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How to DCPs work? Do they hold several versions of a mix (ie, atmos, 7.1, 5.1, stereo) and play according to what type of system is detected? Or does it simply carry the mix with the highest channel count (ie, atmos) and apply some kind of foldown algorithm?

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I spent a bit of time working as a projectionist about five years ago, playing standard DCPs from a Doremi server. All the prints came with a single audio format sent specifically from the distributor for the particular screen. The server outputs discreet channels and these are routed to the speakers. At the cinema I worked at we had a custom switch to do this (though the screen was multi-purpose, not like your local multiplex).

  • so the theater would order specific DCPs formatted for the sound systems they had available in each of their theaters? I'm I understanding you correctly? – Jake Aug 7 '14 at 0:11
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    Yes, as far as I know, but all the screens were 5.1 so it wasn't very complex. Prints also come with a KDM which is like a key to upload the DCP onto the server. You would also have to specify if you needed subtitles or audio description as these would be separate elements on the drive. Dolby make their own cinema servers which compete with the Doremi server I used. Just reading this: dolby.com/us/en/technologies/… it looks like they package their DCP differently cont... – Mark Durham Aug 7 '14 at 7:38
  • ... "Digital cinema packages (DCPs) supporting Dolby Surround 7.1 will be supplied with two composition playlists (CPLs). One CPL will reference a 5.1 discrete audio track, and the second will reference the Dolby Surround 7.1 audio track." You can see the channel list further down on that document. Essentially though, the DCP is a video file and multichannel audio file and the cinema server is just a player for these. I provided 5.1 stems for a low budget film recently and followed this: dcpinfo.com and everything worked fine. The DCP was essentially home made with OpenDCP (google – Mark Durham Aug 7 '14 at 7:52
  • it). I've never tried the same with 7.1 though. – Mark Durham Aug 7 '14 at 8:00
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@ Mark Durham - Thanks so much for your replies Mark!!! Very great and useful stuff!!

I also posted this question on another forum, and got some great insight into the Atmos end of things. I thought I'd share for anyone who might be interested :

The DCP spec and Dolby Atmos are two different things so the Atmos mix has to be replayed through its proprietary Dolby software and hardware, the RMU. The DCP spec allows for 7.1 and 5.1, but no internal downmixing so a separate DCP would be used for those two mixes. Two Channel L R Stereo is not a commercial cinema format and never has been, as far as I know. You need a centre speaker in a cinema to stop the dialogue sounding like its coming from one side of the room.

Auro 3D sneaks itself into the DCP container with some trickery, but there are people on here better qualified to explain that to you.

Hope this helps,

Rob Walker

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