Film-Tech Forum ARCHIVE: Dolby Atmos® DemoTrailer

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Posted by Terry Monohan (Member # 8285) on 06-09-2018, 09:52 AM:

At a recent visit to the Galaxy Theatre in Sparks NV we found something strange. In theatre #11 the big curved screen space the demo trailer for their Dolby Atmos® Blue light system played fine with all the 360 movement around the auditorium. In theatre #10 next door were 'Solo' is playing the demo Dolby Atmos® trailer did not have the bird move around 360 sound, It just stayed in the left surround speakers. While the movie sounded ok with split surrounds and I think ceiling speakers I don't think things are working sound wise. Both of these spaces have the Atmos® system in place. I told my friend Ken who does the live movie intros, he is aware of this problem also. What do you tech guys think is the problem? Is the logo trailer coded wrong into the system, or is the whole movie not being heard in true 360 Dolby Atmos? I e mailed Frank the owner of Galaxy about this problem in Theatre #10. Galaxy Theatres is getting ready to open the former Cinemark Century Victorian SQ in Sparks NV with a complete remodel on July 15 2018. Wait till you see the huge curved screens they will have in a few spaces if you visit. It's GALAXYVISION® at it's finest.

Posted by Harold Hallikainen (Member # 5405) on 06-09-2018, 10:29 AM:

Maybe the Atmos did not run and the mainsound backup ran instead.

Harold

Posted by Victor Liorentas (Member # 5272) on 06-09-2018, 10:35 AM:

So many times I've gone to an Atmos screening where the Atmos seems to have reverted to non Atmos mode.
I would inquire about it and the response is "I don't know,nobody has complained"
It's a know issue on older Atmos processors,where it needs regular rebooting.

Posted by Bobby Henderson (Member # 840) on 06-09-2018, 10:48 AM:

Dolby Atmos-equipped sound systems can be pretty complicated and can be configured very differently from one auditorium to the next. There could be numerous reasons why the same Dolby Atmos sound format trailer sounds very different in two auditoriums.

It's possible there is some kind of software bug, hardware conflict or other technical problem causing the surround panning not to work as well in house #10 as it does in the big #11 house. It's also possible the movie theater chain spent a lot more money on amplifiers and other gear to make Dolby Atmos sound more like it should in house #11. Then they might have cut corners in the other houses.

A theater operator can install a Dolby CP-850 cinema processor, plaster the Atmos logo on the theater marquee yet have something that's no better than a standard 7.1 sound system with a ceiling audio channel added. The CP-850 is still pretty expensive on its own. It costs a lot of money to buy all the extra amplifiers needed to make Atmos really sound like Atmos and not plain 5.1/7.1. Perhaps this will be less of a problem as companies like QSC and Dolby release new amplifier models packing more and more channels and capabilities into a single box. It will get easier to fully trick out an Atmos-capable system without needing a lot of space for several refrigerator sized racks filled with amplifier boxes.

Some movies have great Atmos sound mixes. A bunch of others hardly do anything with it. That problem makes it even more difficult for a theater operator to justify spending tens of thousands of dollars above the cost of a conventional 7.1 surround system just to do Atmos. So now Dolby offers a version of the CP-850 without the Atmos bells and whistles. The hope is theaters will buy the CP-850 for a lot more theater screens and do Atmos upgrades on some of them later.

Posted by Stephan Shelley (Member # 8587) on 06-09-2018, 12:35 PM:

There are many communication issue with Cp850 processors and Atmos playback. The one with Barco Alchemy is discussed elsewhere here. Doremi show vaults also have there own issues and often get to a state where content does not play back in Atmos till the server reboots. It is possible the show vault issue is network congestion related as there is no dedicated Atmos data network it all goes over the management network.

Posted by Buck Wilson (Member # 5885) on 06-09-2018, 02:30 PM:

Terry mentions that the sound is coming out of the left surrounds only in the problem house... I think there's an actual problem and not just a case of cheaping out on one auditorium vs the auditorium next to it.

Posted by Terry Monohan (Member # 8285) on 06-09-2018, 08:13 PM:

Thanks guys for your feedback. Buck no, the sound is coming out on all surrounds ok in theatre #10 Its just the Dolby Atmos® trailer that does not do the 360 wraparound demo. The movie shown in theatre #10 has split surround but does not do any wrap around circle sound like the true Dolby Atmos® demo has and is heard in Theatre #11 next door. Both spaces have the same type of huge curved screens and speakers on the ceiling.

Posted by Monte L Fullmer (Member # 2797) on 06-12-2018, 06:45 PM:

Could be an amp problem.

You got 32 channels of sound to deal with in ATMOS, but if the amps are four channel, 600 watts total in one chassis, it's not to uncommon to have one channel go out within a chassis.

Most of location's personnel don't know what to look for in this case.

Posted by Jarod Reddig (Member # 6363) on 07-01-2018, 04:28 PM:

Its anybodies guess until a proper tech goes in there and checks it out. What needs done sounds like.

Posted by Bobby Henderson (Member # 840) on 07-01-2018, 09:04 PM:

quote: Monte L Fullmer
You got 32 channels of sound to deal with in ATMOS, but if the amps are four channel, 600 watts total in one chassis, it's not to uncommon to have one channel go out within a chassis.

I thought Atmos could support up to 64 discrete channels of output to speakers. In Dolby's materials they mention this along with the rendering engine being able to handle up to 128 objects. I don't know if the "beds" (7 channels worth plus 2 ceiling surround channels) and sub bass channels (.1 for the screen and .2 for the surrounds) count as part of that 128 object limit.

The way it seems, if a theater is actually getting 32 channels worth of audio into an Atmos equipped sound system it's doing pretty good. It's possible for an Atmos rig to deliver a whole lot fewer channels.

Posted by Martin Brooks (Member # 1269) on 07-11-2018, 10:37 PM:

At the Dolby Vision theater at the AMC Empire 25 in NYC I count 50 to 52 "channels". There are 16 overhead speakers, 10 side surrounds x2, 3 rear surrounds x2, 2 auditorium woofers = 44 + either 5.1. or 7.1 if they have Left-Center and Right-Center screen channels. It's possible it's 2 less if they auditorium woofers aren't their own object channels.

Posted by Bobby Henderson (Member # 840) on 07-12-2018, 09:35 AM:

Number of surround speakers is one thing. How many of them are individually amplified and discretely rendered to by the CP-850? There's no way to tell from one Atmos-equipped theater to the next whether some or a bunch of speakers in the surround arrays are being summed together in the same "channel."

Posted by Lyle Romer (Member # 1266) on 07-12-2018, 10:32 AM:

quote: Bobby Henderson
Number of surround speakers is one thing. How many of them are individually amplified and discretely rendered to by the CP-850? There's no way to tell from one Atmos-equipped theater to the next whether some or a bunch of speakers in the surround arrays are being summed together in the same "channel."

You are correct. However, assuming the Empire 25 is a "Dolby Cinema" auditorium, I'd be surprised if Dolby didn't "do it right."

With Dolby Cinema, Dolby is supplying the equipment and getting a cut. If they don't install proper systems, they'd be killing their own brand.

Posted by Marcel Birgelen (Member # 6801) on 07-12-2018, 02:52 PM:

quote: Monte L Fullmer
Could be an amp problem.

You got 32 channels of sound to deal with in ATMOS, but if the amps are four channel, 600 watts total in one chassis, it's not to uncommon to have one channel go out within a chassis.

Most of location's personnel don't know what to look for in this case.

Current Atmos Cinema decoders support up to 64 discrete channels of output. This number of channels isn't a limit of the format, but a limit based on the hardware capabilities of current decoders.

Most personnel doesn't have a clue what to look for, but finding an errant Atmos channel usually isn't really hard for anybody knowing just a little about the system. If it's a problem with the decoder, amplifier or speaker usually is also pretty easy to identify for any halfway knowledgeable person.

It's somewhat of a pity that most of those cinemas run such high-profile theater locations without keeping people on-site that just have a half-way understanding of the technical systems involved... but that's outsourcing working there for you. [Wink]

Then again, there have been plenty of issues with Dolby's CP850 and several brands of servers out there lately. More than is good for many people's health... Those issues have been triggered by software issues and give some people a hard time keeping operations running smoothly in their biggest houses...

Posted by Bobby Henderson (Member # 840) on 07-12-2018, 10:53 PM:

Bugs are an ongoing problem in all types of software. When you're dealing with industry-specific software/hardware (and the limited customer base that goes with it) bugs can be a bigger challenge.

IIRC, Dolby has a technical support service for Atmos-equipped theaters. The cutting edge setups make it easier to spot problems, in part because everything is connected digitally. I don't know all the features in Dolby's DAC3202, which lets you use "legacy" amplifiers. One of those units can support up to 48 speaker feeds. Two are needed for more than that.

quote: Lyle Romer
You are correct. However, assuming the Empire 25 is a "Dolby Cinema" auditorium, I'd be surprised if Dolby didn't "do it right."

I don't think the brand name is any guarantee. The Dolby Cinema @ AMC houses are decent, based on the couple or so I've visited in the OKC and Dallas area. Still, the best Atmos shows I've seen so far have been at the Harkins location in Oklahoma City. I realize the movie's mix is an extremely important factor. I guess the real test will be seeing a new movie with a legitimately great Atmos mix at both types of theaters.

Posted by Martin Brooks (Member # 1269) on 07-14-2018, 12:43 AM:

quote: Bobby Henderson
There's no way to tell from one Atmos-equipped theater to the next whether some or a bunch of speakers in the surround arrays are being summed together in the same "channel."

I can't prove it but my impression is that every speaker is tied to a separate amp channel as that's how Atmos is supposed to be configured and the entire point of objected oriented audio. The theaters can have fewer speakers (as the Dolby screening room on 6th avenue does) but each speaker gets its own amp channel. Some years back when I was consulting for a theater company, I was in the booth, but that was before Atmos.

There's now a second Dolby Vision screen at the AMC 34th Street between 8th-9th avenue, but I believe it's a smaller room, so I haven't been there yet. But since it's newer, it will be interesting to see if it's better executed. Hopefully, it also has a common height screen.

Posted by Marcel Birgelen (Member # 6801) on 07-14-2018, 01:07 AM:

Depending on the size of the auditorium and the actual speaker setup, speakers might even be bi-amped.

A single speaker needs to cover much more ground than a whole array in a discrete channel setup.