iPhoneで繰り返しループするサウンドを鳴らすコードのメモ (Audio Queueのサンプル)

使い方

GBMusicTrack *song = [[GBMusicTrack alloc] initWithPath:[[NSBundle mainBundle] pathForResource:@"BackgroundMusic" ofType:@"mp3"]];
[song setRepeat:YES];
[song play];

GBMusicTrack.h

//
//  GBMusicTrack.h
//  GameBase
//
//  Created by Jake Peterson (AnotherJake) on 7/6/08.
//  Copyright 2008 Jake Peterson. All rights reserved.
//

#import <Cocoa/Cocoa.h>
#import <AudioToolbox/AudioQueue.h>
#import <AudioToolbox/AudioFile.h>

#define NUM_QUEUE_BUFFERS	3

@interface GBMusicTrack : NSObject
{
	AudioFileID						audioFile;
	AudioStreamBasicDescription		dataFormat;
	AudioQueueRef					queue;
	UInt64							packetIndex;
	UInt32							numPacketsToRead;
	AudioStreamPacketDescription	*packetDescs;
	BOOL							repeat;
	BOOL							trackClosed;
	AudioQueueBufferRef				buffers[NUM_QUEUE_BUFFERS];
}

- (id)initWithPath:(NSString *)path;
- (void)setGain:(Float32)gain;
- (void)setRepeat:(BOOL)yn;
- (void)play;
- (void)pause;

// close is called automatically in GBMusicTrack's dealloc method, but it is recommended
// to call close first, so that the associated Audio Queue is released immediately, instead
// of having to wait for a possible autorelease, which may cause some conflict
- (void)close;

extern NSString	*GBMusicTrackFinishedPlayingNotification;

@end

GBMusicTrack.m

//
//  GBMusicTrack.m
//  GameBase
//
//  Created by Jake Peterson (AnotherJake) on 7/6/08.
//  Copyright 2008 Jake Peterson. All rights reserved.
//

#import "GBMusicTrack.h"

static UInt32 gBufferSizeBytes = 0x10000; // 64k

NSString *GBMusicTrackFinishedPlayingNotification = @"GBMusicTrackFinishedPlayingNotification";

@interface GBMusicTrack (InternalMethods)

static void BufferCallback(void *inUserData, AudioQueueRef inAQ, AudioQueueBufferRef buffer);
- (void)callbackForBuffer:(AudioQueueBufferRef)buffer;
- (UInt32)readPacketsIntoBuffer:(AudioQueueBufferRef)buffer;

@end

@implementation GBMusicTrack

#pragma mark -
#pragma mark GBMusicTrack

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

- (void)close
{
	// it is preferrable to call close first, before dealloc if there is a problem waiting for
	// an autorelease
	if (trackClosed)
		return;
	trackClosed = YES;
	AudioQueueStop(queue, YES);
	AudioQueueDispose(queue, YES);
	AudioFileClose(audioFile);
}

- (id)initWithPath:(NSString *)path
{
	UInt32		size, maxPacketSize;
	char		*cookie;
	int			i;
	
	if(!(self = [super init])) return nil;
	if (path == nil) return nil;
	
	// try to open up the file using the specified path
	if (noErr != AudioFileOpenURL((CFURLRef)[NSURL fileURLWithPath:path], 0x01, kAudioFileCAFType, &audioFile))
	{
		NSLog(@"GBMusicTrack Error - initWithPath: could not open audio file. Path given was: %@", path);
		return nil;
	}
	
	// get the data format of the file
	size = sizeof(dataFormat);
	AudioFileGetProperty(audioFile, kAudioFilePropertyDataFormat, &size, &dataFormat);
	
	// create a new playback queue using the specified data format and buffer callback
	AudioQueueNewOutput(&dataFormat, BufferCallback, self, nil, nil, 0, &queue);
	
	// calculate number of packets to read and allocate space for packet descriptions if needed
	if (dataFormat.mBytesPerPacket == 0 || dataFormat.mFramesPerPacket == 0)
	{
		// since we didn't get sizes to work with, then this must be VBR data (Variable BitRate), so
		// we'll have to ask Core Audio to give us a conservative estimate of the largest packet we are
		// likely to read with kAudioFilePropertyPacketSizeUpperBound
		size = sizeof(maxPacketSize);
		AudioFileGetProperty(audioFile, kAudioFilePropertyPacketSizeUpperBound, &size, &maxPacketSize);
		if (maxPacketSize > gBufferSizeBytes)
		{
			// hmm... well, we don't want to go over our buffer size, so we'll have to limit it I guess
			maxPacketSize = gBufferSizeBytes;
			NSLog(@"GBMusicTrack Warning - initWithPath: had to limit packet size requested for file path: %@", path);
		}
		numPacketsToRead = gBufferSizeBytes / maxPacketSize;
		
		// will need a packet description for each packet since this is VBR data, so allocate space accordingly
		packetDescs = malloc(sizeof(AudioStreamPacketDescription) * numPacketsToRead);
	}
	else
	{
		// for CBR data (Constant BitRate), we can simply fill each buffer with as many packets as will fit
		numPacketsToRead = gBufferSizeBytes / dataFormat.mBytesPerPacket;
		
		// don't need packet descriptsions for CBR data
		packetDescs = nil;
	}
	
	// see if file uses a magic cookie (a magic cookie is meta data which some formats use)
	AudioFileGetPropertyInfo(audioFile, kAudioFilePropertyMagicCookieData, &size, nil);
	if (size > 0)
	{
		// copy the cookie data from the file into the audio queue
		cookie = malloc(sizeof(char) * size);
		AudioFileGetProperty(audioFile, kAudioFilePropertyMagicCookieData, &size, cookie);
		AudioQueueSetProperty(queue, kAudioQueueProperty_MagicCookie, cookie, size);
		free(cookie);
	}
	
	// allocate and prime buffers with some data
	packetIndex = 0;
	for (i = 0; i < NUM_QUEUE_BUFFERS; i++)
	{
		AudioQueueAllocateBuffer(queue, gBufferSizeBytes, &buffers[i]);
		if ([self readPacketsIntoBuffer:buffers[i]] == 0)
		{
			// this might happen if the file was so short that it needed less buffers than we planned on using
			break;
		}
	}
	repeat = NO;
	trackClosed = NO;
	return self;
}

- (void)setGain:(Float32)gain
{
	AudioQueueSetParameter(queue, kAudioQueueParam_Volume, gain);
}

- (void)setRepeat:(BOOL)yn
{
	repeat = yn;
}

- (void)play
{
	AudioQueueStart(queue, nil);
}

- (void)pause
{
	AudioQueuePause(queue);
}

#pragma mark -
#pragma mark Callback

static void BufferCallback(void *inUserData, AudioQueueRef inAQ, AudioQueueBufferRef buffer)
{
	// redirect back to the class to handle it there instead, so we have direct access to the instance variables
	[(GBMusicTrack *)inUserData callbackForBuffer:buffer];
}

- (void)callbackForBuffer:(AudioQueueBufferRef)buffer
{
	if ([self readPacketsIntoBuffer:buffer] == 0)
	{
		// End Of File reached, so rewind and refill the buffer using the beginning of the file instead
		packetIndex = 0;
		[self readPacketsIntoBuffer:buffer];
		
		// if not repeating then we'll pause it so it's ready to play again immediately if needed
		if (!repeat)
		{
			AudioQueuePause(queue);
			
			// we're not in the main thread during this callback, so enqueue a message on the main thread to post notification
			// that we're done, or else the notification will have to be handled in this thread, making things more difficult
			[self performSelectorOnMainThread:@selector(postTrackFinishedPlayingNotification:) withObject:nil waitUntilDone:NO];
		}
	}
}

- (void)postTrackFinishedPlayingNotification:(id)object
{
	// if we're here then we're in the main thread as specified by the callback, so now we can post notification that
	// the track is done without the notification observer(s) having to worry about thread safety and autorelease pools
	[[NSNotificationCenter defaultCenter] postNotificationName:GBMusicTrackFinishedPlayingNotification object:self];
}

- (UInt32)readPacketsIntoBuffer:(AudioQueueBufferRef)buffer
{
	UInt32		numBytes, numPackets;
	
	// read packets into buffer from file
	numPackets = numPacketsToRead;
	AudioFileReadPackets(audioFile, NO, &numBytes, packetDescs, packetIndex, &numPackets, buffer->mAudioData);
	if (numPackets > 0)
	{
		// - End Of File has not been reached yet since we read some packets, so enqueue the buffer we just read into
		// the audio queue, to be played next
		// - (packetDescs ? numPackets : 0) means that if there are packet descriptions (which are used only for Variable
		// BitRate data (VBR)) we'll have to send one for each packet, otherwise zero
		buffer->mAudioDataByteSize = numBytes;
		AudioQueueEnqueueBuffer(queue, buffer, (packetDescs ? numPackets : 0), packetDescs);
		
		// move ahead to be ready for next time we need to read from the file
		packetIndex += numPackets;
	}
	return numPackets;
}

@end