NAME

libpipewire-module-loopback - Loopback

DESCRIPTION

The loopback module passes the output of a capture stream unmodified to a playback stream.

It can be used to construct a link between a source and sink but also to create new virtual sinks or sources or to remap channel between streams.

Because both ends of the loopback are built with streams, the session manager can manage the configuration and connection with the sinks and sources.

MODULE NAME

libpipewire-module-loopback

MODULE OPTIONS

node.description: a human readable name for the loopback streams
target.delay.sec: delay in seconds as float (Since 0.3.60)
capture.props = {}: properties to be passed to the input stream
playback.props = {}: properties to be passed to the output stream

GENERAL OPTIONS

Options with well-known behavior. Most options can be added to the global configuration or the individual streams:

remote.name
audio.rate
audio.channels
audio.position
media.name
node.latency
node.description
node.group
node.link.group
node.virtual
node.name : See notes below. If not specified, defaults to 'loopback-PID-MODULEID'.

Stream only properties:

media.class
node.name : if not given per stream, the global node.name will be prefixed with 'input.' and 'output.' to generate a capture and playback stream node.name respectively.

CHANNEL HANDLING

Channels from the capture stream are copied, in order, to the channels of the output stream. The remaining streams are ignored (when capture has more channels) or filled with silence (when playback has more channels).

When a global channel position is set, both capture and playback will be converted to and from this common channel layout. This can be used to implement up or downmixing loopback sinks/sources.

EXAMPLE CONFIGURATION OF SOURCE TO SINK LINK

This loopback links a source node to a sink node. You can change the target.object properties to match your source/sink node.name.

# ~/.config/pipewire/pipewire.conf.d/my-loopback-0.conf
context.modules = [
{   name = libpipewire-module-loopback


    args = {


        capture.props = {


            #  if you want to capture sink monitor ports,


            #  uncomment the next line and set the target.object


            #  to the sink name.


            #stream.capture.sink = true


            target.object = "alsa_input.usb-C-Media_Electronics_Inc._TONOR_TC-777_Audio_Device-00.mono-fallback"


            node.passive = true


            node.dont-reconnect = true


        }


        playback.props = {


            target.object = "alsa_output.usb-0d8c_USB_Sound_Device-00.analog-surround-71"


            node.dont-reconnect = true


            node.passive = true


        }


    }
}
]

EXAMPLE CONFIGURATION OF A VIRTUAL SINK

This Virtual sink routes stereo input to the rear channels of a 7.1 sink.

# ~/.config/pipewire/pipewire.conf.d/my-loopback-1.conf
context.modules = [
{   name = libpipewire-module-loopback


    args = {


        node.description = "CM106 Stereo Pair 2"


        #target.delay.sec = 1.5


        capture.props = {


            node.name = "CM106_stereo_pair_2"


            media.class = "Audio/Sink"


            audio.position = [ FL FR ]


        }


        playback.props = {


            node.name = "playback.CM106_stereo_pair_2"


            audio.position = [ RL RR ]


            target.object = "alsa_output.usb-0d8c_USB_Sound_Device-00.analog-surround-71"


            node.dont-reconnect = true


            stream.dont-remix = true


            node.passive = true


        }


    }
}
]

EXAMPLE CONFIGURATION OF A VIRTUAL SOURCE

This Virtual source routes the front-left channel of a multi-channel input to a mono channel. This is useful for splitting up multi-channel inputs from USB audio interfaces that are not yet fully supported by alsa.

# ~/.config/pipewire/pipewire.conf.d/my-loopback-2.conf
context.modules = [
{   name = libpipewire-module-loopback


    args = {


        node.description = "Scarlett Focusrite Line 1"


        capture.props = {


            audio.position = [ FL ]


            stream.dont-remix = true


            node.target = "alsa_input.usb-Focusrite_Scarlett_Solo_USB_Y7ZD17C24495BC-00.analog-stereo"


            node.passive = true


        }


        playback.props = {


            node.name = "SF_mono_in_1"


            media.class = "Audio/Source"


            audio.position = [ MONO ]


        }


    }
}
]

EXAMPLE CONFIGURATION OF AN UPMIX SINK

This Virtual sink has 2 input channels and 6 output channels. It will perform upmixing using the PSD algorithm on the playback stream.

# ~/.config/pipewire/pipewire.conf.d/my-loopback-3.conf
context.modules = [
{   name = libpipewire-module-loopback


    args = {


        node.description = "Upmix Sink"


        audio.position = [ FL FR ]


        capture.props = {


            node.name = "effect_input.upmix"


            media.class = Audio/Sink


        }


        playback.props = {


            node.name = "effect_output.upmix"


            audio.position = [ FL FR RL RR FC LFE ]


            node.passive = true


            stream.dont-remix = true


            channelmix.upmix = true


            channelmix.upmix-method = psd


            channelmix.lfe-cutoff = 150


            channelmix.fc-cutoff = 12000


            channelmix.rear-delay = 12.0


        }


    }
}
]

EXAMPLE CONFIGURATION OF A DOWNMIX SOURCE

This Virtual source has 2 input channels and a mono output channel. It will perform downmixing from the two first AUX channels of a pro-audio device.

# ~/.config/pipewire/pipewire.conf.d/my-loopback-4.conf
context.modules = [
{   name = libpipewire-module-loopback


    args = {


        node.description = "Downmix Source"


        audio.position = [ AUX0 AUX1 ]


        capture.props = {


            node.name = "effect_input.downmix"


            target.object = "alsa_input.usb-BEHRINGER_UMC404HD_192k-00.pro-input-0"


            node.passive = true


            stream.dont-remix = true


        }


        playback.props = {


            node.name = "effect_output.downmix"


            media.class = Audio/Source


            audio.position = [ MONO ]


        }


    }
}
]