my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Dolby Digital WOW at reel change? (Page 2)

This topic comprises 7 pages: 1  2  3  4  5  6  7

Author Topic: Dolby Digital WOW at reel change? Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 12-29-2005 07:33 PM                    quote: Jason Miller It is possible that it did drop to analog but just didnt register on the display.... quote: Louis Bornwasser Disable analog in order to test digital... Well, I'm not sure how I would be changing the speed of the film going through the basement analog optical sound head by moving the rollers on the Dolby penthouse reader. But to eliminate the possibility, I removed the analog exciter lamp, put the SDDS in bypass (bringing the CP650 online in format 10) and moved the rollers on the Dolby reader up and down. And the result.... Uninterrupted warbling sound. quote: John Hawkinson I'm not sure what a reasonable jitter tolerance for the 650 to have is, or if its any different from the 500 or DA20...but it sounds like you're exceeding whatever tolerance it has. Hmm. Our Cat 702 is mounted on top of our SDDS DFP-D2000's reader. Could the problem be that it's be too far away from the aperture?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-29-2005 09:45 PM                     quote: Mark J. Marshall Hmm. Our Cat 702 is mounted on top of our SDDS DFP-D2000's reader. Could the problem be that it's be too far away from the aperture? Aha!!! NEVER EVER DO THAT. There is a spring loaded roller on the 2000 series reader that will wreak havoc on any digital penthouse also mounted on the projector if the "entire path" is threaded. Instead, change your offset on the cat702 reader such that you thread "straight down" the front instead of zig zagging back and forth to eliminate running over that roller.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 12-30-2005 02:40 AM                     ..wouldn't just one digital format be good to call since all three of them would sound close to the same anywho to the average human ear?  |  IP: Logged Alexander Smith Expert Film Handler Posts: 128 From: Walney Island, Barrow-in-Furness, Cumbria. Registered: Jun 2003 posted 12-30-2005 03:43 AM                     One digital format would only be good if each and every print always had that format, and it was always printed correctly on every print as well. Not all prints have every digital format, and a very small number of those have it printed out of spec so it can't be (reliably) read off the film. Alex.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 12-30-2005 09:41 AM                    Hmm that's interesting. This is the only projector that has the SDDS mounted below another digital reader, so that may be contributing to the constant slight warble that makes it sound like a warped audio cassette. But it doesn't explain why the Dolby doesn't smooth out the incoming data to prevent the warbling in the first place. Brad, I'm assuming you have a 650 there somewhere. Can you reproduce the digital warble by moving the Dolby reader's rollers up and down while the film is running? If you can, then I guess it's supposed to act that way. If you can't then I likely have another problem.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-30-2005 01:43 PM                     Mark, I've got 650s and none of them have exhibited what you claim to have. In fairness though they are all either Kinoton basement readers, a Dolby penthouse on top of the machine without anything else up there, or the triple stack in my screening room...of which I have the threading set up to ignore any spring loaded rollers. Back before I started avoiding the spring loaded rollers, I DID have that problem with CP500s and DA20s though, hence my recommendation to you. It wasn't just at splices though. There was a general speeding up/slowing down problem throughout the movie.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 12-30-2005 02:28 PM                    Thanks, Brad. I appreciate all of the info, and I'll look into re-timing the Dolby so we don't thread the SDDS or moving the SDDS on top of the Dolby or something. But I just want to be clear... are you able to reproduce a warble in your screening room by pushing the rollers up and down while the film is running? What I do is push the two rollers all the way to the bottom, then all the way to the top, then back to the center over the course of about a second and it causes the sound to make very noticeable pitch changes. If yours doesn't do that, then we definitely have something else wrong with our 650. If it does, then I guess it's supposed to act that way, which is stupid. I'm particularly interested in your screening room because the reader is set up so high. Thanks again.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-30-2005 03:13 PM                     First, just moving the SDDS to the top will NOT help the problem. You have to get rid of the threading path that involves that spring loaded roller. As far as intentionally forcing the tension rollers up and down, I've never done this as it would scratch the film.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 12-30-2005 09:40 PM                    I just figured that by having the SDDS above the Dolby reader, at least the film wouldn't be pulled in a jumpy manner. What scratches the film? Nothing touches the film when the rollers move up and down. Maybe I'm not clear. Move both rollers at the same time up and down, not independantly. If you're worried about scratches, can someone try it on an old trailer or a Dolby tone loop or something?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-30-2005 11:04 PM                     The film will come into contact with the bar in front of the sound drum if you force the tension rollers to the extremes like that, meaning scratches.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 12-31-2005 02:10 AM                     Thatsa lotsa rollers that the print has to go through - so much uneeded tension by the time the film hits the upper sprocket, which is pulling film pretty hard by itself there (and causing some extra stress on those two bearings in that upper constant sprocket assembly..) per each revolution. -Monte  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-31-2005 11:37 AM                     The only real drag there is from the SDDS reader. DTS and SRD doesn't really put enough tension on the film to matter.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 01-04-2006 09:57 AM                    I've worked on a projector with an SDDS DFP-D2000 on top of a DTS reader on top of a Cat 699 reader, with all threaded all the time and we've never had a warble from any of them, nor have we gotten any scratches (unless you let a manager do the threading). The Dolby always sounded perfect in that theater. We never had a warble when the cues or splices went through. This was a CP65 / DA20 setup. So, this is the last time I will ask for help on this. I need someone (preferably multiple someones) who know(s) what they're doing to try my experiment and tell me if they can reproduce a warble on a 650. If you're worried about scratching the film, then make a loop out of an old trailer and try it. You'll need something with music in it where you will be able to easily hear a warble if it happens. I'm not asking anyone to scratch King Kong. It sounds like Robert and I are having the same problem. If no other 650s do this, then we have an internal problem in our units. If they all do it, then ... that's pretty stupid on Dolby's part.  |  IP: Logged Max Biela Film Handler Posts: 89 From: Dortmund, Germany Registered: Sep 2003 posted 01-04-2006 10:21 AM                     Hi, I will try it with our CP 650/Cat 702 tomorrow! Max  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 01-04-2006 10:41 AM                    Thank you!  |  IP: Logged

All times are Central (GMT -6:00)

This topic comprises 7 pages: 1  2  3  4  5  6  7

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

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.