Multiple Audio Options?

[DCP-Junkie]

Is it possible to build a DCP and have multiple audio options (one Stereo and one 5.1) that a theater would then choose from? Or, would I just build two different DCP's?

[Carsten]

You need to build two separate 'compositions'. You may call them 'two separate DCPs', but DCP is not the proper term.

DCP means 'Digital Cinema Package'. It has a broader meaning than just 'movie'. A DCP may contain a single version of a movie, multiple versions of a movie, or just a partial package that needs another DCP to build a full composition. The actual movie version that is played is called a composition, or CPL (composition play list). Now, DCP-o-matic does not support multi-cpl-packaging currently. That means, a CPL/version created with DCP-o-matic will always be packed in a single DCP. One CPL per DCP. Other tools allow to wrap multiple CPLs into a single DCP. The practical difference for the cinema is neglectable.

It is important to know that unlike with DVD, Bluray, or typical streaming formats, there is no way in digital cinema to choose audio or subtitle language during playout - a projectionist has to choose exactly one distinct version - CPL - for playout. If a different version should be played, the first one needs to be stopped and another one needs to be selected. I once had to help a filmmaker who actually created a DCP containing 19 different language subtitles in a single CPL. He thought that the cinema could choose which one would be played. However, all 19 subtitles played at the same time over each other. We had to recreate the DCP and created 19 separate CPLs for each subtitle language version. Same for audio.

- Carsten

[DCP-Junkie]

Thank you for the response. The reason I asked is because I received a file with 8 channels which was laid out as channels 1-6 for surround sound and 7-8 for stereo. When I loaded the file though it came up in the audio tab only showing the C channel checked (See Pic 1). I checked the file the only way I know how in Premiere Pro and it appeared to be different sounds coming from each channel. I built a 5.1 mix from that changing the layout to what the person gave me which was L, C, R, Ls, Rs, LFE (See Pic 2, I know this is outside the norm) and the output in the theater today was sound only coming from the center. Can someone help me understand this? I would like to get this fixed and back to the theater to test ASAP.

[Carsten]

L-C-R-Ls-Rs-LFE is the old channel sequence for film workflows (35mm). Some editing systems still offer this export order under the name 'film', so, some may use it for cinema. Or maybe what you got is a file from an older 35mm workflow.

From what I see in your mapping, that should be okay. I think you can skip the stereo. In 35mm days, it was common to exchange an 8ch file with a stereo downmix or Lt/Rt following the surround channels. Typically, the stereo file was for reference, or, mostly, it went to the analog/optical stereo/Dolby track, while the discrete surround went to the Dolby Digital/DTS tracks. The stereo/Lt/Rt part is not used in digital cinema anymore if there is a surround mix available.


Upon import, DCP-o-matic tries to map the audio channels based on file names or channel orders for typical layouts. It would have assigned an L/R/C/LFE/Ls/Rs order for a 5.1/6ch file, but as an 8ch file is no common todays standard, it defaulted to assigning only the first channel to center.

- Carsten

[DCP-Junkie]

Thank you Carsten, I really appreciate you. I guess my confusion is that with me setting it up the way I did, I should get surround sound but the theater is telling me that everything only plays through their C. I did review the file and it looks like there is only sound on the C channel for about 2.5 minutes of the beginning. I wonder if they didn't even skip ahead past that 2.5 minute mark. I would think they would have the surround sound based on the layout I programmed, right?

[Carsten]

Other editors support MXF audio import as well, but, because it offers a straighter access, I prefer the free Audacity with the FFMPEG plugin (separate install).

With it, you can open the MXF audio file that DCP-o-matic creates. This is the actual audio that is played in the cinema, so, if in doubt - install Audacity and the FFMPEG plugin, and open that MXF. The channel order is fixed in this file, so you will see an accurate graphical representation of the multichannel mix. I can usually quickly recognize the typical waveform pattern for L/R, Center, LFE and Ls/Rs. From the waveform, you can not judge correct placement/order of Left/Right or Ls/Rs - but with these channel pairs, Left first is simply the most common order. And on average, Ls/Rs form a stereo pair als L/R, but their average level is noticeable lower than the front Left/Right.

Have a look at this example (a typical commercial movie trailer):

Bildschirmfoto 2018-05-16 um 00.22.42.png

If you see such a file in a DCP, the only reason why it's played wrong at the cinema is the cinema setup itself. Sometimes it is hard to pick the surround channels by ear, as the front channels are usually a lot louder. If you know your mix, you may find parts with very explizit surround occurrence.


- Carsten