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Author
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Topic: Does a 9/11.1 sound system make more sense than Object Based?
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Harold Hallikainen
Jedi Master Film Handler
Posts: 906
From: Denver, CO, USA
Registered: Aug 2009
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posted 06-12-2018 12:50 PM
There was a lot of discussion of this in the SMPTE immersive sound meetings. We discussed "egocentric" versus "allocentric" immersive sound. In egocentric, we consider the direction and distance to a sound source as perceived by the listener. In allocentric, we consider the location of the sound source independent of where the listener is. Egocentric describes object position using spherical coordinates referenced to the listener. Allocentric describes object position in Cartesian (XYZ) coordinates with (almost) no relationship to the listener.
The SMPTE immersive audio standard (based on Atmos) uses allocentric coordinates. DTS-X uses egocentric coordinates.
For virtual reality or home theater where all listeners are at about the same position, egocentric makes sense to me. For larger venues, allocentric makes sense to me.
As pointed out in the original post in this thread, a sound may originate 90 degrees to the left of a listener. But, to people in the front of the auditorium, the sound is to the left and behind them. People in the back of the auditorium hear the sound to the left, but in front of them.
I think, however, that allocentric reflects reality. If a sound source is at a certain position in space, and we are in front of that position, we expect the sound to be behind us. The sound varies depending upon where we are, just as in the real world.
A few comments on the coordinate system. The coordinate system has X going across the room with X=0 at the left wall, and X=1 at the right wall. Y goes front to back with Y=0 being the screen, and Y=1 being the rear wall. Finally, Z is the vertical position with Z=0 being the "base layer" of speakers representing plane (perhaps bent) containing the lowest screen speakers (the traditional LCR) and the lowest surround speakers. Z=1 at the ceiling.
The coordinate system does not allow specifying a sound position outside the room. However, by applying decorrelation and object size and other effects, it's possible to place a sound source on a wall and make it sound as though it is outside the wall.
The SMPTE immersive sound (and Atmos) transmit a channel-based "bed" plus objects that are added to the bed. I think the bed is used for most sound with the objects being used for special sounds that cannot be reproduced accurately using surround arrays. We COULD record a 64 channel sound track with the person doing the original mix panning the various sounds as desired between these 64 channels. In the cinema, the 64 channels would be sent to 64 speakers in the corresponding positions reproducing the dub stage experience (though not precisely since they are different environments). With object-based audio, though, instead of sending the resulting audio streams, we send the individual audio fragments along with the panning instructions (and other metadata). The panning done at the dub stage is reproduced by the object renderer in the cinema. The bed and rendered objects are combined into individual audio channels driving the individual speakers in the auditorium.
It will be interesting to see how the market treats this in the future. What percentage of features will be released with object based sound? What percentage of auditoriums will be able to play object-based sound?
Harold
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 06-12-2018 06:13 PM
quote: Lyle Romer
Does a channel based system provide a more similar to mixing stage experience to more viewers in an auditorium?
That depends on the configuration of the mixing stage versus how the movie theater is configured. Generally speaking I don't think conventional channel-based sound systems found in most theaters do a good job at all of duplicating the listening experience of the mixing stage. The big criticism I have, particularly with the 5.1 layout is the surround field for much of the theater's listening space is just one diffuse sound field with a big left-right stereo effect. 7.1 surround will improve fly-by surround panning effects since a back wall is defined separately from the side walls. Overhead channels will allow for more convincing fly-over effects.
I think sound formats like Atmos have the potential to deliver what was intended in the mix far more accurately. But once again that too depends on how the movie theater is specifically configured. Some Atmos theaters are configured very well and can deliver outstanding surround sound when fed a well-crafted Atmos mix. There are other theaters that are Atmos-equipped, but lack the number of amplifiers or powerful speakers needed to let a great Atmos mix shine.
Speaker/amplifer power is another big variable. There's a lot of commercial theaters playing wimpy audio or audio that is poorly EQ'ed. The sound systems are either under-powered or the fader was simply turned way way down because someone complained. I miss the 1990's when digital sound equipped theaters were less afraid to deliver some rib-rattling sub-bass. Hell, even the IMAX-branded theater here in Lawton doesn't run its audio nearly as loud as it did when the theater first opened.
This is actually a situation where a concept like THX could have done audiences a huge favor. Sadly THX is a mere shadow of what it used to be. The last I heard it has been reduced to a sort of bonus logo thingie in Cinemark XD houses. Nevertheless modern sound system configurations in commercial theaters are sort of all over the map in terms of quality. There's no way for a movie-going customer to tell if an Atmos-equipped movie theater is really doing Atmos right or if they just dropped a CP-850 into the rack of an otherwise conventional sound system. Even if the theater is well equipped you're not going to hear a whole lot of that difference if the whole sound system is turned down to TV speakers volume levels.
quote: Lyle Romer
With Atmos, if a sound is supposed to be directly to the left, it will sound like that to somebody in the center but won't it sound like it is behind and to the left of somebody sitting towards the front or in front of and to the left of somebody sitting in the rear?
Dolby Atmos will allow the sound editor to decide if a sound element coming out of the left wall should come out of more or all of the speakers on the left wall or only a specific speaker or two along the left wall. Atmos will allow the sound designer to track a sound element along the left wall from one speaker to the next and even pan that sound element all around the room and even across specific speakers on the ceiling.
But the commercial movie theater needs to have all the extra wiring and channels of amplification in the sound system to play back such effects in an Atmos mix. If the theater skimped on the amplifiers that left wall array of surround speakers may end up sounding no different than the left surround channel in a conventional 5.1/7.1 room.
quote: Harold Hallikainen
It will be interesting to see how the market treats this in the future. What percentage of features will be released with object based sound? What percentage of auditoriums will be able to play object-based sound?
I really love object-based surround sound when it is done right, but the effort faces two key problems.
One problem is in post production: time. It takes more time to create a well done Atmos mix. Sound editors and mixers often don't have the time needed to create sound mixes that can make full use of a well configured Atmos-equipped sound system. That leads to fewer movies with great sounding Atmos mixes. And then that makes it harder to sell Atmos to movie theater operators.
The other big problem is cost. It still costs a fortune to install Atmos in an auditorium. Even Atmos-done-wrong costs a lot since the CP-850 is still a pretty expensive piece of gear. I don't know what a QSC Q-Sys system costs to pair with a CP-850, but it sure doesn't sound like it would be cheap. I've noticed QSC is now making some amplifier boxes with 8 channels of amplification built-in. Dolby introduced their own multichannel amplifier models boasting 16, 24 or even 32 channels of amplification in one box. I have no idea how well those amplifiers stack up in terms of quality and output power against an industry favorite like QSC. Still, I think Dolby is on the right track with the idea. To do Atmos right the sound rack needs a whole lot of discrete channels of amplification in order for the CP-850 to really do its sound rendering magic.
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 07-06-2018 04:44 PM
quote: Harold Hallikainen
For virtual reality or home theater where all listeners are at about the same position, egocentric makes sense to me. For larger venues, allocentric makes sense to me.
It's interesting you bring up those terms here for the first time, as not many are aware of the implicit challenges regarding both approaches.
I think any future format should support both "coordinate systems", because there are strong arguments for having both, even in the context of a movie and it might even change from scene to scene.
Consider a wide, panoramic shot of some scenery. There an allocentric approach makes perfect sense. I relate myself to the position of that shot. Also, consider a recording of e.g. a symphonic orchestra, also here, the allocentric approach makes sense, because it maps closely to reality.
But, consider almost any movie scene seen from "first person" view. Here the egocentric view makes much more sense. I'm supposed to be looking out of the eyes of this person, no matter where in the room I'm sitting.
quote: Harold Hallikainen
The SMPTE immersive sound (and Atmos) transmit a channel-based "bed" plus objects that are added to the bed. I think the bed is used for most sound with the objects being used for special sounds that cannot be reproduced accurately using surround arrays. We COULD record a 64 channel sound track with the person doing the original mix panning the various sounds as desired between these 64 channels. In the cinema, the 64 channels would be sent to 64 speakers in the corresponding positions reproducing the dub stage experience (though not precisely since they are different environments). With object-based audio, though, instead of sending the resulting audio streams, we send the individual audio fragments along with the panning instructions (and other metadata). The panning done at the dub stage is reproduced by the object renderer in the cinema. The bed and rendered objects are combined into individual audio channels driving the individual speakers in the auditorium.
I still hold the opinion that in any advanced Object Audio format those beds don't have any reason of existence. They should be replaced by virtual audio surfaces. How complex those surfaces need to be can be up for debate, but even if you could only choose between some pure 2D primitives like rectangles and ellipses, it would eliminate the need for beds entirely and would provide an easy solution for anything that can't be simply replaced with a point-source.
quote: Harold Hallikainen
It will be interesting to see how the market treats this in the future. What percentage of features will be released with object based sound? What percentage of auditoriums will be able to play object-based sound?
Essentially all well-funded Hollywood releases are being released in Dolby Atmos. Record companies are desperately looking for new ways to repackage old goods. In the end stereo will disappear and will slowly be replaced by something better, something object oriented, I'm pretty sure about this.
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Elmer Makkinga
Film Handler
Posts: 4
From: Amsterdam, Noord-Holland, The Netherlands
Registered: Jul 2018
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posted 07-18-2018 10:17 AM
Some comic relief: a Dutch television station once rented our largest (but still modest) screening room for the premiere of a TV-documentary about the holocaust. The director and producer came over to check how it played a few weeks in advance and the director couldn't stop complaining about how he wanted more surround sound (the DCP had 5.1 audio). This was baffling to me since the documentary basically only featured some talking heads and voice-over narration from himself (did he want to be immersed in his own voice so badly?). I said he should talk to his sound designer if he was displeased and they could still deliver a new version by next week. So the sound-designer beefed up the surround, gave it more compression so everything would sound louder, but mostly just worse. Sometimes people get so hyped up about surround sound that they forget it's totally irrelevant sometimes.
Another funny thing: probably the most luxuriously upholstered screening room in Amsterdam is Pathé Tuschinski 1. On their website they sing its praise saying it is the most beautiful theater in the Netherlands, has comfortable seats and lots of legroom, they also charge you €1,50 extra for a seat. It even has multiple floors: a ground floor and a balcony. I´ve heard that the balcony is actually where the king sits when he goes to the movies with his kids.
However, the projector (an NEC that needs literally half a minute to change from flat to scope) is mounted up in the clouds, so the projection is al skewiff. All the surround speakers are up on the balcony, so the people on the ground floor gets almost no surround and those on the balcony get only surround and nothing else. So if you ever feel like you're in a subpar theater, think about how the Dutch monarchs have the worst moviegoing experience of anyone.
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 07-18-2018 12:23 PM
You don't go to the Tuschinski in Amsterdam for the best picture or sound, but it's the last grand movie palace in the Netherlands. You go there for the experience.
It's certainly not the best place to watch your high-octane action movie, but I didn't have any problem with the surrounds, with exception to the VIP boxes in the back of the lower tier, which are pretty much a joke for the money they're charging.
The first balcony, the so called "VIP" balcony is actually the best place to watch a movie, especially if you're sitting dead center. The surrounds in this room are pretty small, obviously not to disturb the otherwise gorgeous furniture in this room, but they are present on both the lower tier and both balconies. I've also never had a problem with surrounds overpowering the front speakers.
Sure, the sound in this theater is something to get used to. This room wasn't built for modern style sound systems and therefore features quite a lot of echo and reverberation.
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