Dual Screen DCP playback.. is it possible ?

[Barry Floyd]

Got "ballpark" prices today on PA for both fields.....I was experiencing a little (OK, a lot) sticker shock. They pretty much wanted to lay it out almost exactly like Jack described above. Since we have no electrical power at the screens, we also have to figure in the costs of generator rentals. Got a feeling this is going to be out of their budget.. but maybe not. Still awaiting on GDC to give me a definitive yes or no on the synchronization thing between the servers.

[Carsten Kurz]

During the writing of the SMPTE recommended practice on sound system adjustment, I suggested sync in the first row, but the RP ended up setting sync at the "reference position." This, to me, results in everyone in front of that position getting early sound and messed up brains.

Which is probably not so much of a problem in many of todays smaller auditoriums. Would be nice if the RP mentioned thinking twice for larger auditoriums. That said, we do already have a decent size (length) auditorium, but the seats closest to the screen are rarely used. So, do I optimise for a situation that may be relevant once a year when we are sold out, or do I tailor it to the situation that covers most days attendance? The idea in the RP is probably also that if you set up sync for the front seats, it could simply be off unacceptably for the back seats.

For a similar reason, I now moved our L and R speaker sets more to the left and right. As a matter of fact, the clear majority of movies we play nowadays are scope, and most people use the comfortable rear seats. So why should I narrow the stereo field towards flat presentations, and on top of that with most people sitting in the back of the auditorium?

[Barry Floyd]

GDC finally got back to me on the server synchronization. It can be done, but there is another piece of hardware involved. It's a box called a GEN-10 HD/SD SYNC GENERATOR manufactured by a company called AJA, and utilizes the GPIO ports on the "slave server". The sync generator has to be configured for the correct frame rates, but it looks fairly simple. They sent me instructions on how to do it, and I'd have to get the box from them as they configure it to work with the SR-1000's.

Working out the audio delivery issue is all we have left.

[Marcel Birgelen]

Maybe another idea: What about headphones? The kind of headphones they use nowadays for this phenomenon called "Silent Disco"? I know they can be rented and they seem to use simple FM broadcasting.

[Harold Hallikainen]

Thanks Marcel for the comment on tolerable sound before image. I had not considered that.

Carsten, moving the left and right loudspeakers farther apart reminds me of an issue I had a few years ago. We were testing the LSS-200 in a local theater. The LSS test the various drivers in the screen speakers by sending band limited pink noise. We found that every couple weeks, the high frequencies for the left and right speakers would drop a couple dB for a week, then go back up. FINALLY figured out that the HF was lower when they were showing a flat movie. The left and right speakers were being covered by the masking, dropping the highs a bit.

Harold

[Carsten Kurz]

Yup. This will be the case for our speaker setup as well - but, mostly during preshow. I could probably create another EQ setup on our AP20 for preshow and flat movies to make up for that a little bit.

I know one cinema in germany with a L,LC,C,RC,R front speaker setup - they use the inner LC/RC speakers for flat, and L&R for scope movies.

[Harold Hallikainen]

Interesting! Are Lc/Rc driven at all for scope?I think we did something on one of the JSD processors to do a mix for Lc and Rc with the dialog frequency range attenuated.

[Carsten Kurz]

No, they are not used for scope movies. I understand the original intention was to have a full 5-across setup as they often play classic 70mm and other formats. Once they had them, it turned out simple to switch them for flat vs. scope.

I once read about auditoriums that had L and R on motorized movers for the same purpose...

[Mike Blakesley]

How about creating a "wall" between screen 1 and 2 by getting a bunch of truck drivers to pull semi-trailers in there and line them up end to end between the two fields? That way you would have "some" bleed through but not too much and synchronization wouldn't be as much of an issue.

I figure since we're all spitballing ideas here, anything is possible.

[Martin McCaffery]

Just curious, is this a MAJOR MOTION PICTURE!!! or just some indie thing?
I've had a few studio rentals over the years, at least one brought in all of their own sound equipment (this was in the days before we had stereo). If they want you to do something that requires renting a bunch of equipment because they want to do something you are unequipped to to in your Drive-In, shouldn't they be footing the bill for the equipment THEY are using? Also, paying for its design and setup.

[Marcel Birgelen]

Just curious, is this a MAJOR MOTION PICTURE!!! or just some indie thing?
I've had a few studio rentals over the years, at least one brought in all of their own sound equipment (this was in the days before we had stereo). If they want you to do something that requires renting a bunch of equipment because they want to do something you are unequipped to to in your Drive-In, shouldn't they be footing the bill for the equipment THEY are using? Also, paying for its design and setup.

I guess it depends a bit on what position you're putting yourself in. Events don't organize themselves and I've seen more than once that those people who come up with those ideas aren't the best at managing them. But if you're good at it, why not try to earn a few extra bucks helping to get the event off the ground.

Thanks Marcel for the comment on tolerable sound before image. I had not considered that.

No problem, an interesting source is EBU recomendation R037, which reccomends anything between 40ms before picture and 60ms after picture. There is an ITU recomendation which keeps it between 45ms before picture and 125ms after picture. So, my guideline has always been between 40ms before picture and 80ms after picture if the SMTPE reference of +/- 22ms can't be achieved

[Martin McCaffery]

Those people who come up with the ideas usually have no idea whatsoever. But major studios can fly in a crew of experienced people who know exactly what they are doing and how to do it. Small independents or individual filmmakers are generally just a pain in the ass because there film is the most important film ever made and "everybody" is dying to see it.

[Carsten Kurz]

Well, EBU recommendation is for television, with a typical viewing distance of a few meters. While the typical minimum viewing distance in a decent sized cinema is more like 5-10m.

Also, you have to factor in that they always need to spec tolerances, and the max tolerance should still work for both the closest and the back seats.

[Marcel Birgelen]

Well, EBU recommendation is for television, with a typical viewing distance of a few meters. While the typical minimum viewing distance in a decent sized cinema is more like 5-10m.

Also, you have to factor in that they always need to spec tolerances, and the max tolerance should still work for both the closest and the back seats.

The time the sound needs to travel between the TV and the viewer, since it's for TV applications, is seen as negligible. The specs account for the lipsync issues that can occur in the entire processing and broadcasting chain, where video may have a lot more processing and buffering than audio. The end results are the same though and the viewing distance here isn't really the issue, light is fast enough not to be a problem factor we need to account for.

What is an issue though, is the fact that images are usually much larger than for typical TV applications, but I don't find any conclusive studies that compare lipsync detectability with "perceived image size", so maybe for the sake of simplicity we should omit this factor. There definitely is some factor in it: I watched a lot of dubbed movies on German TV when I was still a kid, this never really bothered me. But seeing dubbed content in a cinema almost freaks me out. (Maybe I'm exaggerating a bit to make a point.)

But what's clear that the SMTPE requirements of +/-22ms won't work for any large setup, with the average speed of sound in air, those +/- 22ms give you a total "wiggle room" of just 15,0 meters or 50 ft, when you consider the center as your zero-point. While that may be good enough for most common rooms, it won't work for any open-air application.

If you take the more lenient -40ms/+80ms, this gives you 41,1m or about 135 ft to work with, where the zero point is at 1/3rds from the front. That's almost the length of an Olympic swimming pool and much more realistic for out-door applications.

[Gordon McLeod]

No, they are not used for scope movies. I understand the original intention was to have a full 5-across setup as they often play classic 70mm and other formats. Once they had them, it turned out simple to switch them for flat vs. scope.

I once read about auditoriums that had L and R on motorized movers for the same purpose...

On the CP200 it allowed to switch to reverse the LE L and RE R for flat and scope