AudioUnit音频发生器在每个音调结束时给我一个唧唧声 [英] AudioUnit tone generator is giving me a chirp at the end of each tone generated

问题描述

我正在为旧的GWBasic PLAY 命令创建一个旧的学校音乐模拟器。为此，我有一个音源和音乐播放器。在播放的每个音符之间，我发出一声唧唧喳喳的声音。以下是我的课程：

I'm creating a old school music emulator for the old GWBasic PLAY command. To that end I have a tone generator and a music player. Between each of the notes played I'm getting a chirp sound that mucking things up. Below are both of my classes:

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

播放小调整创建音乐对象并且玩...

To play little tune create a Music object and play...

[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"];

关于如何消除音符之间啁啾的想法？

Any idea on how to remove the chirp between notes?

推荐答案

我认为你在音符之间停止音频输出的位是罪魁祸首：

I think that the bit where you stop audio output between notes is the culprit:

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

只需让音调单元保持活动状态就可以减少啁啾声。你需要一些其他的方法来产生沉默，可能是让RenderTone继续运行但产生零幅度。

Just leave the tone unit active and you'll have less chirping. You'll need some other way to generate silence, probably by having RenderTone continue to run but generate amplitude zero.

我能够消除由于拥有而留下的轻微唧唧声它，在频率变化时，将幅度淡化为零，更新频率，然后再次淡入。这当然是老式PC扬声器无法做到的事情（除了少数人再次快速开机），但是如果没有唧唧喳喳，你很快就可以获得老派的效果。

I was able to eliminate the slight chirps that remained by having it, on a frequency change, fade the amplitude down to nothing, update the frequenmcy, and fade back in again. This is of course what the old PC speaker couldn't do (except for a few people who rapidly switched it on again), but with a very rapid fade you can probably get the old-school effect without the chirps.

这是我的淡化 RenderTone 函数（目前使用邪恶的全局变量）：

Here's my fading RenderTone function (currently using evil global variables):

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;
}

这篇关于AudioUnit音频发生器在每个音调结束时给我一个唧唧声的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！