For receiving audio in PushtoTalk, channelManager(_:didActivate:) not called when app receives first push after backgrounding

Question

Created Oct ’25

Replies 4

Boosts 0

Participants 3

I'm implementing the PushToTalk framework and have encountered an issue where channelManager(_:didActivate:) is not called under specific circumstances.

What works:

App is in foreground, receives PTT push → didActivate is called ✅
App receives audio in foreground, then is backgrounded → subsequent pushes trigger didActivate ✅

What doesn't work:

App is launched, user joins channel, then immediately backgrounds
PTT push arrives while app is backgrounded
incomingPushResult is called, I return .activeRemoteParticipant(participant)
The system UI shows the speaker name correctly
However, didActivate is never called
Audio data arrives via WebSocket but cannot be played (no audio session)

Setup:

Channel joined successfully before backgrounding
UIBackgroundModes includes push-to-talk
No manual audio session activation (setActive) anywhere in my code
AVAudioEngine setup only happens inside didActivate delegate method
Issue persists even after channel restoration via channelDescriptor(restoredChannelUUID:)

Question: Is this expected behavior or a bug? If expected, what's the correct approach to handle incoming PTT audio when the app is backgrounded and hasn't received audio while in the foreground yet?

Boost

Answer 1

DTS Engineer OP

Apple

Oct ’25

UIBackgroundModes includes push-to-talk

Did you also include "audio"? You actually need both. Strictly speaking, "push-to-talk" allows you to receive PTT pushes while "audio" allows your audio session to activate in the background.

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Kevin Elliott
DTS Engineer, CoreOS/Hardware

0

Answer 2

Algo1 OP

2d

I am having the same issue, channelManager(_:didActivate:) is not called in background. audio is included in UIBackgroundModes. So, it seems the issue in PTT framework itself. I am testing on debug mode, but that shouldn't be a reason, right?

0

Answer 3

DTS Engineer OP

Apple

1d

I am having the same issue, channelManager(_:didActivate:) is not called in the background. audio is included in UIBackgroundModes. So, it seems the issue is in the PTT framework itself.

No, not necessarily. What audio API are you using and, most importantly, do you EVER activate the AudioSession yourself? The PTT framework is built around the same infrastructure as CallKit, which also means that you MUST rely on it for session activation instead of activating the audio session yourself. CallKit's speakerbox sample is a good starting point for how this should work.

I am testing on debug mode, but that shouldn't be a reason, right?

No and, in fact, testing with the debugger tends to make this work "better" than it "should"[1], not worse.

[1] Notably, the debugger disables normal app suspension, so your app ends up being awake in the background in ways that would not normally occur.

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Kevin Elliott
DTS Engineer, CoreOS/Hardware

0

Answer 4

Algo1 OP

1d

No, I am not activating or changing anything in AudioSession. I have pretty straightforward setup; recording an audio using AVAudioEngine and sending to the server (which is running locally for now). And when PTT notification arrives saving url to audio file in incomingPushResult, then downloading and playing that sound using AVAudioPlayer when didActivate is executed. It's working fine on foreground, but when app goes to background incomingPushResult is called as expected but didActivate is not for some reason. Am I missing anything in my setup?

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