of this discussion I will round up 29.97fps to 30fps, and 59.94fields/sec to 60 fields/sec. We both understand why the difference exists but it is unrelated to the problem being discussed.


The DVDs you are complaining about were probably cut from video masters, not film. Even when a movie is originally shot on film, it often goes through an intermediate digital master for the purpose of inserting digital special effects. When time comes to produce a DVD or a live TV broadcast you can avoid one whole generation of copy by using the digital master versus the film interpositive produced from it. The extra image clarity is considered worth it by most studios - even though the resulting frames are often flagged as video and the reverse telecine process cannot be used. (The digital master is also of course not subject to degradation in storage, the primary reason it is favored.)


You could choose to master at 24fps or 30fps after insertion of the graphics. In other words you could do the digital equivalent of Telecine or simply treat the material as if it were always video. If you do the latter the reverse telecine algorithym in your HTPC software player, standalone DVD player, or display cannot function because the fields are not flagged correctly for the original 24fps film, and the judder is not recoverable.


In actual fact the DVD is often a combination of correctly flagged film source scenes and incorrectly flagged video source that originated on film and then remained flagged as video. This is also the one case (badly flagged source) where standalone hardware based DVD players often outperform software players, as cadence detection is used.


The technology of your display also plays a role. For example many flat panel LCDs use flourescent backlighting locked to the powerline frequency just like old CRT interlaced direct-view sets. Such displays may have 1080p resolution but are fixed 60Hz displays that simply drop any extra frames or fields as needed. Nor can they accept 48Hz or 50Hz without an onscreen "Out of Range" indication.


I am one who notices motion judder, my original home theater display was a CRT front projector many moons ago, and I could clearly see the difference when reverse telecining film source films and refreshing at 72Hz versus 60Hz. Now I own an XGA resolution LCD front projector and a 1080p LCD flat panel, both fixed 60Hz displays. I have the worst motion judder with PAL DVDs, by the way. My projector is an older inexpensive data grade model that uses a 60Hz arc lamp as a light source. My Westinghouse 1080p monitor will not accept anything but 60Hz without complaint at 1080p native resolution, although it happily scales and reclocks other resolutions.


In my case the 1080p resolution was the overiding factor and I'm willing to tolerate the judder to get an affordable high resolution flat panel. However in the home theater I am holding out for an affordable 1080p front projector capable of minimally 72Hz or better yet 120Hz refresh. 120Hz would be ideal for both film (at 5X) and video (at 2X720p60 or 4X1080i30). I have hopes that LED or laser light source projector and flat panel technology may help with this goal.


Gary
 

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Discussion Starter · #4 ·
Thanks Gary


What an excellent reply. So for some incorrectly flagged material there is no way to avoid judder. But I see juder on all material that is flagged at 29.97fps, regardless of what refresh rate I use? (the HS60 can do 50Hz, 60Hz and 48Hz.) Is this just the way it is and people tolerate it or as jimmywhite joked, they are conditioned not to notice.


Conor
 

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The theory says that if you can enable IVCT (aka Inverse Telecine or 3:2 pulldown) and recover the original 24fps FILM frames, and then refresh your display at 48Hz, you should have smooth motion without interlacing artifacts or judder on either motion axis.


If you have VIDEO source then the 3:2 algorithym would not be in effect and horizontal motion should be smooth but with "combing" artifacts on the leading and trailing edges. Vertical motion will display the other deinterlacing artifact which is a vertical judder two lines wide. Diagonal motion displays a combination of combing and vertical judder called "stairsteps".


These video artifacts occur on progressive scanned displays when interlaced video source is being deinterlaced and displayed. Because the odd/even fields come from adjacent video frames seperated in time by 1/60th of a second, there is no way to reconstruct a complete original frame as there is with film. The combination of an odd field with an even field from the next frame via simple weave deinterlacing results in "artifacts".


In 50Hz displays film source is simply slightly speeded up and 24fps is displayed at 50Hz instead of 48Hz. Video source is originally 50Hz but subject to the same sort of artifacting as 60Hz interlaced video.


The best technique for reducing video artifacts on a HTPC is to run the adaptive deinterlacer called Dscaler. Experiment with the deinterlacing settings to produce the best picture from video source.


Judder can also be caused by an interaction between the display and the ambient lighting - if you are viewing under partial lighting conditions, try total room darkness except for the display and see if your problem goes away. If it does, you are noticing the 10Hz difference between your 60Hz video source and your 50Hz lighting - that's not really motion judder but is often mistaken for such. It that case switching your room lighting from flourescent to incandescent technology may reduce the flicker just enough to provide relief.


Gary
 

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Is there any current software to reduce judder? I have an 8800GT video card and a 60hz LCD display. HD mkv files have very noticeable judder with any panning movements.
 

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Quote:
Originally Posted by justlnluck /forum/post/15679286


Is there any current software to reduce judder? I have an 8800GT video card and a 60hz LCD display. HD mkv files have very noticeable judder with any panning movements.

holly thread dredging batman.


no you're f'd 60hz != 24hz


Movies = 24fps(23.9 really)

60/24 = 2.5 refresh per frame.


Go buy a 120hz panel then you can get it to work right.


THe original poster had a projector that took 48hz

48/24 = 2 refresh per frame == working.


If your frame rate isn't divisiable by your refresh rate you are out of luck

If your frame rate is greater than your refresh rate(60fps @ 24hz or 48hz) it will have stutter.
 

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Quote:
Originally Posted by Irish_Comer /forum/post/9545345


This really drives me insane to the point that over the years I have been slowly replacing my NTSC disks with PAL disks. I've often wondered do you HTPC guys across the pond not notice the judder or is there a way to eliminate it on a PC?


Using Theatertek 2.4 and Reclock, when I play a NTSC DVD I set my display to 48Hz and they usually play perfectly smoothly. For Pal I just set to 50Hz and all is still rosie.


I have some HD material (Gladiator and I Robot) and it also plays perfectly smooth at 48hz. But the problem is that some HD material seems to be confused as to whether it's 24fps or 29.97fps. I understand the whole process of getting 24fps to fit to 29.97, that's not the issue. I don't know why some material is seen by reclock as 24fps and other material at 29.97. The whole telecine process should have reclock seeing it all at 29.97.


Let's take a NTSC DVD for instance. For it to play smoothly on your TVs from a standard DVD player, it must have a frame rate of 29.97 (something close to half 60Hz). When I set my projector to 60Hz and feed it a NTSC DVD from a standard dvd player I get telecine stutter. This means that somebody in the mix (projector or DVD player) is not doing the 3:2 reverse pulldown thing. The only way I can get perfectly smooth playback is feed the projector 48Hz from a PC. But how the hell does that give smooth playback when the DVD should be converted to 29.97fps? Do most people using standard DVD players just put up with the microstutter or am I missing something here?


Also, what is the frame rate of HD-DVD? At either 60hz or 48hz I get very bad microstutter with PowerDVD 7.2 ultra.


So, what am I asking here?

1. Is there any way with my setup to get smooth playback of NTSC material at 60Hz? or is this as good as it gets?

2. How do I get smooth playback on HD material that is flagged at 29.97fps. I don't believe that anyone could find acceptable, the kind of judder I'm seing on this stuff


My setup is listed below.


HS60 (51A) projector

Core 2 Duo 2.4GHz

1 GB DDR2 RAM (One stick)

XFX GeForce 7900GS 525M 256MB GDDR3

Theatertek 2.4

Reclock

PowerDVD 7.2



Thanks in advance


most of my disks aren't telecined. Some are, but you get used to it.
 
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