Multichannel export converts stereo channel to mono

i’m using 2.02 on osX. However this happens on my Windows 7 machine as well.

Destined to work on fmod, I’m trying to create multichannel wav.
Everything seems to work out fine, however, no matter what I try, when I import the multichannel wav back into Audacity, I notice only the first 2 channels have left/right. The other tracks are all in mono.
Here’s a screenshot of what goes wrong. Here I created a 4-channel multichannel wav.
1/2 are left/right. 3/4, however, are in mono. I can re-set them to left/right and export again but to no avail.

My question is… is this some kind of bug? Or did I make the wrong connections?
Or is this just the way Audacity presents multichannel files?

I hope someone can help.

Did all your channels show up whatever they’re called? Past the first two, there is no L and R. Technically, the first two should have been mono as well. This is not a “stereo” show. The first channel could have been Left-Front…or not. Some of our client multi-channel tapes have completely scrambled channel assignments.

You will also find that depending on what you use to play a multi-channel WAV file, you will get different results. Some play left and right and ignore everything else. Some “add up” the first and third and use that for left, etc.

It’s only when you use a guaranteed multi-channel format like AC3 do you get predictable results.


The situation is complicated because different file formats use different default channel mapping, and there may also be differences due to the playback hardware and software. However, most formats use channels 1 and 2 for front left and front right - this is what you are seeing in the imported file. The exported file itself just contains 4 channels with no positional information, so the playback device will map each channel to a speaker of its choice.

Audacity only has 2 channel playback, so tracks can be “Left”, “Right” or “Mono”. Tracks that are marked “Mono” play through both left and right speakers.
You can set a single channel Audacity track to Left, Right or Mono by clicking on the track name, then select from the drop down menu.

Thanks a lot. This cleared things up.

Indeed I found that the playback software makes a big difference in results.

Luckily I have found that fmod (that is used on game platforms) is actually able to playback these multichannel wavs like it should. Re-importing the multichannel back to Audacity (or Reaper or any other daw, I found) distorted my view on whether they were actually rendered correctly.

I’ll look into AC3 though if that would produce more predictable results.