PipeWire: Combine Stream

PipeWire 1.0.3

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Combine Stream

The combine stream can make:

- a new virtual sink that forwards audio to other sinks
- a new virtual source that combines audio from other sources

The sources and sink that need to be combined can be selected using generic match rules. This makes it possible to combine static nodes or nodes based on certain properties.

# Module Name

`libpipewire-module-combine-stream`

# Module Options

- `node.name`: a unique name for the stream
- `node.description`: a human readable name for the stream
- `combine.mode` = capture | playback | sink | source, default sink
- `combine.latency-compensate`: use delay buffers to match stream latencies
- `combine.on-demand-streams`: use metadata to create streams on demand
- `combine.props = {}`: properties to be passed to the sink/source
- `stream.props = {}`: properties to be passed to the streams
- `stream.rules = {}`: rules for matching streams, use create-stream actions

# General options

Options with well-known behavior.

- PW_KEY_REMOTE_NAME
- PW_KEY_AUDIO_CHANNELS
- SPA_KEY_AUDIO_POSITION
- PW_KEY_MEDIA_NAME
- PW_KEY_NODE_LATENCY
- PW_KEY_NODE_NAME
- PW_KEY_NODE_DESCRIPTION
- PW_KEY_NODE_GROUP
- PW_KEY_NODE_VIRTUAL
- PW_KEY_MEDIA_CLASS

# Stream options

- `audio.position`: Set the stream channel map. By default this is the same channel map as the combine stream.
- `combine.audio.position`: map the combine audio positions to the stream positions. combine input channels are mapped one-by-one to stream output channels.

# Example configuration

context.modules = [
{ name = libpipewire-module-combine-stream
args = {
combine.mode = sink
node.name = "combine_sink"
node.description = "My Combine Sink"
combine.latency-compensate = false
combine.props = {
audio.position = [ FL FR ]
}
stream.props = {
}
stream.rules = [
{
matches = [
# any of the items in matches needs to match, if one does,
# actions are emited.
{
# all keys must match the value. ! negates. ~ starts regex.
#node.name = "~alsa_input.*"
media.class = "Audio/Sink"
}
]
actions = {
create-stream = {
#combine.audio.position = [ FL FR ]
#audio.position = [ FL FR ]
}
}
}
]
}
}
]

Below is an example configuration that makes a 5.1 virtual audio sink from 3 separate stereo sinks.

context.modules = [
{ name = libpipewire-module-combine-stream
args = {
combine.mode = sink
node.name = "combine_sink_5_1"
node.description = "My 5.1 Combine Sink"
combine.latency-compensate = false
combine.props = {
audio.position = [ FL FR FC LFE SL SR ]
}
stream.props = {
stream.dont-remix = true # link matching channels without remixing
}
stream.rules = [
{ matches = [
{ media.class = "Audio/Sink"
node.name = "alsa_output.usb-Topping_E30-00.analog-stereo"
} ]
actions = { create-stream = {
combine.audio.position = [ FL FR ]
audio.position = [ FL FR ]
} } }
{ matches = [
{ media.class = "Audio/Sink"
node.name = "alsa_output.usb-BEHRINGER_UMC404HD_192k-00.pro-output-0"
} ]
actions = { create-stream = {
combine.audio.position = [ FC LFE ]
audio.position = [ AUX0 AUX1 ]
} } }
{ matches = [
{ media.class = "Audio/Sink"
node.name = "alsa_output.pci-0000_00_1b.0.analog-stereo"
} ]
actions = { create-stream = {
combine.audio.position = [ SL SR ]
audio.position = [ FL FR ]
} } }
]
}
}
]

Below is an example configuration that makes a 4.0 virtual audio source from 2 separate stereo sources.

context.modules = [
{ name = libpipewire-module-combine-stream
args = {
combine.mode = source
node.name = "combine_source_4_0"
node.description = "My 4.0 Combine Source"
combine.props = {
audio.position = [ FL FR SL SR ]
}
stream.props = {
stream.dont-remix = true
}
stream.rules = [
{ matches = [
{ media.class = "Audio/Source"
node.name = "alsa_input.usb-046d_HD_Pro_Webcam_C920_09D53E1F-02.analog-stereo"
} ]
actions = { create-stream = {
audio.position = [ FL FR ]
combine.audio.position = [ FL FR ]
} } }
{ matches = [
{ media.class = "Audio/Source"
node.name = "alsa_input.usb-046d_0821_9534DE90-00.analog-stereo"
} ]
actions = { create-stream = {
audio.position = [ FL FR ]
combine.audio.position = [ SL SR ]
} } }
]
}
}
]