Open Radar

 
Summary:
Just displaying an MPVolume View, or tearing one down, or swiping up to display the built-in iOS audio controls, results in several seconds of Wi-Fi network performance degradation -- very bad for VoIP data.

Steps to Reproduce:
1. Start pinging your iPhone 6 or 6 Plus (iOS 8.0, 8.0.2, 8.1 beta 1) from elsewhere on your LAN.  A 1/second ping is fine.
2. We first observed this in a VoIP app starting while a SIP VoIP call was in progress.  Skype is a good test too.
3. Observe good ping times of 2.5 ms.  
4. App just displaying or tearing down an MPVolumeView, or user swiping up to reveal iOS volume controls, results in several seconds of ping times shooting up to 300 ms +/- 100 ms.  Duration is 3-5 seconds, possibly in two bursts.
5. We've also observed that just ending the VoIP call may set the device to slow network ping response -- less noticable because we're not playing audio from network.  And OK because I'm not playing audio.  Don't know yet whether that is because of change in session, or stopping the audio graph.  I mention it in case it's related.
6. We've also observed that backgrounding the app while the VoIP call is going is not a problem -- the red "mic is on" stripe is present, but no network/audio degradation.  It's specifically something about the audio route controls specifically, not competition with other apps or UI.

HYPOTHESIS:  iOS device is aggressively managing itself into some low-power wi-fi optimization mode, and although something about our active VoIP calls makes it behave, just displaying either MPVolumeView or the swipe-up audio controls makes the device immediately drop into the aggressive slow-responding Wi-Fi mode despite the continuing VoIP call and its packets every 20ms and the running audio graph.

We're working on gathering logs, but wanted to submit this immediately in the meantime.  It's very reproducible.


Expected Results:
No dropping into bad network performance, especially while my app is sending/receiving RTP packets every 20ms and has an active audio session and audio graph.

No dropping into bad network performance due to presence or absence of MYVolumeView or other audio route UI elements.

Actual Results:
Reproducible network response degradation as soon as MPVolumeView or built-in audio controls are displayed, lasting several seconds.

Version:
iOS 8.0, 8.0.2, 8.1 beta 1

Notes:


Configuration:
iPhone 6 and 6 Plus