Apple Silicon 5.1 Audio Mapping Issue

[sarahlasley]

I have an interleaved 5.1 (L, R, C, Lfe, Ls, Rs) ProRes file I am trying to create a DCP for. In Quicktime, it plays correctly off M1 Max Macbook Pro through HDMI with all channels correctly mapped to my home theater speakers. Inside DCP-o-Matic, it looks correctly mapped in the audio panel (see screenshot), but when playing it in DCP-o-Matic, the C channel is playing through the subwoofer and the Lfe channel is playing through the center speaker. I know that Apple Silicon computers with multichannel PCM audio via HDMI out are mapped Lfe channel 3 and Center channel 4, but the only way I can get the mapping to play correctly in DCP-o-Matic is to swap channels 3 and 4 in the mapping. I tried swapping them in Audio MIDI Setup, and that didn't work. I'm not sure if it's safe to assume the DCP is being mapped correctly with the default settings, even though it is incorrect in playback, or if this mapping issue needs to be corrected before creating the DCP. Any help is appreciated.

[Carsten]

Did you try the audio mapping in dcp-o-matic prefs?

[sarahlasley]

Yes. And if I set up the speakers like it is in the attached screenshot, everything works fine. Note: the ProRes file when played in Quicktime, maps correctly. The same Quicktime file when played in DCP-o-Matic (before creating a DCP), does this weird C/Lfe swap.

[Carsten]

There are (at least) two different mapping standards for HDMI multichannel audio. I can't tell you why this happens in your specific setup, but it's a known issue:

https://forum.blackmagicdesign.com/view ... 18&t=33551

This may occur also because of HDMI negotiations between your Macbook and the Denon AVR.

Traditionally, home cinema/HDMI and SMPTE/cinema layout is different.

See table 22 on page 69 here:

https://ia801404.us.archive.org/3/items ... -861-B.pdf


But that's why there is an addidional channel mapping option in DCP-o-matic.

When your audio channels are mapped in SMPTE order in DOM in the audio tab, your mapping is correct. HDMI/audio device mapping in prefs only targets your personal playback setup. The actual DCP channel order is established on the file level, HDMI audio mapping in prefs does not interfere with it. Same when you only use a stereo audio device for monitoring - you can still safely create and use a correct multichannel mapping for your DCP.

And, can you also try a screen shot while you click on the device selector in the audio mapping prefs (where it shows DENON-AVR). I'd love to see wether there are other options.

[sarahlasley]

Wow! That was incredibly helpful. Thank you for the level of detail and explanation. I feel much better about my DCP being set up properly. I would have assumed it was ok, except that the Quicktime player mapped it correctly. So I was worried the incorrect mapping was happening at the DOM level. Anyhow, I don't have any other DENON options. This is all I see.

[Kewl]

With the advent of Apple Silicon chips, two things happened: HDMI out is now only at 48 kHz and Lfe is now channel 3.

Go into Audio & MIDI Setup and do this :

Capture d’écran, le 2025-08-17 à 21.42.59.png

[Carsten]

The Quicktime player is a native Apple app, and knows about proper channel handling differences between Intel and Apple Silicon. So it may automatically map file channel 3 and 4 to HDMI channels 4 and 3 when running on Apple Silicon.