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This topic comprises 8 pages: 1 2 3 4 5 6 7 8
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Author
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Topic: ATMOS comes home...
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Daniel Schulz
Master Film Handler
Posts: 387
From: Los Angeles, CA USA
Registered: Sep 2003
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posted 03-29-2016 10:56 PM
quote:
A fair question.
Here are my answers...
2) Call it personal preference but LC/RC are essential to providing a proper sound stage from the screen. Regardless if the sound source is dialog or music/effects. Inherently, a lot of stuff happens in the middle half of the screen and LC/C/RC are in the right places to covey that. L and R are too far outside and in the name of keeping a "stereo image" they can also ruin maintaining a believability in having the sound mate up with the picture.
3 or 2B) I'm a HUGE proponent of panned dialog. Panned dialog doesn't work with just 3-screen channels because the gaps, regardless of screen width/size are just too far apart. LC/RC effectively bridge those gaps and often eliminate the need for any phantom channels that will have phase issues.
I am not disagreeing with you that LC/RC mixes are desirable - but virtually *no* movies have been produced that way, and of those that were those mixes are not available for home video. None of the 70mm films with 5 screen channels are available with that mix on any home video format (and there aren't that many of them to begin with). Likewise, the couple of dozen or so movies that had SDDS-8 mixes are not available with that mix on home video. I just don't know what content you'll be watching that will use the LC/RC, unless you are running 35mm film prints with SDDS tracks or DTS 6-track 70mm prints.
quote: Steve Guttag
Multiple subwoofer channels? Really? Every channel could be full-range and crossed over, if desired but there is a point where the sound is omnidirectional to the point of being just a waste of time to add more of them in a directional sense. I have had success in placing subwoofers in multiple points of a theatre, driving them less hard but having incredible coverage. But still, all one channel.
I wasn't clear here. I didn't mean to imply multiple subwoofer channels, but rather that when budgeting for a home theater build I would plan on having multiple subwoofers (at least 4). As you say though, it would be all one channel, reproducing the LFE plus bass managing everything else.
In any event, I would not expect to see consumer-grade (and priced) processors supporting LC/RC anytime soon. I expect the next addition of channels to be supporting 9.1.6 (7.1 + Wides and 6 instead of 4 height channels). I do really wish the consumer AVR manufacturers would also support an additional pair of side surrounds with Atmos, for home theaters with multiple rows of seating, but that also seems to be low priority.
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 03-30-2016 12:38 PM
They totally screwed the Oklahoma! mix for DCP (can't speak to the Atmos version since I haven't heard it)...but there is the 5.1 version for DCP...which you would expect to play in "typical" theatres. There is the 7.1 mix where you have the SAME 5.1 mix but omit the rear surrounds (yup, tracks 11/12 are dead by design) and then if you wanted a proper 5-across mix...you'd have to get the Atmos version (I don't know what they did with the surrounds).
So theatres that are set up to play classic titles, like Oklahoma! for film, like the AFI/Silver, while they have all five screen channels and run the 6.0 versions of 70mm titles on DTS/Datasat...have to run a crappy 5.1 mix (or a non-7.1 mix). The fools that informed me of this decision are under the impression that there are more Atmos theatres than those that can handle 6.0. And while even that statement MAY be true...the odds a title like Oklahoma! ends up in a theatre that CAN handle 6.0 is FAR FAR higher than it will play in an Atmos theatre that is likely booked with the latest blockbuster. And FURTHERMORE...when you "restore" a title, you start with getting it back to day-1...you preserve the original experience and then branch off from there. Mind you, this is an Academy Award winning soundtrack. It is a good mix. Given that DCPs can have version files, there is no excuse for not offering a 5.1, 6.0 and if desired, an Atmos. The 7.1, particularly as delivered, was a complete waste of time. As you know, with DTS...there were multiple versions of the soundtracks, particularly on the classic 70mm titles to ensure there was a 5.1 AND the original channel configuration...you run what you are capable of. The AFI/Silver has a "DCP 6.0" preset on their sound processors...waiting. They have 5.1, 7.1 and 2.0 as well but the 6.0 could be used in two out of three screens if the studios would give the option of the original mix.
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 03-30-2016 04:14 PM
quote: Marcel Birgelen
Why even bother with Atmos for Consumers? It's a flawed technology to start with. It's even worse than those so called Near Field mixes, it's the ultimate version of a downmix. Not only did they "rebalance" it or you, they decide what gets to stay a distinct object and what gets merged down to drown into someone else's bed. And the best of it: it's amost certainly done by the virtues of the ProTools automagic-merge-and-compress-plugin du jour.
I think you're looking at "immersive audio" as if it is only being produced in perfect world terms.
Those beds you don't like in Atmos are there for two reasons. 1: backward compatibility with 5.1/7.1 audio and 2: no one creates any "immersive" mix comprised entirely of objects. No movie production is giving sound designers nearly enough time to tailor a 100% object based 3D sound mix. Such a thing will never happen either as long as the movie's sound mix continues to be treated no better than an after thought by producers and other decision makers.
It's fully possible for someone to build an entirely object-based Atmos mix. But the beds are there to allow for short cuts. Right now virtually every movie released in Atmos is mixed first in 5.1 or 7.1 and then enhanced with Atmos if they schedule any time to do it. A bunch of already pre-existing, down-mixed stuff gets used in the beds. Then they'll float a few objects in the 3D sound space if they feel like it.
If Atmos took a puritanical stance allowing only for objects no movie production would bother using it. It wouldn't be practical.
quote: Marcel Birgelen
About a month ago, the first home devices supporting DTS:X showed up. Now I'm curious, is this DTS:X for plebs playing the same content as the theatrical releases or are they also merely peddling the homeopathic version?
Who knows? The marketing is very unclear on every aspect of it. Some illustrations have suggested DTS:X use a speaker arrangement similar to that suggested by Auro, such a 2nd row of front stage speakers mounted above the L,C,R speakers for height and then basically doing the same thing in the surround field and then adding a voice of god speaker in the middle of the ceiling. Of course this arrangement is completely different from Atmos' arrangement which merely adds two or more speakers on the ceiling into an existing 7.1 layout.
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 03-30-2016 06:19 PM
quote: Bobby Henderson
I think you're looking at "immersive audio" as if it is only being produced in perfect world terms.
We've had this discussion before and, no, I'm not.
The virtual speaker concept can do everything beds can do and more. It can make it "backward compatible" with not only 5.1, 6.1 or 7.1 but virtually all other speaker layouts there are and ever will be, even Auro 3D. The 5-stage-channel mixes are a great example of the shortcomings of the format itself. The format which should be the last format we ever needed...
The immsound format, one of the companies Dolby bought shortly before releasing Atmos, did have "virtual speakers". The difference between virtual speakers and object point sources is that speakers do have a virtual surface and objects (or "channels" if you will) can be mapped to a virtual speaker. A virtual speaker can therefore easily span more than one physical speaker in an auditorium. The first thngs that leaked trough regarding OpenMDA suggested a similar approach, but unfortunately, DTS kept their DTS:X documents behind expensive paywalls protected with obligatory NDAs.
Now, in order to simulate a classic 5-channel stage-channel mix, you need to put three channels in a bed and put two channels into an object which you position roughly at the location where the LC and RC speaker should've been. Besides being a huge, ugly hack, the beds will be rendered differently than those object point sources by the processor. I'm not even convinced the result will be all that stellar. It will probably be even better to define the other three channels as an object source too.
quote: Bobby Henderson
Who knows? The marketing is very unclear on every aspect of it. Some illustrations have suggested DTS:X use a speaker arrangement similar to that suggested by Auro, such a 2nd row of front stage speakers mounted above the L,C,R speakers for height and then basically doing the same thing in the surround field and then adding a voice of god speaker in the middle of the ceiling. Of course this arrangement is completely different from Atmos' arrangement which merely adds two or more speakers on the ceiling into an existing 7.1 layout.
As far as I know, DTS:X doesn't really enforce a fixed speaker setup, unlike Atmos, which clearly starts with a 7.1 setup as a kind of minimum requirement. (Unless your device is a phone or tablet.*)
Those suggested DTS:X setups all start from a 7.1 setup, to keep the setup itself compatible with "older" mixes. If the stuff we get at home is the real deal, the amount of speakers you're able to install should only be limited by the power of the DSPs in use and your budget, not by the format itself.
* Instead of installing expensive sound systems into our theaters, maybe we should just stream it directly to the patron's Atmos-enabled cellphones. Maybe also leave out the screen and save on the projector too. Let's stream both audio and video to their 4K Dolby Vision enabled tablets.
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 03-30-2016 10:45 PM
quote: Marcel Birgelen
The immsound format, one of the companies Dolby bought shortly before releasing Atmos, did have "virtual speakers". The difference between virtual speakers and object point sources is that speakers do have a virtual surface and objects (or "channels" if you will) can be mapped to a virtual speaker. A virtual speaker can therefore easily span more than one physical speaker in an auditorium.
Are you assuming Dolby Atmos has no phantom imaging capability between speakers? What do you think the Dolby CP-850 is doing when it renders object oriented audio to sound systems that vary in the number of speakers and amplifiers from one theater to the next?
Dolby at least has some recommended standards for movie theaters to follow in terms of speaker placement, number of speakers, amplifiers, etc. for given auditorium sizes. If a theater cuts corners on speakers and amps the system just isn't going to work as well. That goes for Atmos and it also goes for DTS:X too. You can't do immersive sound right without installing a shit-ton of amplifiers and speakers as well as sticking the speakers in the right places.
From the way it sounds DTS:X does none of that. The suggestion seems to be "install how ever many speakers and amps you want, stick 'em wherever you like and it'll stick work just as good even if you install hardly a damned thing at all."
By the way the imm sound format, "virtual speakers" notwithstanding, was a whole lot more elaborate and a whole lot more expensive to deploy than Atmos. The original concept suggested the use of hundreds of speakers and amplifiers. It went nowhere because it was cost prohibitive. Dolby took the idea and tried to tone it down to a more do-able reality. Unfortunately for movie theaters doing Atmos right appears to be too freaking much to handle as well.
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Harold Hallikainen
Jedi Master Film Handler
Posts: 906
From: Denver, CO, USA
Registered: Aug 2009
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posted 03-30-2016 10:55 PM
While there are hardware limits on home versions of immersive sound, another limitation is bandwidth. Atmos supports up to 128 objects or bed channels (add bed channels, lose objects). These are encoded as 48kHz with lossless compression of about 2:1. Of course, not every frame uses all 128, but for a frame that does, the medium (Blu Ray, stream, or whatever) needs to deliver 2,000 samples times 3 bytes per sample times 128 divided by 2 bytes. 384,000 bytes in one frame. Or 3Mb in one frame, or about 73Mbps.
DTS-X uses a similar bitrate. DTS-X does not do compression on the audio (it's all PCM), but they also do not record silence. Atmos allocates 128 channels some of which hold bed channel (used continuously through the composition) and then uses lossless compression to get rid of all those zeroes. MDA (DTS-X) does a more "packetized" audio. If a frame needs audio for a bed or object, it is recorded. If not, it is not recorded. For typical content, the Atmos and MDA bitrates are similar (I have notes on some measurements we did somewhere). But, as the number of simultaneous objects increases, the bitrate of MDA increases faster than that of Atmos due to the compression.
Though it's slow going, I do think SMPTE is finally making some progress on a bitstream that takes the best of Atmos and MDA. I keep pushing to make it as simple as possible, but not simpler.
Harold
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 03-31-2016 01:14 AM
quote: Daniel Schulz
I take your point about branding, and if I was a cinema owner I'd be upset - but speaking as a consumer and home theater enthusiast, Dolby Atmos kicks ass. It's not a flawed technology at all, it is an audible leap forward in home theater sound. I'm pretty happy to have it available (along with its competitors).
I'm not denying that it's a leap forward, but it isn't the leap forward it could've been in my opinion. First off all, it really should've been branded differently. If you're going to sell Atmos to consumers, it better be as good as the thing in the theater or just call it differently.
Within now and about a year or two/three, every top-of-the-line AVR with some beefy microprocessor will be capable of doing the whole theatrical Atmos thing, it's not like you need supercomputers to extract 128 PCM streams and apply some EQ magic on them and mix them into a bunch of output channels. So then, the same Atmos that's available in the theater could be available for premium home theaters. How do you call it then? Atmos Plus? And what's the thing we got in the theater? Just Atmos? As a theater owner, no I wouldn't be all that pleased indeed.
quote: Daniel Schulz
Much like Atmos, the DTS:X codec for home theatre is a bit restricted compared to the cinema deployment. These codecs need to work within the practical limits of hardware available to consumers.
You don't happen to know where one can find what those restrictions are, do you? ![[Smile]](smile.gif)
quote: Bobby Henderson
Are you assuming Dolby Atmos has no phantom imaging capability between speakers? What do you think the Dolby CP-850 is doing when it renders object oriented audio to sound systems that vary in the number of speakers and amplifiers from one theater to the next?
No, I'm not and I'm pretty sure you can make that up from the points I'm trying to make here although, I will try to do it again...
In order to simulate a 5 stage-channel soundtrack, Dolby Atmos has to revert to a ugly hack:
1. Put three channels into a bed and create two object sound sources. Since beds are rendered differently than objects, I'm not sure the end-result will be stellar.
2. Create five object sound sources and skip the beds entirely. Which would at least be a uniform solution, but still a bit cumbersome to implement.
For a supposedly one-size-fits-all future-proof format, this is already proving to work out backwards.
quote: Harold Hallikainen
Atmos allocates 128 channels some of which hold bed channel (used continuously through the composition) and then uses lossless compression to get rid of all those zeroes.
I'm not entirely sure here, but as far as I have seen the actually binary format of the consumer implementation, it seems only to include the zeros from the bed channels, which essentially are objects that are "always active", even if there is no sound. Obviously, that compresses quite well though.
Maybe, this is a major difference between the theatrical format and the consumer version, which is limited in the amount of simultaneously active objects anyway?
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 03-31-2016 10:01 AM
quote: Harold Hallikainen
While there are hardware limits on home versions of immersive sound, another limitation is bandwidth. Atmos supports up to 128 objects or bed channels (add bed channels, lose objects). These are encoded as 48kHz with lossless compression of about 2:1. Of course, not every frame uses all 128, but for a frame that does, the medium (Blu Ray, stream, or whatever) needs to deliver 2,000 samples times 3 bytes per sample times 128 divided by 2 bytes. 384,000 bytes in one frame. Or 3Mb in one frame, or about 73Mbps.
In actual sound mixing practice it sounds like most movies with Atmos mixes are simply making a regular 5.1 or 7.1 mix and then sprinkling in a few objects here and there to let the viewer know those ceiling speakers actually work. The way it sounds to me there's not much out there that would push the home version of Atmos to its 64 object maximum. Add to this the limits in home theater hardware. The home version of Atmos is supposed to be able to support up to 32 speaker outputs. Most Atmos-equipped receivers support only a combination of a base 5.1 or 7.1 setup with 2 or 4 speakers added to the ceiling.
quote: Marcel Birgelen
In order to simulate a 5 stage-channel soundtrack, Dolby Atmos has to revert to a ugly hack:
1. Put three channels into a bed and create two object sound sources. Since beds are rendered differently than objects, I'm not sure the end-result will be stellar.
2. Create five object sound sources and skip the beds entirely. Which would at least be a uniform solution, but still a bit cumbersome to implement.
If you're going to create a sound design layout with tracking dialog on screen, like what Steve wants, you wouldn't waste time farting around with down-mixing dialog elements into beds and then repeating them as objects. The actor's dialog track would be an object that would render its position across the movie screen's stage speaker setup, whether it has 3 columns or 5 columns of speakers. You could have multiple dialog objects rendering on the stage in different positions on screen. The Left, Right and Center channel speakers are not limited to playing only channel-based beds. They can play objects too. The CP-850 can render those stage objects where ever they need to be positioned.
Of course this is all academic since virtually every modern movie keeps dialog confined to the center channel. Add to this the fact very few commercial movie theaters have 5 columns of stage speakers. Home theater is doing virtually nothing to support any 5 stage channel scheme either.
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