AudioUnit音源で各音色の最後にチャープを与えています

Question

古いGWBasic PLAYコマンド用の古い音楽エミュレータを作成しています。その目的のために、私は音源と音楽プレーヤーを持っています。演奏された音符のそれぞれの間で、私はものをつぶすような鳴き声を出しています。以下は私のクラスの両方がある：

ToneGen.h

#import <Foundation/Foundation.h> 

@interface ToneGen : NSObject 
@property (nonatomic) id delegate; 
@property (nonatomic) double frequency; 
@property (nonatomic) double sampleRate; 
@property (nonatomic) double theta; 
- (void)play:(float)ms; 
- (void)play; 
- (void)stop; 
@end 

ToneGen.m

#import <AudioUnit/AudioUnit.h> 
#import "ToneGen.h" 

OSStatus RenderTone(
        void *inRefCon, 
        AudioUnitRenderActionFlags *ioActionFlags, 
        const AudioTimeStamp  *inTimeStamp, 
        UInt32      inBusNumber, 
        UInt32      inNumberFrames, 
        AudioBufferList    *ioData); 
void ToneInterruptionListener(void *inClientData, UInt32 inInterruptionState); 


@interface ToneGen() 
@property (nonatomic) AudioComponentInstance toneUnit; 
@property (nonatomic) NSTimer *timer; 
- (void)createToneUnit; 
@end 


@implementation ToneGen 
@synthesize toneUnit = _toneUnit; 
@synthesize timer = _timer; 
@synthesize delegate = _delegate; 
@synthesize frequency = _frequency; 
@synthesize sampleRate = _sampleRate; 
@synthesize theta = _theta; 

- (id) init 
{ 
    self = [super init]; 
    if (self) 
    { 
     self.sampleRate = 44100; 
     self.frequency = 1440.0f; 
     return self; 
    } 
    return nil; 
} 

- (void)play:(float)ms 
{ 
    [self play]; 
    self.timer = [NSTimer scheduledTimerWithTimeInterval:(ms/100) 
                target:self 
               selector:@selector(stop) 
               userInfo:nil 
               repeats:NO]; 
    [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes]; 
} 

- (void)play 
{ 
    if (!self.toneUnit) 
    { 
     [self createToneUnit]; 

     // Stop changing parameters on the unit 
     OSErr err = AudioUnitInitialize(self.toneUnit); 
     if (err) 
      DLog(@"Error initializing unit"); 

     // Start playback 
     err = AudioOutputUnitStart(self.toneUnit); 
     if (err) 
      DLog(@"Error starting unit"); 
    } 
} 

- (void)stop 
{ 
    [self.timer invalidate]; 
    self.timer = nil; 

    if (self.toneUnit) 
    { 
     AudioOutputUnitStop(self.toneUnit); 
     AudioUnitUninitialize(self.toneUnit); 
     AudioComponentInstanceDispose(self.toneUnit); 
     self.toneUnit = nil; 
    } 

    if(self.delegate && [self.delegate respondsToSelector:@selector(toneStop)]) { 
     [self.delegate performSelector:@selector(toneStop)]; 
    } 
} 

- (void)createToneUnit 
{ 
    AudioComponentDescription defaultOutputDescription; 
    defaultOutputDescription.componentType = kAudioUnitType_Output; 
    defaultOutputDescription.componentSubType = kAudioUnitSubType_DefaultOutput; 
    defaultOutputDescription.componentManufacturer = kAudioUnitManufacturer_Apple; 
    defaultOutputDescription.componentFlags = 0; 
    defaultOutputDescription.componentFlagsMask = 0; 

    // Get the default playback output unit 
    AudioComponent defaultOutput = AudioComponentFindNext(NULL, &defaultOutputDescription); 
    if (!defaultOutput) 
     DLog(@"Can't find default output"); 

    // Create a new unit based on this that we'll use for output 
    OSErr err = AudioComponentInstanceNew(defaultOutput, &_toneUnit); 
    if (err) 
     DLog(@"Error creating unit"); 

    // Set our tone rendering function on the unit 
    AURenderCallbackStruct input; 
    input.inputProc = RenderTone; 
    input.inputProcRefCon = (__bridge void*)self; 
    err = AudioUnitSetProperty(self.toneUnit, 
           kAudioUnitProperty_SetRenderCallback, 
           kAudioUnitScope_Input, 
           0, 
           &input, 
           sizeof(input)); 
    if (err) 
     DLog(@"Error setting callback"); 

    // Set the format to 32 bit, single channel, floating point, linear PCM 
    const int four_bytes_per_float = 4; 
    const int eight_bits_per_byte = 8; 
    AudioStreamBasicDescription streamFormat; 
    streamFormat.mSampleRate = self.sampleRate; 
    streamFormat.mFormatID = kAudioFormatLinearPCM; 
    streamFormat.mFormatFlags = 
    kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved; 
    streamFormat.mBytesPerPacket = four_bytes_per_float; 
    streamFormat.mFramesPerPacket = 1; 
    streamFormat.mBytesPerFrame = four_bytes_per_float;  
    streamFormat.mChannelsPerFrame = 1; 
    streamFormat.mBitsPerChannel = four_bytes_per_float * eight_bits_per_byte; 
    err = AudioUnitSetProperty (self.toneUnit, 
           kAudioUnitProperty_StreamFormat, 
           kAudioUnitScope_Input, 
           0, 
           &streamFormat, 
           sizeof(AudioStreamBasicDescription)); 
    if (err) 
     DLog(@"Error setting stream format"); 
} 

@end 


OSStatus RenderTone(
        void *inRefCon, 
        AudioUnitRenderActionFlags *ioActionFlags, 
        const AudioTimeStamp  *inTimeStamp, 
        UInt32      inBusNumber, 
        UInt32      inNumberFrames, 
        AudioBufferList    *ioData) 

{ 
    // Fixed amplitude is good enough for our purposes 
    const double amplitude = 0.25; 

    // Get the tone parameters out of the view controller 
    ToneGen *toneGen = (__bridge ToneGen *)inRefCon; 
    double theta = toneGen.theta; 
    double theta_increment = 2.0 * M_PI * toneGen.frequency/toneGen.sampleRate; 

    // This is a mono tone generator so we only need the first buffer 
    const int channel = 0; 
    Float32 *buffer = (Float32 *)ioData->mBuffers[channel].mData; 

    // Generate the samples 
    for (UInt32 frame = 0; frame < inNumberFrames; frame++) 
    { 
     buffer[frame] = sin(theta) * amplitude; 

     theta += theta_increment; 
     if (theta > 2.0 * M_PI) 
     { 
      theta -= 2.0 * M_PI; 
     } 
    } 

    // Store the theta back in the view controller 
    toneGen.theta = theta; 

    return noErr; 
} 

void ToneInterruptionListener(void *inClientData, UInt32 inInterruptionState) 
{ 
    ToneGen *toneGen = (__bridge ToneGen *)inClientData; 
    [toneGen stop]; 
} 

Music.h

#import <Foundation/Foundation.h> 

@interface Music : NSObject 
- (void) play:(NSString *)music; 
- (void) stop; 
@end 

Music.m

#import "Music.h" 
#import "ToneGen.h" 

@interface Music() 
@property (nonatomic, readonly) ToneGen *toneGen; 
@property (nonatomic, assign) int octive; 
@property (nonatomic, assign) int tempo; 
@property (nonatomic, assign) int length; 

@property (nonatomic, strong) NSData *music; 
@property (nonatomic, assign) int dataPos; 
@property (nonatomic, assign) BOOL isPlaying; 

- (void)playNote; 
@end 

@implementation Music 
@synthesize toneGen = _toneGen; 
- (ToneGen*)toneGen 
{ 
    if (_toneGen == nil) 
    { 
     _toneGen = [[ToneGen alloc] init]; 
     _toneGen.delegate = self; 
    } 
    return _toneGen; 
} 
@synthesize octive = _octive; 
- (void)setOctive:(int)octive 
{ 
    // Sinity Check 
    if (octive < 0) 
     octive = 0; 
    if (octive > 6) 
     octive = 6; 
    _octive = octive; 
} 
@synthesize tempo = _tempo; 
- (void)setTempo:(int)tempo 
{ 
    // Sinity Check 
    if (tempo < 30) 
     tempo = 30; 
    if (tempo > 255) 
     tempo = 255; 
    _tempo = tempo; 
} 
@synthesize length = _length; 
- (void)setLength:(int)length 
{ 
    // Sinity Check 
    if (length < 1) 
     length = 1; 
    if (length > 64) 
     length = 64; 
    _length = length; 
} 
@synthesize music = _music; 
@synthesize dataPos = _dataPos; 
@synthesize isPlaying = _isPlaying; 


- (id)init 
{ 
    self = [super init]; 
    if (self) 
    { 
     self.octive = 4; 
     self.tempo = 120; 
     self.length = 1; 
     return self; 
    } 
    return nil; 
} 

- (void) play:(NSString *)music 
{ 
    DLog(@"%@", music); 
    self.music = [[music stringByReplacingOccurrencesOfString:@"+" withString:@"#"] 
        dataUsingEncoding: NSASCIIStringEncoding]; 
    self.dataPos = 0; 
    self.isPlaying = YES; 
    [self playNote]; 
} 

- (void)stop 
{ 
    self.isPlaying = NO; 
} 

- (void)playNote 
{ 
    if (!self.isPlaying) 
     return; 

    if (self.dataPos > self.music.length || self.music.length == 0) { 
     self.isPlaying = NO; 
     return; 
    } 

    unsigned char *data = (unsigned char*)[self.music bytes]; 
    unsigned int code = (unsigned int)data[self.dataPos]; 
    self.dataPos++; 

    switch (code) { 
     case 65: // A 
     case 66: // B 
     case 67: // C 
     case 68: // D 
     case 69: // E 
     case 70: // F 
     case 71: // G 
      { 
       // Peak at the next char to look for sharp or flat 
       bool sharp = NO; 
       bool flat = NO; 
       if (self.dataPos < self.music.length) { 
        unsigned int peak = (unsigned int)data[self.dataPos]; 
        if (peak == 35) // # 
        { 
         self.dataPos++; 
         sharp = YES; 
        } 
        else if (peak == 45) // - 
        { 
         self.dataPos++; 
         flat = YES; 
        } 
       } 

       // Peak ahead for a length changes 
       bool look = YES; 
       int count = 0; 
       int newLength = 0; 
       while (self.dataPos < self.music.length && look) { 
        unsigned int peak = (unsigned int)data[self.dataPos]; 
        if (peak >= 48 && peak <= 57) 
        { 
         peak -= 48; 
         int n = (count * 10); 
         if (n == 0) { n = 1; } 
         newLength += peak * n; 
         self.dataPos++; 
        } else { 
         look = NO; 
        } 
       } 

       // Pick the note length 
       int length = self.length; 
       if (newLength != 0) 
       { 
        DLog(@"InlineLength: %d", newLength); 
        length = newLength; 
       } 


       // Create the note string 
       NSString *note = [NSString stringWithFormat:@"%c", code]; 
       if (sharp) 
        note = [note stringByAppendingFormat:@"#"]; 
       else if (flat) 
        note = [note stringByAppendingFormat:@"-"]; 

       // Set the tone generator freq 
       [self setFreq:[self getNoteNumber:note]]; 

       // Play the note 
       [self.toneGen play:(self.tempo/length)]; 
      } 
      break; 

     case 76: // L (length) 
     { 
      bool look = YES; 
      int newLength = 0; 
      while (self.dataPos < self.music.length && look) { 
       unsigned int peak = (unsigned int)data[self.dataPos]; 
       if (peak >= 48 && peak <= 57) 
       { 
        peak -= 48; 
        newLength = newLength * 10 + peak; 
        self.dataPos++; 
       } else { 
        look = NO; 
       } 
      } 
      self.length = newLength; 
      DLog(@"Length: %d", self.length); 
      [self playNote]; 
     } 
      break; 

     case 79: // O (octive) 
      { 
       bool look = YES; 
       int newOctive = 0; 
       while (self.dataPos < self.music.length && look) { 
        unsigned int peak = (unsigned int)data[self.dataPos]; 
        if (peak >= 48 && peak <= 57) 
        { 
         peak -= 48; 
         newOctive = newOctive * 10 + peak; 
         self.dataPos++; 
        } else { 
         look = NO; 
        } 
       } 
       self.octive = newOctive; 
       DLog(@"Octive: %d", self.self.octive); 
       [self playNote]; 
      } 
      break; 

     case 84: // T (tempo) 
      { 
       bool look = YES; 
       int newTempo = 0; 
       while (self.dataPos < self.music.length && look) { 
        unsigned int peak = (unsigned int)data[self.dataPos]; 
        if (peak >= 48 && peak <= 57) 
        { 
         peak -= 48; 
         newTempo = newTempo * 10 + peak; 
         self.dataPos++; 
        } else { 
         look = NO; 
        } 
       } 
       self.tempo = newTempo; 
       DLog(@"Tempo: %d", self.self.tempo); 
       [self playNote]; 
      } 
      break; 

     default: 
      [self playNote]; 
      break; 
    } 
} 


- (int)getNoteNumber:(NSString*)note 
{ 
    note = [note uppercaseString]; 
    DLog(@"%@", note); 

    if ([note isEqualToString:@"A"]) 
     return 0; 
    else if ([note isEqualToString:@"A#"] || [note isEqualToString:@"B-"]) 
     return 1; 
    else if ([note isEqualToString:@"B"] || [note isEqualToString:@"C-"]) 
     return 2; 
    else if ([note isEqualToString:@"C"] || [note isEqualToString:@"B#"]) 
     return 3; 
    else if ([note isEqualToString:@"C#"] || [note isEqualToString:@"D-"]) 
     return 4; 
    else if ([note isEqualToString:@"D"]) 
     return 5; 
    else if ([note isEqualToString:@"D#"] || [note isEqualToString:@"E-"]) 
     return 6; 
    else if ([note isEqualToString:@"E"] || [note isEqualToString:@"F-"]) 
     return 7; 
    else if ([note isEqualToString:@"F"] || [note isEqualToString:@"E#"]) 
     return 8; 
    else if ([note isEqualToString:@"F#"] || [note isEqualToString:@"G-"]) 
     return 9; 
    else if ([note isEqualToString:@"G"]) 
     return 10; 
    else if ([note isEqualToString:@"G#"]) 
     return 11; 
} 

- (void)setFreq:(int)note 
{ 
    float a = powf(2, self.octive); 
    float b = powf(1.059463, note); 
    float freq = roundf((275.0 * a * b)/10); 
    self.toneGen.frequency = freq; 
} 

- (void)toneStop 
{ 
    [self playNote]; 
} 

@end 

は... tune少しMusicオブジェクトを作成し、再生する

[self.music play:@"T180 DF#A L2 A L4 O4 AA P4 F#F# P4 O3 D DF#A L2 A L4 O4 AA P4 GG P4 O3 C#C#EB L2 B L4 O4 BB P4 GG P4 O3 C#C#EB L2 B L4 O4 BB P4 F+F+ P4 O3 DDF#A L2 O4 D L4 O5 DD P4O4 AA P4 O3 DDF#A L2 O4 D L4 O5 DD P4O4 BB P4 EEG L8 B P8 ML B1 L4 MN G#A ML L3 O5 F#1L4 MN D O4 F# ML L2 F# MN L4 E ML L2 B MN L4 AD P8 D8 D4"]; 

ノート間のチャープを削除する方法上の任意のアイデアを再生するには？

Answer 1

私はあなたがノート間のオーディオ出力を停止ビットが犯人であることを考える：

if (self.toneUnit) 
{ 
    AudioOutputUnitStop(self.toneUnit); 
    AudioUnitUninitialize(self.toneUnit); 
    AudioComponentInstanceDispose(self.toneUnit); 
    self.toneUnit = nil; 
} 

だけアクティブトーンユニットを残して、あなたは以下のさえずりを持っています。おそらく、RenderToneを実行し続けて振幅ゼロを生成することによって、無音を生成する別の方法が必要になります。

周波数を変更して振幅を無駄にしないようにし、周波数を更新して再びフェードインすることで、残ったわずかなチャープを除去することができました。これはもちろん、古いPCスピーカーができなかったことです（すぐにもう一度電源を入れ直した少数の人を除いて）が、非常に急速にフェードを起こすと、チャープなしで古い学校の効果を得ることができます。

ここ（現在は邪悪なグローバル変数を使用して）私のフェージングRenderTone機能です：

double currentFrequency=0; 
double currentSampleRate=0; 
double currentAmplitude=0; 

OSStatus RenderTone(
        void *inRefCon, 
        AudioUnitRenderActionFlags *ioActionFlags, 
        const AudioTimeStamp  *inTimeStamp, 
        UInt32      inBusNumber, 
        UInt32      inNumberFrames, 
        AudioBufferList    *ioData) 

{ 
    // Fixed amplitude is good enough for our purposes 
    const double amplitude = 0.5; 

    // Get the tone parameters out of the view controller 
    ToneGen *toneGen = (__bridge ToneGen *)inRefCon; 
    double theta = toneGen.theta; 

    BOOL fadingOut = NO; 
    if ((currentFrequency != toneGen.frequency) || (currentSampleRate != toneGen.sampleRate)) 
    { 
     if (currentAmplitude > DBL_EPSILON) 
     { 
      fadingOut = YES; 
     } 
     else 
     { 
      currentFrequency = toneGen.frequency; 
      currentSampleRate = toneGen.sampleRate; 
     } 
    } 

    double theta_increment = 2.0 * M_PI * currentFrequency /currentSampleRate; 

    // This is a mono tone generator so we only need the first buffer 
    const int channel = 0; 
    Float32 *buffer = (Float32 *)ioData->mBuffers[channel].mData; 

    // Generate the samples 
    for (UInt32 frame = 0; frame < inNumberFrames; frame++) 
    { 
     buffer[frame] = sin(theta) * currentAmplitude; 
     //NSLog(@"amplitude = %f", currentAmplitude); 

     theta += theta_increment; 
     if (theta > 2.0 * M_PI) 
     { 
      theta -= 2.0 * M_PI; 
     } 
     if (fadingOut) 
     { 
      if (currentAmplitude > 0) 
      { 
       currentAmplitude -= 0.001; 
       if (currentAmplitude < 0) 
        currentAmplitude = 0; 
      } 
     } 
     else 
     { 
      if (currentAmplitude < amplitude) 
      { 
       currentAmplitude += 0.001; 
       if (currentAmplitude > amplitude) 
        currentAmplitude = amplitude; 
      } 
     } 

    } 

    // Store the theta back in the view controller 
    toneGen.theta = theta; 

    return noErr; 
} 

Answer 2

少しチャープは、一般的に数学の成果物であることを。耳は基本的に周波数領域の入力信号を分析します。例えば、周波数220Hzの定常的な正弦波はAのように聞こえますが、正弦波が安定していない場合、境界のために他の周波数が現れます。特に、突然音を開始または停止する非常に高い周波数成分のために、ポップが少し得られます。

synthesizer（Obj-CではなくJavascriptではコンセプトは同じですが）これを解決する方法は、300サンプル以上の音をフェードインして音を消すことです音符をオフにして300サンプルほど。境界を全く持たない以外の境界効果を完全に排除する方法はありませんが、小さくて知覚できない量のフェードさえも境界効果を知覚できなくします。