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This topic comprises 2 pages: 1 2
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Author
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Topic: DTS : reader mounting
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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
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posted 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
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 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!"
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John Hawkinson
Film God
Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 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
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