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Topic: Auto-switching of sound format, how does it work?
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David Stambaugh
Film God
Posts: 4021
From: Eugene, Oregon
Registered: Jan 2002
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posted 03-09-2002 06:19 PM
Apologies in advance for asking a newbie-type question, but there are probably other lurkers here besides myself who are curious about this. I couldn't find a definitive explanation of this in a search.How is sound format switching done? Suppose you have a screen equipped with SDDS, DTS, and SR-D. You want to show the feature in SDDS, but maybe some of the trailers don't carry SDDS but do have SR-D, yet you want to show all of them in digital if possible. How is the switching between formats done? Other threads have mentioned using automation cues, or doing it manually (manual switching doesn't seem very practical if you have 20 screens to tend to). So in the real world, how is this normally handled? And is it possible to completely automate this to the point where you prioritize the formats, so if the sound track is present in the preferred format, that format is automatically used, but if it's not present the next highest priority format is used instead, and so on, with analog being the last-ditch fallback? Enquiring minds want to know. 
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Jon Bartow
Master Film Handler
Posts: 287
From: Massachusetts
Registered: Nov 1999
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posted 03-09-2002 10:05 PM
Generally speaking (there are always exceptions of course) if you want to change from one digital format to another you must either change the format manually (i.e. go over and push the apropriate button) or have a cue set up in the automation.
*A cue being a mehtod of tripping the automation actually applied to the film ahead of time by the projectionist. (various cue types range from strips of sticky-backed foil that actually make electrical contact between two rollers, to proximity detectors that "sense" foil dots placed on the film, to bar-coded stickers that are read by a bar-code reader [bar codes are a United Artists Theaters speciality])
*Theater automations are essentially just industrial automations, very similar to any system running an assembly line, etc. When a cue is "read" by the automation it starts a series of timers and relays to control a pre-determined series of events (i.e. curtains, light levels, turret position, sound format, etc)
*The three digital systems (DTS, SR-D, SDDS) do not like being engaged with each other on the same screen at the same time without a controller to prevent interference with each others signals.
-DTS waits for a timecode to be read on the film and if the correct disc is in the player for that film (or trailer) it switches into DTS automaticaly
-SR-D can be set up to switch on in one of two ways: either it waits to receive a signal from the automation or it will engage as soon as it finds a SR-D sound-track on the print (this is referred to as "auto-digital" in the Dolby literature)
-SDDS IIRC behaves the same way as SR-D (either triggered by the automation or automatic) The SDDS DFP-D3000 will do a digital fallback structure incorporating all three Digital formats with a customer preset hierarchy of formats (i.e. SDDS -> SR-D -> DTS -> SR ) I've never seen it done with any other equipment but it is possible. I'm sure others will have much more to add to this but it's a start
Jonathan
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 03-10-2002 04:36 PM
It is often possible (and it is the way I install multiple digitals) to pre-determine the preferred digital priority amungst the digital formats. Sometimes it takes some tricky wiring to get the priority the customer wants. The idea is that the operator threads all readers and if there is valid data on one or more digital systems, the cinema processor will use any or all digital system. If the one with the most priority fails, the next highest digital processor in the priority is already playing in digital to fall back on. How the three systems work (from a logic and channel standpoint) makes setting the priority levels easier or harder for different priorities. Steve ------------------
"Old projectionists never die, they just changeover!"
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