AVAudioPCMBuffer для музыкальных файлов

Это решение, которое я придумал. Это все еще не идеально, но, надеюсь, это поможет кому-то, кто находится в том же затруднительном положении, что и я. Я создал одноэлементный класс для выполнения этой работы. Одно улучшение, которое может быть сделано в будущем, заключается в том, чтобы загружать звуковые эффекты и музыкальные файлы, необходимые для конкретной SKScene, только в то время, когда они нужны. У меня было так много проблем с этим кодом, что я не хочу с ним возиться сейчас. В настоящее время у меня не слишком много звуков, поэтому он не использует чрезмерный объем памяти.

Обзор
Моя стратегия была следующей:

1. Сохраните имена аудиофайлов для игры в plist
2. Прочтите этот список и создайте два словаря (один для музыки, а другой для коротких звуковых эффектов)
   
3. Словарь звуковых эффектов состоит из AVAudioPCMBuffer и AVAudioPlayerNode для каждого из звуков
   .

4. Музыкальный словарь состоит из массива AVAudioPCMBuffers, массива меток времени, когда эти буферы должны воспроизводиться в очереди, AVAudioPlayerNode и частоты дискретизации исходного аудиофайла
   

   • The sample rate is necessary for figuring out the time at which each buffer should be played (you'll see the calculations done in code)

5. Создайте AVAudioEngine и получите основной микшер из движка и подключите все AVAudioPlayerNodes к микшеру (как обычно)

6. Play sound effects or music using their various methods
   • sound effect playing is straightforward...call method -(void) playSfxFile:(NSString*)file; and it plays a sound
   • для музыки я просто не мог найти хорошего решения, не прибегая к помощи сцены, пытаясь воспроизвести музыку. Сцена вызовет -(void) playMusicFile:(NSString*)file; и запланирует воспроизведение буферов в том порядке, в котором они были созданы. Я не мог найти хороший способ заставить музыку повторяться после завершения в моем классе AudioEngine, поэтому я решил заставить сцену проверять в своем методе update:, воспроизводится ли музыка для определенного файла, и если нет, воспроизвести ее. снова (не очень гладкое решение, но оно работает)

AudioEngine.h

#import <Foundation/Foundation.h>

@interface AudioEngine : NSObject

+(instancetype)sharedData;
-(void) playSfxFile:(NSString*)file;
-(void) playMusicFile:(NSString*)file;
-(void) pauseMusic:(NSString*)file;
-(void) unpauseMusic:(NSString*)file;
-(void) stopMusicFile:(NSString*)file;
-(void) setVolumePercentages;
-(bool) isPlayingMusic:(NSString*)file;

@end

AudioEngine.m

#import "AudioEngine.h"
#import <AVFoundation/AVFoundation.h>
#import "GameData.h" //this is a class that I use to store game data (in this case it is being used to get the user preference for volume amount)

@interface AudioEngine()

@property AVAudioEngine *engine;
@property AVAudioMixerNode *mixer;

@property NSMutableDictionary *musicDict;
@property NSMutableDictionary *sfxDict;

@property NSString *audioInfoPList;

@property float musicVolumePercent;
@property float sfxVolumePercent;
@property float fadeVolume;
@property float timerCount;

@end

@implementation AudioEngine

int const FADE_ITERATIONS = 10;
static NSString * const MUSIC_PLAYER = @"player";
static NSString * const MUSIC_BUFFERS = @"buffers";
static NSString * const MUSIC_FRAME_POSITIONS = @"framePositions";
static NSString * const MUSIC_SAMPLE_RATE = @"sampleRate";

static NSString * const SFX_BUFFER = @"buffer";
static NSString * const SFX_PLAYER = @"player";

+(instancetype) sharedData {
    static AudioEngine *sharedInstance = nil;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[self alloc] init];
        [sharedInstance startEngine];
    });

    return sharedInstance;
}

-(instancetype) init {
    if (self = [super init]) {
        _engine = [[AVAudioEngine alloc] init];
        _mixer = [_engine mainMixerNode];

        _audioInfoPList = [[NSBundle mainBundle] pathForResource:@"AudioInfo" ofType:@"plist"]; //open a plist called AudioInfo.plist

        [self setVolumePercentages]; //this is created to set the user's preference in terms of how loud sound fx and music should be played
        [self initMusic];
        [self initSfx];
    }
    return self;
}

//opens all music files, creates multiple buffers depending on the length of the file and a player
-(void) initMusic {
    _musicDict = [NSMutableDictionary dictionary];

    _audioInfoPList = [[NSBundle mainBundle] pathForResource: @"AudioInfo" ofType: @"plist"];
    NSDictionary *audioInfoData = [NSDictionary dictionaryWithContentsOfFile:_audioInfoPList];

    for (NSString *musicFileName in audioInfoData[@"music"]) {
        [self loadMusicIntoBuffer:musicFileName];
        AVAudioPlayerNode *player = [[AVAudioPlayerNode alloc] init];
        [_engine attachNode:player];

        AVAudioPCMBuffer *buffer = [[_musicDict[musicFileName] objectForKey:MUSIC_BUFFERS] objectAtIndex:0];
        [_engine connect:player to:_mixer format:buffer.format];
        [_musicDict[musicFileName] setObject:player forKey:@"player"];
    }
}

//opens a music file and creates an array of buffers
-(void) loadMusicIntoBuffer:(NSString *)filename
{
    NSURL *audioFileURL = [[NSBundle mainBundle] URLForResource:filename withExtension:@"aif"];
    //NSURL *audioFileURL = [NSURL URLWithString:[[NSBundle mainBundle] pathForResource:filename ofType:@"aif"]];
    NSAssert(audioFileURL, @"Error creating URL to audio file");
    NSError *error = nil;
    AVAudioFile *audioFile = [[AVAudioFile alloc] initForReading:audioFileURL commonFormat:AVAudioPCMFormatFloat32 interleaved:NO error:&error];
    NSAssert(audioFile != nil, @"Error creating audioFile, %@", error.localizedDescription);

    AVAudioFramePosition fileLength = audioFile.length; //frame length of the audio file
    float sampleRate = audioFile.fileFormat.sampleRate; //sample rate (in Hz) of the audio file
    [_musicDict setObject:[NSMutableDictionary dictionary] forKey:filename];
    [_musicDict[filename] setObject:[NSNumber numberWithDouble:sampleRate] forKey:MUSIC_SAMPLE_RATE];

    NSMutableArray *buffers = [NSMutableArray array];
    NSMutableArray *framePositions = [NSMutableArray array];

    const AVAudioFrameCount kBufferFrameCapacity = 1024 * 1024L; //the size of my buffer...can be made bigger or smaller 512 * 1024L would be half the size
    while (audioFile.framePosition < fileLength) { //each iteration reads in kBufferFrameCapacity frames of the audio file and stores it in a buffer
        [framePositions addObject:[NSNumber numberWithLongLong:audioFile.framePosition]];
        AVAudioPCMBuffer *readBuffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:audioFile.processingFormat frameCapacity:kBufferFrameCapacity];
        if (![audioFile readIntoBuffer:readBuffer error:&error]) {
            NSLog(@"failed to read audio file: %@", error);
            return;
        }
        if (readBuffer.frameLength == 0) { //if we've come to the end of the file, end the loop
            break;
        }
        [buffers addObject:readBuffer];
    }

    [_musicDict[filename] setObject:buffers forKey:MUSIC_BUFFERS];
    [_musicDict[filename] setObject:framePositions forKey:MUSIC_FRAME_POSITIONS];
}

-(void) initSfx {
    _sfxDict = [NSMutableDictionary dictionary];

    NSDictionary *audioInfoData = [NSDictionary dictionaryWithContentsOfFile:_audioInfoPList];

    for (NSString *sfxFileName in audioInfoData[@"sfx"]) {
        AVAudioPlayerNode *player = [[AVAudioPlayerNode alloc] init];
        [_engine attachNode:player];

        [self loadSoundIntoBuffer:sfxFileName];
        AVAudioPCMBuffer *buffer = [_sfxDict[sfxFileName] objectForKey:SFX_BUFFER];
        [_engine connect:player to:_mixer format:buffer.format];
        [_sfxDict[sfxFileName] setObject:player forKey:SFX_PLAYER];
    }
}

//WARNING: make sure that the sound fx file is small (roughly under 30 sec) otherwise the archived version of the app will crash because the buffer ran out of space
-(void) loadSoundIntoBuffer:(NSString *)filename
{
    NSURL *audioFileURL = [NSURL URLWithString:[[NSBundle mainBundle] pathForResource:filename ofType:@"mp3"]];
    NSAssert(audioFileURL, @"Error creating URL to audio file");
    NSError *error = nil;
    AVAudioFile *audioFile = [[AVAudioFile alloc] initForReading:audioFileURL commonFormat:AVAudioPCMFormatFloat32 interleaved:NO error:&error];
    NSAssert(audioFile != nil, @"Error creating audioFile, %@", error.localizedDescription);

    AVAudioPCMBuffer *readBuffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:audioFile.processingFormat frameCapacity:(AVAudioFrameCount)audioFile.length];
    [audioFile readIntoBuffer:readBuffer error:&error];

    [_sfxDict setObject:[NSMutableDictionary dictionary] forKey:filename];
    [_sfxDict[filename] setObject:readBuffer forKey:SFX_BUFFER];
}

-(void)startEngine {
    [_engine startAndReturnError:nil];
}

-(void) playSfxFile:(NSString*)file {
    AVAudioPlayerNode *player = [_sfxDict[file] objectForKey:@"player"];
    AVAudioPCMBuffer *buffer = [_sfxDict[file] objectForKey:SFX_BUFFER];
    [player scheduleBuffer:buffer atTime:nil options:AVAudioPlayerNodeBufferInterrupts completionHandler:nil];
    [player setVolume:1.0];
    [player setVolume:_sfxVolumePercent];
    [player play];
}

-(void) playMusicFile:(NSString*)file {
    AVAudioPlayerNode *player = [_musicDict[file] objectForKey:MUSIC_PLAYER];

    if ([player isPlaying] == NO) {
        NSArray *buffers = [_musicDict[file] objectForKey:MUSIC_BUFFERS];

        double sampleRate = [[_musicDict[file] objectForKey:MUSIC_SAMPLE_RATE] doubleValue];


        for (int i = 0; i < [buffers count]; i++) {
            long long framePosition = [[[_musicDict[file] objectForKey:MUSIC_FRAME_POSITIONS] objectAtIndex:i] longLongValue];
            AVAudioTime *time = [AVAudioTime timeWithSampleTime:framePosition atRate:sampleRate];

            AVAudioPCMBuffer *buffer  = [buffers objectAtIndex:i];
            [player scheduleBuffer:buffer atTime:time options:AVAudioPlayerNodeBufferInterrupts completionHandler:^{
                if (i == [buffers count] - 1) {
                    [player stop];
                }
            }];
            [player setVolume:_musicVolumePercent];
            [player play];
        }
    }
}

-(void) stopOtherMusicPlayersNotNamed:(NSString*)file {
    if ([file isEqualToString:@"menuscenemusic"]) {
        AVAudioPlayerNode *player = [_musicDict[@"levelscenemusic"] objectForKey:MUSIC_PLAYER];
        [player stop];
    }
    else {
        AVAudioPlayerNode *player = [_musicDict[@"menuscenemusic"] objectForKey:MUSIC_PLAYER];
        [player stop];
    }
}

//stops the player for a particular sound
-(void) stopMusicFile:(NSString*)file {
    AVAudioPlayerNode *player = [_musicDict[file] objectForKey:MUSIC_PLAYER];

    if ([player isPlaying]) {
        _timerCount = FADE_ITERATIONS;
        _fadeVolume = _musicVolumePercent;
        [self fadeOutMusicForPlayer:player]; //fade out the music
    }
}

//helper method for stopMusicFile:
-(void) fadeOutMusicForPlayer:(AVAudioPlayerNode*)player {
    [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(handleTimer:) userInfo:player repeats:YES];
}

//helper method for stopMusicFile:
-(void) handleTimer:(NSTimer*)timer {
    AVAudioPlayerNode *player = (AVAudioPlayerNode*)timer.userInfo;
    if (_timerCount > 0) {
        _timerCount--;
        AVAudioPlayerNode *player = (AVAudioPlayerNode*)timer.userInfo;
        _fadeVolume = _musicVolumePercent * (_timerCount / FADE_ITERATIONS);
        [player setVolume:_fadeVolume];
    }
    else {
        [player stop];
        [player setVolume:_musicVolumePercent];
        [timer invalidate];
    }
}

-(void) pauseMusic:(NSString*)file {
    AVAudioPlayerNode *player = [_musicDict[file] objectForKey:MUSIC_PLAYER];
    if ([player isPlaying]) {
        [player pause];
    }
}

-(void) unpauseMusic:(NSString*)file {
    AVAudioPlayerNode *player = [_musicDict[file] objectForKey:MUSIC_PLAYER];
    [player play];
}

//sets the volume of the player based on user preferences in GameData class
-(void) setVolumePercentages {
    NSString *musicVolumeString = [[GameData sharedGameData].settings objectForKey:@"musicVolume"];
    _musicVolumePercent = [[[musicVolumeString componentsSeparatedByCharactersInSet:
    [[NSCharacterSet decimalDigitCharacterSet] invertedSet]]
    componentsJoinedByString:@""] floatValue] / 100;
    NSString *sfxVolumeString = [[GameData sharedGameData].settings objectForKey:@"sfxVolume"];
    _sfxVolumePercent = [[[sfxVolumeString componentsSeparatedByCharactersInSet:
    [[NSCharacterSet decimalDigitCharacterSet] invertedSet]]
    componentsJoinedByString:@""] floatValue] / 100;

    //immediately sets music to new volume
    for (NSString *file in [_musicDict allKeys]) {
        AVAudioPlayerNode *player = [_musicDict[file] objectForKey:MUSIC_PLAYER];
        [player setVolume:_musicVolumePercent];
    }
}

-(bool) isPlayingMusic:(NSString *)file {
    AVAudioPlayerNode *player = [_musicDict[file] objectForKey:MUSIC_PLAYER];
    if ([player isPlaying])
        return YES;
    return NO;
}

@end