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Philips 901F OLED Motion Blur Reduction

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Offline Andrew Fee

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Philips 901F OLED Motion Blur Reduction
« on: 24 February 2017, 01:43:32 PM »

Just saw your video on YouTube about motion blur on Philips' new OLED.
That's fantastic if we finally have a manufacturer doing something about the sample-and-hold motion blur problem with OLED TVs.
However you say that it achieves this without interpolation or flickering, which has me struggling to think what else it could be doing to improve motion handling.
When you enable this mode on the TV, there appears to be quite distinct double-images in the video when anything moves across the screen.
To me, that suggests that it's using a low-persistence mode (flickering) at double the source framerate - which I assume means a 60 FPS source displayed at 120Hz.
This is really easy to test with a camera that offers manual shutter speed controls.
You just need to display a static image like this one and move the camera while taking the shot.

Multiplying the number of lines displayed in the photograph by the shutter speed will tell you the display's refresh rate.

With my TV set to scan the backlight at 240Hz and the camera shutter speed at 1/60s there are four lines displayed:

Backlight scanning at 120Hz with the shutter speed at 1/60s results in two lines being displayed:

Backlight scanning disabled so that the TV is using sample-and-hold results in a single line which is completely blurred:

If it was scanning the backlight at 60Hz (my TV does not have this option) there would be a single line, but it would be a thin well-defined line like the 120Hz/240Hz images, instead of a blurred line like the sample-and-hold image above.
If you change the shutter speed the number of lines displayed will also change, which allows you to verify these results.
At 1/30s, 60Hz strobing would now display two lines, while sample-hand-hold would still display a single blurred line.
240Hz would now display 8 lines, and 120Hz would display 4.
At 1/40s, 240Hz would display 6 lines, 120Hz would display 3 lines, and so on.
It's a quick and easy way to figure out the refresh rate of a display that is using backlight scanning/strobing/BFI/PWM etc, without requiring any specialized hardware.
The other thing I would add to this, is that if the display is refreshing at something greater than 60Hz - which I assume it must be if you don't notice any flickering - then you would also need to have interpolation enabled to avoid bad judder from those double-images.
Refreshing the display at 120Hz with a 60 FPS (or lower) source is unwatchable in my opinion.
You either need to drop the refresh rate to 60Hz, or interpolate the source to 120 FPS to match the refresh rate.
Otherwise, I would prefer to use sample-and-hold. Motion blur is preferable to judder in my opinion.
Edit: Great, I posted this in the wrong forum.  ::)

Offline Nui

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Re: Philips 901F OLED Motion Blur Reduction
« Reply #1 on: 24 February 2017, 02:16:48 PM »
When you enable this mode on the TV, there appears to be quite distinct double-images in the video when anything moves across the screen.
As you say the motion blur introduced by S&H shows up when you move the camera (or your eyes). Hence this is not the case here.
I think the source material is 24p, and I know the youtube video runs a 24p and was most likely shot at that as well. The TV and the camera are most likely out-of-sync so every frame it captures 2 consecutive frames of the source material. Hence the double images.

Still I also assume its just a form of BFI, low persistence, or-whatever-you-want-to-call-it mode. In fact Vincent Teoh himself states that the Samsung reached higher motion resolution. The duration of the dark phases determines the motion sharpness, light loss and amount of flicker. So I'm not surprised that the philips doesn't flicker, but the samsung does.

I've basically posted the same information in 3 places now.  :rofl: