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Author Topic: Dolby Digital WOW at reel change? Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 02-27-2006 07:11 PM                    Thanks, Ken! Here's some more details. Hope this helps. The bottom part of the loop goes around the projector's upper constant feed sprocket, back up through the top of the projector, behind the two digital penthouse readers, and over the roller that normally carries the film on its way to the projector from the platter. Here's a screen capture showing the top part of the loop. You're right that the loop does bounce quite a bit after I added the cue. That's basically the cue tape stiffening part of the film and causing the bounce when it goes over that top roller. It should be noted that that is exactly what happens when a cue on a print travels over that roller. Then when the cue goes through the reader, it happens again, except it's a bit more of an intense bounce, as the video shows. Because I'm running a loop, the bouncing becomes rhythmic in nature. On an actual print, the rollers bounce a few times as the cue goes through, then they settle back down. The first digital test on the video (without the cue) is much more stable, although there is still a very very slight warble. But I'm also curious as to why it sounds like a higher pitch than the analog version of the Dolby tone. It doesn't sound like the right pitch until I shut the motor off at the end of the video. I've never noticed movies playing at a higher pitch than they should, so I'm really puzzled as to why the Dolby tone loop sounds like that. Thanks again.  |  IP: Logged Ken Jacquart Film Handler Posts: 82 From: San Francisco, CA, USA Registered: Mar 2000 posted 02-28-2006 12:15 PM                        Mark, As you've observed and heard, a film speed change will cause a pitch change. The recovery time of a film bobble will depend upon things mentioned earlier in this thread of messages. Check to be sure that you're airpot piston assembly is not broken. Additionally, if it is not calibrated correctly, that will present a problem. The Dolby Digital tone on the Cat. No. 69T loop is a 1K tone. The analog track "Dolby Tone" is somewhere around 850Hz. That is the difference that you were hearing. The reason for the different frequency on our Dolby Tone loop is mostly as an identifier that it is "our" loop. You'll also hear that repeating "blip" during the tone. This is also an identifier. -ken  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-28-2006 03:37 PM                     In looking at that video, pay attention to the top right SDDS roller. Wow! On page 2 someone said this... quote: Brad Miller 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. That may not eliminate all of your problem, but it sure as shit will knock a LOT of it out. Re-watch that video.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 03-03-2006 09:43 AM                    Yeah yeah yeah, I hear ya. Undaunted by Brad's , I ran the exact same loop on a CP65 / DA20 setup, since in theory, they should all work the same way. Guess what... no warble. I can't even force it to warble by pushing the rollers up and down. Video here. What gives? Oh, and just for you Brad, the second part of that video is me running the same loop on a different CP650, bypassing your spring loaded roller completely. Guess what... warble all over the freakin place. The tests on this video were done at a different theater that is experiencing the same problem. There is also a third theater down the road having this problem with their CP650, and NOT with their CP65. In all cases the CP650 is running with a CAT 702 reader. One of the CP65s is running with a CAT 700 reader. I can't remember what the other reader is, but it is a white light reader. The only thing left that I can do is switch the readers around and see if the problem moves, which is a last resort, and we're not planning to do that at the moment. So I guess since we're all in agreement that the pitch will shift if the film bounces, my question now becomes... why is the CP65 / DA20 setup doing such a better job of handling that piece of film? The film does appear steadier in the reader, but I can't even force a warble on that unit. Why not? What is it doing differently? Regarding the airpot/dashpot/whatever-it-is... how often do they break or go bad? Is this something that needs replacing once a year or so? At least in our case, this is a problem we've been having since it was installed. The other two were installed around the same time as well. Possibly a bad set of units? The CP65s have been in use since The Lion King. By the way, I know you're reading this Rob, and before you blow a gasket, I'm already working with Dave. Rest easy. Thanks again for the replies. Edit: Thank you, Brad. --Mark [ 03-03-2006, 11:46 PM: Message edited by: Mark J. Marshall ]  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 03-03-2006 03:24 PM                     Flip the readers between those houses and let's see what happens.  |  IP: Logged Ken Jacquart Film Handler Posts: 82 From: San Francisco, CA, USA Registered: Mar 2000 posted 03-04-2006 09:56 AM                        Yes, Mark, if you could swap out those two Readers, it would be most helpful information at this point. That is the next logical thing to do in order to come closer to any conclusion. Thanks-  |  IP: Logged System Notices Forum Watchdog / Soup Nazi Posts: 215 Registered: Apr 2004 posted 08-22-2008 04:38 PM                 It has been 902 days since the last post.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 08-22-2008 04:38 PM                     Found this thread from the other one on readers.. I'm willing to bet the wow problem is coming from a simple fact in the design change between the CAT699/700 and later readers..the change in the illumination source. The white light readers featured a "spot" of white light, that would fairly evenly illuminate the entire interperf area. Constant intensity over the entire data block would possibly mean more robust reading of that block. Now the new LED illuminators place a "slit" of light across the data block area, so now instead of essentially getting a snapshot of the entire data block, you're now doing a "scan" of a portion of the block as it moves, which would seem to mean that it would now react more to any variations of speed. Sam, your thoughts on this? Enquiring minds would like to know...  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 08-22-2008 08:39 PM                     How much are you bettin'? Your theory doesn't hold...either light source is essentially scanned one line at a time. The LEDs are more apt to give you a more uniform light from end-to-end though you will be able to "see" the individual LED dots. With a white light reader, you didn't get the dots but you were at the mercy of the light pipe and how it was polished and how it aged and how the lamp was aimed at the light pipe as to how even an illumination you got. Now, the CCD did prefer the white light reader...if you target one of them at 4.5Vp-p on the Whiter-than-white signal, you will obtain a better result (lower error number). Steve  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 08-27-2008 01:35 PM                     Thanks for that info Steve. Now a question for you: I have an older Component Engineering Dolby Digital reader that was used with the light pipe...can it be used with a red LED? I noticed there are two jumpers on the top of the CCD board..do those set overall gain? Or am I gonna have to pay for a newer reader? The CCD board is a Dolby CAT 654R.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 08-27-2008 09:29 PM                    Following up on the posts above the soup nazi, I never did get cooperation from our engineering folks to swap out the reader heads, so I have no idea if this would have moved the problem or not. And unfortunately I no longer have access to that theater. Last I checked, the problem seemed a bit more subtle, but still there. I'm not sure if Dolby tweaked something in their code between now and then or not, but something seems like it improved a bit (and we did nothing to the equipment). Anyway, I'm no longer there, so at the moment, I have no further info. Carry on.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 09-02-2008 06:31 PM                     Steve or Sam, any comments to my last post? I'd really like to know if I can use that older reader with an LED...  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 09-02-2008 09:27 PM                     My suspicion is that it WILL work. You will likely need to refocus the lens (adjust its distance to the CCD) to obtain 100% scan. You will also likely need to reset the jumpers to get the gain. When the conversion from IR to visible occurred....CE DID change out the digital assys but had you retain the analog assy so there may be something that I'm overlooking here. Note, the new CCD boards are not that expensive AND they have the status LED on them for a quick visual indication of adequate video level. If you do get the board, get it from CE...they use gold connectors that, in some areas, make all the difference in reliability. Note too...it is entirely possible, though unlikely, that CE has a trade-up program still in effect for the older readers...it WAS some time ago. Steve  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 09-02-2008 09:50 PM                     Thanks Steve, I'll give it another try. I did already make an attempt to get it to work, but, since my lateral guide's rubber pressure roller was bad, I had a huge amount of jitter (Simplex SH-1000) (In excess of 5-8%) so I could not get a signal lock. Yes I was using the DRAS software and not a scope. I could not get a steady enough lock to find the corners. Before I get too crazy trying to refocus to the CCD I'll see if CE still has that exchange program. I do like the idea of getting the updated CCD board, since it has those signal LED's. This is for my personal projector which is why I'm hoping to avoid spending too much on it right now.  |  IP: Logged Fred Tucker Film Handler Posts: 90 From: Sugar Land, TX Registered: Sep 2007 posted 09-30-2008 09:10 AM                     I habe the same problem on both of my CP650 houses. It is most noticeable when the projector is first started since the theatre's coming soon snipe is musical. Most of the time I end up running in SR instead of SRD, I know its film done wrong but whats a guy to do when your GM is never going to OK a basement reader tha will fix the problem?  |  IP: Logged

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