Fixed buffer size and sample rate changes in iOS background audio

examples/Demo/Builds/iOS/Info-App.plist

@@ -10,6 +10,8 @@
     </dict>
     <key>LSRequiresIPhoneOS</key>
     <true/>
+    <key>NSMicrophoneUsageDescription</key>
+    <string>This app requires microphone input.</string>
     <key>UIViewControllerBasedStatusBarAppearance</key>
     <false/>
     <key>CFBundleExecutable</key>

examples/Demo/JuceDemo.jucer

@@ -35,7 +35,8 @@
     </XCODE_MAC>
     <XCODE_IPHONE targetFolder="Builds/iOS" vstFolder="~/SDKs/vstsdk2.4" rtasFolder="~/SDKs/PT_80_SDK"
                   objCExtraSuffix="Lpywnl" bigIcon="BvyE0d" iosScreenOrientation="portraitlandscape"
-                  customPList="&lt;plist&gt;&#10;&lt;dict&gt;&#10;&#9;&lt;key&gt;NSAppTransportSecurity&lt;/key&gt;&#10;&#9;&lt;dict&gt;&#10;&#9;&#9;&lt;key&gt;NSAllowsArbitraryLoads&lt;/key&gt;&#10;&#9;&#9;&lt;true/&gt;&#10;&#9;&lt;/dict&gt;&#10;&lt;/dict&gt;&#10;&lt;/plist&gt;">
+                  customPList="&lt;plist&gt;&#10;&lt;dict&gt;&#10;&#9;&lt;key&gt;NSAppTransportSecurity&lt;/key&gt;&#10;&#9;&lt;dict&gt;&#10;&#9;&#9;&lt;key&gt;NSAllowsArbitraryLoads&lt;/key&gt;&#10;&#9;&#9;&lt;true/&gt;&#10;&#9;&lt;/dict&gt;&#10;&lt;/dict&gt;&#10;&lt;/plist&gt;"
+                  microphonePermissionNeeded="1">
       <CONFIGURATIONS>
         <CONFIGURATION name="Debug" isDebug="1" optimisation="1" targetName="JuceDemo"
                        osxSDK="default" osxCompatibility="default" osxArchitecture="default"

modules/juce_audio_devices/native/juce_ios_Audio.cpp

@@ -92,7 +92,7 @@ bool getNotificationValueForKey (NSNotification* notification, NSString* key, NS
 - (id) init: (juce::AudioSessionHolder*) holder;
 - (void) dealloc;
 
-- (void) audioSessionDidChangeInterruptionType: (NSNotification*) notification;
+- (void) audioSessionChangedInterruptionType: (NSNotification*) notification;
 - (void) handleMediaServicesReset;
 - (void) handleMediaServicesLost;
 - (void) handleRouteChange: (NSNotification*) notification;
@@ -112,7 +112,7 @@ bool getNotificationValueForKey (NSNotification* notification, NSString* key, NS
         auto centre = [NSNotificationCenter defaultCenter];
 
         [centre addObserver: self
-                   selector: @selector (audioSessionDidChangeInterruptionType:)
+                   selector: @selector (audioSessionChangedInterruptionType:)
                        name: AVAudioSessionInterruptionNotification
                      object: session];
 
@@ -145,7 +145,7 @@ bool getNotificationValueForKey (NSNotification* notification, NSString* key, NS
     [super dealloc];
 }
 
-- (void) audioSessionDidChangeInterruptionType: (NSNotification*) notification
+- (void) audioSessionChangedInterruptionType: (NSNotification*) notification
 {
     NSUInteger value;
 
@@ -263,6 +263,11 @@ public:
         // depending on whether the headphones are plugged in or not!
         setAudioSessionActive (true);
 
+        AudioUnitRemovePropertyListenerWithUserData (audioUnit,
+                                                     kAudioUnitProperty_StreamFormat,
+                                                     handleStreamFormatChangeCallback,
+                                                     this);
+
         const double lowestRate = trySampleRate (4000);
         const double highestRate = trySampleRate (192000);
 
@@ -274,7 +279,12 @@ public:
             rate = jmax (rate, supportedRate);
         }
 
-        trySampleRate (sampleRate);
+        trySampleRate (getCurrentSampleRate());
+
+        AudioUnitAddPropertyListener (audioUnit,
+                                      kAudioUnitProperty_StreamFormat,
+                                      handleStreamFormatChangeCallback,
+                                      this);
 
         for (auto r : rates)
         {
@@ -289,7 +299,7 @@ public:
     {
         Array<int> r;
 
-        for (int i = 6; i < 12; ++i)
+        for (int i = 6; i < 13; ++i)
             r.add (1 << i);
 
         return r;
@@ -487,7 +497,10 @@ public:
             }
 
             if (callback != nullptr)
+            {
+                callback->audioDeviceStopped();
                 callback->audioDeviceAboutToStart (this);
+            }
         }
     }
 
@@ -618,7 +631,8 @@ private:
         actualBufferSize = roundToInt (sampleRate * session.IOBufferDuration);
 
         JUCE_IOS_AUDIO_LOG ("AVAudioSession: sampleRate: " << sampleRate
-                             << "Hz, audioInputAvailable: " << (int) audioInputIsAvailable);
+                             << " Hz, audioInputAvailable: " << (int) audioInputIsAvailable
+                             << ", buffer size: " << actualBufferSize);
     }
 
     void updateCurrentBufferSize()
@@ -703,18 +717,17 @@ private:
 
         AudioUnitInitialize (audioUnit);
 
-        AudioUnitSetProperty (audioUnit, kAudioUnitProperty_MaximumFramesPerSlice,
-                              kAudioUnitScope_Global, 0, &actualBufferSize, sizeof (actualBufferSize));
-
+        updateCurrentBufferSize();
 
         if (AudioUnitGetProperty (audioUnit, kAudioUnitProperty_MaximumFramesPerSlice,
                                   kAudioUnitScope_Global, 0, &framesPerSlice, &dataSize) == noErr
             && dataSize == sizeof (framesPerSlice) && static_cast<int> (framesPerSlice) != actualBufferSize)
         {
-            actualBufferSize = static_cast<int> (framesPerSlice);
-            prepareFloatBuffers (actualBufferSize);
+            prepareFloatBuffers (framesPerSlice);
         }
 
+        AudioUnitAddPropertyListener (audioUnit, kAudioUnitProperty_StreamFormat, handleStreamFormatChangeCallback, this);
+
         return true;
     }
 
@@ -744,6 +757,39 @@ private:
         }
     }
 
+    void handleStreamFormatChange()
+    {
+        AudioStreamBasicDescription desc;
+        zerostruct (desc);
+        UInt32 dataSize = sizeof (desc);
+        AudioUnitGetProperty(audioUnit,
+                             kAudioUnitProperty_StreamFormat,
+                             kAudioUnitScope_Output,
+                             0,
+                             &desc,
+                             &dataSize);
+        if (desc.mSampleRate != getCurrentSampleRate())
+        {
+            updateSampleRateAndAudioInput();
+            const ScopedLock sl (callbackLock);
+            if (callback != nullptr)
+            {
+                callback->audioDeviceStopped();
+                callback->audioDeviceAboutToStart (this);
+            }
+        }
+    }
+
+    static void handleStreamFormatChangeCallback (void* device,
+                                                  AudioUnit,
+                                                  AudioUnitPropertyID,
+                                                  AudioUnitScope scope,
+                                                  AudioUnitElement element)
+    {
+        if (scope == kAudioUnitScope_Output && element == 0)
+            static_cast<iOSAudioIODevice*> (device)->handleStreamFormatChange();
+    }
+
     JUCE_DECLARE_NON_COPYABLE (iOSAudioIODevice)
 };