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fix(audio): include tap in aggregate device creation dictionary #14

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fix(audio): include tap in aggregate device creation dictionary #14

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72 changes: 30 additions & 42 deletions Sources/AudioTeeCore/Core/AudioTapManager.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -27,15 +27,14 @@ public class AudioTapManager {
public func setupAudioTap(with config: TapConfiguration) throws {
AudioTeeLogging.logger.debug("Setting up audio tap manager")

tapID = try createSystemAudioTap(with: config)
deviceID = try createAggregateDevice()
let (createdTapID, tapUUID) = try createSystemAudioTap(with: config)
tapID = createdTapID
deviceID = try createAggregateDevice(tapUUID: tapUUID)

guard let tapID = tapID, let deviceID = deviceID else {
guard tapID != nil, deviceID != nil else {
throw AudioTeeError.setupFailed
}

try addTapToAggregateDevice(tapID: tapID, deviceID: deviceID)

AudioTeeLogging.logger.debug("Audio tap manager setup complete")
}

Expand All @@ -44,7 +43,7 @@ public class AudioTapManager {
return deviceID
}

private func createSystemAudioTap(with config: TapConfiguration) throws -> AudioObjectID {
private func createSystemAudioTap(with config: TapConfiguration) throws -> (AudioObjectID, String) {
AudioTeeLogging.logger.debug("Creating tap description")
let description = CATapDescription()

Expand All @@ -58,6 +57,9 @@ public class AudioTapManager {
description.deviceUID = nil // system default
description.stream = 0 // first stream of output device

// Get the UUID from the description before creating the tap
let tapUUID = description.uuid.uuidString

AudioTeeLogging.logger.debug(
"Tap description configured",
context: [
Expand All @@ -66,6 +68,7 @@ public class AudioTapManager {
"mute": String(describing: description.muteBehavior),
"mono": String(description.isMono),
"exclusive": String(description.isExclusive),
"uuid": tapUUID,
])

// Create the tap
Expand Down Expand Up @@ -97,20 +100,31 @@ public class AudioTapManager {
])
}

return tapID
return (tapID, tapUUID)
}

private func createAggregateDevice() throws -> AudioObjectID {
private func createAggregateDevice(tapUUID: String) throws -> AudioObjectID {
let uid = UUID().uuidString
let description =

// Include the tap in the aggregate device creation dictionary using
// structured sub-tap dictionaries. This is required on macOS 26+ where
// adding the tap via AudioObjectSetPropertyData after creation no longer
// delivers audio data.
let tapList: [[String: Any]] = [
[
kAudioAggregateDeviceNameKey: "audiotee-aggregate-device",
kAudioAggregateDeviceUIDKey: uid,
kAudioAggregateDeviceSubDeviceListKey: [] as CFArray,
kAudioAggregateDeviceMasterSubDeviceKey: 0,
kAudioAggregateDeviceIsPrivateKey: true,
kAudioAggregateDeviceIsStackedKey: false,
] as [String: Any]
kAudioSubTapUIDKey: tapUUID,
kAudioSubTapDriftCompensationKey: true,
]
]

let description: [String: Any] = [
kAudioAggregateDeviceNameKey: "audiotee-aggregate-device",
kAudioAggregateDeviceUIDKey: uid,
kAudioAggregateDeviceTapListKey: tapList,
kAudioAggregateDeviceTapAutoStartKey: false,

@makeusabrew makeusabrew May 22, 2026

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Thanks @sondt2709! Can you confirm the addition of this kAudioAggregateDeviceTapAutoStartKey: false setting has no adverse effects?

kAudioAggregateDeviceIsPrivateKey: true,
kAudioAggregateDeviceIsStackedKey: false,
]

var deviceID: AudioObjectID = 0
let status = AudioHardwareCreateAggregateDevice(description as CFDictionary, &deviceID)
Expand All @@ -123,30 +137,4 @@ public class AudioTapManager {

return deviceID
}

private func addTapToAggregateDevice(tapID: AudioObjectID, deviceID: AudioObjectID) throws {
// Get the tap's UID
var propertyAddress = getPropertyAddress(selector: kAudioTapPropertyUID)
var propertySize = UInt32(MemoryLayout<CFString>.stride)
var tapUID: CFString = "" as CFString
_ = withUnsafeMutablePointer(to: &tapUID) { tapUID in
AudioObjectGetPropertyData(tapID, &propertyAddress, 0, nil, &propertySize, tapUID)
}

// Add the tap to the aggregate device
propertyAddress = getPropertyAddress(
selector: kAudioAggregateDevicePropertyTapList)
let tapArray = [tapUID] as CFArray
propertySize = UInt32(MemoryLayout<CFArray>.stride)

let status = withUnsafePointer(to: tapArray) { ptr in
AudioObjectSetPropertyData(deviceID, &propertyAddress, 0, nil, propertySize, ptr)
}

guard status == kAudioHardwareNoError else {
AudioTeeLogging.logger.error(
"Failed to add tap to aggregate device", context: ["status": String(status)])
throw AudioTeeError.tapAssignmentFailed(status)
}
}
}