Audio channel mapping

[Jonathan Greer]

Hello, I've made a DCP from a prores file (audio codec Linear PCM) and the channel mapping baffles me. The default mapping of L, R, C, Lfe, Ls, Rs had off-centre dialogue - one of my colleagues swapped C and R which seems correct but then they were puzzled that the Ls channel cut out for long periods. I looked at this channel (channel 5), and it looks like the sub to me, so currently I have the mapping L, C, R, Ls, Lfe, Rs - which is an odd order! - but I can't see what else channel 5 could be. I'm not certain if the L & R and Ls & Rs channels are the right way round though.
I emailed the suppliers of the file who say "It should be LCR LS RS LFE".... but like I say the RS channel would look very odd with this mapping.
I've attached a screenshot of the graph of audio levels.

[Carsten]

When solving these puzzles, I usually load the audio into Audacity for a timeline view, and, typically, it is very easy to spot what is what.


You can also switch off/on individual channels in the matrix (or solo in Audacity) and listen to the content. While it is not easy to tell L from R or LS from RS, usually, L/LS ist first, and R/RS is second.

Bildschirmfoto 2023-10-12 um 14.46.32.png

[Jonathan Greer]

Thanks Carsten!

I've received the reply:

"I've spoken with the sound designer and the layout is:

Ch1 Left
Ch2 Right
Ch3 Centre
Ch4 LFE
Ch5 LS
Ch6 RS

Monitor at Dolby 7"

i.e. the default channel mapping - only problem is, it sounds wrongity wrong (to use a technical term) & the audio graph looks wrong too (screenshot attached).
Screening is tonight but the director's coming in ahead of time so should hopefully be able to sort out the soundtrack.

[barber]

Hi,
As Carsten said, loading the file in Audacity is a practical way to identify the channels.
By looking at your screenshots, I would say that your first guess was correct : L, C, R, Ls, Lfe, Rs. But it's not standard, there must have been an error when mapping the channels for the ProRes export and Left/Right could have been swapped too. The suppliers must check!

Best,
Dan

[IoannisSyrogiannis]

That's old news, if the event has past.
Yet, I would advise making the OV as advised and VF files with different configurations.
If the director had the chance to check, they should have been able to tell right from wrong.
(And it wouldn't ask for long encoding time, nor bulky DCP sizes.)