Deactivate the audio session after a call ends using the AVAudioSessionSetActiveOptionNotifyOthersO…

webrtc/modules/audio_device/ios/audio_device_ios.mm

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 68 matching lines @@
 
 // Activates an audio session suitable for full duplex VoIP sessions when
 // |activate| is true. Also sets the preferred sample rate and IO buffer
 // duration. Deactivates an active audio session if |activate| is set to false.
 static void ActivateAudioSession(AVAudioSession* session, bool activate) {
   LOG(LS_INFO) << "ActivateAudioSession(" << activate << ")";
   @autoreleasepool {
     NSError* error = nil;
     BOOL success = NO;
 
-    // Deactivate the audio session and return if |activate| is false.
     if (!activate) {
-      success = [session setActive:NO error:&error];
+      // Deactivate the audio session using an extra option and then return.
+      // AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation is used to
+      // ensure that other audio sessions that were interrupted by our session
+      // can return to their active state. It is recommended for VoIP apps to
+      // use this option.
+      success = [session

[tkchin_webrtc, 2015/11/16 21:40:34]

nit: 
maybe just break it onto next line (you can copy/paste the text to see the
formatting, it's not even width in CR tool)
success =
    [session setActive:NO
           withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation
                 error:&error];

[henrika_webrtc, 2015/11/17 13:52:32]

withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation does not fit
within the 80-char limit if I do so. Keeping as is unless you think I should
break 80 here.

+            setActive:NO
+          withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation
+                error:&error];
       RTC_DCHECK(CheckAndLogError(success, error));
       return;
     }
 
+    // Go ahead and active our own audio session since |activate| is true.
     // Use a category which supports simultaneous recording and playback.
     // By default, using this category implies that our app’s audio is
     // nonmixable, hence activating the session will interrupt any other
     // audio sessions which are also nonmixable.
     if (session.category != AVAudioSessionCategoryPlayAndRecord) {
       error = nil;
       success = [session setCategory:AVAudioSessionCategoryPlayAndRecord
                          withOptions:AVAudioSessionCategoryOptionAllowBluetooth
                                error:&error];
       RTC_DCHECK(CheckAndLogError(success, error));
@@ skipping 811 matching lines @@
   // Read decoded 16-bit PCM samples from WebRTC (using a size that matches
   // the native I/O audio unit) to a preallocated intermediate buffer and
   // copy the result to the audio buffer in the |io_data| destination.
   SInt8* source = playout_audio_buffer_.get();
   fine_audio_buffer_->GetPlayoutData(source);
   memcpy(destination, source, dataSizeInBytes);
   return noErr;
 }
 
 }  // namespace webrtc