[opendtv] Re: Philips ClearLCD technique for motion sharpness
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 21 Jan 2005 11:59:12 -0500
At 8:44 AM -0500 1/21/05, Tom Barry wrote:
>Anybody know if 72p looks any better than 60p? Can people see the
>difference?
Absolutely!
But it only makes a significant difference with fast motion.
Obviously it also helps with slow motion playback, but Thomson/GV is
already delivering a 120 field/sec super slomo HD camera.
A good way to think about this is like shutter speed with a still camera -
faster speeds = less motion blur, and reduced depth of field.
With a video camera we can do a bit of both, by using a shutter speed
that is higher than the frame rate. But we need motion blur with
moving images to deal with lower frame rates, or we will see
artifacts such as strobing and motion discontinuities.
Increasing the frame rate to 72P let's us capture sharper frames
without causing these artifacts. As a side benefit, this actually
helps with video compression, as the motion compensated prediction
routines work much better, and we can use longer GOPs with more B
frames.
>And on a non-blinking fixed pixel display without any fancy rate
>conversion, does displaying at 72p look any better than at 24p or 48p?
Sure. moving objects will be sharper and you can get away with rapid
camera movements. At lower taking rates you must be very careful with
pans and zooms, or you will see motion discontinuities.
>
>And is it hard to make a 60p LCD that could also handle 24p? I thought
>some of them could.
I hope Jeroen addresses this.
My guess is that they just treat 24P as 60P with 3:2 pulldown. I
suspect that the scanning rates and pixel hold times could be
adjusted to accommodate the 24p refresh, but this would add more
complexity to the product.
By the way, most LCD displays for computers accommodate the higher
refresh rates, at least until we start talking about 2 Mpixel or
larger rasters.
Regards
Craig
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