oalplayback.m

This is an example application that shows how to use OpenAL to play sounds on an iPhone.

/*
 
 File: oalPlayback.m
 
 Abstract: An Obj-C class which wraps an OpenAL playback environment. 
 It provides start/stop of playback, and spatial positioning for the 
 listener and a single sound source.
 
 Version: 1.0
 
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 */

#import "oalPlayback.h"
#import "MyOpenALSupport.h"


@implementation oalPlayback

@synthesize isPlaying = _isPlaying;
@synthesize listenerRotation = _listenerRotation;

#pragma mark Object Init / Maintenance

- (id)init
{	
	if (self = [super init]) {
		// Start with our sound source slightly in front of the listener
		_sourcePos = CGPointMake(0., -70.);
		
		// Put the listener in the center of the stage
		_listenerPos = CGPointMake(0., 0.);
		
		// Listener looking straight ahead
		_listenerRotation = 0.;
		
		// Volume at max
		_sourceVolume = 1.;

		// setup our audio session
		OSStatus result = AudioSessionInitialize(NULL, NULL, NULL, self);
		if (result) printf("Error initializing audio session! %d\n", result);
		else {
			UInt32 category = kAudioSessionCategory_AmbientSound;
			result = AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(category), &category);
			if (result) printf("Error setting audio session category! %d\n", result);
			else {
				result = AudioSessionSetActive(true);
				if (result) printf("Error setting audio session active! %d\n", result);
			}
		}
		
		// Initialize our OpenAL environment
		[self initOpenAL];
	}
	
	return self;
}


#pragma mark OpenAL

- (void) initBuffer
{
	ALenum  error = AL_NO_ERROR;
	ALenum  format;
	ALvoid* data;
	ALsizei size;
	ALsizei freq;
	
	NSBundle*				bundle = [NSBundle mainBundle];
	
	// get some audio data from a wave file
	CFURLRef fileURL = (CFURLRef)[[NSURL fileURLWithPath:[bundle pathForResource:@"sound" ofType:@"wav"]] retain];
	
	if (fileURL)
	{	
		data = MyGetOpenALAudioData(fileURL, &size, &format, &freq);
		CFRelease(fileURL);
		
		if((error = alGetError()) != AL_NO_ERROR) {
			printf("error loading sound: %x\n", error);
			exit(1);
		}
		
		// use the static buffer data API
		alBufferDataStaticProc(_buffer, format, data, size, freq);
		
		if((error = alGetError()) != AL_NO_ERROR) {
			printf("error attaching audio to buffer: %x\n", error);
		}		
	}
	else
		printf("Could not find file!\n");
}

- (void) initSource
{
	ALenum error = AL_NO_ERROR;
	alGetError(); // Clear the error
    
	// Turn Looping ON
	alSourcei(_source, AL_LOOPING, AL_TRUE);
	
	// Set Source Position
	float sourcePosAL[] = {_sourcePos.x, _sourcePos.y, kDefaultDistance};
	alSourcefv(_source, AL_POSITION, sourcePosAL);
	
	// Set Source Reference Distance
	alSourcef(_source, AL_REFERENCE_DISTANCE, 50.0f);
	
	// attach OpenAL Buffer to OpenAL Source
	alSourcei(_source, AL_BUFFER, _buffer);
	
	if((error = alGetError()) != AL_NO_ERROR) {
		printf("Error attaching buffer to source: %x\n", error);
		exit(1);
	}	
}


- (void)initOpenAL
{
	ALenum			error;
	ALCcontext		*newContext = NULL;
	ALCdevice		*newDevice = NULL;
	
	// Create a new OpenAL Device
	// Pass NULL to specify the system’s default output device
	newDevice = alcOpenDevice(NULL);
	if (newDevice != NULL)
	{
		// Create a new OpenAL Context
		// The new context will render to the OpenAL Device just created 
		newContext = alcCreateContext(newDevice, 0);
		if (newContext != NULL)
		{
			// Make the new context the Current OpenAL Context
			alcMakeContextCurrent(newContext);
			
			// Create some OpenAL Buffer Objects
			alGenBuffers(1, &_buffer);
			if((error = alGetError()) != AL_NO_ERROR) {
				printf("Error Generating Buffers: %x", error);
				exit(1);
			}
			
			// Create some OpenAL Source Objects
			alGenSources(1, &_source);
			if(alGetError() != AL_NO_ERROR) 
			{
				printf("Error generating sources! %x\n", error);
				exit(1);
			}
			
		}
	}
	
	atexit(TeardownOpenAL);
	alGetError();
	
	[self initBuffer];	
	[self initSource];
}

#pragma mark Play / Pause

- (void)startSound
{
	ALenum error;
	
	printf("Start!\n");
	// Begin playing our source file
	alSourcePlay(_source);
	if((error = alGetError()) != AL_NO_ERROR) {
		printf("error starting source: %x\n", error);
	} else {
		// Mark our state as playing (the view looks at this)
		self.isPlaying = YES;
	}
}

- (void)stopSound
{
	ALenum error;
	
	printf("Stop!!\n");
	// Stop playing our source file
	alSourceStop(_source);
	if((error = alGetError()) != AL_NO_ERROR) {
		printf("error stopping source: %x\n", error);
	} else {
		// Mark our state as not playing (the view looks at this)
		self.isPlaying = NO;
	}
}

#pragma mark Setters / Getters

- (CGPoint)sourcePos
{
	return _sourcePos;
}

- (void)setSourcePos:(CGPoint)SOURCEPOS
{
	_sourcePos = SOURCEPOS;
	float sourcePosAL[] = {_sourcePos.x, _sourcePos.y, kDefaultDistance};
	// Move our audio source coordinates
	alSourcefv(_source, AL_POSITION, sourcePosAL);
}



- (CGPoint)listenerPos
{
	return _listenerPos;
}

- (void)setListenerPos:(CGPoint)LISTENERPOS
{
	_listenerPos = LISTENERPOS;
	float listenerPosAL[] = {_listenerPos.x, _listenerPos.y, 0.};
	// Move our listener coordinates
	alListenerfv(AL_POSITION, listenerPosAL);
}



- (CGFloat)listenerRotation
{
	return _listenerRotation;
}

- (void)setListenerRotation:(CGFloat)radians
{
	_listenerRotation = radians;
	float ori[] = {cos(radians + M_PI_2), sin(radians + M_PI_2), 0., 0., 0., 1.};
	// Set our listener orientation (rotation)
	alListenerfv(AL_ORIENTATION, ori);
}



- (ALfloat)sourceVolume
{
	return _sourceVolume;
}

- (void)setSourceVolume:(ALfloat)volume
{
	_sourceVolume = volume;
	// Set our source volume
	alSourcef(_source, AL_GAIN, _sourceVolume);
}

@end