[dershadi]

As discussed in the thread "30fps gaming at 60hz and the effect of frame-doubling?" (I'd post the url but as I'm new I unfortunately cannot yet, if someone else could get a link up I'd be much obliged), some 30 fps games can exhibit a judder-like effect as a result of frame doubling. This is different from motion blur experienced on LCDs, but fundamentally has to be different than the judder experienced when watching 24p content at 60hz due to 3:2 pull-down, simply because 30 fps divides evenly into 60hz, resulting in a 2:2 pull-down.


My question is, why does this same judder not occur in normal broadcast content (which displays at 30 fps just like these games), and why does this not occur in 24p content displayed at 48hz, 72hz, or 96hz (aside the flicker problems experienced at 48hz on some Panasonic plasmas, but that's a separate issue)? Essentially, why does frame doubling cause this issue in games, while it works fine for video? Does it have something to do with specific games and how they were designed/programmed? Any input or insight is much appreciated.

 

[Jim Burns]

Frame doubling does not cause judder, I am not saying there is not some nasty artifact such as motion shift or stuttering motion due to low frame rate,

Jutter is noticing the difference in film transfers of some frames being shown for 3/60 of a second and the next frame being shown at 2/60 of a second. Your eye notices that one frame sits for longer than another so things appear to go faster at 2/60 and slower at 3/60. This artifact is called jutter.


The other discussion I think is confusing jutter with low frame rate stutter the image looks like a continues series of still pictures not smooth motion. Stutter is the jittery motion seen in old films when the image is not changing enough to fool your eye into creating the illusion of smooth motion. The threshold for smooth motion varies per person and screen luminance but sits somewhere either side of 50 cycles per second.