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confused about 24fps .. pls help.

post #1 of 6
10/20/09 at 5:06pm
Thread Starter 
Given that HDTV can handle 24fps @ 24hz or multiples of it (48hz, 96hz, etc) natively. My HTPC outputs 1920x1080 or 1920x1200 @ 60hz to the TV.

If I play Blu Ray rips that are encoded to 720P @ 23.9fps or 1080P @ 24.9 fps, what would be the end result on the TV? Will there be stutter when screens are moving fast?

If there are stutters shown on the TV, in order to reduce it, do I need to adjust refresh rate to multiple of 24 in the video card?

Thanks.
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post #2 of 6
10/20/09 at 5:33pm
Quote:
Originally Posted by Hawk_Eye View Post

Given that HDTV can handle 24fps @ 24hz or multiples of it (48hz, 96hz, etc) natively. My HTPC outputs 1920x1080 or 1920x1200 @ 60hz to the TV.

If I play Blu Ray rips that are encoded to 720P @ 23.9fps or 1080P @ 24.9 fps, what would be the end result on the TV? Will there be stutter when screens are moving fast?

If there are stutters shown on the TV, in order to reduce it, do I need to adjust refresh rate to multiple of 24 in the video card?

Thanks.

Yes there indeed would be judder...Some people seem to notice it more than others.

Google 2:3 Pulldown it will expain it. Here is quick link I found.

http://www.zerocut.com/tech/pulldown.html

IMO you should run 24p (23.976) fps or even multiples of, if your display is capable. I have an old CRT projector, it will not sync at 24p so the next best thing is running even multiples, hence I run 71.928Hz refresh so each frame is painted 3 times, 48Hz flickers too much IMO. I run all my film based material at that rate. Software like Reclock filter will help insure you maintain 24p. One caveat, Reclock will only run on 32 bit systems as of right now.

http://reclock.free.fr/

Slysoft (AnyDVD) now owns Reclock...And they give it away.

http://forum.slysoft.com/showthread.php?t=19931

IMO many people with displays capable of 24p ignore this issue with HTPC’s.


Mike
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post #3 of 6
10/20/09 at 6:55pm
Thread Starter 
Quote:
Originally Posted by MikeEby View Post

Yes there indeed would be judder...Some people seem to notice it more than others.

Google 2:3 Pulldown it will expain it. Here is quick link I found.

http://www.zerocut.com/tech/pulldown.html

IMO you should run 24p (23.976) fps or even multiples of, if your display is capable. I have an old CRT projector, it will not sync at 24p so the next best thing is running even multiples, hence I run 71.928Hz refresh so each frame is painted 3 times, 48Hz flickers too much IMO. I run all my film based material at that rate. Software like Reclock filter will help insure you maintain 24p. One caveat, Reclock will only run on 32 bit systems as of right now.

http://reclock.free.fr/

Slysoft (AnyDVD) now owns Reclock...And they give it away.

http://forum.slysoft.com/showthread.php?t=19931

IMO many people with displays capable of 24p ignore this issue with HTPC's.


Mike

Thank you. I think your answer coincide with what I have been reading. I think people ignore it because it a) they don't know anything about frame rate and just like the latest and the greatest b) even if they knew about it, they do not want to be bothered since there are some tiwickings involved. c) and this would be my case, that I may not want to change or twick different settings on my PC or on TV set every time I play Blu Ray rips (as some are encoded differently than others).. That would be too tiddious.
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post #4 of 6
10/21/09 at 6:51am
What make/model HDTV do you have? In the US many HDTVs only refresh at 60fps and some newer models display only at 120 fps. If you have a model that can display at a multiple of 24 then it may also have a "PC mode'" for receiving 1080p/24 content so you you don't have to use 23(23.976).
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post #5 of 6
10/21/09 at 8:17am
I'm not up on the new displays that much, but I think the 120Hz HTDV's takes the 60Hz signal and doubles it internally, I didn't know they will actually take a 120Hz input.


Mike
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post #6 of 6
10/21/09 at 10:38am
A 120Hz display either displays each 60Hz frame twice
or
It creates a new frame by interpolating each between pair of 60 Hz frames to creaet a new frame
or
It can take a 24Hz frame and display it 5 time which eliminates Judder since each frame is displayed the same number of times since 5x24=120

There are some other posssible optionss such as accepting 120 fps 3D video or of interpolationg 4 new frames between each pair of 24 fps content.
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