# IPlug2 Sidechain

**URL:** <https://iplug2.discourse.group/t/iplug2-sidechain/414>\
**Category:** Uncategorized\
**Created:** [16 June 2021 18:26 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414 "2021-06-16T18:26:34Z")\
**Posts on this page:** 10\
**Page:** 1

<div class="post-metadata">

**Author:** ![SKyZz](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@SKyZz](https://iplug2.discourse.group/u/SKyZz)\
**Post date:** [16 June 2021 18:26 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/1 "2021-06-16T18:26:34Z")

</div>

Tell me how to enable (docs) the button in DAWs for sidechain, I’m sure there is a code for this in docs. Thanks!!

---

<div class="post-metadata">

**Author:** ![Ric](https://avatars.discourse-cdn.com/v4/letter/r/c77e96/32.png) [@Ric](https://iplug2.discourse.group/u/Ric)\
**Post date:** [17 June 2021 01:44 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/2 "2021-06-17T01:44:21Z")

</div>

I seem to remember it has to do with how you set the I/O channels in config.h

For example try this:

`#define PLUG_CHANNEL_IO "1.1-1"`

---

<div class="post-metadata">

**Author:** ![SKyZz](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@SKyZz](https://iplug2.discourse.group/u/SKyZz)\
**Post date:** [17 June 2021 06:38 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/3 "2021-06-17T06:38:00Z")

</div>

> [@Ric](#):
>
> I seem to remember it has to do with how you set the I/O channels in config.h
> 
> For example try this:

#define PLUG\_CHANNEL\_IO "  
1-1   
1.1-1   
1.2-1   
1.2-2   
2.1-1   
2.1-2   
2-2   
2.2-2"

is there any way to explain this?

---

<div class="post-metadata">

**Author:** ![SKyZz](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@SKyZz](https://iplug2.discourse.group/u/SKyZz)\
**Post date:** [17 June 2021 08:28 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/4 "2021-06-17T08:28:50Z")

</div>

This includes the sidechain button in VST2/3 but what to do with AU?

---

<div class="post-metadata">

**Author:** ![olilarkin](https://yyz2.discourse-cdn.com/free1/user_avatar/iplug2.discourse.group/olilarkin/32/2_2.png) [@olilarkin](https://iplug2.discourse.group/u/olilarkin)\
**Post date:** [17 June 2021 22:57 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/5 "2021-06-17T22:57:29Z")

</div>

There is an example that shows you how in the examples folder

---

<div class="post-metadata">

**Author:** ![Ric](https://avatars.discourse-cdn.com/v4/letter/r/c77e96/32.png) [@Ric](https://iplug2.discourse.group/u/Ric)\
**Post date:** [18 June 2021 01:34 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/6 "2021-06-18T01:34:38Z")

</div>

it says here that different configurations are separated by a space; input and output are separated by a minus sign; and different busses are separated by a dot.

> [@Sidechain input](https://iplug2.discourse.group/t/sidechain-input/64):
>
> Sorry if this is too obvious, but is there currently support for sidechain inputs? If yes, how it needs to be specified? (for example, what is the right PLUG\_CHANNEL\_IO pattern to use?). Thank you in advance, –Stefanos

---

<div class="post-metadata">

**Author:** ![SKyZz](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@SKyZz](https://iplug2.discourse.group/u/SKyZz)\
**Post date:** [18 June 2021 09:07 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/7 "2021-06-18T09:07:06Z")

</div>

I compiled the example, and I didn’t see that sidechain icon in CUbase, for example. However, I have implemented the sidechain process and added a sidechain. But AudioUnit DOESN’T show me the option to specify the input for the sidechain.

![photo5355079866376107021](https://global.discourse-cdn.com/free1/uploads/iplug2/original/1X/b2032a02e92025510494ab4fa284b9b30225a90c.png)

Therefore, I would like to understand why this works in VST2/3 but not in AU, and how to fix it.

---

<div class="post-metadata">

**Author:** ![olilarkin](https://yyz2.discourse-cdn.com/free1/user_avatar/iplug2.discourse.group/olilarkin/32/2_2.png) [@olilarkin](https://iplug2.discourse.group/u/olilarkin)\
**Post date:** [18 June 2021 11:28 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/8 "2021-06-18T11:28:52Z")

</div>

The IPlugSideChain example shows the SideChain input in AUv2 in Logic, and VST3 in Cubase 11 here.

PLUG\_CHANNEL\_IO defines all the valid combinations of input busses

```auto
#define PLUG_CHANNEL_IO "\
1-1 \. <- one mono input bus, one mono output bus (no sidechain)
1.1-1 \ <- two mono input buses, mono output (mono sidechain)
1.2-1 \ <- two input buses, mono output (stereo sidechain)
1.2-2 \ <- two input buses, stereo output (stereo sidechain)
2.1-1 \ <- two input buses, mono output (stereo sidechain)
2.1-2 \ <- two input buses, mono output (stereo sidechain)
2-2 \ <- one stereo input bus, one stereo output bus (no sidechain)
2.2-2" <- two stereo input buses, one stereo output bus (stereo sidechain)

```

---

<div class="post-metadata">

**Author:** ![JohnCrosby](https://yyz2.discourse-cdn.com/free1/user_avatar/iplug2.discourse.group/johncrosby/32/30_2.png) [@JohnCrosby](https://iplug2.discourse.group/u/JohnCrosby)\
**Post date:** [20 June 2021 08:53 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/9 "2021-06-20T08:53:44Z")

</div>

Maybe LogicX does not know yet that the sidechain exists?  
“For anyone reading this thread, the story is: If you change your AU’s channel IO options, you need to also bump the version number for LogicX to detect the new options correctly.”

> [@Implementing 1 input, 2 outputs (i.e. mono -\> stereo)](https://iplug2.discourse.group/t/implementing-1-input-2-outputs-i-e-mono-stereo/240/28):
>
> No, l actually wrote the same you did sweat_smile But anyway, as long as I remember to set the config right the first time I’m good…

---

<div class="post-metadata">

**Author:** ![SKyZz](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@SKyZz](https://iplug2.discourse.group/u/SKyZz)\
**Post date:** [20 June 2021 13:19 UTC](https://iplug2.discourse.group/t/iplug2-sidechain/414/10 "2021-06-20T13:19:07Z")

</div>

I feel like a jerk when it works that way. Thank you!