NLRemoteIOAudioPlayer.h

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//
//  NLRemoteIOAudioPlayer.h
//
//  Created by Nicholas Levin on 3/31/11.
//  Copyright (c) 2010 Thames Galley Software. All rights reserved.
//

#import <AudioToolbox/AudioToolbox.h>	// for Audio Units and Extended Audio File Services APIs.
#import <CoreMedia/CMTime.h>            // for CMTime structs

#pragma mark Sound buffer structure for render callback

// Data structure for mono or stereo sound, to pass to the application's render callback function, 
//    which gets invoked by a RemoteIO unit's input bus when it needs more audio to play.
typedef struct {
    
    BOOL                            isStereo;					// set to true if there is data in the audioDataRightBuffers member
	
	UInt32                          framesPerBuffer;			// regulates how many frames we can play before moving to a new buffer
    UInt32                          readSampleNumber;			// the next audio sample to play
	UInt32                          fixedFramesForThisCallback; // temp storage to hold the number of frames requested by the AU when the callback starts
	
    AudioUnitSampleType             **audioDataLeftBuffers;     // the buffers for the left (or mono) channel of audio data read from an audio file
    AudioUnitSampleType             **audioDataRightBuffers;	// the buffers for the right channel of audio data read from an audio file
	
    unsigned char                   numBuffers;                 // the number of buffers allocated for this Rio Player
    unsigned char                   audioDataCurrentBuffer;     // the buffer that the render callback is currently reading from
    int32_t                         requestNextBuffer;			// indicates to the ring buffer selector when we need a new sample
    
	
} soundStruct, *soundStructPtr;


// As many operations need to update the UI, we have a delegate with a defined protocol
@protocol NLRemoteIOAudioPlayerDelegate

@optional
- (void) updateViewForRemoteIOAudioPlayerState;
- (void) updateViewForRemoteIOAudioPlayerDuration;
- (void) rioPlaybackDidEnd;
- (void) updateViewForRemoteIOAudioPlayerAlbumInfo;

@end


class NLRemoteIOAudioPlayer { 

private:
        
	soundStruct                     soundStructUnit;
    
	
	CFURLRef						audioFileReference;		// refers to our current audio file as indicated by readAudioFileIntoMemoryWithURL
	ExtAudioFileRef					audioFileObject;
    AudioStreamBasicDescription     streamFormat;
	AudioUnit						RioAudioPlayer;
    
	AudioBufferList*				ringBufferList;
    dispatch_queue_t                ringBufferQueue;
    dispatch_source_t               ringBufferCycle;
	
	UInt32							framesToReadFromFile;	// NOTE: Multiples of 1024 are necessary to match the AU's slices.
    UInt64                          framesRemainingInFile;
	SInt64							estimatedIterationsBeforeEOF;
    
	SInt64							extAFSOffset;			// compensating for the EAFS bug that affects AAC and Apple Lossless files 
    
    dispatch_queue_t                scrollQueue;
    uint32_t                        cancelScrollQueue;
    BOOL                            scrollingDuringPlayback;
    
    // setup functions to initialize an Audio Unit
    void                            setupAudioSession();
    void                            setupStreamFormatWithChannels(const short unsigned int &numChannels);
    
    // functions needed to read from a configured EAFS reference 
    void                            setCurrentBuffers(signed char requestedBuffer);
    UInt32                          readFramesFromFile(UInt32 framesToRead);
    void                            readLastSegmentOfFramesFromFile();
    
    // loads the file that this AU needs to read linear PCM data from
    void                            readAudioFileIntoMemoryWithURL(const CFURLRef &sourceURL);
    
    // init this Audio Unit
    void                            configureAndInitializeRioAudioPlayer();
    
    // spun off from readAudioFileIntoMemoryWithURL, as we only need to do this once and shouldn't do it when Rio is reading
    void                            allocRioAudioPlayerBuffers();
    
    // helpful debug methods
    void                            printASBD(const AudioStreamBasicDescription &asbd);
    void                            printErrorMessageWithStatus(const char* errorString, const OSStatus &result);
    
    // ring buffer methods
    void                            allocRingBufferAtPosition(const SInt64 &seekPosition);
    void                            initRingBuffer();
    void                            cycleRingBuffer();
    void                            playRingBufferAudio();
    
    // playback position tracking methods
    SInt64                          convertSecondsToRemoteIOSamples(const float &seconds);
    void                            setFramesBufferedAtSamplePosition(const SInt64 &position);
    void                            incrementFramesElapsed(const UInt32 &numSamples);
    
protected:
	    
	CMTime							framesBuffered;
	CMTime							fileDuration;

	BOOL                            playing;
    BOOL                            interruptedDuringPlayback;
	
public:
    
    NLRemoteIOAudioPlayer();
    ~NLRemoteIOAudioPlayer();
    
    id <NLRemoteIOAudioPlayerDelegate>	_delegate;					
    
    inline BOOL                     isPlaying()                                             { return playing; }
    inline BOOL                     isInterruptedDuringPlayback()                           { return interruptedDuringPlayback; }
    inline void                     setInterruptedDuringPlayback(const BOOL &interrupted)   { interruptedDuringPlayback = interrupted; }
    inline CMTime                   getFramesBuffered()                                     { return framesBuffered; }
    inline CMTime                   getFileDuration()                                       { return fileDuration; }
	inline float 					getFileDurationInSeconds();
    inline const soundStructPtr		getSoundStructUnitPtr()                                 { return &soundStructUnit; }
    
    // starts and stops audio playback (analogous to the functions provided by play/pause buttons)
    void                            startRioAudioPlayer();
    void                            startRioAudioPlayerWithInputURL(const CFURLRef &path);	// used as an initializer
    void                            stopRioAudioPlayer();
    
    // seek methods
    void                            seekToPosition(const float &seekTime);
    
};