Problems with DTS 70mm Playback

[Ryan Gallagher]

We do all the changes here on 24" reels, so both directions (but with an XD10).

A couple other lines of inquiry:

Is this a “new” problem that appeared after you sent out a reader to be copied?

Your description does not sound like you have tried swapping the readers across the machines yet. Might be worth a try to narrow it down, but the fact some 70mm prints work fine would suggest the issue is perhaps elsewhere. If it is easier just flip the ends of the Y cable across readers, effectively the same test.

Print condition is also a consideration, but your average of having this problem on so many points elsewhere too I would think.

The XD20 manual reads like it should be taking the changeovers at the first picture frame regardless, as Marco stated, with no preference to projector (and obviously not playout all the way to end of tail timecode). Do you have timecode status light on the incoming reader at the time the changeover should occur?

Does that LED on the reader follow the AP20 timecode LED indicator and both drop out? etc.

I think the instincts here of the Y cable and wiring being most likely to blame is a good one. But perhaps there is a problematic connection on one of the readers causing similar outcomes.


And yes triple checking your TC Reader Offset for 70mm between the aperture and the reader would be good, remember there is a formula to convert that into the number you put on the XD10/20, if you just put the raw frame count you'll be off, but sync would hopefully reveal that problem. From the manual:

TC Offset.png

Also obviously the trap for people in a hurry is to forget to switch between 35mm and 70mm modes on the XD10/20. (There is also a special venue and smpte modes to avoid as well, unless using them). But hopefully this would reveal first as sync issues rather than change-over issues.

We have a loop of a 70mm DTS print we use to test the readers after configuring for 70mm. It can't test changeover conditions per say... but it might reveal if one reader is having trouble activating promptly with picture and timecode data? For amusement, our victory dance occurs when we hear the cow moo in Dr. Doolittle. ;-)

[Marco Giustini]

but that would mean a BEEP at each P2->P1 reel change? I never really tested that type of changeover though, my changeovers were only one per movie, from P1 to P2 in the middle of the feature.

One final thought, surely unnecessary: Jerry, you're running the latest software, are you?

[Steve Guttag]

What I found was that, early on (DTS 6 days, before the 6D), for changeover, DTS would presume the incoming timecode is what it should shift to. Then, somewhere along the way, they decided that P2 should get priority. So, so long as P2 has valid time code, P1 can't take it back. The changeover back to P1 depends on P2 timecode going away at the end of the reel (or when P2 is turned off). I believe that philosophy was carried forward into the XD10 and XD20 decoders. It was a function of the Timecode board and the chip on it.

I would verify that your Y-cable is wired correctly with P1 going to pin 1 and P2 (wire 1, however) going to Pin 2 and the rest doubled-up. On the reader end of the cable, wire 2 is N/C. Truthfully, at the player, pins 3 and 4 are N/C too.

[Marco Giustini]

very interesting.
I have run DTS on changeover for a few years, if memory serves, the DTS player will consider a "changeover" when the "other projector" is receiving a valid timecode from the following reel - that is, if you're playing R4, a valid changeover can only happen if projector 2 is receiving R5 timecode. This would be to prevent an unintentional changeover if you run the projector by accident (to unthread it for example).

The XD20 manual seems to confirm this behaviour. Do you have a Y cable to the two readers going to the XD20? Is it wired as per the manual?

SCR-20250912-pfes.png

The DTS should do changeover as soon as the FFOA of the following reel reaches the gate, independently from anything else. What happens when you start the second projector? Does the XD20 reflect the new timecode reaching the player? What happens when projector 1 stops? Do you see the timecode from Projector 2 reaching the player or is there a delay? What does the display do?

Where is the reader located and what is the offset for them?

You say all works fine in 35mm: do you mean that if you simply replace the 70mm heads with 35mm heads and you run 35mm CHANGEOVER, it works fine? DTS heads can be problematic, but then you'd see the "TIMECODE" light on the XD20 not lighting up when projector 2 starts. You also say you tried P2->P1 and it has the same issue so heads don't seem to be an issue here.

Could it be that all of this is caused by some automation instead?

[Jerry G. Axelsson]

Hello fellow technicians,

I have an issue which has eluded us for a while.

We have two DP70:s with DTS 70mm readers. DTS XD-20 player. On some 70mm titles, there is an audio drop out of a few seconds when we do a change-over.
The typical scenario is that the DTS player keeps playing the timecode out on the tail leader until it ends, then the player switches to the next reel a few seconds after the change-over.
Some change-overs are fine. We also have tried to swap reels between machines, but the drop-out are still there even if you switch from projector 1 to 2 or 2 to 1.

We have tried another XD-20 player. Recalibrated readers with proper equipment, new cables for the timecode-readers.

What could be the cause of this?

Some 70mm titles with drop out issues on a few change-overs per show:

JOKER, TENET.

Some 70mm prints without issues: INTERSTELAR, THE BRUTALIST.

All 35mm DTS prints run fine with 35mm readers on the same DTS player without drop-outs.

Our readers (which are DTS 70 original) have have been copied by a mechanical shop for another cinema which needed 70mm DTS capability. The same 70mm prints of TENET and JOKER ran there for weeks without drop-out with an XD-10.

Any ideas of what could be the cause? We are drawing a blank here to yet solve the issue.

Any suggestions would be helpful.

Thank you in advance.