Audiotool board archive

Mid-Side Processing

Giles · started 2019-02-24 18:16 · updated 2019-02-27 00:13

Anybody had any experience with routing devices for some mid-side processing? I tried transferring the method I've used in Pro Tools, which uses some mono channels and auxiliary buses, but that was a bit of a headache to do in AT and in the end it didn't sound quite right anyway. Thanks!

Comments (14)

Jordi Moragues
2019-02-24 23:31 · 2019-02-24

How did you transfer your method? What was your signal chain? Just curious about it.

Giles · reply
2019-02-25 01:20 · 2019-02-25

I split the signal 3 ways to begin with, sending one through a stereo enhancer to make it mono (to be the mid), then panning the other two hard left and hard right (to be the sides). Then I inverted the phase of the right signal and merged it with the left signal to make a kind of stereo side bus, which I then split in two, with those two signals panned hard left and hard right as well, with the right signal also phase inverted at this stage. Finally I summed that with the mono (mid) signal from the beginning. It sounded a bit off though, possibly because throughout the signal chain I'm multiplying the signal, rather than having it pass through an auxiliary channel.

Giles · reply
2019-02-25 01:23 · 2019-02-25

I was hoping to remove the bass from the sides via phase cancellation, and then with this setup I hoped to compress and EQ the middle and sides of the mix separately.

Giles · reply
2019-02-25 01:26 · 2019-02-25

Here's an example:

Jordi Moragues
2019-02-25 17:31 · 2019-02-25

The problem with your method, at least the two initial steps, is that you're not separating what is common to your original stereo pair (the mono component) in one channel and what is different (the stereo component) to another. You're collapsing the whole contents of your original stereo pair to each of your three signals (mono, left and right). In other words, the Stereo Enhancer doesn't extract the mono component of your signal. It collapses -everything- to mono. Same for hard panning. Therefore you're applying your different processing to everything. Probably that's why it sounds strange. That said, I'm still not sure about the best way to properly do mid-side in AT, or if it's possible.

Giles · reply
2019-02-25 18:00 · 2019-02-25

I thought that maybe as something panned hard left disappears when you try and pan it right later on, that that would be the same for the left and right components of a stereo signal, it'd just be a matter of keeping the gain consistent. Although I did think there'd be a good few things which I hadn't considered. Thanks for that!

Known As I
2019-02-27 00:13 · 2019-02-27

I created an effect chain which allows to insert separate effects for mid- and side-channel: https://www.audiotool.com/app/#/cye001swgikx

  • The Heisenberg creates a sound which is composed of a pure center square wave and a pure stereo sawtooth
  • The signal is fed into
    • A:Panorama which substacts both channels leaving us with the stereo signal (sawtooth)
    • C:Panorama which adds both channels leaving us with a pure mono signal (square wave)
  • I added a Waveshaper as a stereo-enhancer as an example for a Side-channel effect
  • I added a Pitch-Reverb as an example for a Mid-channel (center) effect
  • The Merger at the end of the chain combines the channels as follows:
    • left = center - side
    • right = center + side
  • the useless devices (Center Merger + Center Panorama) were inserted to compensate for latency between both paths. This won't compensate for different effect devices in both chains, though.
    Disclaimer: I didn't make sure that I didn't reverse some polarity and the levels might not be correct. But I think this gets you started.

A real mid-side splitter and merger would be nice.

Known As I · reply
2019-02-27 00:32 · 2019-02-27

I created a second setup which is fairly self-explanatory. I added a bookmark for both versions: https://www.audiotool.com/app/#/cye001swgikx (this hopefully works)
If you like you can merge the left and right side-channels before feeding them into an effect.
Please see the device's names for some hints.

Giles · reply
2019-02-27 02:03 · 2019-02-27

Whoa this sounds fantastic! I'd love to have a look but I'm denied access in the app.

Giles · reply
2019-02-27 02:10 · 2019-02-27

Is there a way of knowing the latency caused by different effects in order to keep it consistent between signals split into mid and side?

Known As I · reply
2019-02-27 10:01 · 2019-02-27

I was wrong about the latency - just remove the devices and don't worry :)
I'll have a look about the permission.

Known As I · reply
2019-02-27 10:19 · 2019-02-27

I invited you

Giles · reply
2019-02-27 12:44 · 2019-02-27

Thanks for that!