This is topic DTS : reader mounting in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Serge Bosschaerts (Member # 298) on 05-28-2002, 12:16 PM:
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.
Posted by Paul Mayer (Member # 355) on 05-28-2002, 12:57 PM:
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
Posted by Brad Miller (Member # 2) on 05-28-2002, 05:36 PM:
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.
Posted by Karen Hultgren (Member # 395) on 05-28-2002, 06:29 PM:
It is best not to go over '70' on the OFFSET (DTS delay setting on the player).Karen at DTS
khultgren@dtsonline.com
Posted by Frank Angel (Member # 248) on 05-28-2002, 07:12 PM:
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
Posted by Brad Miller (Member # 2) on 05-28-2002, 11:54 PM:
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.
Posted by Gordon McLeod (Member # 33) on 05-29-2002, 08:49 AM:
Frank mount the DTS so it points out the back of the penthouse towards the lamphouse and that will lower it.
Posted by Karen Hultgren (Member # 395) on 05-29-2002, 12:06 PM:
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
Posted by Brad Miller (Member # 2) on 05-29-2002, 01:39 PM:
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.
Posted by Steve Guttag (Member # 268) on 05-30-2002, 09:00 AM:
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!"
Posted by Gordon McLeod (Member # 33) on 05-30-2002, 09:42 AM:
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
Posted by John Hawkinson (Member # 1135) on 05-30-2002, 11:14 AM:
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
Posted by Gordon McLeod (Member # 33) on 05-30-2002, 11:23 AM:
Actually it shouldn't effect properly done changeovers because of the pullup printed the outgoing for the income reel
Posted by Karen Hultgren (Member # 395) on 05-30-2002, 04:36 PM:
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
Posted by Karen Hultgren (Member # 395) on 05-30-2002, 04:44 PM:
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
Posted by Steve Guttag (Member # 268) on 05-30-2002, 10:05 PM:
>>"This is assuming, of course, that that the change-over is done properly."<<But of course 
Steve
------------------
"Old projectionists never die, they just changeover!"