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-- Volume limiter for Hammerspoon |
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-- Limits system output volume depending on the *active* output device. |
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-- |
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-- Configuration ---------------------------------------------------------------- |
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local volumeLimiter = {} |
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-- Max volume per device UID (0–100). |
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-- To discover UIDs, call `volumeLimiter.dumpOutputDevices()` from the Hammerspoon console. |
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volumeLimiter.limitsByUID = { |
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-- ["AppleHDAEngineOutput:1B,0,1,1:0"] = 25, -- Example: built-in speakers |
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-- ["Some-USB-DAC-UID"] = 80, |
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} |
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-- Optional: max volume per device *name* (used if UID is not in the table). |
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volumeLimiter.limitsByName = { |
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-- ["MacBook Pro Speakers"] = 30, |
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-- ["LG HDR 4K"] = 40, |
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} |
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-- Fallback if no UID/name match is found: |
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volumeLimiter.defaultLimit = 100 -- set to e.g. 50 if you want a global hard cap |
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-- Internal state ---------------------------------------------------------------- |
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local currentOutputDevice = nil |
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-- Helpers ----------------------------------------------------------------------- |
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-- Get the limit for a given device |
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function volumeLimiter.limitForDevice(dev) |
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if not dev then return volumeLimiter.defaultLimit end |
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local uid = dev:uid() |
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local name = dev:name() |
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if uid and volumeLimiter.limitsByUID[uid] then |
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return volumeLimiter.limitsByUID[uid] |
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end |
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if name and volumeLimiter.limitsByName[name] then |
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return volumeLimiter.limitsByName[name] |
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end |
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return volumeLimiter.defaultLimit |
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end |
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-- Enforce the limit on a specific device (or on the current default output) |
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function volumeLimiter.enforce(dev) |
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dev = dev or hs.audiodevice.defaultOutputDevice() |
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if not dev then return end |
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local limit = volumeLimiter.limitForDevice(dev) |
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if not limit then return end |
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-- Prefer outputVolume() for output devices |
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local vol = dev:outputVolume() or dev:volume() |
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if not vol then return end |
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if vol > limit then |
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dev:setOutputVolume(limit) |
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-- Optional: visual feedback |
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hs.alert.show(string.format( |
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"Volume limited to %d%% on %s", |
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limit, |
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dev:name() or dev:uid() or "output" |
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), 1) |
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end |
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end |
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-- Attach a per-device watcher to the current default output device |
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local function attachOutputDeviceWatcher() |
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local dev = hs.audiodevice.defaultOutputDevice() |
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if not dev then |
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currentOutputDevice = nil |
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return |
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end |
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-- Stop watcher on previous device (if any) |
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if currentOutputDevice and currentOutputDevice:watcherIsRunning() then |
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currentOutputDevice:watcherStop() |
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end |
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currentOutputDevice = dev |
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dev:watcherCallback(function(uid, event, scope, element) |
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-- We only care about output volume changes |
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if scope == "outp" and event == "vmvc" then |
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volumeLimiter.enforce(dev) |
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end |
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end) |
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dev:watcherStart() |
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-- Immediately clamp in case current volume is already too high |
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volumeLimiter.enforce(dev) |
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end |
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-- Global watcher: re-attach when default output device changes |
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hs.audiodevice.watcher.setCallback(function(event) |
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-- dOut = default output changed, sOut = system output changed |
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if event == "dOut" or event == "sOut" then |
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attachOutputDeviceWatcher() |
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end |
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end) |
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hs.audiodevice.watcher.start() |
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-- Public helper: dump output devices with name + UID (for filling the config) |
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function volumeLimiter.dumpOutputDevices() |
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local devs = hs.audiodevice.allOutputDevices() |
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for _, dev in ipairs(devs) do |
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print(string.format("Name: %-30s | UID: %s", |
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dev:name() or "<no name>", |
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dev:uid() or "<no uid>" |
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)) |
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end |
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end |
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-- Initialise on load |
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attachOutputDeviceWatcher() |
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-- Export if you want to require this from another file |
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return volumeLimiter |
