Can't create 4in/2 out routing for Fab Filter Pro L2 (for side chain stem limiting)

[Ideosound]

Hi. There is an issue where it is not currently possible to set a 4in/2out routing for a channel (where 3/4 inputs are for side chain) when using Fab Filter Pro L2. Pro-L 2 supports surround processing, when you create it on a 4-channel track, Reaper asks it if it can work with four channels I/O. And Pro-L 2 can do this and creates itself in a quad configuration, so it actually has 8 channels of input and 4 channels of output.

I've already reached out to Fab Filter support and someone else in the FF forum could not get it to work:
https://www.fabfilter.com/forum/3113...put-and-reaper

Fab filter said this:

"Over the past week, we've been in close contact with Justin Frankel from Reaper about this and it turns out that it's due to the way you work with side chains in Reaper. As you know, to use a side chain with a stereo plugin, you have to create a four-channel track and route the side chain data to channel 3/4.

However, because Pro-L 2 also supports surround processing, when you create it on a 4-channel track, Reaper asks it if it can work with four channels I/O. And Pro-L 2 can do this and creates itself in a quad configuration, so it actually has 8 channels of input and 4 channels of output. Of course that's not going to work.

Note that there is a bug in the currently shipping version of Reaper that causes it to end up in a LCR config with 6/3 I/O.

As we see it, Reaper needs to provide a way to indicate how many channels you want in a plugin that can support surround formats, so the user can choose whether to create plugin with e.g. a 4 in/2 out config, or a true quad config (L/R/Ls/Rs) when using a 4-channel track.

Unfortunately Justin believes that *we* should change Pro-L 2 to add some way to fix it to a particular channel configuration. We don't want to do that because it would only be needed in Reaper; all other hosts work differently with side chains so the problem doesn't exist there. So that's more or less where we are now and I haven't succeeded in convincing him of our view. I'm sorry I don't have better news at the moment!

Maybe it would help if you would email him as well to explain your situation? "

I really want this to get sorted because this is only an issue in Reaper and no other DAW. What can we do! I've already emailed Justin to show my concern..... not sure if FF will want to change Pro L2 so it will work with how Reaper currently handles multichannel audio.

[DarkStar]

Maybe I've misunderstood (and this could be nonsense), but is this a workaround?

Set the Reaper track to 8 channels and load the plug-in. Does the plug-in then create its 8 channels of input and 4 channels of output?

The main audio will be routed on channels 1+2. For the sidechain input, route it to channels 5+6.

Or, on a 4-chanel track, open the plug-in's Pin Connector and change the sidechain channels (3+4) to inputs 5+6.

[Ideosound]

Originally Posted by DarkStar

Maybe I've misunderstood (and this could be nonsense), but is this a workaround?

Set the Reaper track to 8 channels and load the plug-in. Does the plug-in then create its 8 channels of input and 4 channels of output?

The main audio will be routed on channels 1+2. For the sidechain input, route it to channels 5+6.

Or, on a 4-chanel track, open the plug-in's Pin Connector and change the sidechain channels (3+4) to inputs 5+6.

I tried this with the AU and VST3 version and they both handle the routing differently and not correctly. I don't have the time to show exactly what happened but then I noticed there is a standard VST version of Pro L2. I tried this on a 4 channel track and it seems now correct! 4 in (3/4 correctly seeing side chain) and 2 stereo outs. I will test it and hopefully using the VST works. Thanks for your advice. I still believe there are issues with the AU / VST3 routing handling.

[Justin]

If you try 5.71rc2 (see the pre-release forum), it fixes some bugs in the VST3 support, however due to limitations it does require a bit of a workaround:

If you want to do a stereo sidechain, you need to make the track 4 channel, which causes the plug-in to go 4 channel, but then you must open the pin connection window and disconnect the second stereo pair and connect them to the sidechain. I imagine the plug-in will still work correctly processing stereo in 4 channel mode, aside from being less efficient...

VST2 and AU versions -- I wouldn't recommend using them at this time for this purpose.

[DarkStar]

^^^^
What is the problem with the VST2 edition of FabFilter's Pro-L2?

[Justin]

Originally Posted by DarkStar

^^^^
What is the problem with the VST2 edition of FabFilter's Pro-L2?

There are some odd interactions between the logic on each end, haven't gotten to the bottom of them yet, so probably best to use the VST3 if you want to use sidechain.

[DarkStar]

OK, thank you.

[Ideosound]

Thanks for the info, will look into it. So hopefully this will be ironed out eventually?