Export "up to" recorded number of audio channels?

We got a request from a production. It goes like this: the audio being recorded on set can vary from 2 audio channels up to 8 audio channels. The show’s editors asked if we can deliver “up to” 8 channels of audio, but only if 8 channels of audio were recorded. If the clip only had 6 channels of audio recorded, editorial only wants a clip with 6 channels of audio. If only 4 channels were recorded, the Avid clip should only have 4 audio channels. You see the pattern.

So with the Cortex deliverables, I can set up which input audio channel goes to which output audio channel. We usually have audio like so:
1 -> 1
2 -> 2
3 -> 3, etc.

Is there any way to have Cortex not create an audio channel if there’s no input channel? As described above, have Cortex create a clip’s audio channel only if an input audio channel is present. I have a feeling this would add quite a bit of headache in the deliverable logic. Let me know if you think this could be implemented, or if you have no plans to do so. (Honestly I’m fine either way - just need to report back.)

If I’m understanding correctly, this is exactly what “pass through” does.


Duh, I guess that does make sense. But is there some sort of conversion of the audio when using channel mapping versus pass through? Or in both cases does the audio simply get rewrapped in an Avid MXF container?

Whether you pass through or use the mapper/mixer, the deliverable will respect your choice of “Embed/mux in file” “seperate broadcast wav” or “both”

Basically what @amy said.

The ‘Pass Through’ setting just creates an identity mixer based on the number of audio channels in your source, so its equivalent to clicking all those little buttons and using a different config for each clip depending on how many channels are in your source.

There is no special audio processing that is done when your mixer is an identity mixer other than basic trimming. If your framerates or sample rates don’t match, Cortex will also resample the audio.

Of course, if your deliverable uses audio compression, that processing will also occur in the encoder.

Avid DNxHD and ProRes deliverables both use PCM encoded audio though, so there is no compression in those cases.


Beautiful. Thank you @amy and @dave for clarification!