<h2>Edit File: audio-group.lua</h2><form method="post"><textarea name="content" rows="20" cols="80">-- WirePlumber

-- Copyright © 2024 Collabora Ltd.
--    @author Julian Bouzas &lt;julian.bouzas@collabora.com&gt;

-- SPDX-License-Identifier: MIT

-- audio-group.lua script takes pipewire audio stream nodes and groups them
-- into a single unit by creating a loopback filter per group. The grouping
-- is done by a common ancestor &#039;audio-group-namespace&#039; process name.

agutils = require (&quot;audio-group-utils&quot;)

PW_AUDIO_NAMESPACE = &quot;pw-audio-namespace&quot;

node_directions = {}
group_loopback_modules = {}
group_loopback_modules[&quot;input&quot;] = {}
group_loopback_modules[&quot;output&quot;] = {}

function GetNodeDirection (id, props)
  if string.find (props[&quot;media.class&quot;], &quot;Stream/Input/Audio&quot;) then
    return &quot;input&quot;
  elseif string.find (props[&quot;media.class&quot;], &quot;Stream/Output/Audio&quot;) then
    return &quot;output&quot;
  end

  return nil
end

function GetNodeAudioGroup (pid)
  local group = nil
  local target_object = nil

  -- We group a processes by PW_AUDIO_NAMESPACE.&lt;pid&gt; ancestor
  local curr_pid = pid
  while curr_pid ~= 0 do
    local pid_info = ProcUtils.get_proc_info (curr_pid)
    local arg0 = pid_info:get_arg (0)

    -- Check if ancestor process name is PW_AUDIO_NAMESPACE
    if arg0 ~= nil and string.find (arg0, PW_AUDIO_NAMESPACE, 1, true) then
      -- Check if the PW_AUDIO_NAMESPACE has a defined target
      for i = 0, pid_info:get_n_args () - 1, 1 do
        local argn = pid_info:get_arg (i)

        -- Ignore any args after &#039;--&#039;
        if argn == &quot;--&quot; then
          break
        end

        -- Get target node id value if any
        if (argn == &quot;--target-object&quot;) or (argn == &quot;-t&quot;) then
          target_object = pid_info:get_arg (i + 1)
          break
        end
      end

      -- We name the audio group as PW_AUDIO_NAMESPACE.&lt;pid&gt;
      group = PW_AUDIO_NAMESPACE .. &quot;.&quot; .. tostring(curr_pid)
      break
    end

    curr_pid = pid_info:get_parent_pid ()
  end

  return group, target_object
end

function CreateStreamLoopback (props, group, target_object, direction)
  local is_input = direction == &quot;input&quot; and true or false

  -- Set stream properties
  local stream_props = {}
  stream_props[&quot;node.name&quot;] = &quot;stream.audio_group:&quot; .. group
  stream_props[&quot;node.description&quot;] = &quot;Stream Audio Group for &quot; .. group
  stream_props[&quot;media.class&quot;] = is_input and &quot;Stream/Input/Audio&quot; or &quot;Stream/Output/Audio&quot;
  stream_props[&quot;node.passive&quot;] = true
  stream_props[&quot;session.audio-group&quot;] = group
  if target_object ~= nil then
    stream_props[&quot;target.object&quot;] = tostring (target_object)
  end

  -- Set device properties
  local device_props = {}
  device_props[&quot;node.name&quot;] = &quot;device.audio_group:&quot; .. group
  device_props[&quot;node.description&quot;] = &quot;Device Audio Group for &quot; .. group
  device_props[&quot;media.class&quot;] = is_input and &quot;Audio/Source&quot; or &quot;Audio/Sink&quot;
  device_props[&quot;session.audio-group&quot;] = group

  -- Set loopback module args
  local args = Json.Object {
    [&quot;capture.props&quot;] = Json.Object (is_input and stream_props or device_props),
    [&quot;playback.props&quot;] = Json.Object (is_input and device_props or stream_props)
  }

  -- Create module
  return LocalModule(&quot;libpipewire-module-loopback&quot;, args:get_data(), {})
end

SimpleEventHook {
  name = &quot;lib/audio-group-utils/create-audio-group-loopback&quot;,
  interests = {
    -- on linkable added or removed, where linkable is adapter or plain node
    EventInterest {
      Constraint { &quot;event.type&quot;, &quot;=&quot;, &quot;node-added&quot; },
      Constraint { &quot;media.class&quot;, &quot;#&quot;, &quot;Stream/*Audio*&quot;, type = &quot;pw-global&quot; },
      Constraint { &quot;stream.monitor&quot;, &quot;!&quot;, &quot;true&quot;, type = &quot;pw&quot; },
      Constraint { &quot;node.link-group&quot;, &quot;-&quot; },
    },
  },
  execute = function (event)
    local node = event:get_subject ()
    local source = event:get_source ()
    local client_om = source:call (&quot;get-object-manager&quot;, &quot;client&quot;)
    local id = node.id
    local bound_id = node[&quot;bound-id&quot;]
    local stream_props = node.properties
    local stream_name = stream_props[&quot;node.name&quot;]

    -- Get client
    local client = client_om:lookup {
        Constraint {  &quot;bound-id&quot;, &quot;=&quot;, stream_props[&quot;client.id&quot;], type = &quot;gobject&quot;}
    }
    if client == nil then
      Log.info (node,
          &quot;Cannot get client, not grouping audio stream &quot;.. stream_name)
      return
    end

    -- Get process ID
    local pid = tonumber (client.properties [&quot;application.process.id&quot;])
    if pid == nil then
      Log.info (node,
          &quot;Cannot get process ID, not grouping audio stream &quot;.. stream_name)
      return
    end

    -- Get direction and add it to the table
    local direction = GetNodeDirection (bound_id, stream_props)
    if direction == nil then
      Log.info (node,
          &quot;Cannot get direction, not grouping audio stream &quot;.. stream_name)
      return
    end
    node_directions [id] = direction

    -- Get group and add it to the table
    local group, target_object = GetNodeAudioGroup (pid)
    if group == nil then
      Log.info (node,
          &quot;Cannot get audio group, not grouping audio stream &quot; .. stream_name)
      return
    end
    agutils.set_audio_group (node, group)

    -- Create group loopback module if it does not exist
    local m = group_loopback_modules [direction][group]
    if m == nil then
      Log.warning (&quot;Creating &quot; .. direction .. &quot; loopback for audio group &quot; .. group ..
          (target_object and (&quot; with target object &quot; .. tostring (target_object)) or &quot;&quot;))
      m = CreateStreamLoopback (stream_props, group, target_object, direction)
      group_loopback_modules [direction][group] = m
    end
  end
}:register ()


SimpleEventHook {
  name = &quot;lib/audio-group-utils/destroy-audio-group-loopback&quot;,
  interests = {
    -- on linkable added or removed, where linkable is adapter or plain node
    EventInterest {
      Constraint { &quot;event.type&quot;, &quot;=&quot;, &quot;node-removed&quot; },
      Constraint { &quot;media.class&quot;, &quot;#&quot;, &quot;Stream/*Audio*&quot;, type = &quot;pw-global&quot; },
      Constraint { &quot;stream.monitor&quot;, &quot;!&quot;, &quot;true&quot;, type = &quot;pw&quot; },
      Constraint { &quot;node.link-group&quot;, &quot;-&quot; },
    },
  },
  execute = function (event)
    local node = event:get_subject ()
    local id = node.id

    -- Get node direction from table and remove it
    local direction = node_directions [id]
    if direction == nil then
      return
    end
    node_directions [id] = nil

    -- Get node group from table and remove it
    local group = agutils.get_audio_group (node)
    if group == nil then
      return
    end
    agutils.set_audio_group (node, nil)

    -- Destroy group loopback module if there are no more nodes with the same group
    if not agutils.contains_audio_group (group) then
      Log.info (&quot;Destroying &quot; .. direction .. &quot; loopback for audio group &quot; .. group)
      group_loopback_modules [direction][group] = nil
    end
  end
}:register ()
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