Film-Tech Forum ARCHIVE: SRD Sync problem

This is topic SRD Sync problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=004594

Posted by Mike Rendall (Member # 1499) on 02-24-2003, 12:04 PM:

We have been having an intermittant fault with our SRD. Occasionally it will go out of sync (i.e. lags behind picture by 0.5seconds or so). This occurs in effect randomly perhaps once every three films or so for about 2 mins. We obviously have to drop to SR and keep an eye on it. I don't understand what is going on. It is not dropping out at splices, nor is it failing, it just seems to be suddenly playing out of sync.

I am thinking of taking the cards out and checking them over, I am thinking a possible dry joint on the edge connector or maybe the sync pot?

Equipment as follows :

Cinemeccanica Vic 8, Basement SR-D reader,
Dolby CP65, with DA20 Digital adapter and dts-6D.

Any suggestions? We have recently moved so I am wondering if there are cards that have become unseated in the DA20. There are no problems with the dts.

Union films webpage

Posted by Bill Langfield (Member # 818) on 02-24-2003, 12:19 PM:

I vote it's the basement reader. (Are you keeping them VERY clean with a q-tip cotton bud. I think they might be collecting dust the way they are mounted at an upward angle)

We ditched SR-D out of 3 cinema's because they just could not be trusted and put DTS in them.

In hind sight it might have been better to have put 701 penthouse readers, seeing that all (well almost) ads and trailers are srd.

I think there other threads that have covered this (lag) and even DTS having the same lag problem. (Moulen Rouge(sp?) comes to mind)

My main gripe about using DTS (and it's not their fault) is that only 75% of prints come with the disks. (I'm talking brand new first run)

If you have DTS and SRD on the same screen, why not just run DTS?

Bill.

Posted by Michael Schaffer (Member # 1204) on 02-24-2003, 01:56 PM:

I wonder how it could be the reader (I am not saying you are wrong, I am just wondering if it could do that), since the Dolby reader simply takes an analogue image of the fixel blocks. The image is then concerted into a digital video image and processed. I would think a phenomenon like this would be more likely to be caused by a problem in the digital domain.
If I remember correctly, the digital video image is buffered, processed twice and then the data are passed on. I think there might be a problem with the video acqusition system.

Posted by Brad Miller (Member # 2) on 02-24-2003, 02:32 PM:

It's in your DA20. I've seen that problem once before, but I can't remember which card was at fault.

Posted by William Phillips (Member # 1162) on 02-24-2003, 02:42 PM:

I have also had the same problem about 2 years ago. The sound went out of sync on SR.D so put it into SR switched the processor off and on and the problem has never come back. Dont know to this day what caused it.

Posted by Antonio Marcheselli (Member # 373) on 02-24-2003, 03:52 PM:

I agree with Michael that it is strange that the reader can affect the sync of sound.

I do not know DA10/20. How it manage the reader's offset? Is it a mechanical switch like DTS? Can be a defective or dirt switch?

Bye
Antonio

Posted by Michael Schaffer (Member # 1204) on 02-24-2003, 06:01 PM:

Yes, there are three rotary switches on the Cat.No.611A CP interface board to set the delays by hundreds, tens, and single perforations.
The DA20 manual says "Digital soundhead delay is set by switches on the Cinema Processor Interface Card (Cat.No.611A). If synchonization becomes incorrect during a show, press Format 10. This re-sends a delay turn-on command to the Cat.No.611A."

This certainly points to a problem with the Cat.No.611A rather than the video acquisition system as I suggested earlier.

Posted by Mike Rendall (Member # 1499) on 02-25-2003, 02:49 AM:

Cheers for your help, I will have a poke around and see if I can track down the problem.

Mike

Posted by William Phillips (Member # 1162) on 02-25-2003, 05:25 AM:

So by the sounds of it the sound going out of sync is something that can happen for no reason, just like a computer crashing?.

Posted by Michael Schaffer (Member # 1204) on 02-25-2003, 07:25 AM:

In a way, yes. The DA20 manual even refers to that and admits that complex digital systems can sometimes simply hang themselves up. Of course, other factors, just as thermic or mechanical influences can add to a problem.
I once had a problem with a trailer which had a bit of digital code on it which reset the CP500s delay and the digital sound was out of sync until reboot.
A problem like this can be spotted by observing the error rate display. When it displays an "L" (I think it stands for learning), it means that the processor is reading code other than sound data.

Posted by Christopher Seo (Member # 7) on 02-25-2003, 11:19 AM:

Whoa, Michael, are you saying that a trailer forced the CP into Learn mode? Did you actually see an "L"? I didn't think Dolby ever encoded trailers with code updates, trailers probably being too short for one thing. Did all copies of that trailer do that, or just the one? (And was more than one processor affected as well?)

Posted by Michael Schaffer (Member # 1204) on 02-25-2003, 08:07 PM:

All copies of the trailer (Billy Elliott) did that. I haven`t found out yet what piece of code did it. I hope to meet some people on ShoWest from Dolby who can enlighten me about that.
Yes, I saw the "L". I was there and all I could do was to witness the madness (and while I did that, I pressed the SR button).