60Hz LCD displays...yuck!

[Duffinator]

Excellent Thread

I have nothing to add to this thread other than it's an excellent disucssion. Keep it coming.

 

[MDS]

I have seen no evidence that any TV simply quintuples each frame. I read a response from a Toshiba engineer somewhere that explained why it is not done. They do the 3:2 pulldown to get to 60 Hz and apply a frame interpolation algorithm to calculate the in-between frames for display at 120 Hz. Toshiba calls their algorithm 'Motion Vector Frame Interpolation' and other manufacturers have similar processing with their own trademarked name.

It may require a lot of complex math and a lot of processing power to do motion interpolation 'correctly' and the result may not yet be as good as we would like, but that seems to be the way that all current gen LCD handle 24 fps film.

 

[BMXTRIX]

To explain things a bit further (with a picture!)...

Look at the photo below:

This was shot at 1/40th of a second - well within the bounds of motion picture cameras.

Now, think about the two obvious points of motion that are going on.

1 - The bat is moving left to right across the frame in an arc.
2 - The ball is moving downward diagonally.

In normal motion pictures, the next frame would have very similar blurring with the start of the blur beginning right where the old blur left off.

With improper tweening, there would merely be a new frame inserted between the two which would contain half the blur from the first frame and half the blur from the second frame... GREAT! Except, for every frame seen on screen the motion would appear jerky because the ball and bat would actually move halfway BACKWARDS through motion that it has already covered. While not something someone may easily identify, it will definitely be noticable, and may be part of the complaints about the new 120hz displays that perform some sort of tweening process.

The proper way to create a tween frame would be to take the photo above and actually de-blur it by 50%. This would require restoration of the background and proper determination of the motion of the different objects in the frame. That is, the ball going one direction would have to be shown over a period of 1/80th of a second (or less) and the bat would have to be shown, as well, over a period of 1/80th of a second (or less). Then the new frame would need to occur duing the next 1/80th of a second and contain the blurring that was removed from the first frame - along with, perhaps, some white space to account for the shutter closing during the film.

Full, and proper implemenation of 120hz frame tweening from a 24fps (hz) source, would actually require about a 5 fold reduction in blurring and then 4 new frames be created with the proper blur on each and every frame.

...

or - just repeat the same frame five times and call it a day with proper 24hz playback.

 

[MDS]

The proper way to create a tween frame would be to take the photo above and actually de-blur it by 50%. This would require restoration of the background and proper determination of the motion of the different objects in the frame.

That is exactly what motion vector interpolation tries to accomplish. Whether that process is better or worse than simply displaying a single frame 5 times, I don't know. I think the argument against simply duping the frame 5 times is due to 'retinal persistence' (google it).

 

[BMXTRIX]

...They do the 3:2 pulldown to get to 60 Hz and apply a frame interpolation algorithm to calculate the in-between frames for display at 120 Hz. Toshiba calls their algorithm 'Motion Vector Frame Interpolation' and other manufacturers have similar processing with their own trademarked name.

This is actually a published spec of motion tweening and is similar to the incorrect way of tweening that I described above. It, more or less, introduces judder into the image as it shifts objects backward in time and brings down image quality.

Realistically, I have no idea why a company would do things this way instead of simply repeating a frame 5 times to accurately represent the original film content.

Seriously: Why would a manufacturer intentionally mess up film? They actually seem to work hard to TRY to mess up the film content! I don't mind the concept of tweening, but I would think that no matter what 'cool' feature is added, that a simple click or two of the remote can put it back to the way it is supposed to look. Skip the 3:2 pulldown please.

 

[Buckeyefan 1]

Because they want less of a power hog, no burn, less weight and less if any reflections (to name a few) for starters.

My 37" LCD display is excellent for Discovery HD, as well as HD prime time shows. When the noise reduction is turned off, the picture is awesome. If I'm watching football Of faced paced movies/sports) in HD, the pixelation is a bit too obvious when the noise reduction is turned off. There are three settings for noise reduction - low, medium and high. The low and medium settings do a great job with sports, without affecting the sharpness of the picture. On high, the picture becomes too soft. The slight loss in sharpness is a small price to pay for an anti-glare, non burn-in screen.