How to mix 7 mono channels to stereo?

What is the proper way to mix 7 mono channels to stereo with Audacity?

I demuxed 8 mono channels from a 7.1 audio and discarded the LFE channel.
I’m left with front_left, front_right, front_center, back_left, back_right, side_left, side_right.

So far, I imported into Audacity front_left, back_left, side_left, front_center. I have set Pan settings to 100% Left for front_left, back_left, and side_left. And… I’m stuck.

Could someone explain how to do a correct stereo mix. I’m new to Audacity.

Using Windows 10 64-bit, Audacity 2.3.2.

Have you been able to work out which is which?
(some of the standard channel maps are listed here: Surround sound - Wikipedia though other channel allocations exist)

Yes.

I just need instructions on how to mix front_left, back_left, side_left and front_center to left channel, and front_right, back_right, side_right, and front_center to right channel.

What are Pan settings for the front_center channel?

Is the front_center channel mixed two times (once to the left, and once to the right), or just one?

Should I decrease volume of certain channels?

You will need to start with all tracks as mono tracks. (https://manual.audacityteam.org/man/splitting_and_joining_stereo_tracks.html)


front_left, back_left, side_left: Pan all the way to the left.
front_right, back_right, side_right: Pan all the way to the right.
centre: pan centre.

Yes you will need to reduce the volume of the tracks - probably all of the tracks.
You can do this either with the track “Gain” sliders, or use the sliders in “View menu > Mixer Board”.

As a starting point, try lowering the track levels as follows:
Centre, Front Right, Front Left: -6 dB
All others: -12 dB

Tweak the levels to whatever sounds best to you - keep an eye on the playback meter to avoid distortion (the level is not critical as we shall normalize later, just keep the overall level of the mix below 0dB.

When you’re happy with the mix:
“Ctrl + A” (Select All)
Tracks menu > Mix > Mix and Render"

Then apply the “Normalize” effect. I’d recommend normalizing to -0.5 dB for WAV files, or -2 dB for MP3.
Then Export (File menu).

So far, I imported into Audacity front_left, back_left, side_left, front_center. I have set Pan settings to 100% Left for front_left, back_left, and side_left. And… I’m stuck.The surround channels are normally mixed-in at reduced levels.

[u]Here are some downmix tables[/u].* Of course, you don’t have to use those settings if you don’t like the way it sounds.

I don’t think I’ve ever seen a DVD with surround that didn’t also have a stereo track (a separate original mix) so in the real world the standard mixdown is rarely used. And, a Dolby AC3 track also has mixdown metadata so on a DVD or Blu-Ray player you might not get the standard mixdown when you play the 5.1 track on a stereo playback system.

When you export you should see [u]Advanced Mixing Options[/u] where you can select the number of channels (2) and direct the tracks appropriately.

Mixing is done by summation, so to prevent clipping I recommend you export to floating-point WAV (which can go over 0dB without clipping). Then re-import the stereo file and Amplify or Normalize to bring the peaks down (If necessary) to 0dB (or less).



\

  • To make that useful you need to convert to dB:
    Those charts show a factor (or ratio) so in case you don’t know how to make the calculation: dB = 20 x log (ratio). 1/ square root of 2 = .707, and 20 x log(.707) = -3dB. A ratio of 1/2 is -6dB.

That is not required when making a stereo mix. The only things that matter are the pan and gain settings.