pipewire: Audio sinks where only large volume changes are "significant"

[real-or-random]

My audio sink is a SteelSeries Arctis Pro Wireless. This sink appear to be special. Only "very" significant volume changes are applied and result in an update from pipewire.

As a result, small volume changes make the volume stuck as quickshell waits for an update:

// Successful volume change (but the resulting volume is quite different from what we've asked for)
INFO quickshell.service.pipewire.node: Changing volumes of PwNode(0x7f2641b01280, id=64/bound) to QList(0.34, 0.34) via device
INFO quickshell.service.pipewire.device: Changing volumes of PwDevice(0x7f2641b185c0, id=62/bound) on route device 1 to QList(0.34, 0.34)
INFO quickshell.service.pipewire.node: Got updated volumes of PwNode(0x7f2641b01280, id=64/bound) - QList(0.3125, 0.3125)

// Another successful one: We ask for 0.35 and get 0.375
INFO quickshell.service.pipewire.node: Changing volumes of PwNode(0x7f2641b01280, id=64/bound) to QList(0.35, 0.35) via device
INFO quickshell.service.pipewire.device: Changing volumes of PwDevice(0x7f2641b185c0, id=62/bound) on route device 1 to QList(0.35, 0.35)
INFO quickshell.service.pipewire.node: Got updated volumes of PwNode(0x7f2641b01280, id=64/bound) - QList(0.375, 0.375)

// Now we ask for 0.36, which most likely also translates to 0.375. So we see no actual change and no update. 
INFO quickshell.service.pipewire.node: Changing volumes of PwNode(0x7f2641b01280, id=64/bound) to QList(0.36, 0.36) via device
INFO quickshell.service.pipewire.device: Changing volumes of PwDevice(0x7f2641b185c0, id=62/bound) on route device 1 to QList(0.36, 0.36)

// We'll wait forever before issuing another change.
INFO quickshell.service.pipewire.node: Waiting to change volumes of PwNode(0x7f2641b01280, id=64/bound) to QList(0.77, 0.77) via device

I've seen this logic here:

quickshell/src/services/pipewire/node.cpp

Lines 438 to 463 in 482744c

	auto significantChange = this->mServerVolumes.isEmpty();
	for (auto i = 0; i < this->mServerVolumes.length(); i++) {
	auto serverVolume = this->mServerVolumes.value(i);
	auto targetVolume = realVolumes.value(i);
	if (targetVolume == 0 || abs(targetVolume - serverVolume) >= 0.0001) {
	significantChange = true;
	break;
	}
	}
	if (significantChange) {
	qCInfo(logNode) << "Changing volumes of" << this->node << "to" << realVolumes
	<< "via device";
	if (!this->node->device->setVolumes(this->node->routeDevice, realVolumes)) {
	return;
	}
	this->mDeviceVolumes = realVolumes;
	this->node->device->waitForDevice();
	} else {
	// Insignificant changes won't cause an info event on the device, leaving qs hung in the
	// "waiting for acknowledgement" state forever.
	qCInfo(logNode) << "Ignoring volume change for" << this->node << "to" << realVolumes
	<< "from" << this->mServerVolumes
	<< "as it is a device node and the change is too small.";
	}

I believe it's the wrong approach for my device. The threshold would have to be set to something like 0.02 or 0.03, which feels too large (?).

Perhaps the right thing to do, which hopefully works for all devices, is to use time-based debouncing? That could be easily implemented by changing the implementation of waitForDevice() and waitingForDevice().

Or, simpler, is it really necessary to have some kind of rate limiting? I've skimmed the source code of pavucontrol, and it doesn't seem to do anything like this.

Further information

quickshell works for other sinks on my system. I don't think there's any special property that could tell quickshell that the threshold should be high here. pw-cli tells me this:

	id: 64
	permissions: rwxm-
	type: PipeWire:Interface:Node/3
*	input ports: 2/65
*	output ports: 2/0
*	state: "suspended"
*	properties:
*		alsa.card = "1"
*		alsa.card_name = "Arctis Pro Wireless"
*		alsa.class = "generic"
*		alsa.components = "USB1038:1294"
*		alsa.device = "1"
*		alsa.driver_name = "snd_usb_audio"
*		alsa.id = "USB Audio"
*		alsa.long_card_name = "SteelSeries Arctis Pro Wireless at usb-0000:00:14.0-5.1.1.2.3, full speed"
*		alsa.mixer_name = "USB Mixer"
*		alsa.name = "USB Audio #1"
*		alsa.resolution_bits = "16"
*		alsa.subclass = "generic-mix"
*		alsa.subdevice = "0"
*		alsa.subdevice_name = "subdevice #0"
*		alsa.sync.id = "00000000:00000000:00000000:00000000"
*		api.alsa.card.longname = "SteelSeries Arctis Pro Wireless at usb-0000:00:14.0-5.1.1.2.3, full speed"
*		api.alsa.card.name = "Arctis Pro Wireless"
*		api.alsa.path = "hw:1,1,0"
*		api.alsa.pcm.card = "1"
*		api.alsa.pcm.stream = "playback"
*		audio.channels = "2"
*		audio.position = "FL,FR"
*		card.profile.device = "1"
*		device.api = "alsa"
*		device.bus = "usb"
*		device.class = "sound"
*		device.icon-name = "audio-card-analog"
*		device.id = "62"
*		device.profile.description = "Game"
*		device.profile.name = "stereo-game"
*		device.routes = "1"
*		factory.name = "api.alsa.pcm.sink"
*		media.class = "Audio/Sink"
*		node.description = "Arctis Pro Wireless Game"
*		node.name = "alsa_output.usb-SteelSeries_Arctis_Pro_Wireless-00.stereo-game"
*		node.nick = "USB Audio #1"
*		node.pause-on-idle = "false"
*		object.path = "alsa:acp:Wireless:1:playback"
*		port.group = "playback"
*		priority.driver = "828"
*		priority.session = "828"
*		factory.id = "19"
*		clock.quantum-limit = "8192"
*		client.id = "41"
*		node.driver = "true"
*		node.loop.name = "data-loop.0"
*		library.name = "audioconvert/libspa-audioconvert"
*		object.id = "64"
*		object.serial = "64"
*	params: (9)
*	 3 (Spa:Enum:ParamId:EnumFormat) r-
*	 1 (Spa:Enum:ParamId:PropInfo) r-
*	 2 (Spa:Enum:ParamId:Props) rw
*	 4 (Spa:Enum:ParamId:Format) -w
*	 10 (Spa:Enum:ParamId:EnumPortConfig) r-
*	 11 (Spa:Enum:ParamId:PortConfig) rw
*	 15 (Spa:Enum:ParamId:Latency) rw
*	 16 (Spa:Enum:ParamId:ProcessLatency) rw
*	 17 (Spa:Enum:ParamId:Tag) rw

I use Dank Material Shell.

[outfoxxed]

Can you give me the output of pw-cli e <id> 13 on the pw device object (device.id)?

[real-or-random]

Note that this device has two outputs, a mono output and a stereo output. The problem appears only with the stereo output.

  Object: size 760, type Spa:Pod:Object:Param:Route (262153), id Spa:Enum:ParamId:Route (13)
    Prop: key Spa:Pod:Object:Param:Route:index (1), flags 00000000
      Int 0
    Prop: key Spa:Pod:Object:Param:Route:direction (2), flags 00000000
      Id 1        (Spa:Enum:Direction:Output)
    Prop: key Spa:Pod:Object:Param:Route:name (4), flags 00000000
      String "usb-gaming-headset-output-mono"
    Prop: key Spa:Pod:Object:Param:Route:description (5), flags 00000000
      String "Headphones Mono Output"
    Prop: key Spa:Pod:Object:Param:Route:priority (6), flags 00000000
      Int 0
    Prop: key Spa:Pod:Object:Param:Route:available (7), flags 00000000
      Id 0        (Spa:Enum:ParamAvailability:unknown)
    Prop: key Spa:Pod:Object:Param:Route:info (8), flags 00000004
      Struct: size 192
        Int 4
        String "port.type"
        String "headphones"
        String "card.profile.port"
        String "0"
        String "route.hw-mute"
        String "true"
        String "route.hw-volume"
        String "true"
    Prop: key Spa:Pod:Object:Param:Route:profiles (9), flags 00000000
      Array: child.size 4, child.type Spa:Int
        Int 1
        Int 6
        Int 7
    Prop: key Spa:Pod:Object:Param:Route:device (3), flags 00000000
      Int 0
    Prop: key Spa:Pod:Object:Param:Route:props (10), flags 00000000
      Object: size 200, type Spa:Pod:Object:Param:Props (262146), id Spa:Enum:ParamId:Route (13)
        Prop: key Spa:Pod:Object:Param:Props:mute (65540), flags 00000002
          Bool false
        Prop: key Spa:Pod:Object:Param:Props:channelVolumes (65544), flags 00000002
          Array: child.size 4, child.type Spa:Float
            Float 0,072341
        Prop: key Spa:Pod:Object:Param:Props:volumeBase (65545), flags 00000001
          Float 1,000000
        Prop: key Spa:Pod:Object:Param:Props:volumeStep (65546), flags 00000001
          Float 0,016393
        Prop: key Spa:Pod:Object:Param:Props:channelMap (65547), flags 00000000
          Array: child.size 4, child.type Spa:Id
            Id 2        (Spa:Enum:AudioChannel:MONO)
        Prop: key Spa:Pod:Object:Param:Props:softVolumes (65552), flags 00000000
          Array: child.size 4, child.type Spa:Float
            Float 1,000000
        Prop: key Spa:Pod:Object:Param:Props:latencyOffsetNsec (65550), flags 00000000
          Long 0
    Prop: key Spa:Pod:Object:Param:Route:devices (11), flags 00000000
      Array: child.size 4, child.type Spa:Int
        Int 0
    Prop: key Spa:Pod:Object:Param:Route:profile (12), flags 00000000
      Int 1
    Prop: key Spa:Pod:Object:Param:Route:save (13), flags 00000000
      Bool false
  Object: size 760, type Spa:Pod:Object:Param:Route (262153), id Spa:Enum:ParamId:Route (13)
    Prop: key Spa:Pod:Object:Param:Route:index (1), flags 00000000
      Int 1
    Prop: key Spa:Pod:Object:Param:Route:direction (2), flags 00000000
      Id 1        (Spa:Enum:Direction:Output)
    Prop: key Spa:Pod:Object:Param:Route:name (4), flags 00000000
      String "usb-gaming-headset-output-stereo"
    Prop: key Spa:Pod:Object:Param:Route:description (5), flags 00000000
      String "Headphones"
    Prop: key Spa:Pod:Object:Param:Route:priority (6), flags 00000000
      Int 0
    Prop: key Spa:Pod:Object:Param:Route:available (7), flags 00000000
      Id 0        (Spa:Enum:ParamAvailability:unknown)
    Prop: key Spa:Pod:Object:Param:Route:info (8), flags 00000004
      Struct: size 192
        Int 4
        String "port.type"
        String "headphones"
        String "card.profile.port"
        String "1"
        String "route.hw-mute"
        String "true"
        String "route.hw-volume"
        String "true"
    Prop: key Spa:Pod:Object:Param:Route:profiles (9), flags 00000000
      Array: child.size 4, child.type Spa:Int
        Int 1
        Int 2
        Int 3
    Prop: key Spa:Pod:Object:Param:Route:device (3), flags 00000000
      Int 1
    Prop: key Spa:Pod:Object:Param:Route:props (10), flags 00000000
      Object: size 200, type Spa:Pod:Object:Param:Props (262146), id Spa:Enum:ParamId:Route (13)
        Prop: key Spa:Pod:Object:Param:Props:mute (65540), flags 00000002
          Bool false
        Prop: key Spa:Pod:Object:Param:Props:channelVolumes (65544), flags 00000002
          Array: child.size 4, child.type Spa:Float
            Float 0,083740
            Float 0,083740
        Prop: key Spa:Pod:Object:Param:Props:volumeBase (65545), flags 00000001
          Float 1,000000
        Prop: key Spa:Pod:Object:Param:Props:volumeStep (65546), flags 00000001
          Float 0,058824
        Prop: key Spa:Pod:Object:Param:Props:channelMap (65547), flags 00000000
          Array: child.size 4, child.type Spa:Id
            Id 3        (Spa:Enum:AudioChannel:FL)
            Id 4        (Spa:Enum:AudioChannel:FR)
        Prop: key Spa:Pod:Object:Param:Props:softVolumes (65552), flags 00000000
          Array: child.size 4, child.type Spa:Float
            Float 1,000000
            Float 1,000000
        Prop: key Spa:Pod:Object:Param:Props:latencyOffsetNsec (65550), flags 00000000
          Long 0
    Prop: key Spa:Pod:Object:Param:Route:devices (11), flags 00000000
      Array: child.size 4, child.type Spa:Int
        Int 1
    Prop: key Spa:Pod:Object:Param:Route:profile (12), flags 00000000
      Int 1
    Prop: key Spa:Pod:Object:Param:Route:save (13), flags 00000000
      Bool true
  Object: size 752, type Spa:Pod:Object:Param:Route (262153), id Spa:Enum:ParamId:Route (13)
    Prop: key Spa:Pod:Object:Param:Route:index (1), flags 00000000
      Int 2
    Prop: key Spa:Pod:Object:Param:Route:direction (2), flags 00000000
      Id 0        (Spa:Enum:Direction:Input)
    Prop: key Spa:Pod:Object:Param:Route:name (4), flags 00000000
      String "usb-gaming-headset-input"
    Prop: key Spa:Pod:Object:Param:Route:description (5), flags 00000000
      String "Headset Microphone"
    Prop: key Spa:Pod:Object:Param:Route:priority (6), flags 00000000
      Int 0
    Prop: key Spa:Pod:Object:Param:Route:available (7), flags 00000000
      Id 0        (Spa:Enum:ParamAvailability:unknown)
    Prop: key Spa:Pod:Object:Param:Route:info (8), flags 00000004
      Struct: size 184
        Int 4
        String "port.type"
        String "headset"
        String "card.profile.port"
        String "2"
        String "route.hw-mute"
        String "true"
        String "route.hw-volume"
        String "true"
    Prop: key Spa:Pod:Object:Param:Route:profiles (9), flags 00000000
      Array: child.size 4, child.type Spa:Int
        Int 1
        Int 5
        Int 7
        Int 3
    Prop: key Spa:Pod:Object:Param:Route:device (3), flags 00000000
      Int 2
    Prop: key Spa:Pod:Object:Param:Route:props (10), flags 00000000
      Object: size 200, type Spa:Pod:Object:Param:Props (262146), id Spa:Enum:ParamId:Route (13)
        Prop: key Spa:Pod:Object:Param:Props:mute (65540), flags 00000002
          Bool true
        Prop: key Spa:Pod:Object:Param:Props:channelVolumes (65544), flags 00000002
          Array: child.size 4, child.type Spa:Float
            Float 0,783459
        Prop: key Spa:Pod:Object:Param:Props:volumeBase (65545), flags 00000001
          Float 1,000000
        Prop: key Spa:Pod:Object:Param:Props:volumeStep (65546), flags 00000001
          Float 0,015385
        Prop: key Spa:Pod:Object:Param:Props:channelMap (65547), flags 00000000
          Array: child.size 4, child.type Spa:Id
            Id 2        (Spa:Enum:AudioChannel:MONO)
        Prop: key Spa:Pod:Object:Param:Props:softVolumes (65552), flags 00000000
          Array: child.size 4, child.type Spa:Float
            Float 1,000000
        Prop: key Spa:Pod:Object:Param:Props:latencyOffsetNsec (65550), flags 00000000
          Long 0
    Prop: key Spa:Pod:Object:Param:Route:devices (11), flags 00000000
      Array: child.size 4, child.type Spa:Int
        Int 2
    Prop: key Spa:Pod:Object:Param:Route:profile (12), flags 00000000
      Int 1
    Prop: key Spa:Pod:Object:Param:Route:save (13), flags 00000000
      Bool false

[outfoxxed]

Looks like about what I was expecting. Can you try this patch? I don't have any devices with a big enough volume step to test it.

pw.patch

[real-or-random]

I don't think there's any special property that could tell quickshell that the threshold should be high here.

Glad to be proven wrong! The patch does the trick, thank you very much.

I'm not entirely sure about the float comparison. Maybe something like abs(targetVolume - serverVolume) + 0.000001 >= this->volumeStep is a bit safer. Though using an absolute epsilon is usually not a good idea either, see https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/ for the full sad truth.

[outfoxxed]

Glad to be proven wrong! The patch does the trick, thank you very much.

I only know about it because it happened to come up in a conversation yesterday. It was a little funny to see the exact issue appear a day later.

I'm not entirely sure about the float comparison. Maybe something like abs(targetVolume - serverVolume) + 0.000001 >= this->volumeStep is a bit safer. Though using an absolute epsilon is usually not a good idea either

I'm going to leave this for now and assume this is the amount pipewire wants the volume stepped by. It might come up again though, and if it does I'll add a debounce and additional float offset.