pipewire 2 channel to 8 (7.1 / 2 + 5.1) channel filter

[DeIM]

I was looking for something to distribute 2 channel audio source to 8 channel output (it's generic but my setup is something like headphones on FL FR and rest is connected to 5.1 loudspeaker)
I often got audio only from headphones. I manually connected channels in helvum but it was reset each time new audio played.
So I decided to solve it somehow and I found filter which makes opposite - 8 channels to 2 channels.
I made dirty custom changes which I would like to share, ask for review and tuning.

Code: Select all

# 2 to 8 channels sink
#
# Copy this file into a conf.d/ directory such as
# ~/.config/pipewire/filter-chain.conf.d/
#
context.modules = [
    { name = libpipewire-module-filter-chain
        flags = [ nofail ]
        args = {
            node.description = "Virtual Surround Sink DeIM"
            media.name       = "Virtual Surround Sink DeIM"
            filter.graph = {
                nodes = [
                    # duplicate inputs
                    { type = builtin label = copy name = copyFL  }
                    { type = builtin label = copy name = copyFR  }
                    { type = builtin label = copy name = copyFC  }
                    { type = builtin label = copy name = copyRL  }
                    { type = builtin label = copy name = copyRR  }
                    { type = builtin label = copy name = copySL  }
                    { type = builtin label = copy name = copySR  }
                    { type = builtin label = copy name = copyLFE }

                    # stereo output
                    { type = builtin label = mixer name = mixFL }
                    { type = builtin label = mixer name = mixFR }
                    { type = builtin label = mixer name = mixFC }
                    { type = builtin label = mixer name = mixLFE }
                    { type = builtin label = mixer name = mixRL }
                    { type = builtin label = mixer name = mixRR }
                    { type = builtin label = mixer name = mixSL }
                    { type = builtin label = mixer name = mixSR }
                ]
                links = [                    
                   { output = "copyFL:Out" input = "mixFL:In 1" }
                   { output = "copyFR:Out" input = "mixFR:In 2" }
                   { output = "copyFL:Out" input = "mixFC:In 3" }
                   { output = "copyFR:Out" input = "mixLFE:In 4" }
                   { output = "copyFL:Out" input = "mixRL:In 5" }
                   { output = "copyFR:Out" input = "mixRR:In 6" }
                   { output = "copyFL:Out" input = "mixSL:In 7" }
                   { output = "copyFR:Out" input = "mixSR:In 8" }
                ]
                inputs  = [ "copyFL:In" "copyFR:In" "copyFC:In" "copyLFE:In" "copyRL:In" "copyRR:In" "copySL:In" "copySR:In" ]
                outputs = [ "mixFL:Out" "mixFR:Out"  "mixFC:Out" "mixLFE:Out" "mixRL:Out" "mixRR:Out" "mixSL:Out" "mixSR:Out" ]
            }
            capture.props = {
                node.name      = "effect_input.virtual-surround-7.1-deim"
                media.class    = Audio/Sink
                audio.channels = 8
                audio.position = [ FL FR FC LFE RL RR SL SR ]
            }
            playback.props = {
                node.name      = "effect_output.virtual-surround-7.1-deim"
                node.passive   = false
                audio.channels = 8
                audio.position = [ FL FR FC LFE RL RR SL SR ]
            }
        }
    }
]