Playout/Downmix of sound channels

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Carsten
Posts: 1215
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Playout/Downmix of sound channels

Post by Carsten » Sun Mar 10, 2019 2:38 pm

I know there were issues and I think and an entry on Mantis about this, also a few discussions on this forum. When I just checked back into this issue in the current test version, it looks as if this is solved (at least basically). As I haven't seen it marked on Mantis or in the changelog, I thought I'll mention it here: (edit: https://dcpomatic.com/mantis/view.php?id=1281)

Current test versions 2.13.xxx will downmix all 5.1 channels of a surround mix during sound playout in both DCP-o-matic main and player. Previously, only Left/Center/Right were used for the downmix.

That means, when playing out 5.1 source content or DCPs on a normal 'stereo' equipped machine, the downmix is as follows:

Left->Left
Right->Right
Center->Left&Right
LFE->Left&Right
LeftSurround->Left
RightSurround->Right

Currently, neither HI/VI-N nor BackSurroundLeft/BackSurroundRight (for 7.1 mixes) is part of the downmix. That's probably okay for most users. To hear a temporary reproduction of the channels not in the general downmix scheme, you can always remap them in the content audio matrix. E.g. to hear HI, simply map it onto any of the channels that are part of the downmix. E.g. map HI to L, VI-N to R, or BackSurround Left to Left/LeftSurround, Backsurround Right to Right/RightSurround. Dont't forget to reset that special mapping later when you are about to create the DCP, or your 'advanced' source channels HI/VI-N/BsR/BsL will go to the wrong channels.

Make sure when adding sound content with more than L/R that you have setup the DCP to enough audio channels under the DCP->Audio Tab. You won't see and hear e.g. HI/VI-N or BsL/BsR if your DCP is set to the default 5.1 only.

- Carsten

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