Film-Tech Forum ARCHIVE: DTS - moment of silence?

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Posted by Scott Magie (Member # 368) on 05-07-2000, 12:23 AM:

Let me preface this post by saying that the following situation has occurred ONCE. Shows prior to and after this have run perfectly. Could this just be a DTS gremlin that dropped by for a one-time visit or is it a sign that something bad is going on?

Here's the situation...
Today, someone comes out of Frequency and politely (yeah right) informs me that there is no sound. I peak in the auditorium on my way to the booth and the DTS is booming away. The man mumbles something like, "Well, it WASN'T working... and we missed like two minutes of important stuff!" I paused to feel the man's pain, then headed to the booth, where everything was perfectly normal... reader was reading, disks were blinking their proper cadence, etc.
I pay my dues by watching things for a few minutes, then return to the concession stand. Two minutes later a different person emerges, this one even more "polite" than the first. I repeat my procedure, but this time I'm able to personally witness the lack of sound in the auditorium. "Yup, that's a problem," I say as I bolt for the booth. The person kindly informs me that I'm right, it IS a problem, "and especially because this is an action, suspense movie." Like she would want to watch a romantic comedy without any sound! Anyway, when I reach the booth, I notice that everything looks fine still. Instinctively, I punch the SR button, to appease the maddening crowd.
So anyway, that's my story. What get's me is that it didn't switch to SR if there was a problem with the DTS. In the past, that's what has happened. But it stayed on DTS, pumping silence into the auditorium.

So I'm at a loss. And please, I'd appreciate it if your answers were dumbed down a bit. I've learned everything I know by trial and error and I'm just starting to fiddle with some of the sound stuff but I don't know anything about. Even stuff like cards and processors bring a blank look to my face, so if there's a simple explanation for what happened, I'd love to hear it. If a more technical explanation is necessary, fire away but I'll be giving my computer that blank stare, guaranteed.

And again, remember... we've had perfect showings of Frequency before and after this incident.

------------------
Scott A. Magie

scoooot@hotmail.com
"Anybody wanna peanut?"

Posted by Andrew D'Vrey (Member # 285) on 05-07-2000, 12:27 AM:

What type of Fader are you using?

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"And the monkey flips the switch."
- Major Don West, "Lost In Space"

Andrew D'Vrey
IATSE Local 219

Posted by Brad Miller (Member # 2) on 05-07-2000, 04:06 AM:

Fader???

Tell us what kind of projector the DTS reader is mounted on, if there are any other digital readers mounted on top of it as well as the DTS one, what order (from top to bottom) the digital readers are mounted, what kind of platter is handling the film, what kind of sound processor you are using (Dolby, Ultra Stereo, SMART, etc and the model number), and finally, do you have a 2 drive or a 3 drive DTS unit? Also, please let us know if the cd rom drives are the originals. All of these things can cause the problem you described and are generally easily remedied.

Then we can help.

Posted by Dustin Mitchell (Member # 372) on 05-07-2000, 10:25 AM:

I don't why its dropping out in the first place, but as to why its not switching back to SR, I have an idea. We had this problem a little while ago, the processor would just not switch back to SR, not for non-DTS trailers, not for anything. We originaly thought it was a problem with the SMART processor, but after our tech talked to SMART on the phone, we found out that it was in fact the DTS unit. You see, when the DTS unit 'senses' that their isn't any sound, it should send a signal to the SMART unit telling it to switch to SR. Ours wasn't sending this signal. Check for a broken wire or lose connection. If its not that your unit may have to be sent in for repair.

Or I could be completely wrong . This is just one possibility. All I know is when Green Mile dropped out of DTS, and therefore had no sound, for 5 minutes when our district manager was sitting in there with a sold out crowd-which we had to give refund tickets too-we pulled the unit and sent it in for repairs immediatly, no questions asked .

Posted by Gordon McLeod (Member # 33) on 05-07-2000, 10:39 AM:

The length of pulse that the DTS sends out to revert to analogue may not be longesnough to trigger the format switching in the processor
This is a big problem with CP65's and UltraStereo
To the processor manufacturers credit the long pulse length is required to increase noise imunity but the reversion problem suck
I finally got so pissed at one theatre we are order a bunch of the CP200 breakout relay boards and cutting the input to the EQ traces on the Ultrastereo and route it throuh this board as I have never not seen them work
Not elegant but it will work
(If it doesn't it is a thermal nuclear device for it)
Also is it one of the newer or the older white units.

Posted by Mark Gulbrandsen (Member # 72) on 05-07-2000, 02:45 PM:

Gord, Yes the inputs to all Dolby and Ultras and most other ptrocessors are debounced. This does require a bit longer hold but this is really more of a DTS problem not providing adaqute pulse duration. Typically 80 to 100 milliseconds or so should do it for most. You could build a small pulse stretcher circuit quite easily to install on the DTS line rather than go through all the trouble with the CP-200 kludge cards.
Mark

Posted by Gordon McLeod (Member # 33) on 05-07-2000, 02:53 PM:

Dolby provides a pulse stretcher for the CP65 for use with the DA20 already.
It is still not the most reliable

Posted by Steve Guttag (Member # 268) on 05-07-2000, 05:23 PM:

Gord:

Are you referring to the Cat. 410? If so, it isn't a pulse stretcher but a time-constant contractor!

It places a smaller value resistor in parallel to the debounce resistor to allow it to switch faster to format 05 so as to minimize the "pop" and no sound time.

Whom ever thought it was a good idea to wait until the very last bit left the processor before sending the "fallback" signal (ie go to SR) should be taken out back and beaten sensless. When you KNOW you are going to lose digital signal (and with the Dolby digital system, it knows it is going to lose digital when the buffer isn't full up to the sync delay) why wait to the last bit...switch .5 sec early, it really doesn't matter since you are not going to switch back and forth in the .5 second (or you shouldn't if you don't want to call attention to the problem).

Steve

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"Old projectionists never die, they just changeover!"

Posted by Joe Redifer (Member # 3) on 05-07-2000, 05:49 PM:

I personally have never had any problems with the DTS switching formats on the CP65's, but have had that problem on the Ultra's. Not every Ultra in the building, though, just some of them.

Posted by Gordon McLeod (Member # 33) on 05-07-2000, 06:17 PM:

On the Ultras they have optoisolators on the input lines and I think the fet output is what is determining the time constant of the switching
The relay board is the most simple method
I tend to belive in the Kiss principle under these circumstances
"Keep It Simple Stupid"

Posted by Brad Miller (Member # 2) on 05-07-2000, 06:33 PM:

Still needing the specifics on the equipment here, but one thing that has happened before is if the unit was recently moved (or someone was in the back of the rack for whatever reason), the jumper to switch back to "A" or "SR" could've fallen off of the automation board with a CP65.

Posted by Tom Ferreira (Member # 70) on 05-08-2000, 07:39 AM:

Good Lord, guys-Scott asked if you could please dumb it down!

I had this problem for a while-do you have the 6D(three drive)unit, or the old two drive? Mine turned out to be a bad patch cable between the DTS unit and the Smart processor.
Make sure the reader is clean and free of gunk-I blow it out everyday. Where it isn't a continuous problem(Is it kicking out at the same point every showing?),it it is, it could be the print-I've also had bad disks-it is a possibility. Is there a possibility the drives could need to be cleaned? Do check all your wiring and connections.

Posted by Tom Ferreira (Member # 70) on 05-08-2000, 07:42 AM:

OK-so Scott did say it didn't happen again-could it have been dust in the reader? I'd keep a close eye on it...

Posted by Scott Magie (Member # 368) on 05-08-2000, 11:27 PM:

Okay sorry it took so long for me to get back with more details.
-DTS is only digital reader
-Century projector
-some Potts Inc. platter system
-3 drive DTS unit (don't know if they're original drives or not)
-I'll have to check on the processor, but I'm leaning toward Dolby... no clue on model number since I'm not even sure it's Dolby.

Sorry for the sketchy details. This is my new theater and I've been too busy cleaning 1/2 inch of coagulated peanut oil off of the popper to memorize what I have in my booths yet. I'll check on model numbers, etc. and post again Tuesday night.

------------------
Scott A. Magie

scoooot@hotmail.com
"Anybody wanna peanut?"
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ps- The reader is not dirty. I've seen very dirty readers working fine and this one was freshly cleaned days ago.

Posted by Joe Redifer (Member # 3) on 05-09-2000, 01:29 AM:

If you have a 3 drive DTS unit and are playing movies less than 2 years old, it doesn't matter if the jumper that says "SR" or "A" is engaged or not. The DTS disc tells the unit what format to fall back into as the mixers of the disc know what analog format the film is in. I purposely leave all of these jumpers off and have never ever had a problem. The jumper is provided for those people who don't have SR, at least in my guess. Otherwise it serves no purpose whatsoever (for me). It is useful if you don't want the digital falling into Non-Sync during the credits, which many DTS discs tell the player to do if the timecode disappears during that period of the film.

Posted by Brad Miller (Member # 2) on 05-09-2000, 01:53 AM:

Joe, he might not have SR cards if he's got an Ultra unit or a CP55. That's where the forced fallback to "A" is important. Until a dropout actually occurs, no one would even realize the failsafe would be pulsing into a non-existent format.

Also, I've witnessed a DTS6D hooked into an Ultra unit where the projector was shaking enough where it wouldn't track a solid timecode and lost timecode for a few minutes at a time. The problem with it not reverting was that jumper had fallen off as units were moved around! Once it was replaced, analog fallback commenced again normally. This was just last year. Besides, no studio is making "A" tracks anymore, so a forced fallback to SR wouldn't matter if you have the cards. The jumper is desirable in most cases, but as you pointed out is not necessary in a booth like yours that is fully equipped.

Knowing the model number of the processor will help greatly.

Regardless, since it never happened before and hasn't happened since, this will be very hard to track down. Heck, it could just be that the platter's brain wasn't threaded quite on track that one show and was bouncing the film. I've seen this sort of misthread happen once on a Strong platter where the film was bouncing significantly, and a Potts is basically the same thing.

Posted by Karen Hultgren (Member # 395) on 05-09-2000, 12:44 PM:

Hello Scott,

Sorry for the delayed response, but I just read your posting.

If DTS drops out, it should always revert to an optical format. If this is not happening, be sure the logic board to the CP is connected. Then check the DTS unit by removing the movie discs and loading in a Setup disc (hopefully you have one of these). Once loaded, the disc should play by itself and automatically switch the CP into the format that DTS is using (format depends on the CP). Then, eject the disc and the DTS should pluse the CP into an optical sound format.

If this is not happening, then call your service tech and ask for a full check on DTS and the CP (maybe the CP automation has a problem?).

Karen at DTS

Posted by Scott Magie (Member # 368) on 05-09-2000, 11:57 PM:

Okay, it's a Dolby CP-65 and I'm sure if we ever had DTS Setup disks, they are long gone. Like I said, I've just been hired here and it's a somewhat neglected independent theater, so who knows... there may be setup disks somewhere, but I've only just begun to explore some of the weird little cubby-holes in this place.

Another thing that is probably related, but may or may not help diagnose the problem. Today it wasn't kicking into DTS AT ALL! I have no clue how this (or any) automation is wired, but I've been doing all my lights, douser, and sound selecting manually because I'm in the process of figuring out how this cueing system is set up. They haven't been cueing the movies when they build them, because until I came, it was basically high school kids running the place (no offense to you young whipper-snappers out there). So I'm wondering if the DTS isn't kicking on when the automation "thinks" that we're still in intermission. But from my limited experience with this sort of thing, I'd think that it wouldn't matter. If the reader finds timecode, it sends it to the drives... if the drives find the same timecode, they tell the processor to change over to DTS... right? This should be totally independent of the automation, right?
I just can't think of anything ELSE that it would be. The light on the reader is uninterrupted, so it's gotta be the drives.
Karen- can I order some setup disks... or even better, can you (or someone else there) send me some free ones to show off your incredible customer service?! If you do, I'll be sure to post a topic here entitled, "Golly, DTS sure does rock!"

------------------
Scott A. Magie

scoooot@hotmail.com
"Anybody wanna peanut?"

Posted by Karen Hultgren (Member # 395) on 05-12-2000, 06:35 PM:

You will need a DTS setup disc of some sort to check out the system. If DTS is not kicking in/out the CP, then it sounds like the logic pulses from the DTS player to the CP's automation are not making it to their destination. There should be a logic cable from the DTS player to the CP. There should also be a DTS interface board connected to the CP.

You may want to check that the CP automation is working OK. Use a peice of wire from ground to each sound format connection. See if the CP will switch properly.

Please give me a call at (800) 959-4109 Monday thru Friday from 9am until 6pm pacific time. We'll discuss the details.

Thanks !! Karen at DTS

Posted by Ethan Harper (Member # 472) on 05-16-2000, 10:53 PM:

Here is an interesting question for you,
I use to work at skinemark im sorry i meant cinemark tinseltown 20

we had recently got some new drives in for our dts and on a couple of instances for some strange reason, it would play the wrong soundtrack for the trailer on screen.
For example we were once showing a kids movie with a kids trailer but,... it was playing the soundtrack for some evil movie. this scared the kids of course. kinda funny. could not figure it out. oh well just something funny i thought i should share.

THX
EH

Posted by Jim Ziegler (Member # 86) on 05-18-2000, 01:47 PM:

I have had similar problems (random drop outs) on several units. However, it only seems to happen on the units running the old firmware. I have had to upgrade several units over he last year (CD-ROMS kept dying) and none of the upgraded units have dropped out. The assumption I have always been operating on is that the old firmware simply had a bug that caused the system to crash if it got confused..

Posted by Scott Magie (Member # 368) on 05-19-2000, 12:19 AM:

Jim, I'm not afraid to admit that I'm a big dummy, so what is "firmware" and how might I know if I have "old" or "new". Is it something simple?

Today I was able to observe the DTS "dropout" for a long time because no one was in the auditorium (Battlefield Earth... SURPRISE!) Anyway, what happens is this. The DTS kicked in for the attached preview and was perfect until maybe 15-25 minutes into the show. Then, out of nowhere (not at a reel-change or anything) it went silent. So I now know for sure that it is failing to switch to SR when this problem occurs. Here's the weird thing... it's not completely silent. There are pulses of sound that occur slightly more than once a second (but not quite twice a second). I counted 75 pulses per minute. At first, they were long enough to sometimes catch a syllable or sound effect from the actual soundtrack, but eventually, the pulses were shortened to just a regular cadence of clicking. This was my observation in the auditorium. Then I went up to the booth to see what I could see. The light on the DTS timecode reader remained perfectly steady, so apparently the timecode was being read properly. But on the DTS unit itself, there were some interesting things going on. The indicator lights on the two drives in use were blinking to the same cadence as the sound pulses (which could also be heard thru the monitor). Also blinking to that same cadence was the indicator light marked "digital". With the movie still playing, I ejected the disks (the CP55 still didn't switch to SR) and re-loaded them. The same clicking resumed once the unit found the timecode on the disks.
This is not the first film to have problems in this auditorium, but we HAVE had a few flawless shows here and there, so it doesn't seem to be consistent.
Once again, I ask for your dumbed-down assistance. I'd like to get this figured out so I'll know what parts to order before the tech-guy comes... otherwise I'll have to install them... and I'd rather let someone who has half of a clue be responsible for the expensive stuff.

------------------
Scott A. Magie

scoooot@hotmail.com
"Anybody wanna peanut?"

Posted by Jim Ziegler (Member # 86) on 05-19-2000, 05:55 AM:

The firmware is the DTS's operating software. The software is programmed onto a chip located an the same board as the status lights. The easiest way to check what version you have is to look on the back of the unit, as it may have a sticker that says what version you have. If it does not, you can remove the top fo the unit and look at the chip itself (it is about an inch long and a half inch tall and is located pretty much dead center of the board). The chip will have the version number printed on it. Basically, find out the version, call DTS and see if it is current, if it is not, order a replacement chip.

Posted by Steve Kraus (Member # 476) on 05-21-2000, 10:17 AM:

I'd like to mention that DTS errs in the way that the soundfiles are prepped before the disks are cut. It's a subtle error that will only affect those running reel to reel using timecode derived changeovers with a malfunctioning timecode reader.

The problem is that DTS allows the audio files to run to the end of the reel, including leaders, tail pop, vocal identity. They should be edited to cut off immediately at the end of active audio.

Why?

The newer DTS units can be set up for direct control of changeover but the traditional way (and the only way on the older units AFAIK) is that the audio changeover is controlled by the timecode. When the box sees timecode from the new reel it switches over to the new audio file for the new reel. It's automatic.

The problem is that if the timecode reader on the incoming machine is defective or, in my case one evening, out of adjustment vis a vis the lateral position of the timecode on THAT (the incoming) reel, there won't be any timecode from the new machine. That would be no problem if the audio file of the outgoing reel ended dead with the end of the reel. In that case with the file at an end and no new timecode the box would simply switch the CP back to analog (which would be on the new projector since the analog track has changed-over). But because the audio files tend to run out the reel under such conditions the DTS won't drop out for many seconds leaving the audience with (variously) silence, a beep, audio gobbledygook, etc.

DTS standards should therefore include ending the audio file at the end of active audio as this would force a timely dropout in the event of a timecode failure across the reel change. Not something that comes up too often for too many people but entirely unnecessary.