60Hz screens

[purpleman2k]

Hello,

Since most PC LCD monitors (and LCD TV's) are limited to 60Hz input on the native resolution, and most film-shot video content is 23.976 fps, would it be right to conclude that it is impossible to get non-jerky playback of the content on these monitors?

(even with ReClock, best it can do is speedup to 24fps, but it would still not produce a stutter-free playback, if I understand correctly).

Thanks!

 

[Jong]

Without Reclock you will get an additional burst of judder periodically that will be noticeable inferior to the same material played on your TV, broadcast or from, say, a DVD player. With Reclock you will get the regular 3:2 cadence that many are used to and some do not even notice. But you are right, it is not as smooth as playing back at a multiple of 23.976Hz (or 24Hz).

 

[purpleman2k]

Without Reclock you will get an additional burst of judder periodically that will be noticeable inferior to the same material played on your TV, broadcast or from, say, a DVD player. With Reclock you will get the regular 3:2 cadence that many are used to and some do not even notice. But you are right, it is not as smooth as playing back at a multiple of 23.976Hz (or 24Hz).

All ReClock does on my machine (according to what it says) is speedup from 23.976fps to 24.000fps. How will that change anything in the judder?

 

[Jong]

Because 24fps displayed at 60Hz can perfectly adopt 3:2 pulldown in the same way as 23.976Hz material displayed at 59.940Hz. Movies, which are originally filmed @24fps are deliberately slowed down to 23.976Hz precisely so they can be displayed properly with 3:2 pulldown @59.940Hz (the "normal" NTSC refresh rate). If they were not there would be additional periodic judder. Reclock allows this same technique to be applied when using a "true" 60Hz display.

By the way, a side benefit is that you get the original movie speed and original soundtrack pitch, although nobody but leeperry can hear the 0.1% slowdown normally introduced

 

[leeperry]

nobody but leeperry can hear the 0.1% slowdown normally introduced

in an A/B, all you need is listen carefully...try it, it's very audible.

well, you'll get butter smooth 29.97fps videos...not that bad

 

[purpleman2k]

Because 24fps displayed at 60Hz can perfectly adopt 3:2 pulldown in the same way as 23.976Hz material displayed at 59.940Hz. Movies, which are originally filmed @24fps are deliberately slowed down to 23.976Hz precisely so they can be displayed properly with 3:2 pulldown @59.940Hz (the "normal" NTSC refresh rate). If they were not there would be additional periodic judder. Reclock allows this same technique to be applied when using a "true" 60Hz display.

By the way, a side benefit is that you get the original movie speed and original soundtrack pitch, although nobody but leeperry can hear the 0.1% slowdown normally introduced

Thanks for the info. However - a normal NTSC Television is true 60hz because it's field based. but LCD TV and PC Monitor are progressive (frame based). That being the case, 3:2 pulldown cannot take place. So when I'm playing a 24fps file, which component (the tv? video renderer) is performing the 24f->60 pulldown you mention? Is it done automatically for 24fps and not for 23.976fps?

Also, if I use ReClock with MPC-HC, what happens if I load subtitles? The subtitles are synced to 23.976. Will they lose sync or keep it?

Thank you again.

 

[Jong]

Thanks for the info. However - a normal NTSC Television is true 60hz because it's field based. but LCD TV and PC Monitor are progressive (frame based). That being the case, 3:2 pulldown cannot take place. So when I'm playing a 24fps file, which component (the tv? video renderer) is performing the 24f->60 pulldown you mention? Is it done automatically for 24fps and not for 23.976fps?

Also, if I use ReClock with MPC-HC, what happens if I load subtitles? The subtitles are synced to 23.976. Will they lose sync or keep it?

Thank you again.

No, a normal NTSC TV is not true 60Hz it is 59.940Hz and that is why movies on DVD/Blu-ray are 23.976Hz. A PC monitor often IS 60Hz so needs movies speeding up to 24Hz for pulldown to be correctly applied.

But you are right progressive displays do not display things in the way on old field-based display would. However, a modified form of 3:2 pulldown is still applied, adapted for a progressive display. With 24p material I would say the result is close to indistinguishable. If you are sending your TV/Monitor 59.940Hz or 60Hz it is your PC that does it. There are some HDTVs that accept a "24p" input but still display @59.940Hz; In this case the TV needs to do it.

Display of subtitles is fine whatever speedup or slowdown is applied. You can even show 23.976fps movies sped up to 25p (for display on a 50Hz PAL TV) without issue.

The bigger problem for progressive displays vs interlaced displays is acceptable display of interlaced material. Here the more modern graphics cards with more advanced de-interlacing algorithms can help.

 

[purpleman2k]

In this case the TV needs to do it.

This makes no sense to me. The TV gets a 60Hz signal from my PC. That signal is identical whether I'm showing the desktop, playing a 23.976 fps or playing 24fps. So if by using ReClock to achieve 24fps the jerkyness stops it means that something is getting the 24fps video and knows how to play it right on a 60Hz, and that is most definitely not the TV becuase it always gets a 60Hz output no matter what.

So who really treats the video differently? Is it my graphics card? The video renderer? (EVR, in my case).
If it applies some sort of 3:2 pulldown to achieve 24->60hz, surely it must be documented somewhere. Because right now we're just guessing that it's having a hard time dealing with 23.976 but knows how to deal with 24.

Thanks again!

 

[Jong]

This makes no sense to me. The TV gets a 60Hz signal from my PC. That signal is identical whether I'm showing the desktop, playing a 23.976 fps or playing 24fps. So if by using ReClock to achieve 24fps the jerkyness stops it means that something is getting the 24fps video and knows how to play it right on a 60Hz, and that is most definitely not the TV becuase it always gets a 60Hz output no matter what.

So who really treats the video differently? Is it my graphics card? The video renderer? (EVR, in my case).
If it applies some sort of 3:2 pulldown to achieve 24->60hz, surely it must be documented somewhere. Because right now we're just guessing that it's having a hard time dealing with 23.976 but knows how to deal with 24.

Thanks again!

Read the post again. I said the TV has to do it if you send it a 24p signal, i.e. 23.976Hz, instead of 59.940Hz.

We are not guessing. It is mathematically clear and physically observable that you can apply a regular cadence to 23.976fps material for display at 59.940Hz and for 24fps material @60hz, but 23.976Hz displayed at 60hz will result in regular periodic judder.

 

[purpleman2k]

Read the post again. I said the TV has to do it if you send it a 24p signal, i.e. 23.976Hz, instead of 59.940Hz.

We are not guessing. It is mathematically clear and physically observable that you can apply a regular cadence to 23.976fps material for display at 59.940Hz and for 24fps material @6)hz, but 23.976Hz displayed at 60hz will result in regular periodic judder.

Okay, so the question remains - when I use ReClock to change 23.976fps to 24fps, what exactly performs the 3:2 "pulldown" to 60Hz? As stated before, it can't be the TV, because it's already getting the "altered" 60Hz output from the graphics card.

 

[Jong]

I said it before.

.....If you are sending your TV/Monitor 59.940Hz or 60Hz it is your PC that does it.

This normally means the graphics card driver although it is possible to introduce specialised filters/renderers that can undertake this in software/outside the driver (it gets more complicated with technology like CUDA) if you wish. More normally this is done not for 3:2 pulldown but when interpolating additional frames e.g to display @120Hz.

 

[purpleman2k]

I appreciate your help!

One last question: How can we know for sure that the graphics card driver does 3:2 to 60hz if it gets 24fps video? (That's what I meant before when I said we're guessing, I wasn't arguing that it's possible).

 

[Jong]

What is an alternative way of displaying 24 frames per second @60Hz that does not interpolate 24frames-> 30 or 60 frames and offers a regular cadence?

 

[leeperry]

What is an alternative way of displaying 24 frames per second @60Hz that does not interpolate 24frames-> 30 or 60 frames and offers a regular cadence?

c'mon, it's easy! 30 seconds to go, 29, 28, 27..

one thing I keep wondering about is those NTSC TV's that IVTC in realtime..does that mean that ppl in the US have been getting proper 24p since the 60's? or have they all been watching 23.976 judder for the past 50 years?