Atmos trailers

[Mike Blakesley]

I've seen a few trailers come through lately that have an Atmos soundtrack. They seem to play OK but on one I've tried ("Elvis") the dialog track seems to be quieter than usual. Is that normal and is there any other pitfalls to playing Atmos trailers on a 5.1 system?

[Harold Hallikainen]

SMPTE is recommending that mainsound on IAB DCPs be silent except for HI/VI/FSKSync/MotionData/SignLanguage tracks. So, if people follow that recommendation, you would not hear anything on the 5.1 system. Also, is the "backup" in mainsound 5.1 or 7.1? There's no standard here (that I know of).

Harold

[Steve Guttag]

Why would SMPTE recommend MOS on Atmos (IAB) titles of anything? That is absurd. Are the recommending that theatres have issues?

[Marco Giustini]

Atmos is a completely separate track from 5.1 or 7.1. Your server/processor are NOT converting/adapting the Atmos track but playing the standard 7.1/5.1 PCM backup track which any Atmos DCP will have anyways.

So no, assuming the backup PCM track they mastered with the trailer is the same used on a non-atmos trailer, there won't be any audible or measurable difference.

[Carsten Kurz]

Harold - I think the 'silent mainsound' reccomendation is only for real ATMOS equipped screens while they are playing ATMOS content. All non-Atmos installations will play just mainsound in ATMOS DCPs, as if it was a standard 5.1 or 7.1 DCP.

However, it is not recommended generally to ingest ATMOS DCPs on non-ATMOS systems. They do cause issues occasionally, even on servers running latest software.

I played a few ATMOS trailers myself on our systems without problems, just trying, but usually I stick with the plain 5.1 or 7.1 trailer. There is no benefit in ingesting an ATMOS trailer when you have no ATMOS system - on the contrary, it will occupy a lot more server space with useless data. For trailers and main features, I usually see separate VFs for ATMOS and plain 5.1/7.1 now (wasn't always the case).

- Carsten

[Jon Dent]

The latest Top Gun trailer we received had Atmos and there was no 5.1 only version. It did sound a little odd to me but that just might be the trailer itself (95% of the time the sound mixes suck on those).

[Steve Guttag]

Harold - I think the 'silent mainsound' reccomendation is only for real ATMOS equipped screens while they are playing ATMOS content. n

That's just stupid too. Again, do people WANT customer complaints and problem. I can understand wanting to alert the staff of an equipment malfunction but should the audience have to suffer too? Come up with a better way to alert the staff. Blink a light, send an email...have a means for the TMS to alert the staff...anything but set up the situation where the audience has to suffer.

[Harold Hallikainen]

I'm having trouble finding the SMPTE document, and I don't know if it has been published yet. But, as I recall, there is a recommendation ("should" not "shall") that all tracks in mainsound other than HI/VI/FskSync/MotionData/SignLanguage be silent.

Harold

[Mike Blakesley]

The latest Top Gun trailer we received had Atmos and there was no 5.1 only version.

That was the other one I was thinking of. I can't quite describe what's different about it but SOMETHING is. And there is no 5.1 version. I've had other trailers (Sing 2 is the most recent I've seen) where there is a 7.1 version but no 5.1.

I suppose this will be the new thing now, they will try to find some kind of one-size-fits-all for trailers and make them all sound compromised.

Perfect, let's advertise our product by making it sound ... less good? Probably time to go back to Brad's old recommendation of running mono sound on the trailers.

[Carsten Kurz]

I'm having trouble finding the SMPTE document, and I don't know if it has been published yet. But, as I recall, there is a recommendation ("should" not "shall") that all tracks in mainsound other than HI/VI/FskSync/MotionData/SignLanguage be silent.

Harold, what do you mean with 'silent'? No signal on the PCM tracks, or that the processor needs to mute them? If there was no signal on the standard DCP PCM tracks, there would be no fallback/backup track for the case that the ATMOS fails. My understanding is that the ATMOS DCP should contain a standard 5.1 or 7.1 mix in the audio reels, in addition to the ATMOS aux data file. As long as ATMOS plays successfully, mainsound should be muted. When ATMOS fails, mainsound should become audible. This could be done/implemented in different ways.


All ATMOS DCPs I played so far on our non-ATMOS system had main sound/5.1 or 7.1 populated with a standard mix - otherwise, I simply would not have had any audio.


This is from Dolbys ATMOS Whitepaper: https://www.hollandfilmnieuws.nl/fil...dolbyatmos.pdf

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2.3.4 In the Cinema

The DCP containing a Dolby Atmos track le will be recognized by all servers
as a valid package, and ingested accordingly. In theaters with Dolby Atmos, the Dolby Atmos track le will be ingested into the server and during playback will be streamed to the Dolby Atmos cinema processor for rendering. Having both Dolby Surround 7.1 (or 5.1) and Dolby Atmos audio streams available, the Dolby Atmos cinema processor can switch between them if necessary. This switching is analogous to the Dolby Digital and Dolby SR tracks on 35 mm prints, whereby a system that is equipped for Dolby Digital replay will do so from a single inventory print, but a system that cannot use the Dolby Digital track (or one that encounters a print or hardware issue) will seamlessly revert to the Dolby SR track to keep the show running.
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3.4 Mastering

During the mastering session, the stems, objects, and metadata are brought together in a Dolby Atmos package that is signed o in the dubbing theater and will remain untouched through to exhibition in the cinema. The Dolby Atmos package will also contain the backward-compatible Dolby Surround 7.1 or 5.1 theatrical mix.
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4.4 Digital Cinema Package Distribution

This single DCP can then be delivered to any DCI-compliant server. Any installations that are not suitably equipped will simply ignore the additional track le containing the Dolby Atmos soundtrack and will use the existing main audio track le for standard playback. Those installations equipped with a Dolby Atmos cinema processor will be able to ingest and replay the Dolby Atmos soundtrack where applicable, reverting to the standard audio track as necessary.
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5.1.2 Integration with Cinema Servers

The Dolby Atmos cinema processor is connected to the digital cinema server
with the existing 8 × AES main audio connection and an Ethernet connection for streaming Dolby Atmos audio data. Playback of Dolby Surround 7.1 or 5.1 content uses the existing AES audio connection. Dolby Atmos audio data is streamed over Ethernet to the cinema processor for decoding and rendering, and communication between the server and the cinema processor allows the audio to be identi ed and synchronized. In the event of any issue with the Dolby Atmos track playback, sound is reverted back to Dolby Surround 7.1 or 5.1 PCM audio.
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So, main sound needs to be populated with a failsafe/backup track?!

[Harold Hallikainen]

I agree a backup would be nice, but ST 429-19 section 7.1.2 says "MainSound should only carry channels that do not contribute to the Immersive Sound program or any defined soundfield. For example, Hearing Impaired tracks, Visually Impaired Narration tracks, or other tracks can be carried in MainSound." That is not a prohibition of including audio for "any defined soundfield," but it is a recommendation.

[Steve Guttag]

I step away from the standards community for a few minutes and this is the sort of thing they come up with? I'd be embarrassed. Seriously, no good will come of not having the 5.1 or 7.1 track with the IAD mix...just audience annoyance...and for what benefit?

I'm already embarrassed that any of the PCM tracks carry anything but MainSound audio. We should have built in "Aux Track" that would have been lower bandwidth to handle such tracks as HI/VI, and any sync tracks. The fact that out of 16 discrete audio PCMs we are now devoting 6 of them to something other than a channel for presentation is a poor utilization of the tracks and will stifle non-proprietary channel assignments other than 5.1/7.1...which is why there were 16 channels to begin with. In the end, 7.1 in both SDS and DS configurations have been protected (LC/RC and Rear Surrounds) but that is it. We have audio tracks being used to sync motion chairs, immersive audio, and ADA...all of which could have utilized a low-bit rate, low bandwidth track and left the 16 audio tracks alone. DTS had it right...on the XD10/XD20, the ADA tracks were kept separate because they don't need to be above telephone quality. They are just spoken word, not full range wide-dynamic tracks.

[Carsten Kurz]

Harold, you seem to be right, I just found this in RDD52:

Bildschirmfoto 2022-04-03 um 00.59.49.png

Yes, it is 'shall', but still. What happened to the backup/failsafe that is quoted in Dolby's ATMOS whitepaper? Would only 'IAB' need to be RDD52/ST-429-19 compliant? Would the failsafe be an ATMOS exclusive feature? Would ATMOS then be non-compliant? Weird...

Do we have to assume that all ATMOS DCPs/trailers currently circulating WITH a common 5.1/7.1 mix in mainsound are not SMPTE/RDD52 compliant? I guess we need to bring this up on the next ISDCF meeting. I have never so far seen/played an ATMOS DCP/trailer without main sound being populated with 5.1/7.1
What is the actual reason for this? What benefit is there in recording silence on these tracks? How could active, useful signals in main sound be a problem?


I see ALL current ATMOS VFs and KDMs being named as e.g. '51-ATMOS' or '71-ATMOS' - that wouldn't make any sense at all if they didn't carry a 5.1 or 7.1 main sound?

I do understand that it makes sense to not have any audio in mainsound that is intended to be part of an ATMOS/IAB playback. So, not have dialog in main sound + ATMOS audio. But having a full backup/single inventory mix in main sound is a different thing. As long as ATMOS/IAB is playing successfully, mute all other channels, except HI/VI-N. That would not necessarily have to be the server, the ATMOS/audio processor could do it just as well in order so secure a graceful fallback to main sound if necessary. Yes, there have been many occasions of ATMOS playback failing in the past. It could also be speakers or amps causing issues, and the press of a button could force the processor to main sound playback.

[Harold Hallikainen]

RDD is a Registered Document Disclosure, so it does not have the "force" of a standard (which is voluntary anyway). RDDs are mostly a way for companies or groups to say "this is the way we are doing it, if you want to be compatible with us, do it this way." I THINK I heard the argument for doing this was that people THOUGHT they were playing IAB but were not (they were constantly in fallback mode). I argued that it was better to play something in such a failure mode, but I did not win that argument. ST 429-19 uses "should," so one is still compliant if they include backup in mainsound. But, what is that backup? 5.1? 7.1? Is it identified somewhere?

Harold

[Carsten Kurz]

The DCNC name and metadata should indicate wether the system should fall back to 5.1 or 7.1 Strictly speaking, a fallback main sound could just as well be always 5.1 as the lowest common denominator.

Heck, what could be the problem with people just THINKING they could be playing 5.1 or ATMOS? The audience has no choice anyway, and the operator could just look up an 'ATMOS: GOOD' indicator on the TMS or ATMOS processor. In the typical TMS driven multiplex, an ATMOS show failing with no sound would practically mean a lost show. An operator would have to stop playback, identify the issue properly, check if there is a plain 5.1 or 7.1 VF on that server, check for a suitable KDM, restart the new CPL, recue, and issue all necessary automation cues manually. Now how likely would that happen?