This is topic Will DTS work with change-overs? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Scott Balko (Member # 438) on 01-17-2001, 08:03 AM:
I understand how DTS can work with platters and an uninterrupted flow, but what about with a c-o setup?
Posted by Ken Layton (Member # 133) on 01-17-2001, 08:30 AM:
DTS was designed with 2 projector changeover capability. It reads the incoming machine time code before the actual changeover.
Posted by Scott Norwood (Member # 30) on 01-17-2001, 09:22 AM:
I've seen several DTS changeover setups, including DTS-70. As it was explained to me, the sound changeover occurs as soon as the reader on the second machine detects a higher-humbered timecode signal than the first reader does. The operator still needs to activate the manual sound changeover, but only for optical backup if DTS fails (unlikely).
DTS seems like the easiest of the digital systems to set up for changeover operation, since it only requires mounting the second timecode reader and plugging it in. Dolby requires installing motor-start relays on the motor switches for the projectors, and I don't know about SDDS, other than that there's more to it than simply mounting a second reader.
Posted by Karen Hultgren (Member # 395) on 01-17-2001, 12:16 PM:
DTS works perfectly with change-overs. DTS will work seamlessly with any size edit. Our buffer circuit makes this possible.Karen at DTS
Posted by Aaron Sisemore (Member # 145) on 01-17-2001, 03:03 PM:
To answer another question before it gets asked: ALL of the major digital formats support 2-projector changeover operaion. All thats needed is a second digital reader and in the case of DTS a special Y-cable is also necessary (SRD and SDDS have separate inputs for readers 1 and 2).
Aaron
Posted by Brett Rankin (Member # 31) on 01-17-2001, 08:48 PM:
So just out of curiosity, where do each of the digital soundtracks reside in relation to the picture (i.e. anaolg is 21 frames ahead, etc.)?
Posted by Aaron Sisemore (Member # 145) on 01-17-2001, 09:29 PM:
The digital soundtracks have variable delay settings to the picture, as the digital reader's location varies from projector to projector. on some its ahead of the picture, on others it can be behind a considerable amount.Aaron
Posted by Brett Rankin (Member # 31) on 01-17-2001, 11:32 PM:
I realise that there are variable delays for digital readers/processors, I was just curious as to where the actual corresponding soundtrack is. It's gotta be somewhere. I know it's not of much practical use, but I thrive on learning this stuff...
Posted by Christos Mitsakis (Member # 143) on 01-18-2001, 06:43 AM:
Dolby Digital data are 26 frames ahead of picture.
SDDS data are with the corresponding image frame and I supose DTS time code is much the same as SDDS.
I run both SRD and DTS with change over with no problem. Sorry! No SDDS in Greece 
Christos.
Posted by Stefan Scholz (Member # 147) on 01-19-2001, 09:57 AM:
SDDS changeover on DFP 3000 and 2500 unit (current gear) uses motor start like DA 20's do. They can be wired in parallel.
DFP 2000 (discontinued early type) detects a contact closure and defaults to the 2.nd projector after an adjustable time. It requires the installation of a latching motor start relay operated from the projector control logic or motor circuit.
Easyest c/o is DTS. the Ycable is simple. Disadvantage: Both projectors need to have exactly the same offset for the DTS readers.
With SDDS the offset is independently adjustable for each projector. (Firmware rev. 2.20T with 2000 units, any with new gear.)
DD requires two identical projectors offsets, which is bad in my case. I do have one projector with basement reader, and another with CAT 699 in one setup.
Posted by Antonio Marcheselli (Member # 373) on 01-19-2001, 05:41 PM:
DTS c/o is better than DD one. Just for one little detail: you have to remember to NEVER start Proj. 2 while Proj, 1 is working.
Another projectionst started Proj. 2 during a DTS encoded film (he had a problem and would like to test the projector making it run without lamp for few seconds) and DTS changed immediately to Proj. 2...
This because DTS is completely independent from Projector or Dolby.
But this is not a problem of DTS 
Bye
Antonio
Posted by Steve Guttag (Member # 268) on 01-19-2001, 10:45 PM:
DTS' changeover is firmware based and has changed over the various versions. In fact, the some of the various firmware 1.3X were due to accomodating some specific changeover installations (where the two machines might not run at the exact same speed due to async motors).I always liked the earliest DTS changeover scheme where it always looked to see when the "next" projector come on line...this was the case I think on v1.01-1.04. You could changeover from R2 to R1 if the next projector had the lower reel number.
Then a simpler scheme was used...the machine that has "proj 1" has priority. That is, if "proj 1" has valid timecode, then that is the one that will play. You can run the one connected to "proj 2" but if "proj 1" has valid code, "proj 1" plays. If "proj 1" doesn't have valid code then it looks at "proj 2" and if it has valid code, it will play that. If neither has valid code, it defaults to analog. Therefore, you can "run down" whichever machine is connected to "proj 2" (typically the closest to the player since the cable for "proj 2" is shorter) without fear of messing up the sound from "proj 1"...the reverse is not true though.
On SDDS...for the 2000 series, I designed and made and OEMed to Sony an adapter board called the SCI (and later the SCIv2) that allowed the installer to use motor relays like with Dolby's changeover scheme. In fact, I put a set of male and female 9-pin "D" connectors so the SCI and the DA-10/20 could be daisy-chained. We have sold about 325 of the boards and they have gone world-wide.
When the 3000 series came out, Sony realized their design flaw of the 2000 series circuit so our SCI was no longer needed.
On of the really nice features of the Sony changeover scheme is that the changeover delay is adjustable so that picture and sound sync are precise. With DTS and Dolby, the time-delay is firmware controlled. As such, you must make your changeovers to the preset timing.
Steve
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"Old projectionists never die, they just changeover!"
Posted by System Notices (Member # 2357) on 01-08-2008, 02:12 PM:
It has been 2544 days since the last post.
Posted by Sebastian Binz (Member # 4567) on 01-08-2008, 02:12 PM:
Ahh, great thread, thats exactly what I was looking for, even if the last post was a million lightyears ago...
Now that DTS is explained, can anyone tell me exactly how DD does the C/O? I know about the relay switch already, but is there some kind of c/o cue within the SR.D signal? What will happen if the c/o isn't done properly, lets say the projectionist had too much coffee and hits the c/o button too quickly? Is it necessary to have the right leader that matches to the film or can you take one from another?
We are to install a c/o SR.D (DA20) and DTS (DTS-6) rack soon in our house and Im quite curious about these questions...We don't have any dousers though, just one button to start the motor and a second (c/o) button to ignite the lamp and apply power to the analog laser.
thx
Sebastian Binz
Posted by Peter Castle (Member # 1997) on 01-09-2008, 03:45 AM:
There's only one problem with these digital systems: they all only have one delay for the two projectors. This means that a changeover only works if both projectors are set up identically.
We have all three systems installed and at one time were using changeovers - prior to digital. But we only set up SDDS and SRD on one projector each, with DTS on both (cheapest reader). Unfortunately the delay for the DTS timecode/audio synch was different on each projector. When we changed one projector to a different model, we didn't even try.
We now use one projector only with all three systems on it.
Posted by Steve Guttag (Member # 268) on 01-09-2008, 08:59 AM:
Actually, SDDS always had the ability to handle different delays from different projectors in a changeover system. DTS NOW has that ability for the XD10 system. Starting with firmware 2.1 on the XD10, one can set up separate 35mm and 70mm lip-sync delays. The selection of the delay can be routed to the I/O connector on the rear. Thus, this could be utilized also as a machine 1, machine 2 delay by selecting "70mm" when on machine 2, which will change the lip sync for it.
Dolby never had the ability to handle different delays, that is true and I hear some Hollywood systems used two DA20s just to allow for a non-shared head-end.
As to the question at hand...the DA20 will monitor your changeover line as well as the motor relays. The motor relays let the DA20 know when it needs to start looking at the incoming projector and start loading the buffer with the new data. It looks to the changeover command to know the precise point that this should occur. If you do an early changeover, the DA20 will obey the changeover command and drop you to SR on the incoming machine until the buffer catches up. Likewise, if you are late on the changeover, the buffer will run out of data from the outgoing machine and drop you to SR for the outgoing machine. How much overlap Dolby allows I do not know but as a rule, drops to SR are very rare in a changeover set up on reel-changes. I would think that the splice cache would also augment this since the data immediately before/after a reel change is slowly loaded throughout the reel to ensure no drop outs on reel changes.
Steve