audio_levels

Peak levels of the sinks and sources mantle.audio:set_level_meters names; nil before the first call this session.

mantle.audio:on_change(function(audio)
    local ids = {}
    for _, sink in ipairs(audio.sinks) do
        if sink.active then
            ids[#ids + 1] = sink.id
        end
    end
    mantle.audio:set_level_meters(ids)
end)

return rect {
    height = 6,
    background = "#A6E3A1",
    width = mantle.audio_levels:map(function(levels)
        local level = levels.levels[1]
        return level and level.peak * 2 or 0
    end, 0),
}

State

mantle.audio_levels:get() returns AudioLevelsState, nil before the first push. A field marked ? may be absent.

mantle.audio_levels’ payload: the peaks of the devices mantle.audio:set_level_meters names, pushed at most 30 times a second and only when one moves by 1 % or more.

Field	Type	Description
`levels`	`AudioLevel[]`	One entry per metered device that has sent audio since the call, ordered by `id`.

`AudioLevel`

One metered sink or source.

Field	Type	Description
`id`	`integer`	The `sinks[].id` or `sources[].id`.
`peak`	`number`	The loudest sample since the last push, in percent of full scale, `0` to `100`; linear, not the cubic scale of `volume`. A sink’s is read from its monitor, which PipeWire takes before the sink’s own volume unless the sink sets `monitor.channel-volumes`.

Actions

None: read-only, so any method but get, map and on_change raises.

Backend

Source	Feeds
One PipeWire capture stream per id `mantle.audio:set_level_meters` names: a sink’s monitor or a source, stereo (FL and FR) at 60 samples a second with `resample.peaks`, so each sample is the peak of the graph samples it replaces	`levels`: each buffer’s loudest sample across both channels, held until the next push

Meters run only between a set_level_meters call naming ids and the next call, an empty one stops them all, and none runs before the first call: reading audio_levels alone opens no stream. A reload keeps them until the next call; a replaced Renderer’s stop. The streams share audio’s thread, and a push goes out at most every 33 ms, only when a level moved by 1 point or more, so a silent or steady device costs no pushes.

Gotchas

An id that is not a current sink or source is skipped, not waited for, and a meter ends with its device. A device that comes back, or PipeWire restarting, gives new ids: call set_level_meters again from mantle.audio:on_change, which runs no meter twice.
A metered device keeps running: a sink no longer suspends when nothing plays, since its monitor is being read.
Metering a microphone reads it, so mantle.privacy lists the Supervisor among microphone_users. A sink’s monitor is not listed.
peak is linear in full scale, while volume is cubic. A sink’s monitor carries its streams before the sink’s own volume, unless the sink sets monitor.channel-volumes as Mantle’s null sinks do, so turning a hardware sink down need not lower its peak.

Source: supervisor/src/capabilities/audio/mixer/meters.rs

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