Film-Tech Cinema Systems
Film-Tech Forum


Post New Topic  Post A Reply
my profile | my password | register | search | faq & rules | forum home
  next oldest topic   next newest topic
» Film-Tech Forum   » Operations   » Digital Cinema Forum   » Film Judder (Page 1)

 
This topic comprises 2 pages: 1  2 
 
Author Topic: Film Judder
Richard May
Phenomenal Film Handler

Posts: 1038
From: Floral Park, NY USA
Registered: Aug 2004


 - posted 08-17-2017 04:52 PM      Profile for Richard May   Email Richard May   Send New Private Message       Edit/Delete Post 
I'm getting what I assume is judder when running either BluRay or off a PC to the projector. The motion is not smooth mostly in panning and movement. Any ideas?

 |  IP: Logged

Frank Cox
Phenomenal Film Handler

Posts: 1974
From: Melville Saskatchewan Canada
Registered: Apr 2011


 - posted 08-17-2017 05:49 PM      Profile for Frank Cox   Author's Homepage   Email Frank Cox   Send New Private Message       Edit/Delete Post 
The time that I had that here (it looked like the film was dragging and getting stuck in the projector) the problem was a bad spot on a hard drive that spent too much time re-trying before giving up and moving on to the next data packet.

In your case, it's likely insufficient speed of data transfer from the source device to the projector, which is actually the same problem as I had. The cause is slightly different, though; what are you using to transfer the data from the source to the projector? Are you sure the cables and connections are adequate to the task?

 |  IP: Logged

Richard May
Phenomenal Film Handler

Posts: 1038
From: Floral Park, NY USA
Registered: Aug 2004


 - posted 08-17-2017 06:26 PM      Profile for Richard May   Email Richard May   Send New Private Message       Edit/Delete Post 
Going from a computer via HDMI into the GDC IMB. I used a Bluray player with a different movie and had the same effect. Our OPPO decks haven't come in yet so we were using a cheap deck.

 |  IP: Logged

Stephan Shelley
Jedi Master Film Handler

Posts: 700
From: castro valley, CA, usa
Registered: Nov 2014


 - posted 08-17-2017 07:03 PM      Profile for Stephan Shelley   Email Stephan Shelley   Send New Private Message       Edit/Delete Post 
Do you have the option to use a DVI input on the projector? Those often work better than the IMS/IMB HDMI inputs.

 |  IP: Logged

Richard May
Phenomenal Film Handler

Posts: 1038
From: Floral Park, NY USA
Registered: Aug 2004


 - posted 08-17-2017 07:08 PM      Profile for Richard May   Email Richard May   Send New Private Message       Edit/Delete Post 
I do but I would have to reroute the audio then.

 |  IP: Logged

Stephan Shelley
Jedi Master Film Handler

Posts: 700
From: castro valley, CA, usa
Registered: Nov 2014


 - posted 08-17-2017 07:42 PM      Profile for Stephan Shelley   Email Stephan Shelley   Send New Private Message       Edit/Delete Post 
You should try it for testing purposes anyway. If you look back in other posts on here HDMI inputs are often problematic.

 |  IP: Logged

Richard May
Phenomenal Film Handler

Posts: 1038
From: Floral Park, NY USA
Registered: Aug 2004


 - posted 08-17-2017 08:27 PM      Profile for Richard May   Email Richard May   Send New Private Message       Edit/Delete Post 
Just tried DVI-D. Same result.

 |  IP: Logged

Tom Bert
Expert Film Handler

Posts: 100
From: Belgium
Registered: Apr 2010


 - posted 08-18-2017 04:32 AM      Profile for Tom Bert   Email Tom Bert   Send New Private Message       Edit/Delete Post 
Are you playing interlaced or progressive?
What framerate is set on the player: could be fractional 23,...

 |  IP: Logged

Marcel Birgelen
Film God

Posts: 2610
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012


 - posted 08-18-2017 04:42 AM      Profile for Marcel Birgelen   Email Marcel Birgelen   Send New Private Message       Edit/Delete Post 
Have you checked alternative content too? Maybe your problem is in the content itself as a result of a previous down-conversion from e.g. 30 fps to 24 fps or 23.976 fps.

Also, when playing from a PC, check the refresh rate of your HDMI output in your operating system. Ideally, it should match the framerate of your content, if that's not possible, it should be as high as possible (At 60 Hz, judder effects should be unnoticeable for average human beings, at least if the rest matches up). Most modern players do have the possibility to set the refresh rate of your output dynamically to match the frame rate of your content, as long as your video card supports it. You want to use this feature, if it works.

In some cases, when playing from a PC, you get horizontal "tearing lines", this is caused by your player not syncing up with the "vertical blanking" of your video card. Most players do have an option for this.

 |  IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12209
From: Annapolis, MD
Registered: Dec 1999


 - posted 08-18-2017 07:09 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Judder (when motion is not fluid...doesn't require pans can even be people just walking will have a non-fluid motion) is almost always caused by frame rate conversions.

If your source material was originally shot at 24fps and your player is up-converting that to 30 or 60fps it runs the risk of causing judder. When possible, you want to run things at their native frame rate.

Blu-rays are normally pretty good about being able to keep the native frame rate as many consumer TVs are 24fps aware but though many have a 24fps mode, internally they are still ramping them up to 60fps and can possibly introduce judder.

DVDs are almost always frame rate converted to 30fps, regardless of source. Better players, like the Oppo can bring them back down to 24fps and they look MUCH better. Often a DVD/Blu-ray player will have some mode setting that allows one to select "film" or "video" Most are left in Auto, which means the player has to figure it out. Using "film" presumes that the source material was shot at 24fps.

 |  IP: Logged

Carsten Kurz
Film God

Posts: 3777
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 08-18-2017 07:17 AM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Richard - you either have trouble with the natural 24fps motion sequence, which is at the lower end of acceptable temporal resolution for moving images, or, your BluRay Player is set for 60fps output. Check it's setting for HDMI output frame rate or a '24fps'. This may have other names in the player setup.

- Carsten

 |  IP: Logged

Richard May
Phenomenal Film Handler

Posts: 1038
From: Floral Park, NY USA
Registered: Aug 2004


 - posted 08-18-2017 07:53 AM      Profile for Richard May   Email Richard May   Send New Private Message       Edit/Delete Post 
I figure when we get the OPPO's, that will correct the issue when using the deck. My bigger problem is playing from a computer (PC). The content looks fine on the computer screen. It's very smooth. Then you look at the screen and it looks like crap. Refresh rate is set to 60hz. I tried the HDMI in on the IMB and I tried the DVI-D in on the projector. No difference. It's not that big of a deal. It would be nice to figure it out for the VERY few times we would run of a PC (like last night).

 |  IP: Logged

Carsten Kurz
Film God

Posts: 3777
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 08-18-2017 08:12 AM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Both deck and PC need to be set to 24fps output rate (or, the PC at 48fps). It is not easy to set up a PC for decent playout quality. A cheap 60US$ Bluray player does better than that. IF you set it to 24fps.

- Carsten

 |  IP: Logged

Jim Cassedy
Phenomenal Film Handler

Posts: 1553
From: San Francisco, CA
Registered: Dec 2006


 - posted 08-18-2017 10:22 AM      Profile for Jim Cassedy   Email Jim Cassedy   Send New Private Message       Edit/Delete Post 
quote: Richard May
My bigger problem is playing from a computer (PC).
Without knowing more about your exact setup and the equipment involved,
I can't comment authoritatively about what's causing your problem.

There are several things that could be causing your problem, frame rate
conversions or mis-matches being one of them, as others have mentioned.

But, anecdotally, whenever I've had the issue you describe, it was almost
always a matter of 'computer resources' not being up to the task.

As I've mentioned before in other posts, I often use "Playback-Pro" at
various shows, and I sometimes ran into this problem.

In my case, I went & got a Macbook Pro, with the most memory available,
and replaced the standard drive with one that spins at 7200rpm.- - and I
use this Mac ONLY for video playback, so it doesn't have a lot of other 'crap'
on it. I realize you may not have the time or resources to do this, but I'm
just sayin that once I upgraded and de-cluttered my "playback computer" ,
I've never had the 'motion jidder' problem again. That's what worked for me.

 |  IP: Logged

Richard May
Phenomenal Film Handler

Posts: 1038
From: Floral Park, NY USA
Registered: Aug 2004


 - posted 08-18-2017 10:27 AM      Profile for Richard May   Email Richard May   Send New Private Message       Edit/Delete Post 
Yeah, the Macs seem to always play okay as I recall. I may grab someone's mac here and try it.

 |  IP: Logged



All times are Central (GMT -6:00)
This topic comprises 2 pages: 1  2 
 
Post New Topic  Post A Reply Close Topic    Move Topic    Delete Topic    next oldest topic   next newest topic
 - Printer-friendly view of this topic
Hop To:



Powered by Infopop Corporation
UBB.classicTM 6.3.1.2

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.

© 1999-2018 Film-Tech Cinema Systems, LLC. All rights reserved.