CurtPalme.com Home Theater Forum

[SYC]

I know how it works, so don't explain it. I thought I had seen it before, but I was wrong. What I saw wasn't judder. Can someone tell me what it look like and some movie sections to see it?

SYC

[k.berger]

Actually the easiest part of the movie to see and learn how to recognize judder, are... CREDITS... (as long as they roll vertically). If you pay attention, you will see that their movement is jerky, they sort of stop and go!
Of course, it applies to any movement, but is harder to spot on regular material, since we are accustomed to it from TV.

Kris

[Clarence]

Slow pans... especially on opening/closing credits. Opening scene of "Sahara" (5 second .ts clip, 10Mb file) has always been a good test scene for me. We watched "The Wrestler" on BD last week... same type of opening... slow pans across newspaper clips with lines and small text detail.

60Hz vs 71.928Hz is subtle, but once you teach yourself to find judder in 1% of all scenes, you'll be ruined. Just like FFTB... only in 1% of all scenes, but once you learn to look for it, you appreciate it more when it's done right.

I'd say the difference is similar to roller-blades on a sidewalk vs on a smooth road... instead of the 60Hz bumpty-bumpty-bump you get from the cracks in the sidewalk, you get a nice 72Hz ride on the smoother road.

Or rolling a golf ball on a home's hardwood floor seems smooth enough until you compare it to rolling a golf ball on a bowling alley lane (72Hz).

[SYC]

I will try hard to find. But how is 48Hz compared with 72Hz for film source?

SYC

[k.berger]

Well, neither one creates judder, as they are multiples of 24fps (assuming of course, that the source is film). 48Hz refresh creates slightly visible flicker,specially on large, white areas, whether 72 does not.
Some people are more sensitive/tolerant on 48Hz flicker than others.
Bear in mind that either one requires video processor or HTPC as there are no blu-ray players capable of 48/72Hz output.
Flicker can be minimized by manipulating porches in video settings of VP/HTPC, forcing longer time for each frame to "stay" ON, and shorter time "in-between" frames. That's what I am doing personally (PS3 -> LumagenHDP -> Purelink HDMI-VGA -> Ampro 4200). I find that very slight flicker adds to cinematic experience, since it is present in film projection (at movie theaters frames are refreshed usually at 48Hz rate).
Some people prefer removing it altogether by using 72Hz refresh rate, even though it usually results in slightly softer image, due to higher bandwidth of video signal, which is generally at the edge of most PJ's capabilities.

[SYC]

[k.berger]

Not difficult at all, except that it my require little tweaking for porches, and of course you will have to create new signal entry and then reconverge PJ.
Make sure that you have updated firmware installed on Lumagen. In case you didn't do it before, you will need serial 9pin (null) cable, updater software and firmware file from Lumagen's Site. And of course PC
Before you update, and change anything, use updater utility to back-up HDP's configuration.
If you use PS3 at 1080i/60, you most likely have disabled 1080p/24, otherwise PS3 would most likely default to it for film material. You will need to re-enable 24Hz playback.
Next I would suggest for you to create signal entry in NEC, and reset PHASE, SHIFT, BLANKING and possibly SIZE to neutral positions. I started from scratch by definition, since the PJ I got was totally screwed-up . But still, in my opinion it's better to do as many adjustments to the image as possible in VP, leaving the PJ to "do" as little as possible.
If you have it, (I would suggest for you to get it, if you don't), put DVE test disk and select geometry/overscan pattern.
Than go to Lumagen's advanced settings -> custom timings, and for output select 48Hz (it will ask you if you want "real" 48, or 47.97(or something?). select the latter.
That should get you something on the screen.
Check, if you can see whole width of image, or edges are cut-off?
Regardless, try to minimize Horizontal Porches, it will lover the required bandwidth and minimize flicker.
Don't forget to save settings in Lumagen.
For DVDs, if you use PS3 as player, associate 48Hz output (in Lumagen) with 1080i/60, this way Lumagen will apply reverse pull-down processing extracting 24fps from video signal (and then double it to 48Hz).
If you watch TV (video shot at 1080i/60), you will need your old settings preserved, so associate the new ones with different input settings on Lumagen (you can have 4 per physical input).
You can also create custom resolution for 2.35:1, 24fps material: set screen AR to 2.35:1 and output resolution to 817x1080, it will conserve bandwidth even further.
For each setting try using Lumagen's controls, which are very flexible, to get the image positioned, cropped (or rather NOT cropped) to fit the screen as best as possible, before you adjust PJ.

Have fun,

Kris

PS when playing with Lumagen, remember that custom res. controls are somewhat interactive - when you enter values beyond limits and test the output, sometimes VP will adjust other parameters, like resolution. Make sure each time, that you stay with 1080x1920, or 817x1920, or VP will be unnecessary scaling the image.

K.

[MikeEby]

If you have movie Harry Potter and the Order of the Phoenix at the beginning of the movie there is an opening shot of the City and a slow pan that ends looking down at a play ground, I noticed judder or jerky pan at 60Hz but at 71.928 its very smooth.


Mike