JUCE/modules/juce_audio_devices/native/juce_ios_Audio.cpp

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license/

   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.

   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.

   -----------------------------------------------------------------------------

   To release a closed-source product which uses other parts of JUCE not
   licensed under the ISC terms, commercial licenses are available: visit
   www.juce.com for more information.

  ==============================================================================
*/

class iOSAudioIODevice;

static const char* const iOSAudioDeviceName = "iOS Audio";

//==============================================================================
struct AudioSessionHolder      : public AsyncUpdater
{
    AudioSessionHolder();
    ~AudioSessionHolder();

    void handleAsyncUpdate() override;

    void handleStatusChange (bool enabled, const char* reason) const;
    void handleRouteChange (const char* reason);

    CriticalSection routeChangeLock;
    String lastRouteChangeReason;
    Array<iOSAudioIODevice*> activeDevices;

    id nativeSession;
};

static const char* getRoutingChangeReason (AVAudioSessionRouteChangeReason reason) noexcept
{
    switch (reason)
    {
        case AVAudioSessionRouteChangeReasonNewDeviceAvailable:         return "New device available";
        case AVAudioSessionRouteChangeReasonOldDeviceUnavailable:       return "Old device unavailable";
        case AVAudioSessionRouteChangeReasonCategoryChange:             return "Category change";
        case AVAudioSessionRouteChangeReasonOverride:                   return "Override";
        case AVAudioSessionRouteChangeReasonWakeFromSleep:              return "Wake from sleep";
        case AVAudioSessionRouteChangeReasonNoSuitableRouteForCategory: return "No suitable route for category";
        case AVAudioSessionRouteChangeReasonRouteConfigurationChange:   return "Route configuration change";
        case AVAudioSessionRouteChangeReasonUnknown:
        default:                                                        return "Unknown";
    }
}

bool getNotificationValueForKey (NSNotification* notification, NSString* key, NSUInteger& value) noexcept
{
    if (notification != nil)
    {
        if (NSDictionary* userInfo = [notification userInfo])
        {
            if (NSNumber* number = [userInfo objectForKey: key])
            {
                value = [number unsignedIntegerValue];
                return true;
            }
        }
    }

    jassertfalse;
    return false;
}

} // juce namespace

//==============================================================================
@interface iOSAudioSessionNative  : NSObject
{
@private
    juce::AudioSessionHolder* audioSessionHolder;
};

- (id) init: (juce::AudioSessionHolder*) holder;
- (void) dealloc;

- (void) audioSessionChangedInterruptionType: (NSNotification*) notification;
- (void) handleMediaServicesReset;
- (void) handleMediaServicesLost;
- (void) handleRouteChange: (NSNotification*) notification;
@end

@implementation iOSAudioSessionNative

- (id) init: (juce::AudioSessionHolder*) holder
{
    self = [super init];

    if (self != nil)
    {
        audioSessionHolder = holder;

        auto session = [AVAudioSession sharedInstance];
        auto centre = [NSNotificationCenter defaultCenter];

        [centre addObserver: self
                   selector: @selector (audioSessionChangedInterruptionType:)
                       name: AVAudioSessionInterruptionNotification
                     object: session];

        [centre addObserver: self
                   selector: @selector (handleMediaServicesLost)
                       name: AVAudioSessionMediaServicesWereLostNotification
                     object: session];

        [centre addObserver: self
                   selector: @selector (handleMediaServicesReset)
                       name: AVAudioSessionMediaServicesWereResetNotification
                     object: session];

        [centre addObserver: self
                   selector: @selector (handleRouteChange:)
                       name: AVAudioSessionRouteChangeNotification
                     object: session];
    }
    else
    {
        jassertfalse;
    }

    return self;
}

- (void) dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver: self];
    [super dealloc];
}

- (void) audioSessionChangedInterruptionType: (NSNotification*) notification
{
    NSUInteger value;

    if (juce::getNotificationValueForKey (notification, AVAudioSessionInterruptionTypeKey, value))
    {
        switch ((AVAudioSessionInterruptionType) value)
        {
            case AVAudioSessionInterruptionTypeBegan:
                audioSessionHolder->handleStatusChange (false, "AVAudioSessionInterruptionTypeBegan");
                break;

            case AVAudioSessionInterruptionTypeEnded:
                audioSessionHolder->handleStatusChange (true, "AVAudioSessionInterruptionTypeEnded");
                break;

            // No default so the code doesn't compile if this enum is extended.
        }
    }
}

- (void) handleMediaServicesReset
{
    audioSessionHolder->handleStatusChange (true, "AVAudioSessionMediaServicesWereResetNotification");
}

- (void) handleMediaServicesLost
{
    audioSessionHolder->handleStatusChange (false, "AVAudioSessionMediaServicesWereLostNotification");
}

- (void) handleRouteChange: (NSNotification*) notification
{
    NSUInteger value;

    if (juce::getNotificationValueForKey (notification, AVAudioSessionRouteChangeReasonKey, value))
        audioSessionHolder->handleRouteChange (juce::getRoutingChangeReason ((AVAudioSessionRouteChangeReason) value));
}

@end

//==============================================================================
namespace juce {

#ifndef JUCE_IOS_AUDIO_LOGGING
 #define JUCE_IOS_AUDIO_LOGGING 0
#endif

#if JUCE_IOS_AUDIO_LOGGING
 #define JUCE_IOS_AUDIO_LOG(x)  DBG(x)
#else
 #define JUCE_IOS_AUDIO_LOG(x)
#endif

static void logNSError (NSError* e)
{
    if (e != nil)
    {
        JUCE_IOS_AUDIO_LOG ("iOS Audio error: " << [e.localizedDescription UTF8String]);
        jassertfalse;
    }
}

#define JUCE_NSERROR_CHECK(X)     { NSError* error = nil; X; logNSError (error); }

#if JUCE_MODULE_AVAILABLE_juce_graphics
#include <juce_graphics/native/juce_mac_CoreGraphicsHelpers.h>
#endif

//==============================================================================
class iOSAudioIODevice::Pimpl      : public AudioPlayHead,
                                     private AsyncUpdater
{
public:
    Pimpl (iOSAudioIODevice& ioDevice)
        : owner (ioDevice)
    {
        sessionHolder->activeDevices.add (&owner);
    }

    ~Pimpl()
    {
        sessionHolder->activeDevices.removeFirstMatchingValue (&owner);
        owner.close();
    }

    static void setAudioSessionActive (bool enabled)
    {
        JUCE_NSERROR_CHECK ([[AVAudioSession sharedInstance] setActive: enabled
                                                                 error: &error]);
    }

    static double trySampleRate (double rate)
    {
        auto session = [AVAudioSession sharedInstance];
        JUCE_NSERROR_CHECK ([session setPreferredSampleRate: rate
                                                      error: &error]);
        return session.sampleRate;
    }

    Array<double> getAvailableSampleRates()
    {
        Array<double> rates;

        // Important: the supported audio sample rates change on the iPhone 6S
        // 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);

        for (double rate = lowestRate; rate <= highestRate; rate += 1000)
        {
            const double supportedRate = trySampleRate (rate);

            rates.addIfNotAlreadyThere (supportedRate);
            rate = jmax (rate, supportedRate);
        }

        trySampleRate (owner.getCurrentSampleRate());

        AudioUnitAddPropertyListener (audioUnit,
                                      kAudioUnitProperty_StreamFormat,
                                      handleStreamFormatChangeCallback,
                                      this);

        for (auto r : rates)
        {
            ignoreUnused (r);
            JUCE_IOS_AUDIO_LOG ("available rate = " + String (r, 0) + "Hz");
        }

        return rates;
    }

    Array<int> getAvailableBufferSizes()
    {
        Array<int> r;

        for (int i = 6; i < 13; ++i)
            r.add (1 << i);

        return r;
    }

    String open (const BigInteger& inputChannelsWanted,
                 const BigInteger& outputChannelsWanted,
                 double targetSampleRate, int bufferSize)
    {
        close();

        owner.lastError.clear();
        owner.preferredBufferSize = bufferSize <= 0 ? owner.getDefaultBufferSize() : bufferSize;

        //  xxx set up channel mapping

        owner.activeOutputChans = outputChannelsWanted;
        owner.activeOutputChans.setRange (2, owner.activeOutputChans.getHighestBit(), false);
        owner.numOutputChannels = owner.activeOutputChans.countNumberOfSetBits();
        monoOutputChannelNumber = owner.activeOutputChans.findNextSetBit (0);

        owner.activeInputChans = inputChannelsWanted;
        owner.activeInputChans.setRange (2, owner.activeInputChans.getHighestBit(), false);
        owner.numInputChannels = owner.activeInputChans.countNumberOfSetBits();
        monoInputChannelNumber = owner.activeInputChans.findNextSetBit (0);

        setAudioSessionActive (true);

        // Set the session category & options:
        auto session = [AVAudioSession sharedInstance];

        const bool useInputs = (owner.numInputChannels > 0 && owner.audioInputIsAvailable);

        NSString* category = (useInputs ? AVAudioSessionCategoryPlayAndRecord : AVAudioSessionCategoryPlayback);

        NSUInteger options = AVAudioSessionCategoryOptionMixWithOthers; // Alternatively AVAudioSessionCategoryOptionDuckOthers
        if (useInputs) // These options are only valid for category = PlayAndRecord
            options |= (AVAudioSessionCategoryOptionDefaultToSpeaker | AVAudioSessionCategoryOptionAllowBluetooth);

        JUCE_NSERROR_CHECK ([session setCategory: category
                                     withOptions: options
                                           error: &error]);

        fixAudioRouteIfSetToReceiver();

        // Set the sample rate
        trySampleRate (targetSampleRate);
        owner.updateSampleRateAndAudioInput();
        updateCurrentBufferSize();

        prepareFloatBuffers (owner.actualBufferSize);

        owner.isRunning = true;
        handleRouteChange ("Started AudioUnit");

        owner.lastError = (audioUnit != 0 ? "" : "Couldn't open the device");

        setAudioSessionActive (true);

        return owner.lastError;
    }

    void close()
    {
        if (owner.isRunning)
        {
            owner.isRunning = false;

            if (audioUnit != 0)
            {
                AudioOutputUnitStart (audioUnit);
                AudioComponentInstanceDispose (audioUnit);
                audioUnit = 0;
            }

            setAudioSessionActive (false);
        }
    }

    void start (AudioIODeviceCallback* newCallback)
    {
        if (owner.isRunning && owner.callback != newCallback)
        {
            if (newCallback != nullptr)
                newCallback->audioDeviceAboutToStart (&owner);

            const ScopedLock sl (callbackLock);
            owner.callback = newCallback;
        }
    }

    void stop()
    {
        if (owner.isRunning)
        {
            AudioIODeviceCallback* lastCallback;

            {
                const ScopedLock sl (callbackLock);
                lastCallback = owner.callback;
                owner.callback = nullptr;
            }

            if (lastCallback != nullptr)
                lastCallback->audioDeviceStopped();
        }
    }

    bool setAudioPreprocessingEnabled (bool enable)
    {
        auto session = [AVAudioSession sharedInstance];

        NSString* mode = (enable ? AVAudioSessionModeMeasurement
                                 : AVAudioSessionModeDefault);

        JUCE_NSERROR_CHECK ([session setMode: mode
                                       error: &error]);

        return session.mode == mode;
    }

    //==============================================================================
    bool canControlTransport() override                    { return owner.interAppAudioConnected; }

    void transportPlay (bool shouldSartPlaying) override
    {
        if (! canControlTransport())
            return;

        HostCallbackInfo callbackInfo;
        fillHostCallbackInfo (callbackInfo);

        Boolean hostIsPlaying = NO;
        OSStatus err = callbackInfo.transportStateProc2 (callbackInfo.hostUserData,
                                                         &hostIsPlaying,
                                                         nullptr,
                                                         nullptr,
                                                         nullptr,
                                                         nullptr,
                                                         nullptr,
                                                         nullptr);

        ignoreUnused (err);
        jassert (err == noErr);

        if (hostIsPlaying != shouldSartPlaying)
            handleAudioTransportEvent (kAudioUnitRemoteControlEvent_TogglePlayPause);
    }

    void transportRecord (bool shouldStartRecording) override
    {
        if (! canControlTransport())
            return;

        HostCallbackInfo callbackInfo;
        fillHostCallbackInfo (callbackInfo);

        Boolean hostIsRecording = NO;
        OSStatus err = callbackInfo.transportStateProc2 (callbackInfo.hostUserData,
                                                         nullptr,
                                                         &hostIsRecording,
                                                         nullptr,
                                                         nullptr,
                                                         nullptr,
                                                         nullptr,
                                                         nullptr);
        ignoreUnused (err);
        jassert (err == noErr);

        if (hostIsRecording != shouldStartRecording)
            handleAudioTransportEvent (kAudioUnitRemoteControlEvent_ToggleRecord);
    }

    void transportRewind() override
    {
        if (canControlTransport())
            handleAudioTransportEvent (kAudioUnitRemoteControlEvent_Rewind);
    }

    bool getCurrentPosition (CurrentPositionInfo& result) override
    {
        if (! canControlTransport())
            return false;

        zerostruct (result);

        HostCallbackInfo callbackInfo;
        fillHostCallbackInfo (callbackInfo);

        if (callbackInfo.hostUserData == nullptr)
            return false;

        Boolean hostIsPlaying               = NO;
        Boolean hostIsRecording             = NO;
        Float64 hostCurrentSampleInTimeLine = 0;
        Boolean hostIsCycling               = NO;
        Float64 hostCycleStartBeat          = 0;
        Float64 hostCycleEndBeat            = 0;
        OSStatus err = callbackInfo.transportStateProc2 (callbackInfo.hostUserData,
                                                         &hostIsPlaying,
                                                         &hostIsRecording,
                                                         nullptr,
                                                         &hostCurrentSampleInTimeLine,
                                                         &hostIsCycling,
                                                         &hostCycleStartBeat,
                                                         &hostCycleEndBeat);
        if (err == kAUGraphErr_CannotDoInCurrentContext)
            return false;

        jassert (err == noErr);

        result.timeInSamples = (int64) hostCurrentSampleInTimeLine;
        result.isPlaying     = hostIsPlaying;
        result.isRecording   = hostIsRecording;
        result.isLooping     = hostIsCycling;
        result.ppqLoopStart  = hostCycleStartBeat;
        result.ppqLoopEnd    = hostCycleEndBeat;

        result.timeInSeconds = result.timeInSamples / owner.sampleRate;

        Float64 hostBeat = 0;
        Float64 hostTempo = 0;
        err = callbackInfo.beatAndTempoProc (callbackInfo.hostUserData,
                                             &hostBeat,
                                             &hostTempo);
        jassert (err == noErr);

        result.ppqPosition = hostBeat;
        result.bpm         = hostTempo;

        Float32 hostTimeSigNumerator = 0;
        UInt32 hostTimeSigDenominator = 0;
        Float64 hostCurrentMeasureDownBeat = 0;
        err = callbackInfo.musicalTimeLocationProc (callbackInfo.hostUserData,
                                                    nullptr,
                                                    &hostTimeSigNumerator,
                                                    &hostTimeSigDenominator,
                                                    &hostCurrentMeasureDownBeat);
        jassert (err == noErr);

        result.ppqPositionOfLastBarStart = hostCurrentMeasureDownBeat;
        result.timeSigNumerator          = (int) hostTimeSigNumerator;
        result.timeSigDenominator        = (int) hostTimeSigDenominator;

        result.frameRate = AudioPlayHead::fpsUnknown;

        return true;
    }

    //==============================================================================
   #if JUCE_MODULE_AVAILABLE_juce_graphics
    Image getIcon (int size)
    {
        if (owner.interAppAudioConnected)
        {
            UIImage* hostUIImage = AudioOutputUnitGetHostIcon (audioUnit, size);
            if (hostUIImage != nullptr)
                return juce_createImageFromUIImage (hostUIImage);
        }
        return Image();
    }
   #endif

    void switchApplication()
    {
        if (! owner.interAppAudioConnected)
            return;

        CFURLRef hostUrl;
        UInt32 dataSize = sizeof (hostUrl);
        OSStatus err = AudioUnitGetProperty(audioUnit,
                                            kAudioUnitProperty_PeerURL,
                                            kAudioUnitScope_Global,
                                            0,
                                            &hostUrl,
                                            &dataSize);
        if (err == noErr)
            [[UIApplication sharedApplication] openURL:(NSURL*)hostUrl];
    }

    //==============================================================================
    void invokeAudioDeviceErrorCallback (const String& reason)
    {
        const ScopedLock sl (callbackLock);

        if (owner.callback != nullptr)
            owner.callback->audioDeviceError (reason);
    }

    void handleStatusChange (bool enabled, const char* reason)
    {
        const ScopedLock myScopedLock (callbackLock);

        JUCE_IOS_AUDIO_LOG ("handleStatusChange: enabled: " << (int) enabled << ", reason: " << reason);

        owner.isRunning = enabled;
        setAudioSessionActive (enabled);

        if (enabled)
            AudioOutputUnitStart (audioUnit);
        else
            AudioOutputUnitStop (audioUnit);

        if (! enabled)
            invokeAudioDeviceErrorCallback (reason);
    }

    void handleRouteChange (const char* reason)
    {
        const ScopedLock myScopedLock (callbackLock);

        JUCE_IOS_AUDIO_LOG ("handleRouteChange: reason: " << reason);

        fixAudioRouteIfSetToReceiver();

        if (owner.isRunning)
        {
            invokeAudioDeviceErrorCallback (reason);
            owner.updateSampleRateAndAudioInput();
            updateCurrentBufferSize();
            createAudioUnit();

            setAudioSessionActive (true);

            if (audioUnit != 0)
            {
                UInt32 formatSize = sizeof (format);
                AudioUnitGetProperty (audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &format, &formatSize);
                AudioOutputUnitStart (audioUnit);
            }

            if (owner.callback != nullptr)
            {
                owner.callback->audioDeviceStopped();
                owner.callback->audioDeviceAboutToStart (&owner);
            }
        }
    }

    void handleAudioUnitPropertyChange (AudioUnit,
                                        AudioUnitPropertyID propertyID,
                                        AudioUnitScope,
                                        AudioUnitElement)
    {
        const ScopedLock myScopedLock (callbackLock);

        switch (propertyID)
        {
            case kAudioUnitProperty_IsInterAppConnected: return handleInterAppAudioConnectionChange();
            default: return;
        }
    }

    void handleInterAppAudioConnectionChange()
    {
        UInt32 connected;
        UInt32 dataSize = sizeof (connected);
        OSStatus err = AudioUnitGetProperty (audioUnit, kAudioUnitProperty_IsInterAppConnected,
                                             kAudioUnitScope_Global, 0, &connected, &dataSize);
        ignoreUnused (err);
        jassert (err == noErr);

        JUCE_IOS_AUDIO_LOG ("handleInterAppAudioConnectionChange: " << (connected ? "connected"
                                                                                  : "disconnected"));

        if (connected != owner.interAppAudioConnected)
        {
            const ScopedLock myScopedLock (callbackLock);

            owner.interAppAudioConnected = connected;

            UIApplicationState appstate = [UIApplication sharedApplication].applicationState;
            bool inForeground = (appstate != UIApplicationStateBackground);

            if (owner.interAppAudioConnected || inForeground)
            {
                setAudioSessionActive (true);
                AudioOutputUnitStart (audioUnit);

                if (owner.callback != nullptr)
                    owner.callback->audioDeviceAboutToStart (&owner);
            }
            else if (! inForeground)
            {
                AudioOutputUnitStop (audioUnit);
                setAudioSessionActive (false);
            }
        }
    }

private:
    //==============================================================================
    iOSAudioIODevice& owner;
    SharedResourcePointer<AudioSessionHolder> sessionHolder;
    CriticalSection callbackLock;

    AudioStreamBasicDescription format;
    AudioUnit audioUnit {};

    AudioSampleBuffer floatData;
    float* inputChannels[3];
    float* outputChannels[3];
    bool monoInputChannelNumber, monoOutputChannelNumber;

    void prepareFloatBuffers (int bufferSize)
    {
        if (owner.numInputChannels + owner.numOutputChannels > 0)
        {
            floatData.setSize (owner.numInputChannels + owner.numOutputChannels, bufferSize);
            zeromem (inputChannels, sizeof (inputChannels));
            zeromem (outputChannels, sizeof (outputChannels));

            for (int i = 0; i < owner.numInputChannels; ++i)
                inputChannels[i] = floatData.getWritePointer (i);

            for (int i = 0; i < owner.numOutputChannels; ++i)
                outputChannels[i] = floatData.getWritePointer (i + owner.numInputChannels);
        }
    }

    //==============================================================================
    OSStatus process (AudioUnitRenderActionFlags* flags, const AudioTimeStamp* time,
                      const UInt32 numFrames, AudioBufferList* data)
    {
        OSStatus err = noErr;

        if (owner.audioInputIsAvailable && owner.numInputChannels > 0)
            err = AudioUnitRender (audioUnit, flags, time, 1, numFrames, data);

        const ScopedTryLock stl (callbackLock);

        if (stl.isLocked() && owner.callback != nullptr)
        {
            if ((int) numFrames > floatData.getNumSamples())
                prepareFloatBuffers ((int) numFrames);

            if (owner.audioInputIsAvailable && owner.numInputChannels > 0)
            {
                short* shortData = (short*) data->mBuffers[0].mData;

                if (owner.numInputChannels >= 2)
                {
                    for (UInt32 i = 0; i < numFrames; ++i)
                    {
                        inputChannels[0][i] = *shortData++ * (1.0f / 32768.0f);
                        inputChannels[1][i] = *shortData++ * (1.0f / 32768.0f);
                    }
                }
                else
                {
                    if (monoInputChannelNumber > 0)
                        ++shortData;

                    for (UInt32 i = 0; i < numFrames; ++i)
                    {
                        inputChannels[0][i] = *shortData++ * (1.0f / 32768.0f);
                        ++shortData;
                    }
                }
            }
            else
            {
                for (int i = owner.numInputChannels; --i >= 0;)
                    zeromem (inputChannels[i], sizeof (float) * numFrames);
            }

            owner.callback->audioDeviceIOCallback ((const float**) inputChannels, owner.numInputChannels,
                                                   outputChannels, owner.numOutputChannels, (int) numFrames);

            short* const shortData = (short*) data->mBuffers[0].mData;
            int n = 0;

            if (owner.numOutputChannels >= 2)
            {
                for (UInt32 i = 0; i < numFrames; ++i)
                {
                    shortData [n++] = (short) (outputChannels[0][i] * 32767.0f);
                    shortData [n++] = (short) (outputChannels[1][i] * 32767.0f);
                }
            }
            else if (owner.numOutputChannels == 1)
            {
                for (UInt32 i = 0; i < numFrames; ++i)
                {
                    const short s = (short) (outputChannels[monoOutputChannelNumber][i] * 32767.0f);
                    shortData [n++] = s;
                    shortData [n++] = s;
                }
            }
            else
            {
                zeromem (data->mBuffers[0].mData, 2 * sizeof (short) * numFrames);
            }
        }
        else
        {
            zeromem (data->mBuffers[0].mData, 2 * sizeof (short) * numFrames);
        }

        return err;
    }

    void updateCurrentBufferSize()
    {
        NSTimeInterval bufferDuration = owner.sampleRate > 0 ? (NSTimeInterval) ((owner.preferredBufferSize + 1) / owner.sampleRate) : 0.0;

        JUCE_NSERROR_CHECK ([[AVAudioSession sharedInstance] setPreferredIOBufferDuration: bufferDuration
                                                                                    error: &error]);
        owner.updateSampleRateAndAudioInput();
    }

    //==============================================================================
    static OSStatus processStatic (void* client, AudioUnitRenderActionFlags* flags, const AudioTimeStamp* time,
                                   UInt32 /*busNumber*/, UInt32 numFrames, AudioBufferList* data)
    {

        return static_cast<Pimpl*> (client)->process (flags, time, numFrames, data);
    }

    //==============================================================================
    void resetFormat (const int numChannels) noexcept
    {
        zerostruct (format);
        format.mFormatID = kAudioFormatLinearPCM;
        format.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked | kAudioFormatFlagsNativeEndian;
        format.mBitsPerChannel = 8 * sizeof (short);
        format.mChannelsPerFrame = (UInt32) numChannels;
        format.mFramesPerPacket = 1;
        format.mBytesPerFrame = format.mBytesPerPacket = (UInt32) numChannels * sizeof (short);
    }

    bool createAudioUnit()
    {
        if (audioUnit != 0)
        {
            AudioComponentInstanceDispose (audioUnit);
            audioUnit = 0;
        }

        resetFormat (2);

        AudioComponentDescription desc;
        desc.componentType = kAudioUnitType_Output;
        desc.componentSubType = kAudioUnitSubType_RemoteIO;
        desc.componentManufacturer = kAudioUnitManufacturer_Apple;
        desc.componentFlags = 0;
        desc.componentFlagsMask = 0;

        AudioComponent comp = AudioComponentFindNext (0, &desc);
        AudioComponentInstanceNew (comp, &audioUnit);

        if (audioUnit == 0)
            return false;

       #if JucePlugin_Enable_IAA
        AudioComponentDescription appDesc;
        appDesc.componentType = JucePlugin_IAAType;
        appDesc.componentSubType = JucePlugin_IAASubType;
        appDesc.componentManufacturer = JucePlugin_ManufacturerCode;
        appDesc.componentFlags = 0;
        appDesc.componentFlagsMask = 0;
        OSStatus err = AudioOutputUnitPublish (&appDesc,
                                               CFSTR(JucePlugin_IAAName),
                                               JucePlugin_VersionCode,
                                               audioUnit);

        // This assert will be hit if the Inter-App Audio entitlement has not
        // been enabled, or the description being published with
        // AudioOutputUnitPublish is different from any in the AudioComponents
        // array in this application's .plist file.
        jassert (err == noErr);

        err = AudioUnitAddPropertyListener(audioUnit,
                                           kAudioUnitProperty_IsInterAppConnected,
                                           audioUnitPropertyChangeDispatcher,
                                           this);
        jassert (err == noErr);
       #endif

        if (owner.numInputChannels > 0)
        {
            const UInt32 one = 1;
            AudioUnitSetProperty (audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &one, sizeof (one));
        }

        {
            AudioChannelLayout layout;
            layout.mChannelBitmap = 0;
            layout.mNumberChannelDescriptions = 0;
            layout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
            AudioUnitSetProperty (audioUnit, kAudioUnitProperty_AudioChannelLayout, kAudioUnitScope_Input,  0, &layout, sizeof (layout));
            AudioUnitSetProperty (audioUnit, kAudioUnitProperty_AudioChannelLayout, kAudioUnitScope_Output, 0, &layout, sizeof (layout));
        }

        {
            AURenderCallbackStruct inputProc;
            inputProc.inputProc = processStatic;
            inputProc.inputProcRefCon = this;
            AudioUnitSetProperty (audioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, 0, &inputProc, sizeof (inputProc));
        }

        AudioUnitSetProperty (audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input,  0, &format, sizeof (format));
        AudioUnitSetProperty (audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &format, sizeof (format));

        UInt32 framesPerSlice;
        UInt32 dataSize = sizeof (framesPerSlice);

        AudioUnitInitialize (audioUnit);

        updateCurrentBufferSize();

        if (AudioUnitGetProperty (audioUnit, kAudioUnitProperty_MaximumFramesPerSlice,
                                  kAudioUnitScope_Global, 0, &framesPerSlice, &dataSize) == noErr
            && dataSize == sizeof (framesPerSlice) && static_cast<int> (framesPerSlice) != owner.actualBufferSize)
        {
            prepareFloatBuffers (static_cast<int> (framesPerSlice));
        }

        AudioUnitAddPropertyListener (audioUnit, kAudioUnitProperty_StreamFormat, handleStreamFormatChangeCallback, this);

        return true;
    }

    void fillHostCallbackInfo (HostCallbackInfo& callbackInfo)
    {
        zerostruct (callbackInfo);
        UInt32 dataSize = sizeof (HostCallbackInfo);
        OSStatus err = AudioUnitGetProperty (audioUnit,
                                             kAudioUnitProperty_HostCallbacks,
                                             kAudioUnitScope_Global,
                                             0,
                                             &callbackInfo,
                                             &dataSize);
        ignoreUnused (err);
        jassert (err == noErr);
    }

    void handleAudioTransportEvent (AudioUnitRemoteControlEvent event)
    {
        OSStatus err = AudioUnitSetProperty (audioUnit, kAudioOutputUnitProperty_RemoteControlToHost,
                                             kAudioUnitScope_Global, 0, &event, sizeof (event));
        ignoreUnused (err);
        jassert (err == noErr);
    }

    // If the routing is set to go through the receiver (i.e. the speaker, but quiet), this re-routes it
    // to make it loud. Needed because by default when using an input + output, the output is kept quiet.
    static void fixAudioRouteIfSetToReceiver()
    {
        auto session = [AVAudioSession sharedInstance];
        auto route = session.currentRoute;

        for (AVAudioSessionPortDescription* port in route.inputs)
        {
            ignoreUnused (port);
            JUCE_IOS_AUDIO_LOG ("AVAudioSession: input: " << [port.description UTF8String]);
        }

        for (AVAudioSessionPortDescription* port in route.outputs)
        {
            JUCE_IOS_AUDIO_LOG ("AVAudioSession: output: " << [port.description UTF8String]);

            if ([port.portName isEqualToString: @"Receiver"])
            {
                JUCE_NSERROR_CHECK ([session overrideOutputAudioPort: AVAudioSessionPortOverrideSpeaker
                                                               error: &error]);
                setAudioSessionActive (true);
            }
        }
    }

    void handleAsyncUpdate() override
    {
        owner.handleRouteChange ("Stream format change");
    }

    void handleStreamFormatChange()
    {
        AudioStreamBasicDescription desc;
        zerostruct (desc);
        UInt32 dataSize = sizeof (desc);
        AudioUnitGetProperty(audioUnit,
                             kAudioUnitProperty_StreamFormat,
                             kAudioUnitScope_Output,
                             0,
                             &desc,
                             &dataSize);

        if (desc.mSampleRate != owner.getCurrentSampleRate())
            triggerAsyncUpdate();
    }

    static void handleStreamFormatChangeCallback (void* device,
                                                  AudioUnit,
                                                  AudioUnitPropertyID,
                                                  AudioUnitScope scope,
                                                  AudioUnitElement element)
    {
        if (scope == kAudioUnitScope_Output && element == 0)
            static_cast<Pimpl*> (device)->handleStreamFormatChange();
    }

    static void audioUnitPropertyChangeDispatcher (void* data, AudioUnit unit, AudioUnitPropertyID propertyID,
                                                   AudioUnitScope scope, AudioUnitElement element)
    {
        Pimpl* device = (Pimpl*)data;
        device->handleAudioUnitPropertyChange (unit, propertyID, scope, element);
    }

    void handleMidiMessage (MidiMessage msg)
    {
        if (owner.messageCollector != nullptr)
            owner.messageCollector->addMessageToQueue (msg);
    }

    static void midiEventCallback (void *client, UInt32 status, UInt32 data1, UInt32 data2, UInt32)
    {
        return static_cast<Pimpl*> (client)->handleMidiMessage (MidiMessage ((int) status,
                                                                             (int) data1,
                                                                             (int) data2,
                                                                             Time::getMillisecondCounter() / 1000.0));
    }

    JUCE_DECLARE_NON_COPYABLE (Pimpl)
};


//==============================================================================
iOSAudioIODevice::iOSAudioIODevice (const String& deviceName)
    : AudioIODevice (deviceName, iOSAudioDeviceName),
     #if TARGET_IPHONE_SIMULATOR
      defaultBufferSize (512),
     #else
      defaultBufferSize (256),
     #endif
      sampleRate (0), numInputChannels (2), numOutputChannels (2),
      preferredBufferSize (0), actualBufferSize (0), isRunning (false),
      audioInputIsAvailable (false), interAppAudioConnected (false),
      callback (nullptr), messageCollector (nullptr),
      pimpl (new Pimpl (*this))
{
    updateSampleRateAndAudioInput();
}

//==============================================================================
int iOSAudioIODevice::getOutputLatencyInSamples()     { return roundToInt (sampleRate * [AVAudioSession sharedInstance].outputLatency); }
int iOSAudioIODevice::getInputLatencyInSamples()      { return roundToInt (sampleRate * [AVAudioSession sharedInstance].inputLatency); }

//==============================================================================
AudioPlayHead* iOSAudioIODevice::getAudioPlayHead() const           { return pimpl; }
void iOSAudioIODevice::close()                                      { pimpl->close(); }
void iOSAudioIODevice::start (AudioIODeviceCallback* callbackToUse) { pimpl->start (callbackToUse); }
void iOSAudioIODevice::stop()                                       { pimpl->stop(); }
Array<double> iOSAudioIODevice::getAvailableSampleRates()           { return pimpl->getAvailableSampleRates(); }
Array<int> iOSAudioIODevice::getAvailableBufferSizes()              { return pimpl->getAvailableBufferSizes(); }
bool iOSAudioIODevice::setAudioPreprocessingEnabled (bool enabled)  { return pimpl->setAudioPreprocessingEnabled (enabled); }
void iOSAudioIODevice::switchApplication()                          { return pimpl->switchApplication(); }

//==============================================================================
void iOSAudioIODevice::handleStatusChange (bool enabled, const char* reason)   { pimpl->handleStatusChange (enabled, reason); }
void iOSAudioIODevice::handleRouteChange (const char* reason)                  { pimpl->handleRouteChange (reason); }

#if JUCE_MODULE_AVAILABLE_juce_graphics
Image iOSAudioIODevice::getIcon (int size)                                     { return pimpl->getIcon (size); }
#endif

//==============================================================================
String iOSAudioIODevice::open (const BigInteger& inChans, const BigInteger& outChans, double requestedSampleRate, int requestedBufferSize)
{
    return pimpl->open (inChans, outChans, requestedSampleRate, requestedBufferSize);
}

void iOSAudioIODevice::updateSampleRateAndAudioInput()
{
    auto session = [AVAudioSession sharedInstance];
    sampleRate = session.sampleRate;
    audioInputIsAvailable = session.isInputAvailable;
    actualBufferSize = roundToInt (sampleRate * session.IOBufferDuration);

    JUCE_IOS_AUDIO_LOG ("AVAudioSession: sampleRate: " << sampleRate
                         << " Hz, audioInputAvailable: " << (int) audioInputIsAvailable
                         << ", buffer size: " << actualBufferSize);
}

//==============================================================================
class iOSAudioIODeviceType  : public AudioIODeviceType
{
public:
    iOSAudioIODeviceType()  : AudioIODeviceType (iOSAudioDeviceName) {}

    void scanForDevices() {}
    StringArray getDeviceNames (bool /*wantInputNames*/) const       { return StringArray (iOSAudioDeviceName); }
    int getDefaultDeviceIndex (bool /*forInput*/) const              { return 0; }
    int getIndexOfDevice (AudioIODevice* d, bool /*asInput*/) const  { return d != nullptr ? 0 : -1; }
    bool hasSeparateInputsAndOutputs() const                         { return false; }

    AudioIODevice* createDevice (const String& outputDeviceName, const String& inputDeviceName)
    {
        if (outputDeviceName.isNotEmpty() || inputDeviceName.isNotEmpty())
            return new iOSAudioIODevice (outputDeviceName.isNotEmpty() ? outputDeviceName : inputDeviceName);

        return nullptr;
    }

private:
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (iOSAudioIODeviceType)
};

//==============================================================================
AudioIODeviceType* AudioIODeviceType::createAudioIODeviceType_iOSAudio()
{
    return new iOSAudioIODeviceType();
}

//==============================================================================
AudioSessionHolder::AudioSessionHolder()    { nativeSession = [[iOSAudioSessionNative alloc] init: this]; }
AudioSessionHolder::~AudioSessionHolder()   { [nativeSession release]; }

void AudioSessionHolder::handleAsyncUpdate()
{
    const ScopedLock sl (routeChangeLock);
    for (auto device: activeDevices)
        device->handleRouteChange (lastRouteChangeReason.toRawUTF8());
}

void AudioSessionHolder::handleStatusChange (bool enabled, const char* reason) const
{
    for (auto device: activeDevices)
        device->handleStatusChange (enabled, reason);
}

void AudioSessionHolder::handleRouteChange (const char* reason)
{
    const ScopedLock sl (routeChangeLock);
    lastRouteChangeReason = reason;
    triggerAsyncUpdate();
}

#undef JUCE_NSERROR_CHECK