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Author Topic: DTS : reader mounting
Serge Bosschaerts
Film Handler

Posts: 70
From: Schoten, Belgium
Registered: Jan 2000


 - posted 05-28-2002 12:16 PM      Profile for Serge Bosschaerts   Author's Homepage   Email Serge Bosschaerts   Send New Private Message       Edit/Delete Post 
Hello All,

What's the max. distance you can mount a DTS reader on a projector ?
I.o.w. is it possible to mount a DTS reader on top of a magnetic 4 track penthouse ?
Shown on the left is the penthouse in question.


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Paul Mayer
Oh get out of it Melvin, before it pulls you under!

Posts: 3836
From: Albuquerque, NM
Registered: Feb 2000


 - posted 05-28-2002 12:57 PM      Profile for Paul Mayer   Author's Homepage   Email Paul Mayer   Send New Private Message       Edit/Delete Post 
Serge,

I think 56 is the maximum number of frames one can have between the DTS reader and the projector aperture. I got that number by working backwards through DTS' formula (on P.12 of the DTS6D installation manual in the Film-Tech Manuals Section).

Since '70' is the maximum value that can be set into the offset switches, working backwards yields:

70 + 1 = 71
71 / 1.25 = 56.8
Rounding down gives = 56 frames

Cheers!

Paul
One week to go to a walking cast and a return to the booth (maybe)...
Crown Theatres Neonopolis 14
Neon National Forest, NV USA

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 05-28-2002 05:36 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
You can easily mount a dts unit on top of that projector. I've never gotten an answer as to why the dts reader shouldn't be set higher than 70 on the offset, but I do know at Northpark our offset was 97 on one of the machines and we never had a problem.

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Karen Hultgren
Master Film Handler

Posts: 492
From: Agoura Hills, CA, USA
Registered: Mar 2000


 - posted 05-28-2002 06:29 PM      Profile for Karen Hultgren   Author's Homepage   Email Karen Hultgren   Send New Private Message       Edit/Delete Post 
It is best not to go over '70' on the OFFSET (DTS delay setting on the player).

Karen at DTS
khultgren@dtsonline.com

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Frank Angel
Film God

Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999


 - posted 05-28-2002 07:12 PM      Profile for Frank Angel   Author's Homepage   Email Frank Angel   Send New Private Message       Edit/Delete Post 
Serge, we sit the DTS reader right on top of the Simplex mag penthouse (it requires a LOT of stove washers to raise it about the penthouse "hump," but it works just fine. Then we mount a 6000ft magazine on top of both of them. I have no idea what we are going to do if and when we get the Dolby reader. The Kelmar cleaning unit for FilmGuard had to be relegated to bench-top use -- it proved to be one to many penthouse on top of penthouse add-ons.

Frank

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 05-28-2002 11:54 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
So Karen, why? I've always wondered why the units should not be ran over 70 on the offset. What happens? Like I said, we never had any problems with that one running at 97.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 05-29-2002 08:49 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Frank mount the DTS so it points out the back of the penthouse towards the lamphouse and that will lower it.

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Karen Hultgren
Master Film Handler

Posts: 492
From: Agoura Hills, CA, USA
Registered: Mar 2000


 - posted 05-29-2002 12:06 PM      Profile for Karen Hultgren   Author's Homepage   Email Karen Hultgren   Send New Private Message       Edit/Delete Post 
Brad,

The reason you do not want to go over '70' is that the buffer will empty before the incoming reel timecode can be stored. This can cause a moment of silence before sound from the incoming reel will play. We have done software upgrades to remedy the situation so you won't have this problem with movies released in and after 1999.

Karen at DTS
khultgren@dtsonline.com

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 05-29-2002 01:39 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Aha, I've always wondered what the reason was! That might explain a brief dropout in the mid 90's we had at one theater where the dts unit was mounted on top of a Century JJ (the offset wasn't over 70, but it was up there due to the magnetic penthouse). Thanks.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 05-30-2002 09:00 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
The buffer will empty? Now I'm curious! If that was the case, then software couldn't fix it since the buffer is a memory situation.

My next question is...the DTS isn't using the buffer more due to the sync offset is it? If so, that is a silly design. The lip sync switches should only have to provide a time-code offset. There is no point in storing more in the buffer than what it takes to D/A convert in a continious stream. What does the player care where the reader is?

For instance, if the reader puts the time code 25 frames ahead of picture sync (including the time it takes to convert to analog and whatever other processing). Then the player should mearly be told, take the time-code, subtract 25 frames and read from the CD-ROM into the buffer. Likewise, if the reader is 70 frames ahead of picture sync...just subtract 70 frames from the read time-code. The difference in the data stored in the buffer between a 25 frame offset and a 70 frame offset should be zero.

If this isn't how the DTS player works with the time-code, might I suggest a better method?

Steve

------------------
"Old projectionists never die, they just changeover!"

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 05-30-2002 09:42 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
What would happen if one plugged more Ram into the Mother Board would that allow more buffering or is the buffer sized locked in software on the firmware chip

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John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002


 - posted 05-30-2002 11:14 AM      Profile for John Hawkinson   Email John Hawkinson   Send New Private Message       Edit/Delete Post 
Steve,
Notice Karen was talking about the "incoming reel". Subtracting timecode isn't going to work when you're at the end of R1 and coming up on R2, since the timecode resets on each reel, and DTS is really reading Serial# or Reel#+Timecode#.
Of course, you could have the DTS processor know the length of each reel, and have it translate timecode "off the end of R1" into "timecode on R2", but I can certainly imagine why they wouldn't want to do that.
Now, you might say this doesn't matter, they should just store the difference in timecode versus realtime and forget about it, but that reduces the ability to deal with arbitrary edits (which is something that DTS likes to be proud of being able to deal with), as well as complicating their algorithm, since they'd need something to work for the "common case" but something else to work for the "extreme case."
The other problem with that is assuming that projectors use a fixed timebase, which they often don't, and one is going to run slightly faster than the other. I guess you could accept the frequency change in the space of the first second or two of the reel, but that feels "kludgey." This only matters for change-over, of course ;-)

--jhawk


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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 05-30-2002 11:23 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Actually it shouldn't effect properly done changeovers because of the pullup printed the outgoing for the income reel


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Karen Hultgren
Master Film Handler

Posts: 492
From: Agoura Hills, CA, USA
Registered: Mar 2000


 - posted 05-30-2002 04:36 PM      Profile for Karen Hultgren   Author's Homepage   Email Karen Hultgren   Send New Private Message       Edit/Delete Post 
The buffer is still used but now the unit freewheels a little longer even if the buffer is empty (of timecode info).

Karen at DTS
khultgren@dtsonline.com

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Karen Hultgren
Master Film Handler

Posts: 492
From: Agoura Hills, CA, USA
Registered: Mar 2000


 - posted 05-30-2002 04:44 PM      Profile for Karen Hultgren   Author's Homepage   Email Karen Hultgren   Send New Private Message       Edit/Delete Post 
There is no problem for change-overs because the buffer holds a good 4 seconds of timecode data before it empties. That is plenty of time for timecode from the incoming reel to reach the buffer. And, as mentioned, the freewheeling time for the unit has increased a few seconds so there really is no chance for new movies to have a moment of silence between reels - even with the OFFSET (DTS delay) set to '99'. This is assuming, of course, that that the change-over is done properly.

Karen at DTS
khultgren@dtsonline.com

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