.TH "libpipewire-module-loopback" 7 "1.6.8" "PipeWire" \" -*- nroff -*-
.ad l
.nh
.SH NAME
libpipewire-module-loopback \- Loopback 
.SH DESCRIPTION
.PP
The loopback module passes the output of a capture stream unmodified to a playback stream\&.

.PP
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\&.

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

.PP
.SH "MODULE NAME"
.PP

.PP
\fRlibpipewire-module-loopback\fP

.PP
.SH "MODULE OPTIONS"
.PP

.PP
.IP "\(bu" 2
\fRnode\&.description\fP: a human readable name for the loopback streams
.IP "\(bu" 2
\fRtarget\&.delay\&.sec\fP: delay in seconds as float (Since 0\&.3\&.60)
.IP "\(bu" 2
\fRcapture\&.props = {}\fP: properties to be passed to the input stream
.IP "\(bu" 2
\fRplayback\&.props = {}\fP: properties to be passed to the output stream
.PP

.PP
.SH "GENERAL OPTIONS"
.PP

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

.PP
.IP "\(bu" 2
\fBremote.name\fP
.IP "\(bu" 2
\fBaudio.rate\fP
.IP "\(bu" 2
\fBaudio.channels\fP
.IP "\(bu" 2
\fBaudio.layout\fP
.IP "\(bu" 2
\fBaudio.position\fP
.IP "\(bu" 2
\fBmedia.name\fP
.IP "\(bu" 2
\fBnode.latency\fP
.IP "\(bu" 2
\fBnode.description\fP
.IP "\(bu" 2
\fBnode.group\fP
.IP "\(bu" 2
\fBnode.link.group\fP
.IP "\(bu" 2
\fBnode.virtual\fP
.IP "\(bu" 2
\fBnode.name\fP : See notes below\&. If not specified, defaults to 'loopback-PID-MODULEID'\&.
.PP

.PP
Stream only properties:

.PP
.IP "\(bu" 2
\fBmedia.class\fP
.IP "\(bu" 2
\fBnode.name\fP : 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\&.
.PP

.PP
.SH "CHANNEL HANDLING"
.PP

.PP
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)\&.

.PP
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\&.

.PP
.SH "EXAMPLE CONFIGURATION OF SOURCE TO SINK LINK"
.PP

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

.PP
.PP
.nf
# ~/\&.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
        }
    }
}
]
.fi
.PP

.PP
.SH "EXAMPLE CONFIGURATION OF A VIRTUAL SINK"
.PP

.PP
This Virtual sink routes stereo input to the rear channels of a 7\&.1 sink\&.

.PP
.PP
.nf
# ~/\&.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
        }
    }
}
]
.fi
.PP

.PP
.SH "EXAMPLE CONFIGURATION OF A VIRTUAL SOURCE"
.PP

.PP
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\&.

.PP
.PP
.nf
# ~/\&.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 ]
        }
    }
}
]
.fi
.PP

.PP
.SH "EXAMPLE CONFIGURATION OF AN UPMIX SINK"
.PP

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

.PP
.PP
.nf
# ~/\&.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
        }
    }
}
]
.fi
.PP

.PP
.SH "EXAMPLE CONFIGURATION OF A DOWNMIX SOURCE"
.PP

.PP
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\&.

.PP
.PP
.nf
# ~/\&.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 ]
        }
    }
}
]
.fi
.PP

.PP
.SH "SEE ALSO"
.PP

.PP
\fRpw-loopback\fP : a tool that loads the loopback module with given parameters\&.