Mixing audio for DCP delivery

D

David Evans

Well-known member
Hi guys,

I've got a finished 24min short film and now it's time to create a DCP for film festivals. I've done DCPs in the past but I've always had this question regarding the audio.

It seems to me that LCR is the minimum for a decent audio mix in theatre, because of how far the L and R speakers are from each other. This way I would make sure my dialogues are all in the center channel. So, to me, this is pretty easy:

1 - I export just the dialogues and voice overs to a .wav file and then export the remaining channels to another .wav file.
2 - Make each .wav file into a mono channel.
3 - Create the DCP.

But now I was wondering if I should deliver empty tracks in the remaining 5.1 channels or if I should add the L+R to those channels as well and deliver a 5.1 very basic mix.

My film was mixed in stereo.

Is duplicating L+R to the surround channels ok? Is there a better, yet simple, way to do it?

Software I use:

Davinci Resolve
Open DCP
Audacity

Thanks

EDIT:

Actually, I have a more important question than that. I mixed my audio in a certain way on Resolve and everything is mixed as I want. If I export the dialogues track into a mono channel (Center) and the rest goes to L+R (two separate mono .wav files), does this mean my mixing can be affected? I mean, will the L and R channels duplicate the volume since there are two mono files of the same sounds? Sorry if this question is dumb...
 
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I'd recommend, mono, dual mono or stereo. I've heard and read about film festival audio nightmares with not incorrectly set-up and/or not calibrated sound systems. I recall a 5:1 downmix that removed the dialog (scary). This was discussed recently here or over at DVinfo audio.
 
I've always just done a stereo mix with the dialogue panned center. I would try and idiot proof as much as possible. The more tracks you give them the more chance there is for someone to screw something up.
 
Thanks guys. I asked this because I've read on countless sites that LCR is the minimum for a decent DCP mix, because of phase issues, dynamics, clarity of the vocals, etc. For me, it shouldn't be a problem as I don't have any dialogue, just voice over. So it's very easy to just export a voice over track and create a center channel with that.

Maybe I should do two DCPs, one with dual mono and other with LCR for bigger, more reliable festivals?
 
David W. Jones said:
LCR, but why not consider having someone do a 5.1 up mix for you if you have the time?
Click to expand...

I probably will, David. Still doing some market research on that. But, if doing a 3.0 mix, I should leave SR, SL and LFE channels empty, right? That is, without any .wav file in the mxf.
 
I have never actually heard of a LCR track being used in a released film. So I would wory that you are giving them something out of the ordinary and it will cause problems.

What are the specs from the festival?

If they only have stereo then you run the risk of them not playing one track.

Personally I would do stereo. It is the most likely to play correctly in the most situations.

If you do go with more than stereo you should not duplicate the LR into the surrounds, they will play too loud and sound weird. Part of that weird will vary around the theatre because of the time lag between the front speakers and the rear speakers. If you don't do a real surround mix don't put anything in the surrounds.
 
Hi, I've made 200+ DCPs for indie filmmakers over the last four years. You are correct that LCR is the minimum requirement in the DCI spec, but a stereo DCP *can* be made. And while it's technically out of spec, I've never had playback issues on a cinema server, and I've never had a theater reject it. So don't let that force you into doing an LCR mix.

If there is any reason, it's so your dialogue and most effects are anchored to the screen. BTW, that's an important distinction. It's not just dialogue you'd want in the center channel. Like if you've got a dialogue scene and one character is chopping wood. You don't want those chop effects in L & R while dialogue is in C. it'll be weird.
 
Thanks Zak. That makes sense! Btw, how would you do a 5.1 upmix on a stereo mixed film? Run some sort of algorithm or would you remix the film?
 
I hope I'm not misleading, for actually I haven't done it. However, it looks to me fairly simple and straight forward:

In DaVinci Resolve (at least in the latest Studio version), in the 'Deliver' work space, you can deliver (or render, or conform) the video with 'easyDCP' format, and the audio as 'Main (5.1 film)'. In your case, some of the 5.1 audio tracks will have no content, however, that isn't a problem at all. The 'Main' refers to the mixed track in the 'Fairlight' work space, see below.

Prior to that, in the 'Edit' work space, you can have as many audio tracks as needed. Each track can be either mono or stereo.

In the 'Fairlight' (audio) work space, there is a mixer which sows all the audio tracks on the timeline, while each track has its own volume control, surround pan control, effects, EQ, and Dynamics. All the separate audio tracks are mixed into one 'Main' audio track, which has its own volume control, Effects, and EQ.

So, mix the audio to your taste and needs in Resolve, deliver it as DCP with 5.1 audio channels and that's it. No one is going to check how many of the 5.1 audio channels have content and how many don't have content.
 
davefisk said:
I've always just done a stereo mix with the dialogue panned center. I would try and idiot proof as much as possible. The more tracks you give them the more chance there is for someone to screw something up.
Click to expand...

GAWD, do I agree with this!

I am SOO tired of horrible screwed up audio because the playback system isn't set up EXACTLY right.

Unless you have some VERY SPECIFIC and VERY IMPORTANT reason to have some sound NOT be just in a normal stereo field, then providing anything more than that is begging for disappointment.

LCR is at least "reasonably dependable", but take note of Zak's tip on SFX anchoring.
 
I have done this for a film that was finished in stereo, by someone else, and they had nothing but the stereo mix. He had sme deal and he needed to deliver a "5.1" mix.

There really isn't a proper way to do that but $$ on the table and after explaining the limitations he was fine with it.

There are some "unfold" type plugins that try to create a 5.1 from stereo but... Basically you take the stereo and treat it like a LtRt. L = L-R, R= R-L, C = L+R. Take L+R and filter everything over 80Hz and call that the LFE take your L and your R and send them through some reverb and put them in the subs at a really low level. You need to do this while monitoring in surround so you can catch any weird artifacts. For instance the "mixer" might have done something really non standard like done "stereo" dialog. In that case you may be kind of screwed on the center channel. But since they must have faked the stereo you might be able to undo it. Hard to tell.

In the end you are not getting a 5.1 mix but a mix with something in all channels that should playback in 5.1 and not sound any worse than the stereo mix.

To do an actual 5.1 mix you really need to reedit. You can probably just add to the stereo mix and pull all the dialog center, along with all the Foley and maybe some other SFX. But the surrounds should be mostly "new" stuff. The surround is stuff that is not on the screen with a bit of bounce maybe from what is on screen. So it is really it's own thing.

I don't recommend it unless you can mix in an environment similar to the one most people will watch your film in. So if you are headed for the big screen you really should mix in a mix stage. If you are really only in the home video market you can do that in a home studio.

The reason is things like EQ and reverb can change rather radically when moving to a larger space. A mixer who has done enough shows may be able to compensate but if you haven't heard the difference it will be a big surprise. And generally not a good one.

Side note, this is true for picture edits also. A few frames of black on a video can be just right but on a big screen people will start looking at their watches. There is always something going on in the environment watching video but a big screen that is black is a problem really fast. Of course you can also use that to your advantage...
 
Noiz2 said:
To do an actual 5.1 mix you really need to reedit. You can probably just add to the stereo mix and pull all the dialog center, along with all the Foley and maybe some other SFX. But the surrounds should be mostly "new" stuff. The surround is stuff that is not on the screen with a bit of bounce maybe from what is on screen. So it is really it's own thing.

I don't recommend it unless you can mix in an environment similar to the one most people will watch your film in. So if you are headed for the big screen you really should mix in a mix stage. If you are really only in the home video market you can do that in a home studio.

The reason is things like EQ and reverb can change rather radically when moving to a larger space. A mixer who has done enough shows may be able to compensate but if you haven't heard the difference it will be a big surprise. And generally not a good one.
Click to expand...

I couldn't agree with this more. If you want a true 5.1 mix you really need to actually do it from scratch.
 
Why not just put empty files in the rear channels?
The rear channels are not used "*very commonly*" anyway.

It seemed this is what the OP was asking about - can a stereo or LCR mix be brought into a 5:1 format without redoing the entire mix into a native 5:1 remixed creation. I don't see any reason why not, unless there's some technical aspect I'm missing.
Sure, you have to re-render in 5:1, but I read that to be assumed.
 
How do the levels work ?
Film sound levels are different from web levels. I'm still confused about these.. I peak the web sound at -3 db.

Now I have unwrapped the stereo to 3 LCR mono channels. What happens to the levels ? I dont see LEQ(m) anywhere - I am still metering in db.
 
DCP-O-Matic offers two different ways to upmix stereo to 5.1. I've never used it myself and would not do it unless I can first check the whole film in a cinema and compare to a stereo mix. But it might work. Would be interested in hearing if anyone has tried it?

http://dcpomatic.com/manual/html/ch07.html
 
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