/*

    File:       CoreAudioPlayback.c

    Abstract:   Utility functions for building a simple AUGraph

                 to play buffers of audio data.

    Version:    1.0

                Originally introduced at WWDC 2005 at Session 201:

                "Harnessing the Audio Capabilities of QuickTime 7" 

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    MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

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    OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.

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    Copyright © 2005-2008 Apple Inc. All Rights Reserved.

*/

#include "CoreAudioPlayback.h"

// Return a ComponentDescription for a default output device AU

static void ConfigureOutputDescription(ComponentDescription *inOutputDesc)

{

    inOutputDesc->componentType = kAudioUnitType_Output;

    inOutputDesc->componentSubType = kAudioUnitSubType_DefaultOutput;

    inOutputDesc->componentManufacturer = kAudioUnitManufacturer_Apple;

    inOutputDesc->componentFlags = 0;

    inOutputDesc->componentFlagsMask = 0;

}

// Set the stream format on the output device AU.

// This only needs to set the input scope, since the output describes the audio hw settings.

static OSStatus SetOutputUnitStreamFormat(AudioUnit outputUnit, AudioStreamBasicDescription *asbd)

{

    return (AudioUnitSetProperty(outputUnit, kAudioUnitProperty_StreamFormat,

                                 kAudioUnitScope_Input, 0, asbd, sizeof(AudioStreamBasicDescription)));

}

// Set the channel layout on the output device AU.

// This only needs to set the input scope, since the output describes the audio hw settings.

// Setting the channel layout here helps route channels properly, but note that the OutputAU

// does not do channel mixdown.

static OSStatus SetOutputUnitChannelLayout(AudioUnit outputUnit, QTPropertyValuePtr layoutProperty, UInt32 size)

{

    return (AudioUnitSetProperty(outputUnit, kAudioUnitProperty_AudioChannelLayout,

                                 kAudioUnitScope_Input,0, layoutProperty, size));

}

// Return a ComponentDescription for a ScheduledSoundPlayer AU

static void ConfigureScheduledPlayerDescription(ComponentDescription *inPlayerDesc)

{

    inPlayerDesc->componentType = kAudioUnitType_Generator;

    inPlayerDesc->componentSubType = kAudioUnitSubType_ScheduledSoundPlayer;

    inPlayerDesc->componentManufacturer = kAudioUnitManufacturer_Apple;

    inPlayerDesc->componentFlags = 0;

    inPlayerDesc->componentFlagsMask = 0;

}   

// Set the stream format on the ScheduledSoundPlayer AU.

// This only needs to set the output scope, since the unit doesn't have an input scope.

static OSStatus SetPlayerUnitStreamFormat(AudioUnit playerUnit, AudioStreamBasicDescription *asbd)

{

    return (AudioUnitSetProperty(playerUnit, kAudioUnitProperty_StreamFormat,

                                 kAudioUnitScope_Output, 0, asbd, sizeof(AudioStreamBasicDescription)));

}

// Build a simple AUGraph containing a Default Output AU sourced by a ScheduledSoundPlayer AU.

// This allows us to schedule (from any thread) buffers of audio data to play automatically.

OSStatus BuildAUGraphPlayer(AudioChannelLayout *layout, UInt32 layoutSize,

                            AudioStreamBasicDescription *asbd,

                            AUGraphPlayerRef *graphUnit, AudioUnit *thePlayerUnit)

{

    OSStatus err = noErr;

    // Create a new AUGraph

    *graphUnit = nil;

    err = NewAUGraph(graphUnit);

    if (err) 

    {

        goto bail;  

    }

    // Add an output unit, and a scheduled sound player unit

    // Configure the two units.  

    ComponentDescription    output_desc, player_desc;

    ConfigureOutputDescription(&output_desc);

    ConfigureScheduledPlayerDescription(&player_desc);

    // Create new nodes inside our AUGraph for the output unit

    // and the AUScheduledSoundPlayer unit.

    AUNode outputNode, playerNode;

    err = AUGraphAddNode(*graphUnit, &output_desc, &outputNode);

    if (err)        

    {

        goto bail;

    }   

    err = AUGraphAddNode(*graphUnit, &player_desc, &playerNode);

    if (err) 

    {

        goto bail;

    }

    // Connect the two graph nodes together and specify the way inputs are ordered.

    // The player node will route its output to the output node

    // connect the player to the output unit. 

    err = AUGraphConnectNodeInput(*graphUnit, playerNode, 0, outputNode, 0);

    if (err) 

    {

        goto bail;

    }                                 

    // Open the graph: Instantiates every Audio Unit in the graph.

    err = AUGraphOpen(*graphUnit);

    if (err) 

    {

        goto bail;  

    }

    // Get the output unit & the player unit from their respective nodes    

    AudioUnit theOutputUnit;

    err = AUGraphNodeInfo(*graphUnit, outputNode, NULL, &theOutputUnit);

    if (err) 

    {

        goto bail;

    }   

    err = AUGraphNodeInfo(*graphUnit, playerNode, NULL, thePlayerUnit);

    if (err) 

    {

        goto bail;

    }

    // Configure stream formats of the output and player to the specified format

    err = SetOutputUnitStreamFormat(theOutputUnit, asbd);

    if (err) 

    {

        goto bail;

    }   

    err = SetPlayerUnitStreamFormat(*thePlayerUnit, asbd);

    if (err) 

    {

        goto bail;

    }

    // Get the extraction channel layout and map the output device

    err = SetOutputUnitChannelLayout(theOutputUnit, layout, layoutSize);

    if (err) 

    {

        goto bail;

    }                                   

    // Initialize the graph

    err = AUGraphInitialize(*graphUnit);

    if (err) 

    {

        goto bail;

    }   

bail:

    if (err && (*graphUnit != nil))

    {

        AUGraphClose(*graphUnit);

    }   

    return (err);       

}

// Start the player graph running.

OSStatus StartAUGraphPlayer(AUGraphPlayerRef graphUnit)

{

    OSStatus    err = noErr;

    UInt32      numNodes;

    AudioUnit   playerUnit = nil;

    // Start the AUGraph

    err = AUGraphStart(graphUnit);

    if (err)

    {

        goto bail;

    }

    // Locate the AUScheduledSoundPlayer that we need to start.

    // It was added last, so its node number is the node count.

    err = AUGraphGetNodeCount(graphUnit, &numNodes);

    if (!err)

    {

        err = AUGraphNodeInfo(graphUnit, numNodes, NULL, &playerUnit);

    }   

    if (err || (playerUnit == nil))

    {

        goto bail;

    }

    // Start playback of the scheduledPlayer unit by setting its start time.

    AudioTimeStamp theTimeStamp = {0};

    theTimeStamp.mFlags = kAudioTimeStampSampleTimeValid;

    theTimeStamp.mSampleTime = -1.;     // start now

    err = AudioUnitSetProperty(playerUnit,

                kAudioUnitProperty_ScheduleStartTimeStamp, kAudioUnitScope_Global, 0,

                &theTimeStamp, sizeof(theTimeStamp));

bail:

    return (err);

}

void StopAUGraphPlayer(AUGraphPlayerRef graphUnit)

{

    if (graphUnit != nil) 

    {   

        (void) AUGraphStop(graphUnit);

        (void) AUGraphUninitialize(graphUnit);

    }

}

void CloseAUGraphPlayer(AUGraphPlayerRef graphUnit)

{

    if (graphUnit != nil) 

    {   

        StopAUGraphPlayer(graphUnit);

        (void) AUGraphClose(graphUnit);

    }

}