# Sidechain input

**URL:** <https://iplug2.discourse.group/t/sidechain-input/64>\
**Category:** Uncategorized\
**Created:** [25 April 2020 22:06 UTC](https://iplug2.discourse.group/t/sidechain-input/64 "2020-04-25T22:06:01Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![etl17](https://avatars.discourse-cdn.com/v4/letter/e/c89c15/32.png) [@etl17](https://iplug2.discourse.group/u/etl17)\
**Post date:** [25 April 2020 22:06 UTC](https://iplug2.discourse.group/t/sidechain-input/64/1 "2020-04-25T22:06:01Z")

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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

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**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:** [26 April 2020 10:00 UTC](https://iplug2.discourse.group/t/sidechain-input/64/2 "2020-04-26T10:00:49Z")

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Hi Stefanos,

It’s not obvious because this is something that is not quite finished yet, and sidechain will not work correctly yet in iPlug2. It’s a high priority to fix it soon.

The idea with PLUG\_CHANNEL\_IO is that different supported IO bus/channel configurations “IOConfigs” are specified separated by a space token. Inputs and outputs are separated by a hyphen token. Multiple buses are separated by a dot/period token.

- An FX plug-in that can work on mono-mono or stereo-stereo tracks would have a PLUG\_CHANNEL\_IO `1-1 2-2`

- An Instrument plugin that has multiple output buses (e.g. drumsynth) might have `0-2 0-2.2 0-2.2.2` indicating it can work with up to three stereo output buses.

- An FX plug-in with a stereo or mono side-chain input (multiple input buses) could have it set to `1.1-1 2.2-2`

There will be a method to tell you the current IOConfig from the plugin’s ProcessBlock() method

Unfortunately this is quite tricky and i’m still working on it.

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**Author:** ![etl17](https://avatars.discourse-cdn.com/v4/letter/e/c89c15/32.png) [@etl17](https://iplug2.discourse.group/u/etl17)\
**Post date:** [26 April 2020 16:58 UTC](https://iplug2.discourse.group/t/sidechain-input/64/3 "2020-04-26T16:58:41Z")

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Thank you, Oli.  
Is there a specific branch that reflects the current work on sidechain inputs? Is there anything I can do the help accelerate that work? Perhaps I could take on some of that work if you think it would be helpful.

Best,  
–Stefanos

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**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:** [27 April 2020 15:55 UTC](https://iplug2.discourse.group/t/sidechain-input/64/4 "2020-04-27T15:55:05Z")

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> **[iPlug2/iPlug2](https://github.com/iPlug2/iPlug2/tree/VST3/setbusarrangements2)**
>
> C++ Audio Plug-in Framework for desktop, mobile and web \[PRE-RELEASE\] - iPlug2/iPlug2

and

> **[iPlug2/iPlug2](https://github.com/iPlug2/iPlug2/tree/examples/drumsynth)**
>
> C++ Audio Plug-in Framework for desktop, mobile and web \[PRE-RELEASE\] - iPlug2/iPlug2

is where some of this work is happening. I need to have a look again, I think it will be quite hard for anyone else to jump in on this particular aspect