Hello! Thank you for bringing the new iPhone experience with the PushToTalk framework.
I have a working walkie talkie app based on the PushToTalk framework. Everything works fine except for an intermittent bug that I face from time to time on different devices with different iOS versions, from iOS 18 to iOS 26.2 Beta.
Sometimes the app goes into a state where the AVAudioInputNode input node tap returns buffers with a constant size that contain only silence. Leaving and rejoining a channel helps, but relaunching or reinstalling (from Xcode) the app does not. Rebooting the device or deleting and reinstalling the app also helps.
I do not activate the audio session in my app. I only configure it on launch using
setCategory(.playAndRecord, options: [.defaultToSpeaker, .allowBluetooth])
So the flow is:
channelManager?.requestBeginTransmitting(channelUUID: globalChannelUUID)
func channelManager(
_ channelManager: PTChannelManager,
channelUUID: UUID,
didBeginTransmittingFrom source: PTChannelTransmitRequestSource
)
func channelManager(
_ channelManager: PTChannelManager,
didActivate audioSession: AVAudioSession
) {
/// ...
installTapAndStart()
}
private func installTapAndStart() {
let inputNode = audioEngine.inputNode
let hardwareFormat = inputNode.outputFormat(forBus: 0)
guard let targetFormat = AVAudioFormat(
commonFormat: .pcmFormatFloat32,
sampleRate: configuration.audioSampleRate,
channels: configuration.audioChannelsCount,
interleaved: true
) else {
handleError(RecorderError.invalidAudioFormat)
return
}
let converter = AVAudioConverter(from: hardwareFormat, to: targetFormat)!
print("[QUICOpusRecorder]: installTap")
inputNode.installTap(onBus: 0, bufferSize: tapBufferSize, format: hardwareFormat) { [weak self] buffer, _ in
guard let self else { return }
// Here I handle audio data and sometimes get silence
}
//...
do {
audioEngine.prepare()
try audioEngine.start()
} catch {
print(" ⚠️ Audio engine start error: \(error)")
handleError(error)
}
}
Moreover, if the app is in the foreground and PushToTalk gets stuck in this “silence bug”, I can avoid relying on the PushToTalk flow and simulate audio session activation manually in code. In this case I do not request a transmission and do not use any PushToTalk related code, and the app captures audio data perfectly.
Once I leave the channel and rejoin it again, the issue is fixed and I start to receive non silent buffers of varying size, as expected.
It works for a while. It can work fine for a day or more, communicating without launching the app, or with the app in the foreground. But it can also go into the “silence” state 30 minutes after working normally.
I have no clue why this happens.
The only thing I notice is that when the app is in this “stuck silence bug” state, iOS does not play its “chirp” system sound when audio recording starts.
P.S. Channel descriptor restoration code:
extension PushToTalkEngine: PTChannelRestorationDelegate {
public func channelDescriptor(restoredChannelUUID channelUUID: UUID) -> PTChannelDescriptor {
print("☀️ \(#function) channelUUID: \(channelUUID)")
Task { @MainActor in
// Here I fetch more detailed channel data asynchronously
do {
await initChannelManagerIfNeeded(channelUUID: channelUUID)
let channelDescriptor = currentChannelDescriptor()
lastChannelDescriptorName = channelDescriptor.name
try await channelManager?.setChannelDescriptor(
channelDescriptor,
channelUUID: channelUUID
)
} catch {
handleError(error)
}
}
return PTChannelDescriptor(name: "Loading...", image: nil)
}
}
private func initChannelManagerIfNeeded(channelUUID: UUID? = nil) async {
guard let channelUUID = channelUUID ?? currentUser?.globalChannelUUID else {
print("❌ No global channel uuid found")
return
}
do {
guard channelManager == nil else {
try await channelManager?.setTransmissionMode(.halfDuplex, channelUUID: channelUUID)
return
}
channelManager = try await PTChannelManager.channelManager(
delegate: self,
restorationDelegate: self
)
try await channelManager?.setTransmissionMode(.halfDuplex, channelUUID: channelUUID)
} catch {
handleError(error)
}
}