We have been successfully using the PTT (Push-to-Talk) framework in our application since the release of iOS 17. Audio is recorded by pressing a PTT button and speaking after the PTT framework initiates an AVAudioSession.
While the PTT framework has generally worked well since the iOS 17 release, we have received reports that, on occasion, after the app has been idle for a while ( when I have seen it my phone has been in flightmode over night), it suddenly records only silent audio. This issue does not occur every time but sporadically. For users experiencing this problem, pressing the PTT button results in no “PTT framework start sound,” and only “empty sound” is recorded. The only solution to restore audio is restarting the device. Restarting the app alone is insufficient, though leaving the PTT channel and rejoining it also resolves the issue.
I have reproduced the problem several times and observed that everything appears normal within the app. We receive an active AVAudioSession from the PTT framework, and it seems like the app is recording, but all recorded sound packets are silent.
Upon reviewing logs from the phone (via the Console app), I noticed that the app is muted when starting the recording and unmuted after stopping the recording. For example:
• Start recording ≈ 15:01:30
• Stop recording ≈ 15:01:44
• 15:01:30.124144+0100 audiomxd -CMSessionMgr- MXCoreSessionSetProperty: Session ‘sid:0xa80037, AppName(2717), ‘prim’’ isRecordingMuted updated to ‘1’
• 15:01:44.384208+0100 audiomxd -CMSessionMgr- MXCoreSessionSetProperty: Session ‘sid:0xa80037, AppName(2717), ‘prim’’ isRecordingMuted updated to ‘0’
When the system functions normally, the isRecordingMuted flag toggles between 0 and 1, but remains at 0 (non-muted) during recording. After stopping the recording, this state does not change anymore, unlike in the error state.
There is no difference in behavior whether the app is in the foreground or background when starting the transmission, or whether the PTT framework’s “Talk” button is used once the device enters the “error state.”
I have filed a bug report with logs provided on 28 November 2023 that is still open but no feedback. We now have customers that are reporting this issue again on 17.5.1 and its starting to be a big issue. Anyone else that have similar problems ?