PC Monitor vs. LCD TV

[Ryu77]

Something I have been wondering is... How is it that my PC hooked up to my dedicated monitor can play content at various frame rates and still do so perfectly smooth when left at it's native refresh rate of 60Hz?

I would understand if I play 23.976fps or 29.98fps content as this this can be all played smoothly on a 60Hz display. However, 25fps material also plays perfectly smooth with no jitter effect when still in 60Hz mode.

When I connect this same PC to my Sony Bravia (200Hz) TV, I need to adjust the refresh rate according to the material being played. For example 23.976fps material I can use 24Hz or 60Hz, 29.98fps I use 60Hz.... But for 25fps, if I do not select 50Hz the motion jitters.

Is there any logical reason why a PC monitor can achieve what a LCD TV can not?

[rotty]

Something I have been wondering is... How is it that my PC hooked up to my dedicated monitor can play content at various frame rates and still do so perfectly smooth when left at it's native refresh rate of 60Hz?

I would understand if I play 23.976fps or 29.98fps content as this this can be all played smoothly on a 60Hz display. However, 25fps material also plays perfectly smooth with no jitter effect when still in 60Hz mode.

When I connect this same PC to my Sony Bravia (200Hz) TV, I need to adjust the refresh rate according to the material being played. For example 23.976fps material I can use 24Hz or 60Hz, 29.98fps I use 60Hz.... But for 25fps, if I do not select 50Hz the motion jitters.

Is there any logical reason why a PC monitor can achieve what a LCD TV can not?

Hi Ryu77

This is hard for me to explain in words but ill try.

Imagine a flagpole on screen and the camera pans across so the flagpole moves left to right across the screen.
On a CRT display, as you know the picture is made by scanning across line by line and moving down to the bottom of the screen to complete the image.

Now take our flagpole shown on a CRT display, as the image is scanned, the top part of the screen can show the flagpole (say in centre of screen) but by the time the scan has got to the bottom of the screen the image has moved a bit to right and the CRT shows this, in otherwords there is a gradual difference between the top of screen to bottom, this gives our eyes/brain a nice smooth transistion with real time and looks "pleasent"

Now take the solid state type screens, these show a complete frame at a time, just like movie film, so there is NO real time change during the shown frame, it is static, a frozen image only changing between frames and NOT changing with time during the same frame as CRT can do.

This is the fundamental difference between CRT and other types of display.

Its so hard as I said to put into words but I hope ive made sense.

All the very best and happy new year to you and everybody.

Rotty

[um3k]

There most certainly is a jitter at all frame rates except 15, 30, and 60. You just aren't sensitive enough to detect it. Consider yourself lucky.

[rotty]

There most certainly is a jitter at all frame rates except 15, 30, and 60. You just aren't sensitive enough to detect it. Consider yourself lucky.

Hi um3k

Happy new year

Im also in that unfortunate catagory of fast retanal response and have got used to ignoring greenish lag on plasma phosphors but love the realism of plasma over LCD.

New tech brings new niggles and we moan, me included but HI DEF is bloody great and perfection may happen one day eh.

All the best

[Ryu77]

Hi Ryu77

This is hard for me to explain in words but ill try.

Imagine a flagpole on screen and the camera pans across so the flagpole moves left to right across the screen.
On a CRT display, as you know the picture is made by scanning across line by line and moving down to the bottom of the screen to complete the image.

Now take our flagpole shown on a CRT display, as the image is scanned, the top part of the screen can show the flagpole (say in centre of screen) but by the time the scan has got to the bottom of the screen the image has moved a bit to right and the CRT shows this, in otherwords there is a gradual difference between the top of screen to bottom, this gives our eyes/brain a nice smooth transistion with real time and looks "pleasent"

Now take the solid state type screens, these show a complete frame at a time, just like movie film, so there is NO real time change during the shown frame, it is static, a frozen image only changing between frames and NOT changing with time during the same frame as CRT can do.

This is the fundamental difference between CRT and other types of display.

Its so hard as I said to put into words but I hope ive made sense.

All the very best and happy new year to you and everybody.

Rotty

Whoops!!.... I forgot to mention that I have an LCD PC Monitor and it is connected via DVI so they are both connected digitally.

There most certainly is a jitter at all frame rates except 15, 30, and 60. You just aren't sensitive enough to detect it. Consider yourself lucky.

I can assure you that there is no frame jitter on my LCD PC Monitor as there is on my LCD TV. The PC Monitor is 22" and the TV is 52". That being said the size of the PC Monitor is ample enough to be able to detect frame jitter.

I also sell TV's and Home Theatre for a living so I have developed quite a trained eye and ear for imperfections in either category.

I can assure you that my TV will have a slight jitter once every second as it adjusts to the incorrect fitting frame rate to the chosen refresh rate but my PC Monitor will still remain perfectly smooth playing 25fps content when left in 60Hz mode... Bizarre.

I thought there might be an answer for this.

I was even hoping that my recent upgrage from my 46" (24Hz/50Hz/60Hz) LCD TV to the 52" (24Hz/50Hz/60Hz/200Hz) LCD might rectify this problem but it hasn't. I would really love to know why my LCD PC Monitor can achieve what my TV can not.

[Tagert]

Maybe it has something to do with your pc lcd having less millisecond delay than your LCD TV?

[Ryu77]

Maybe it has something to do with your pc lcd having less millisecond delay than your LCD TV?

Thank you for the reply but I don't see how that would compensate for a frame jitter occuring at regular intervals. For example when watching 25fps on my LCD TV in 60Hz mode as the screen is panning I can see a slight jitter once every second. This is obviously becase there are 25fps being fed into a multiple of 30 (60Hz). Obviously when I change the TV to 50Hz this problem is fixed but the thing that baffles me is why I do not need to do this on my PC monitor.

Response time would only help with motion blur as the colour from each pixel from the previous frame may not have responded quickly enough to dissipate the colour ready for the next frame, therefore creating a slight blurring effect. Anything faster than 10ms is extremely hard to be detected by the human eye. Both displays are faster than this. My Asus LCD Monitor is 2ms and the Sony Bravia LCD is 5ms.

[zilog jones]

Does your TV have any sort of motion interpolation stuff turned on? I think Sony call it MotionFlow on their sets. Try turning it off if it is on, IMO these do horrible things to the picture and can cause jittering if they get it wrong.

Anything faster than 10ms is extremely hard to be detected by the human eye. Both displays are faster than this. My Asus LCD Monitor is 2ms and the Sony Bravia LCD is 5ms.

I'd take any response time claims with a grain of salt - they could be using different types of measurements (grey to grey, black to white, etc.). Also, your PC monitor is likely to have some overdriving function ("Response Time Compensation") which will reduce response time to something such as the 2ms claim but cause ghosting - see if this can be disabled too. I don't know if TVs use RTC too.

[2Bdecided]

25p on 60fps doesn't jitter just once per second. Typically you get something a bit like the "normal" "NTSC" 3-2 pulldown pattern, but with extra 2-frame sequences. Whatever, there's plenty of jitter.

Maybe your PC's LCD displays this as-is, while your TV changes it yet again - maybe even adding a highly visible 4-frame sequence? And/Or maybe the two displays have slightly different actual refresh rates (despite both being nominally 60fps), causing the frame repeat pattern to be slightly different?

Cheers,
David.

[7ekno]

Turn off all the signal extras on the TV, there should be a setting that effectively makes it bahave as a PC screen (some TVs call it PC mode, others Console Mode, others Direct Mode, others need all the extras like "Motion Flow" and "Smooth Flow" disabled, etc) ...

Since it's a Sony, have a look in the TV manual for the settings they recommend for a PS3 and use those settings ;)

7

[invisible]

I don't know why they didn't just use 24.00 fps for all movies from now on instead of that NTSC side effect of 24000/1001. Then we could use 72hz on monitors perfectly. Oh, well, at least there's no such thing as PAL bluray, is there? I hope not.

[2Bdecided]

There's 50i, and 25p-in-50i, but no native 25p - which is a real shame.

Sadly, thanks to the PS3 (the common American version of which choke on 50i), and global disc sales, lots of 50i content is being standards converted to 60i for release on BluRay - even in the UK. This includes hybrid 50i + 25p-in-50i content. It's a mess.

Cheers,
David.

[Ghitulescu]

I don't know why they didn't just use 24.00 fps for all movies from now on instead of that NTSC side effect of 24000/1001. Then we could use 72hz on monitors perfectly. Oh, well, at least there's no such thing as PAL bluray, is there? I hope not.

Oh yeah, the 25 multiples for fps are already in the standard.

[Ryu77]

Yes, there is 25fps material found on commercially released Blu-ray discs. The Australian release of "City of Ember" is one that comes to mind.

[Mark Rejhon]

I don't know why they didn't just use 24.00 fps for all movies from now on instead of that NTSC side effect of 24000/1001. Then we could use 72hz on monitors perfectly. Oh, well, at least there's no such thing as PAL bluray, is there? I hope not.

Oh yeah, the 25 multiples for fps are already in the standard.I am able to use PowerStrip to reconfigure Radeon and Geforce cards to 47.952 Hz and 71.928 Hz (looks identical on LCoS displays, no flicker). PowerStrip can fine-tune modern graphics cards in fractional Hz increments. I did that for my earlier home theater, on a LCOS projector that had autosync.

Alternatively, Reclock ffdshow filter can automatically "genlock" (not quite the proper word, but similiar effect) the 23.976fps to 24.000fps and resample the audio to follow, but there will be audio aritifacts. Reclock is still useful even at 23.976 fps playing back to a display at 71.928 Hz, as there's always a tiny difference as the clocks in the video card output are often independent of the clocks in the player software, and there will be a once-every-several-seconds judder caused by microscopic differences in the clocks. Reclock fixes that, assuming no other CPU-eating stuff (i.e. Windows Update, etc) causes further burps in video. I was able to achieve perfect HTPC-based "24p"-like playback from DVD that looks like native Blu-Ray player 24p (except for the reduced sharpness of DVD) using the 47.952 Hz PowerStrip trick plus the reclock ffdshow filter, zero dupe/dropped frame repeat. As LCD/LCoS are generally non-flicker store-and-hold display, 23.976 vs 47.952 vs 71.928 often look identical unless display circuitry have different handlings for each or if display buffers it (unwanted refreshrate conversion) and keep motion interpolation disabled, which I don't like for movie material anyway...

This is however, only, for advanced HTPC users.

P.S. I actually help founded the AVSFORUM HTPC forum -- I was the world's first moderator of the world's first Home Theater Computers forum in the year 1999! Google my history there.

[hyed1pin]

Does your TV have any sort of motion interpolation stuff turned on? I think Sony call it MotionFlow on their sets. Try turning it off if it is on, IMO these do horrible things to the picture and can cause jittering if they get it wrong.


You are a life-saver!
In my case, 120hz Sony HDTV, it was the CineMotion, which seems to improve the film based content. Anyway, on my divx/xvid videos from europe which had 25fps, I always had jitters, and it was NEVER smooth. Until I read your comment and I turned off Cinemotion.
It sure is a lot blurrier now (since I have 52" display, I can see everything) but no more jitters!!

It has nothing to do with Motionflow.
:thanks::thanks::thanks: