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

# ~/.config/pipewire/pipewire.conf.d/my-combine-stream-1.conf
 
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 emitted.
                    {
                        # 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.

# ~/.config/pipewire/pipewire.conf.d/my-combine-stream-2.conf
 
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.

# ~/.config/pipewire/pipewire.conf.d/my-combine-stream-3.conf
 
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 ]
                } } }
        ]
    }
}
]