1 //  MXAudioPlayerFadeOperation.m

     2 //

     3 //  Created by Andrew Mackenzie-Ross on 30/11/10.

     4 //  mackross.net.

     5 //

     6 

     7 #import "MXAudioPlayerFadeOperation.h"

     8 #import <AVFoundation/AVFoundation.h>

     9 

    10 #define SKVolumeChangesPerSecond 15

    11 

    12 @interface MXAudioPlayerFadeOperation ()

    13 @property (nonatomic, retain, readwrite) AVAudioPlayer *audioPlayer; 

    14 - (void)beginFadeOperation;

    15 - (void)finishFadeOperation;

    16 @end

    17 

    18 @implementation MXAudioPlayerFadeOperation

    19 #pragma mark -

    20 #pragma mark Properties

    21 @synthesize audioPlayer = _audioPlayer;

    22 @synthesize fadeDuration = _fadeDuration;

    23 @synthesize finishVolume = _finishVolume;

    24 @synthesize playBeforeFade = _playBeforeFade;

    25 @synthesize pauseAfterFade = _pauseAfterFade;

    26 @synthesize stopAfterFade = _stopAfterFade;

    27 @synthesize delay = _delay;

    28 

    29 #pragma mark -

    30 #pragma mark Accessors

    31 - (AVAudioPlayer *)audioPlayer {

    32   AVAudioPlayer *result;

    33   @synchronized(self) {

    34     result = [_audioPlayer retain];

    35   }

    36   return [result autorelease];

    37 }

    38 

    39 - (void)setAudioPlayer:(AVAudioPlayer *)anAudioPlayer {

    40   @synchronized(self) {

    41     if (_audioPlayer != anAudioPlayer) {

    42       [_audioPlayer release];

    43       _audioPlayer = [anAudioPlayer retain];

    44     }

    45   }

    46 }

    47 

    48 #pragma mark -

    49 #pragma mark NSOperation

    50 -(id) initFadeWithAudioPlayer:(AVAudioPlayer*)player toVolume:(float)volume overDuration:(NSTimeInterval)duration withDelay:(NSTimeInterval)timeDelay {

    51   if (self = [super init]) {

    52     self.audioPlayer = player;

    53     [player prepareToPlay];

    54     _fadeDuration = duration;

    55     _finishVolume = volume;

    56     _playBeforeFade = YES;

    57     _stopAfterFade = NO;

    58     _pauseAfterFade = (volume == 0.0) ? YES : NO;

    59     _delay = timeDelay;

    60   }

    61   return self;

    62 }

    63 

    64 - (id)initFadeWithAudioPlayer:(AVAudioPlayer*)player toVolume:(float)volume overDuration:(NSTimeInterval)duration {

    65   return [self initFadeWithAudioPlayer:player toVolume:volume overDuration:duration withDelay:0.0];

    66 }

    67 

    68 - (id)initFadeWithAudioPlayer:(AVAudioPlayer*)player toVolume:(float)volume {

    69   return [self initFadeWithAudioPlayer:player toVolume:volume overDuration:1.0];

    70 }

    71 

    72 - (id)initFadeWithAudioPlayer:(AVAudioPlayer*)player {

    73   return [self initFadeWithAudioPlayer:player toVolume:0.0];

    74 }

    75 

    76 - (id) init {

    77   ALog(@"Failed to init class (%@) with AVAudioPlayer instance, use initFadeWithAudioPlayer:",[self class]);

    78   return nil;

    79 }

    80 

    81 - (void)main {

    82   NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    83   [NSThread sleepForTimeInterval:_delay];

    84   if ([self.audioPlayer isKindOfClass:[AVAudioPlayer class]]) {

    85     [self beginFadeOperation];

    86   }

    87   else {

    88     ALog(@"AudioPlayerFadeOperation began with invalid AVAudioPlayer");

    89   }

    90   

    91   [pool release];

    92 }

    93 

    94 - (void)beginFadeOperation {

    95   if (![self.audioPlayer isPlaying] && _playBeforeFade) [self.audioPlayer play];

    96   

    97   if (_fadeDuration != 0.0) {

    98     

    99     NSTimeInterval sleepInterval = (1.0 / SKVolumeChangesPerSecond);

   100     NSTimeInterval startTime = [[NSDate date] timeIntervalSinceReferenceDate];

   101     NSTimeInterval now = startTime;

   102     

   103     float startVolume = [self.audioPlayer volume];

   104     

   105     while (now < (startTime + _fadeDuration)) {

   106       float ratioOfFadeCompleted = (now - startTime)/_fadeDuration;

   107       float volume = (_finishVolume * ratioOfFadeCompleted) + (startVolume * (1-ratioOfFadeCompleted));

   108       [self.audioPlayer setVolume:volume];

   109       [NSThread sleepForTimeInterval:sleepInterval];

   110       now = [[NSDate date] timeIntervalSinceReferenceDate];

   111     }

   112     

   113     [self.audioPlayer setVolume:_finishVolume];

   114     [self finishFadeOperation];

   115   }

   116   else {

   117     [self.audioPlayer setVolume:_finishVolume];

   118     [self finishFadeOperation];

   119   }

   120 }

   121 

   122 - (void)finishFadeOperation {

   123   if ([self.audioPlayer isPlaying] && _pauseAfterFade) [self.audioPlayer pause];

   124   if ([self.audioPlayer isPlaying] && _stopAfterFade) [self.audioPlayer stop];

   125 }

   126 

   127 - (void)dealloc {

   128   releaseAndNil(_audioPlayer);

   129   [super dealloc];

   130 }

   131 

   132 @end

   133