OpenAL的简单示例

首先，需要导入AudioToolbox.framework和OpenAL.framework。

 

OpenALViewController.h

 

#import <UIKit/UIKit.h>
#import <OpenAL/alc.h>

@interface OpenALViewController : UIViewController {
	ALCcontext *mContext;
	ALCdevice *mDevice;
	NSUInteger sourceID;
	NSUInteger bufferID;
	
	BOOL isPlaying;
}

- (IBAction)playPause:(id)sender;

@end

 

OpenALViewController.m

 

#import "OpenALViewController.h"
#import <AudioToolbox/AudioFile.h>
#import <OpenAL/al.h>

@implementation OpenALViewController

- (void)initOpenAL {
	mDevice = alcOpenDevice(NULL); 
	if (mDevice) {
		mContext = alcCreateContext(mDevice, NULL);
		alcMakeContextCurrent(mContext);
	}
}

- (AudioFileID)openAudioFile:(NSString *)filePath {
	AudioFileID outAFID;
	NSURL *afUrl = [NSURL fileURLWithPath:filePath];
    
#if TARGET_OS_IPHONE
	OSStatus result = AudioFileOpenURL((CFURLRef)afUrl, kAudioFileReadPermission, 0, &outAFID);
#else
	OSStatus result = AudioFileOpenURL((CFURLRef)afUrl, fsRdPerm, 0, &outAFID);
#endif
	if (result != 0) NSLog(@"cannot open file: %@", filePath);
	return outAFID;
}

- (UInt32)audioFileSize:(AudioFileID)fileDescriptor {
	UInt64 outDataSize = 0;
	UInt32 thePropSize = sizeof(UInt64);
	OSStatus result = AudioFileGetProperty(fileDescriptor, kAudioFilePropertyAudioDataByteCount, &thePropSize, &outDataSize);
	if(result != 0) NSLog(@"cannot find file size");
	return (UInt32)outDataSize;
}

- (void)cleanUpOpenAL {
	alDeleteSources(1, &sourceID);
	alDeleteBuffers(1, &bufferID);
	alcDestroyContext(mContext);
	alcCloseDevice(mDevice);
}

- (IBAction)playPause:(id)sender {
	UIButton *btnPlay = (UIButton *)sender;
	if(!isPlaying) {
		alSourcePlay(sourceID);
		isPlaying = YES;
		[btnPlay setTitle:@"Pause" forState:UIControlStateNormal];
	} else {
		alSourceStop(sourceID);
		isPlaying = NO;
		[btnPlay setTitle:@"Play" forState:UIControlStateNormal];
	}
}

#pragma mark -

- (void)viewDidLoad {
    [super viewDidLoad];
	
	isPlaying = NO;		
	
	[self initOpenAL];
    
	NSString *fileName = [[NSBundle mainBundle] pathForResource:@"outSound" ofType:@"caf"];
	AudioFileID fileID = [self openAudioFile:fileName];
	UInt32 fileSize = [self audioFileSize:fileID];
    
	unsigned char *outData = malloc(fileSize);
	OSStatus result = noErr;
	result = AudioFileReadBytes(fileID, false, 0, &fileSize, outData);
	AudioFileClose(fileID); 
	
	if (result != 0) NSLog(@"cannot load effect: %@", fileName);
    
	alGenBuffers(1, &bufferID);
	alBufferData(bufferID, AL_FORMAT_STEREO16, outData, fileSize, 8000); 
	alGenSources(1, &sourceID); 
	alSourcei(sourceID, AL_BUFFER, bufferID);
	alSourcef(sourceID, AL_PITCH, 1.0f);
	alSourcef(sourceID, AL_GAIN, 1.0f);
	alSourcei(sourceID, AL_LOOPING, AL_TRUE);
    
	if (outData) {
		free(outData);
		outData = NULL;
	}
}

- (void)dealloc {
	[self cleanUpOpenAL];
    [super dealloc];
}

@end