Film-Tech Forum ARCHIVE: Dropping out of Digital Alarm

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Posted by Markus Lemm (Member # 3456) on 10-26-2007, 01:13 PM:

Just wondering if there is a way to setup an alarm that sounds when the processor drops out of digital.
At my cinema we have a CP55 that goes into AUX when processing digital and goes to SR when the digital cuts out. Is there a way to add a circuit that rings a bell when the processor switches out of AUX?

Posted by Pete Naples (Member # 761) on 10-26-2007, 04:03 PM:

Whilst it wouldn't be difficult to do something like this by using the status outputs of the CP55, I have to ask, why?! If it's reverting when the SR.D track is not playable for whatever reason, it's doing it's job!

Or have you been watching 'Das Boot'?

ALARM!!!!!!!!!!

Posted by Jack Ondracek (Member # 1466) on 10-26-2007, 06:30 PM:

I could think of one practical reason for this.

We've had prints that were so hacked up, the SRD was useless. However, that didn't keep the Dolby from trying. At 6-F error rate the sound can be pretty ragged. If it hunts back & forth from SR to SRD whenever it gets a decent section of film, it can sound downright awful. In cases like that, we've bypassed the SRD, but not before the problem lasting much longer than we would have liked.

Some kind of audible that would indicate a problem would be handy in a case like this.

quote:
ALARM!!!!!!!!!!

Posted by Pete Naples (Member # 761) on 10-26-2007, 06:35 PM:

In which case, switch the SR.D off whilst the distributor organises a decent print. Surely prints are rehearsed before public exhibition?

Posted by Ken McFall (Member # 845) on 10-27-2007, 04:46 AM:

"surely prints are rehearsed before public exhibition..."

and now back to the real world.

Prints often arrive on the morning of the opening date or there is no time allowed for print rehersal in the budget.

Therefore an audible indication would be most helpful especially during the first run to let the operator know if there is a fault with the print's SRD track.

You need to know you have a problem before you decide to bypass SRD.

Being Proactive rather than Reacitive may best describe such a need. Sort it out before the audience complain.

and now we returm you back to the fantasy world where everything is rehersed and nothing ever goes wrong.

Posted by Steve Guttag (Member # 268) on 10-27-2007, 08:20 AM:

Simple...turn off the analog LED....when the audience comes out demanding their money back for lack of sound...you will get your audible alarm!

But on the CP55, where they have status ID lines designed to light LEDs on a remote (ID0 - ID7), you could use those lines to trigger an alarm. Note, they are current limited via a resistor to just have enough current to light an LED (20-30mA) so you will most likely need to use a transistor to fire something to make the visual or audible alarm.

Steve

Posted by Markus Lemm (Member # 3456) on 10-27-2007, 09:21 AM:

Thanks for the input. I'll see if I can make use of the pulse that causes the jump to AUX. As for previewing a print before we show it is not an option since we usually only show a film a couple times than change the films. We are a second run theatre that does double bills and alot of films come by bus the day of the show.

Posted by Jack Ondracek (Member # 1466) on 10-27-2007, 09:24 AM:

quote: Pete Naples
In which case, switch the SR.D off whilst the distributor organises a decent print. Surely prints are rehearsed before public exhibition?

It's an extreme case for us, but it has happened. If I get a crappy print on Friday afternoon, I'm shot until at least Saturday. Being a drive-in operator, "rehearsing" shows is a luxury I don't have. Puts a bit more pressure on during inspections!

Posted by Brad Miller (Member # 2) on 10-27-2007, 10:14 AM:

I totally understood the point of this thread until this post...

quote: Markus Lemm
Thanks for the input. I'll see if I can make use of the pulse that causes the jump to AUX. As for previewing a print before we show it is not an option since we usually only show a film a couple times than change the films. We are a second run theatre that does double bills and alot of films come by bus the day of the show.

So let's see what we have here.

*Your CP55 automatically switches to SR in the event the digital fails.

*Your prints usually arrive the day of the show so there is no time to pre-check the print and order another.

*You generally only run prints for maybe 2 days before you ship them.

So in your situation what difference does it make? By the time that alarm goes off, you can't get another print anyway and it will just default to SR. (The 6-F problem is the only legitimate reason I can see for this, but note that usually is NOT enough to kick the processor out of digital, hence your alarm wouldn't go off anyway.)

Posted by Markus Lemm (Member # 3456) on 10-27-2007, 10:30 AM:

Well Brad,
I'm interested in giving the best possible presentation every time, which is very difficult based on the amount of print traffic and sometimes total garbage condition of prints that I handle on a daily basis.
The alarm is there so I can do something about the problem right away instead of having the film jump from analog to digital and back throughout the print, which sounds like crap.

Posted by Chris Slycord (Member # 4239) on 10-27-2007, 10:49 AM:

Could you rig up an alarm that goes off if the error rate goes above a certain point?

That said, it's not that uncommon for a print to go to "F" for just one moment and not have it happen again during a show.

Posted by Louis Bornwasser (Member # 3063) on 10-27-2007, 11:30 AM:

What you need is an alarm that does not go off if an occasional "SR" happens, but say 5 revisions in 3 minutes would trigger it so that you can then disable the DIGITAL led. Older revisions would then "time out" after 3 minutes.

While an occasional "bad print" can be a problem, this kind of digital trouble, even on second run, even in "the sticks" would point me to a less-than-ideal Dolby Digital alignment issue. I have not seen "failure" to be a problem with a correctly set-up system, even on some very bad prints. Louis

Posted by Brad Miller (Member # 2) on 10-27-2007, 01:03 PM:

Louis, it is prevalent all around actually. I can understand his reasoning, but fact of the matter is that there are many machines that if you do not use FilmGuard or some sort of film lubricant on them, the SRD tracks WILL get scraped right off rendering even a perfectly aligned Kinoton SRD reader that would typically track at 0-1s nothing but Fs. Century projectors however are not one of them, and I know that is probably 90% of your client base. [Wink]

After Markus' most recent post, I think his best solution is to upgrade his analog system. There shouldn't be THAT much of a difference when the two formats switch back and forth. Even if his system is perfectly aligned, the offset may be just a tad bit off giving that "skipping" effect. This is why I prefer to set SRD offset via a known loop of dialogue as compared to the SR track, rather than the sync pop test film.

Posted by Scott Norwood (Member # 30) on 10-27-2007, 01:23 PM:

quote: Brad Miller
there are many machines that if you do not use FilmGuard or some sort of film lubricant on them, the SRD tracks WILL get scraped right off rendering even a perfectly aligned Kinoton SRD reader that would typically track at 0-1s nothing but Fs

What kind of crappy projectors are those? Simplexes don't do this, either. Nor do Kinotons or Cinemeccanicas.

Posted by Josh Kirkhart (Member # 1046) on 10-27-2007, 02:38 PM:

Go get an old DTS-6D and otherwise use SR.

If print holdover is that short and print condition so bad why attempt to keep SR.D. With a 6AD you have better chance of great sound on a crappy print than SR.D(if you can get the discs! Maybe a partnership with a first run for discs)

clean the prints!

Posted by Markus Lemm (Member # 3456) on 10-27-2007, 02:55 PM:

The problem is actually with DTS dropping out. The condition of discs is the issue. When we do get discs they are usually bent because someone put them at the bottom of the can instead of between the reels. A lot of discs have scratches on them especially the burned sets that we get.

Posted by Louis Bornwasser (Member # 3063) on 10-27-2007, 03:07 PM:

Wow! Just another reason for sound-on-film! Nevermind. I agree with Brad, SR, when done perfectly is NEARLY equal to the best digital audio, so I feel you should work on that aspect and not try for digital unless it too is perfect. Louis

Posted by Monte L Fullmer (Member # 2797) on 10-27-2007, 03:16 PM:

quote: Markus Lemm
A lot of discs have scratches on them especially the burned sets that we get.

..now, that's a bit interesting: "Burnt ones?"

Sounds like, with your sound system the way it is, (difference in Digital and optical, DTS dropping out at times, et.al.) needs a visit from a tech for sure.

Posted by Brad Miller (Member # 2) on 10-27-2007, 04:17 PM:

Scott, even Kinotons can scrape the SRD track off. It is usually seen on PK60s that are mounted to other lamphouses without enough heat protection.

As far as Simplexes, it depends on the vintage. I agree with you on the Cinemeccannica though.

Posted by Scott Norwood (Member # 30) on 10-27-2007, 05:13 PM:

Interesting. The only PK60s that I know of in this town have Kinoton lamphouses and don't damage film or SRD tracks. FP30s, of course, have Kinoton lamphouses built in and don't have this problem either.

[ 10-27-2007, 06:30 PM: Message edited by: Scott Norwood ]

Posted by Steve Guttag (Member # 268) on 10-27-2007, 08:11 PM:

Wait a minute...PK60s with Kinoton lamphouses? Really? Why bother with that set up when you can skip the middle man and just get a FP30? Had loose pedestals lying around?

My own experience with PK60s has been such that no SRD damage whatsoever...lamphouses have been Strong and even Christie (CK20s...not known for being cool).

Steve

Posted by Scott Norwood (Member # 30) on 10-27-2007, 08:45 PM:

See the pics for Boston Museum of Fine Arts. They put in the lamphouses first and upgraded the heads (from E7s) later. Ceiling height is an issue there and I don't know if FP30s would have fit anyway.

Posted by Greg Routenburg (Member # 1742) on 10-28-2007, 06:28 PM:

Could you not build an S-R Latch with a couple of NAND gates, connect the SR Automation Pin on the DTS unit to the Set side of the latch, a momentary push button to the Reset side for an alarm silence button? You'd still have to use a transistor on the output of the latch to drive any real loads like a buzzer or something. By using the connection on the CP55 for the remote box, wouldn't it trigger the alarm even when the processor was running in SR for a movie that had no DTS track?

Posted by Brad Miller (Member # 2) on 10-28-2007, 08:28 PM:

Ummm, wrong Steve-o. Check out this picture.

That is not one of my installs, but is precisely what happens if you dare put a non-Kinoton lamphouse with more than a 2K bulb behind a PK60 without heat filters and water cooling. The delrin melts and cracks away. The result is total destruction of the SRD and SDDS tracks. For extra fun, the aperture gets melted to the delrin as well, so when the operator switches lenses, the arm gets bent. Meanwhile the picture starts shaking uncontrollably as the intermittent coupler turns to mush.

Posted by Steve Guttag (Member # 268) on 10-28-2007, 08:53 PM:

Brad....my findings are my findings...I believe I only have two PK60s with more than 2KW and no water cooling...they are Strong Super Lume-X lamphouses though.

That said, I don't dispute your findings...since I don't have extensive experience with greater than 2KW on a PK60 using various brands of lamphouses/consoles.

I have a friend that has a mess of PK60s on Big Sky consoles and has not reported any problems like the ones you dipict, however. I'll ask and see how many are above 2KW and what the water cooling status is.

Posted by Lyle Romer (Member # 1266) on 10-28-2007, 09:33 PM:

If you do build the alarm you need to do it with some type of state machine not just simply connect to something to drive the buffer.

You need the alarm to go off if SR gets pulsed after AUX has been pulsed and then silence if AUX gets pulsed again. I'd have to whip out my engineering books to actually design it. If I get bored in the next couple of days I'll sketch it out. You'll need a couple of logic gates and a transistor to drive the alarm on the output.

If you want to keep it simple I guess you can just have the alarm go off whenever SR is active but then you'll get the alarm annoying you during trailers that aren't in digital.

To the question of alarming on a certain error rate, I'd think the only way to do that would be to use a microprocessor to read the serial data (pulling the error rate out) and then writing a program. Or you could hack the error correction card and use the lines that drive the LED display to drive some logic that alarms whenver the lines that are "hot" are the ones that make up 6 or 7.

If it was 1993 again, I'd suggest to Dolby that they include this as a programmable output of the DA-10/20 that could be used to drive alarms. Now I think the only alarm they would care about is one to tell you that the 3D filter isn't spinning right.

Posted by Louis Bornwasser (Member # 3063) on 10-29-2007, 10:48 AM:

Lyle; the trouble is with dts not playing. I, too thought he had "Dolby trouble." Also, remember the Dolby fault can be quite high and still work reliably. It can also be quite low and still revert. Louis

Posted by Daryl C. W. O'Shea (Member # 1303) on 10-30-2007, 12:34 PM:

Not a dig at you Kyle, but I love it how everything requires a microprocessor these days. The other day I saw a pair of ice skates with heated blades that required a microprocessor to control them. It's insane.

You should be able to build something around a shift register and a timer to count the number of reversions (and alarm when too many reversions occur) in a certain time interval.

Posted by Markus Lemm (Member # 3456) on 10-30-2007, 01:41 PM:

Thanks for all the advice.
When I build something and get it working I'll share my results here.