Dolby System Support

Anything and everything to do with DCP-o-matic.
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Santiago
Posts: 3
Joined: Thu Dec 14, 2017 11:58 pm
Location: Mendoza, Argentina

Dolby System Support

Post by Santiago » Thu Jan 11, 2018 3:08 pm

Hello everyone! I'm new in this group.

I've read something about Dolby supported -at least- on recently versions. I found it out when i was making a DCP project and there was a moment when i wanted to adjust audio levels for the right volume. Soon i will make a DCP for a cinema that has Dolby Atmos.

"Current versions of DCP-o-matic only know about the Dolby CP650 and CP750"

Kind of a feature request: Would be possible to have Dolby Atmos support as well? I think i could help giving some information about the equipment next time i be there, in the projection room.


Thank you.
Santiago

Carsten
Posts: 1240
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Dolby System Support

Post by Carsten » Thu Jan 11, 2018 4:30 pm

Hi,

Dolby was 'always' supported by DCP-o-matic, but there was a problem with some of the recent test versions that prevented DCPs to play on select Dolby and Barco servers. That has been fixed now.

'Current versions of DCP-o-matic only know about the Dolby CP650 and CP750' - that only refers to volume adjustment based on the cinema specific 'Dolby Level'. It's a feature that probably few people actually use. It doesn't indicate any special Dolby support, just one possible way to choose audio levels in addition to the standard +/- dB approach.

ATMOS is very far away. I know a free DCP creation software supporting ATMOS - but it only puts a standard ATMOS sync audio track into the DCP. That doesn't help much, you still need to do the whole ATMOS audio mastering and packaging. There is much to say about ATMOS, but for now, a 'real', working ATMOS solution is beyond the possibilities of open source software. This may change once SMPTE finishes the standard for object based audio.

DCPs created with DCP-o-matic simply play on all ATMOS systems, as all ATMOS systems have standard cinema Stereo, 5.1 or 7.1 modes. You just don't have the benefit of the individual speaker addressing (among many other aspects of ATMOS).

- Carsten

Santiago
Posts: 3
Joined: Thu Dec 14, 2017 11:58 pm
Location: Mendoza, Argentina

Re: Dolby System Support

Post by Santiago » Thu Jan 11, 2018 5:25 pm

Carsten, thank you for the answer!
Sorry, i was not clear for the first time. What I'm trying to say is:

I know that Dolby has position numbers that refers to audio levels in dB. (I think most systems work at fader 7 as maximum). Is that panel in dcp-o-matic compatible with that? I mean, if I want to adjust level to 85dB (Dolby level 7) and -27 LUFS, is it work this way? I think I'm a little confused

Thanks!

Carsten
Posts: 1240
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Dolby System Support

Post by Carsten » Thu Jan 11, 2018 7:14 pm

Yes, the Dolby Fader adjustment is based on the idea of the Dolby Fader reference.

'7' ? We'll see...

The Idea is, you want to create your DCP so that the cinema can use it's standard audio fader setting, but for some reason, your DCP is too loud or too weak. You then adjust the level in the cinema so that you like the level that you hear - say, 4.5. You then tell DCP-o-matic, 'This DCP plays fine at 4.5, but I want it to sound at the same loudness with the cinema standard fader setting'. Dial in those numbers, and DCP-o-matic will create the gain or attentuation needed to achieve that. This calculation is based on the specific fader curve of Dolby processors (a specific number - dB relationship). DCP-o-matic has this relationship stored for Dolby processors. Other manufacturers use slightly different curves/relationships, e.g. USL, or Datasat. If someone tells Carl (the programmer) their specific processors number/dB relationship, Carl could implement these curves as well.
Yes, in theory, the cinema standard playback fader level SHOULD always be 7, but everyone working in cinema projection knows that no one uses that reference, at least not during pre-show. Typical actual fader settings that I have seen and hear about over the years vary between 4 and 6 for main features. Our standard fader setting is 5.5 (we play preshow at 4.5). I often adjust the main feature slighty up from there, towards 6, rarely 6.5. Only VERY rarely do I have to reduce main feature level below 5.5 to make it acceptable. Maybe once in two or three years.


LUFS is not a proper cinema loudness scale. It's for broadcast - TV, radio, starting to get used for internet media as well. But the calculation for this (complex) analysis is available through FFMPEG, one of the underlying frameworks DCP-o-matic uses, so, Carl can use it easily. dB LEQ(m) is the proper cinema standard, but that is not available through FFMPEG (yet), and it would be too much work for Carl to implement it all on his own. It's better to wait until dB LEQ(m) turns up in FFMPEG, and use LUFS until then.

As LUFS and dB LEQ(m) use different methods and references, you can not simply compare numbers. dB LEQ(m) for instance uses typical numbers in the 70-80 range, e.g. 82 or 85 dB LEQ(m), while typical LUFS numbers are in the range -15 to -30. Lower LUFS numbers (note they are negated, so mathematically, they are higher values) mean more loudness, while with dB LEQ(m), higher numbers mean more loudness. There is no simple relation between these numbers, although one could establish one that allows to use LUFS in cinema with some confidence.

Remember, though, that neither LUFS nor dB LEQ(m) actually indicate 'target values'. They only indicate max allowable loudness. It's a complaint level. If you choose to make a short film with people whispering to each other, and level to 85 dB LEQ(m), or -14 LUFS, their whisper will sound like a hurricane. Something MEANT to be perceived soft, must be played back soft. On the other hand, if DCP-o-matic indicates -12 LUFS for a dialog short or advertising spot, something is severly wrong with it, because it is far over complaint loudness.
As such, it is completely okay if your clip is indicated at LUFS -30, IF it is a very soft trailer and intended to play like that. It doesn't violate any regulation.
But if people actually speak in it at their normal voice level, there is probably something wrong, and a cinema audience will not understand what is said.

IF, however, you are working in advertising, then the max allowable loudness IS indeed your target level, because you are not paid to care for subtlety, but to create your spots at the maximum allowed loudness to compete with everyone else's. Kidding. Or not?

So, if you're mad about proper audio level in cinema, you need to take your DCP to a properly calibrated cinema and play it there. Using LUFS is just there to get into the right ball park. I consider 'normal' informative spots, trailers, etc, around -20 LUFS as 'okay'. If there is spoken word and music, people will understand what is being said, and the music wont blow their heads off. Fine tuning MUST then be done on a calibrated system, especially if your content varies wildly in loudness over it's length.

Broadcast LUFS standard is -23LUFS. However, that is based on typical long term living room TV or radio listening - people expect and tolerate higher loudness in a cinema, so allowed cinema LUFS number should be lower (which means higher loudness). Therefore, I think -20 LUFS is a useful number and easy to memorize.


By the way - as DCP-o-matic can import DCPs, and perform LUFS calculation on them, it's a nice education to load a range of 'real' DCP ads and trailers into it and watch their LUFS values.


- Carsten
Last edited by Carsten on Fri Oct 19, 2018 5:45 pm, edited 16 times in total.

Carsten
Posts: 1240
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Dolby System Support

Post by Carsten » Fri Jan 12, 2018 12:23 am

Have a look at some interesting examples (keep in mind, these files are actual official trailer DCPs, not trailers ripped from YouTube and converted...):

The first one is cinematic Trailer D for Star Wars 8, currently in cinemas. US TASA regulations demand that trailers have to obey a limit of 85dB LEQ(m). As Star Wars 8 is a high profile release, certainly only highly skilled people are allowed to master these trailers, and they are certainly mixed to spec.
The german version of this trailer computes to -14.11 LUFS. That is very loud. As I wrote earlier, we play preshow at Dolby Level 4.5, because trailers always max out their allowed limits and we don't want to annoy our audience before the main feature even starts.
But, even at 4.5, these trailers still play 'loud'.

StarWars8_TrD_de.jpg
StarWars8_TrD_de.jpg (108.95 KiB) Viewed 2725 times

The original english version of the same trailer computes to -13.37 LUFS. Even a tiny bit louder (though in fact, not noticeably). That's an action packed SciFi Trailer. I don't think you find something louder than this when you visit a cinema.

StarWars8_TrD_eng.jpg
StarWars8_TrD_eng.jpg (110.08 KiB) Viewed 2725 times

So that is certainly the upper level. Let's assume -14 LUFS to roughly equal 85 dB LEQ(m)?

Now here is an interesting one - it's a short that we played last year on the international day against homophobia. It is not a high profile cinematic production, it's stereo, and it probably hasn't received a professional cinema audio mastering. We played it immediately before our main feature, after the preshow program.
The day after we played it, we received an email complaint by a patron who found the short much too loud, especially towards the end, where 'high impact' music is played. We rarely ever receive such explicit complaints afterwards, so, unless this person was extremely sensitive, I was sure there was something wrong about this clip. I loaded it into DCP-o-matic for an R128 analysis, and found this:

PorUnBeso.jpg
PorUnBeso.jpg (85.68 KiB) Viewed 2725 times

It's indeed very loud. At 13.89 LUFS, it reaches the same values as the StarWars 8 trailer. And this is not an action packed SciFi trailer.
And that using only the two Left and Right speakers. Watch the StarWars 8 trailer achieving the same loudness using all speakers, Left, Right, Center, Surround, LFE...
But was it actually TOO loud? Yes, because I played it after the preshow program, our cinema sound processor was already set to main feature fader setting, up to 5.5 from 4.5...
Remember I wrote earlier that LUFS and LEQ(m) indicate 'complaint levels'? Well, there we are, it seems that -14LUFS or our assumed 85dB LEQ(m) is indeed our complaint level. I should have played it at 4.5 as the pre show program, and we might have avoided that complaint...
I wrote an excuse to the complaining patron and admitted, that while I actually did check the volume during a test run, it had escaped me that I tested it in the auditorium at preshow level of 4.5, before I created the show playlist and missed the fact that the new fader level 5.5 cue was placed before the short, not after it...
Last edited by Carsten on Fri Jan 12, 2018 11:38 am, edited 11 times in total.

Carsten
Posts: 1240
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Dolby System Support

Post by Carsten » Fri Jan 12, 2018 12:40 am

And another one from the opposite side of the scale...

This is a local advertising spot we currently play as the first clip in all our shows. It's a commercial spot for a local media agency.
We received it in DCP format, so someone claimed he knew what he was doing and he certainly was paid quite some money... ;)
Obviously, it did not receive a professional audio mastering either, it is stereo, and much too soft:

Rheinland.jpg
Rheinland.jpg (88.04 KiB) Viewed 2717 times

This one annoys me, because only very reserved audiences will understand the dialog spoken in it. In situations with a 'normal' crowd, the speech intelligibility drops to near zero. Why? Because it's at a mere -28.76 LUFS. With a normal attendance in our auditorium, the audio is practically wasted. See how the RMS is hovering just below -30dB FS? That is far too low for a commercial, featuring an off-voice and some music. Even if I'd play it at 5.5 instead of 4.5 preshow level, it would still be too soft. So I took it into DCP-o-matic and created a new DCP, raising the audio by +10dB.

So, find yourself somewhere between -28 and -14 LUFS. I suggest to start around -18 to -22 LUFS, depending on your own estimate wether your clip/short/movie should be perceived as more intense, or more on the subtle side. Then take it to a cinema, ask the projectionist to play it at their normal level (for either preshow, or main feature, depending on your content), sit down around the back third of the auditorium, and listen to it.

If your auditorium session is time or staff limited, you may create three versions of your clip at different levels. Say, one around -23 LUFS, one around -20 LUFS, one around -17 LUFS. (+/- 3dB gain). Have all three ingested and played for a comparison.

DCP-o-matic is so fast in creating DCPs with audio gain changes only, you could even do that with a notebook in the auditorium, and immediately have these versions ingested from a USB stick or portable disc.

- Carsten

Santiago
Posts: 3
Joined: Thu Dec 14, 2017 11:58 pm
Location: Mendoza, Argentina

Re: Dolby System Support

Post by Santiago » Sun Jan 14, 2018 9:41 pm

Carsten,

Thank you very much for your time and your words! It took me some days to sit down with my computer and analyze all this. Definitely, this information helps me a lot. Now, i should go to the cinema and do some tests.

I will write you soon

Thank you

Santiago

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