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

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Dolby Digital WOW at reel change? (Page 1)

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

Author Topic: Dolby Digital WOW at reel change? Robert Schultz Film Handler Posts: 28 From: Tehachapi, CA, USA Registered: Mar 2004 posted 12-28-2005 07:54 PM                        I have a customer that is complaining of a WOW problem on 4 Dolby CP650 units. All of these units only show the problem at a reel change, and it's mostly audible during a scene with music. The systems are about 3 years old, using CAT 701 readers on top of Simplex Millennium Projectors. Anyone have this problem or know how to fix it?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-28-2005 08:44 PM                     This just screams of a poor splice to me. (I've never seen this problem before though.)  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 12-28-2005 09:44 PM                    I'm convinced (although I seem to be the only one) that this is an incredibly stupid software design decision in the CP650. There is NO reason at all not to have the software identify an average speed of the film, and smooth out the incoming data so that it doesn't warble. To me, ours sounds like a warped audio cassette tape. You can only hear it during music scenes. We've switched back to SDDS in that house for now. Is it something mechanical that can be fixed? Maybe. But the CP650 should be able to deal with that problem and make it unnoticeable. Dolby needs to fix that.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 12-28-2005 10:37 PM                     ..yet, question: How could digital data information warble since the information on the film is just "ones" and "zeros" with nothing inbetween? (or, could be a final editing problem with the analog mastering that hit a warble when the digital tracks were recorded..and missed QA when prints were struck) If that complex has more than one print of this movie, how is the other print and did the prints get switched to see if the other print does the warbling.. Odd, yet interesting.. -Monte  |  IP: Logged Paul Linfesty Phenomenal Film Handler Posts: 1383 From: Bakersfield, CA, USA Registered: Nov 1999 posted 12-28-2005 10:44 PM                     Can't warbling happen if the splices create a momentary unsteadiness of the film, causing some bits to be read out of order?  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 12-29-2005 12:18 AM                    If you move the little rollers that sit between the sound drum and the sprockets on the Dolby reader up and down while the film is running, you can hear the pitch change. Assuming the sound playing is one where you'll be able to detect a change in pitch. Do it during a music scene or a snipe that you've heard a hundred times for maximum effect. I'd be interested to hear if anyone else can reproduce this.  |  IP: Logged Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 12-29-2005 01:27 AM                     quote: Mark J. Marshall If you move the little rollers that sit between the sound drum and the sprockets on the Dolby reader up and down while the film is running, you can hear the pitch change. Really? And this is in digital? Or when you manipulate the film and move the little rollers, does it switch to analog?  |  IP: Logged Robert Schultz Film Handler Posts: 28 From: Tehachapi, CA, USA Registered: Mar 2004 posted 12-29-2005 02:11 AM                        This guy has four theatres all doing the same thing. I arrived to the theatre today and listened to the problem on two of the screens. I heard this problem in "King Kong" and "Cheaper By the Dozen". I was in the auditorium for both of these, but I never heard a drop out of digital. The owner of the theatre says that this problem is audible in all the auditoriums that have CP650 units as long as there is music crossing the splice area. After hearing this I went up to the booth and watched the splices pass through the CAT 701 penthouse readers. I didn't notice anything out of the ordinary and I never saw a film drop out of digital during a splice.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 12-29-2005 02:23 AM                     quote: Richard Hamilton Or when you manipulate the film and move the little rollers, does it switch to analog I was wondering about that since the digital information can't be read too well by the camera with such a variance of speed, causing the system to goto default SR (05). I've done this on purpose by bouncing the rollers to watch the error rate take a leap and watch it drop from (10) down to (05), then right back to (10) when the film feed is constant again. But, if this all checked out as mentioned, wonder if he has a brain problem with bad splices that causes the film to jump some in the reader and maybe dropping out of digital to optical..but that just a guess now since that's been already observed..  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-29-2005 08:32 AM                     quote: Paul Linfesty Can't warbling happen if the splices create a momentary unsteadiness of the film, causing some bits to be read out of order? You've got to have 4 blocks of data in a row read improperly before it would default to analog..... Also the data being sent from the CCD camera is normally unsteady to some extent.... this can be seen on a scope. If your scope has a calibrated adjustable delay setting this unsteadiness can actually be measured, this is also true of SDDS or any other mechanical form of data being read, it is completely normal. However there are circuits inside the processor that re-clock that incomming data into an extremely stable data stream and I suspect this is where your problem may be. I've never seen this happen on any 650's that we installed,,, none have failed yet, but I do agree on the software issue. Going with Linux was a stupid mistake... its slow and the boot up time on the 650 is way, way, way too long. Manufactuirers are using it because its basically free. To be fair the XD-10 software system is even worse than the 650... and just as slow at boot up. If you shut the XD-10 down during boot up there's a 50/50 chance of corrupting the data on the HD... then you have a dead XD-10 that will read out "initialization" till kingdom come. Its best to have a UPS supply on an XD-10. I've run out of fingers counting the number of times we've had this happen. Shipping one back and forth so they can repair it is a hundred bucks worh of UPS and insurance. With the recent death of the 6D I will be pushing 650's again. I just don't like selling equipment that can't be repaired on site in the booth..... In warranty or out.... Mark  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 12-29-2005 08:45 AM                     This might not relate to your problem, but I had an issue where some DA20's were acting strange at the same time Dolby had just done a 'with the soundtrack' software upgrade. So, if you really can't find why it's not working right, you might ask them if one was done recently.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 12-29-2005 09:38 AM                    Yes, Richard, it's still in digital. If it dropped to analog, it wouldn't be warbling because that part of the projector runs steady. When the cue goes through for the lights to come up at the start of the credits, it causes a bad warble that always makes the audience laugh out loud. Since it's the end of the film, it's always on a big orchestral "Taaa-Daaaaaaaaaa" which instead sounds like "Taaaa-Daaaaaaowawawawaaa". I posted about that here and was told to check this and that, change my cue tape thickness, etc., but I don't think that's it. We need some people with CP650s to try my experiment and post here if they can create a warble by doing it. It may not be a widespread problem, but it will be interesting to see if others have this problem so we can narrow it down. Maybe as some have suggested, there is a bad card, or there's some incompatible software/hardware versions or something. BTW, my reader is a CAT 702.  |  IP: Logged Jason Miller Expert Film Handler Posts: 241 From: Little Rock, AR, Registered: Mar 2004 posted 12-29-2005 05:58 PM                    It is possible that it did drop to analog but just didnt register on the display. since the displays are the last thing to update during remission, the decoder could have picked back up digital before the display had a chance to change. that could explain the warble at cues/splices.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 12-29-2005 06:00 PM                        Disable analog in order to test digital. Easiest way is to unplug the analog input or turn off the analog LED. Reversions will then be heard as silence. Louis  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 12-29-2005 07:12 PM                     Would the "vertical jitter" setting from DRAS be the right thing to be looking at here? [I don't have any DRAS experience.] 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. --jhawk  |  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.