volume level: soundcard vs monitors for mixing

[ryanjf]

Thanks for the reply, for Digital Cinema I mean those cinemas with DCI compliant servers, projectors and speakers.

I'm a bit confused now to be honest, for web and TV delievery, dialogue usually peaks around -12dBFS, can I do the same for my Digital Cinema Package? so I just need to have one master mixdown, or do I need to decrease the volume a few dBs specificly for theatrical release so dialogue peaks around -20dBFS? Are speakers in a standard digital cinema adjustable by projectionist? so they don't have a fixed volume to avoid films that are too loud?

Dialogue can certainly peak higher than -12dBFS for theatrical. The AVERAGE (not peak) can/might be around -20dBFS for theatrical. We're not saying it has to, but it can. Remember that mixers mix by ear if they are in a calibrated room. If it sounds good, it is good; if it's too loud, then it's too loud. For TV delivery, each broadcaster has their own specs so that varies. There is a great sticky on Gearslutz (post production forum) about this that is a great read. For web, there really isn't any standard.

Printmasters are sent directly to the DCP "authorers" so there is no change in level that I know of. Yes speakers can be adjusted by the projectionist and typically are at regular theaters. The projectionist can choose to play the film "at level" but more often than not, they turn it down a few dB.

EDIT: DCPs are 48kHz @ 24bit @ 24FPS so whether you'll be creating that version (or the client) is a different issue.

[ryanjf]

Wow really? if the speakers in the cinema are calibrated as -20dBFS equals 85dBSPL, won't they instantly make the audience deaf? or the projectionist will adjust the calibration prior to the first public screening to a acceptable level? like we use our remote control to "+" and "-" when we watch TV....

Yes. That means in your DAW, you have 20dB of headroom (to digital 0) which means that if you have an explosion that hits 0dBFS, then that sound is played at 105 SPL or higher. Hopefully that explosion (or whatever it may be) is not sustained at that level because it does hurt. Have you watched the train wreck sequence in Super 8 in theaters??! You'll notice that that sequence is LOUD! I watched Super 8 at two different theaters and the second theater definitely turned it down. It was almost a no brainer what the projectionist did.

[marvinhello]

Yes. That means in your DAW, you have 20dB of headroom (to digital 0) which means that if you have an explosion that hits 0dBFS, then that sound is played at 105 SPL or higher. Hopefully that explosion (or whatever it may be) is not sustained at that level because it does hurt. Have you watched the train wreck sequence in Super 8 in theaters??! You'll notice that that sequence is LOUD! I watched Super 8 at two different theaters and the second theater definitely turned it down. It was almost a no brainer what the projectionist did.

Thanks, I think I'll just mix the 5.1 surround at the same level as web/TV version... and tell the projectionist to adjust the volume as required... it's a student film which is going to be screened in a small digital cinema (takes DCP), so I don't have access to a professionally calibrated room or funds to hire a mixer...

[paulears]

I think that is the problem - the end users, be it home or cinemas set their own levels. The big players in the superbly fitted studio complexes can set their own levels but sometimes the output sounds like a brick wall limiter to keep the level below the prescribed point - while others are really expanded - so although the peaks are high, far too much happens at a level below the noise floor in the listening space. One small multi space cinema near me has amazingly noisy air handling - so the solution is to really push the levels, and peaks are very unpleasant. Explosions and that kind of sound effects are very rough! It's a habit that even the audio CD people are now doing - mixing too low and expanding the dynamic range to a point where the listener in the imperfect space cannot cope.

[Noiz2]

How are you going to get the tracks in a format compatible with the projector? I haven't done a Digital Cinema mix so personally don't know but if you haven't checked with them you should.

You can not for instance encode a Dolby Digital (big screen version) on your own. I could be wrong but I suspect that there may be issues getting your tracks encoded in a way that the projector can read.

I would also not recommend trying a 5.1 mix in a non calibrated mix stage let alone a non calibrated room, for playback on the big screen. There is a HUGE difference in how your room sounds compared to a theatre and you can't do a decent mix, especially a 5.1 one, that way. At least I would stay away from 5.1. The surrounds and sub could make watching the film Very distracting and or painful.


Cinemas are "supposed" to set the Dolby decoder at "7", but since trailers, ads and sometimes films come in at blistering levels they often turn them down. It's a hot debate with mixers, most of whom think Dolby ought to lock the level.

Personally I don't think you can lock out the theatre owner as long as you don't have a working standard for what kind of loudness is allowed to show up at the theatre. If it's too loud people walk out and want their money back. The studio sure isn't going to compensate them for that so...

It would be nice if there were something like the Dialog Normal number that gets encoded into DVDs, IF it were implemented as it was supposed to be. Networks require mixers to mix to a DiaN number a lot of times now. It was supposed to be a number that the network used to adjust the level on their end. Thus the mixing would be the same but at the playback end the level could be intelligently altered to fit the networks standards, time of day, etc.

[marvinhello]

Hi Noiz, Digital Cinema Initiative (DCI) is built entirely on open standards, audio to be specific, is just 24bit 48Khz uncompressed LPCM mono tracks, two mono tracks for 2.0, six mono tracks for 5.1, 8 tracks for 7.1

Picture wise, it's 12bit X'Y'Z colour space, encoded in JPEG2000 sequence and wrapped in MXF.

BTW, your idea on Dialogue Normal number is really interesting

[ryanjf]

Hi Noiz, Digital Cinema Initiative (DCI) is built entirely on open standards, audio to be specific, is just 24bit 48Khz uncompressed LPCM mono tracks, two mono tracks for 2.0, six mono tracks for 5.1, 8 tracks for 7.1

Picture wise, it's 12bit X'Y'Z colour space, encoded in JPEG2000 sequence and wrapped in MXF.

BTW, your idea on Dialogue Normal number is really interesting

Also, audio has to be 24FPS!

[Noiz2]

Also, audio has to be 24FPS!

Ryan, sound doesn't have a frame rate. The only way the frame rate would affect the sound is IF you were working with pulled down version of the film, OR your supplying sound with a TC stripe for sync.

There is no reason you would be working at anything but the correct frame rate these days and I don't imagine your sending sound on a separate tape (actually any tape at all but...).

[Noiz2]

Also, audio has to be 24FPS!

And actually no. It supports a lot of frame rates.

Technical specifications

The DCP root folder (in the storage medium) contains a number of files, some used to store the image and audio contents, and some other used to organize and manage the whole playlist.^[4]
[edit]Picture MXF files

Picture contents may be stored in one or more reels corresponding to one or more MXF files. Each reel contains pictures asMPEG-2 or JPEG 2000 essence, depending on the adopted codec. MPEG-2 is no longer compliant with the DCI specification. JPEG 2000 is the only accepted compression format.

• Supported frame rates are:
  
  • SMPTE (JPEG 2000)
    
    • 24, 25, 30, 48, 50, and 60 fps @ 2K
    • 24, 25, and 30 fps @ 4K
    • 24 and 48 fps @ 2K stereoscopic
  • MXF Interop (JPEG 2000) – Deprecated
    
    • 24 and 48 fps @ 2K (MXF Interop can be encoded at 25 frame/s but support is not guaranteed)
    • 24 fps @ 4K
    • 24 fps @ 2K stereoscopic
  • MXF Interop (MPEG-2) – Deprecated
    
    • 23.976 and 24 fps @ 1920×1080
• Maximum frame sizes are 2048×1080 for 2K DC, and 4096×2160 for 4K DC. Common formats are:
  
  • SMPTE (JPEG 2000)
    
    • Flat (1998×1080 or 3996×2160), ~1.85:1 aspect ratio
    • Scope (2048×858 or 4096×1716), ~2.39:1 aspect ratio
    • HDTV (1920×1080 or 3840×2160), 16:9 aspect ratio (although not specifically defined in the DCI specification, this resolution is DCI compliant per section 3.2.1.2).
    • Full (2048×1080 or 4096×2160) (Official name by DCI is Full Container)
  • MXF Interop (MPEG-2) – Deprecated
    
    • Full Frame (1920×1080)
• 12 bits per pixel precision (36 bits total)
• XYZ colorspace
• Maximum bit rate is 250 Mbit/s (1.3 MBytes per frame at 24 frame/s)

[edit]Sound MXF files

Sound contents are stored in reels, too, corresponding to picture reels in number and duration. In case of multilingual features, separate reels are required to convey different languages. Each file contains linear PCM essence.

• Sampling rate is 48,000 or 96,000 samples per second
• Sample precision of 24 bits
• Linear mapping (no companding)
• Up to 12 independent channels.
• WAV container

[edit]Asset map file

[Petrus]

Wow really? if the speakers in the cinema are calibrated as -20dBFS equals 85dBSPL, won't they instantly make the audience deaf? or the projectionist will adjust the calibration prior to the first public screening to a acceptable level? like we use our remote control to "+" and "-" when we watch TV....

If the peaks were at -20 dBFS you would be wasting over 3 bits of resolution. Dialog should sit somewhere around that figure, but certainly the peaks should go to about -6 dBFS to -3 dBFS, but not higher for clipping safety. If the dialog is kept at around -20 dBFS it is the job of the sound mixer to make the audio listenable with systems which are calibrated at 85 dB SLP for -20 dBFS signals, which means 102 dB SPL peaks with -3 dBFS peak level. With clean sound and good system our ears can take it, after all cinema audio is not like pop rock leaning on a limiter. Thank god there still are some standards, rules and best practices which ensures that, like keeping the dialog levels naturally low. Cinema sound can be dynamic as there is no competition in the theater, the problem is the DVD etc listened at home, which might need a slight compression compared to a theatre release.