Я тоже расследую это. Я думаю, что AudioQueue API - это, вероятно, правильный путь.
Вот, насколько я понял, похоже, все в порядке.
Файл: BleepMachine.h
//
// BleepMachine.h
// WgHeroPrototype
//
// Created by Andy Buchanan on 05/01/2010.
// Copyright 2010 Andy Buchanan. All rights reserved.
//
#include <AudioToolbox/AudioToolbox.h>
// Class to implement sound playback using the AudioQueue API's
// Currently just supports playing two sine wave tones, one per
// stereo channel. The sound data is liitle-endian signed 16-bit @ 44.1KHz
//
class BleepMachine
{
static void staticQueueCallback( void* userData, AudioQueueRef outAQ, AudioQueueBufferRef outBuffer )
{
BleepMachine* pThis = reinterpret_cast<BleepMachine*> ( userData );
pThis->queueCallback( outAQ, outBuffer );
}
void queueCallback( AudioQueueRef outAQ, AudioQueueBufferRef outBuffer );
AudioStreamBasicDescription m_outFormat;
AudioQueueRef m_outAQ;
enum
{
kBufferSizeInFrames = 512,
kNumBuffers = 4,
kSampleRate = 44100,
};
AudioQueueBufferRef m_buffers[kNumBuffers];
bool m_isInitialised;
struct Wave
{
Wave(): volume(1.f), phase(0.f), frequency(0.f), fStep(0.f) {}
float volume;
float phase;
float frequency;
float fStep;
};
enum
{
kLeftWave = 0,
kRightWave = 1,
kNumWaves,
};
Wave m_waves[kNumWaves];
public:
BleepMachine();
~BleepMachine();
bool Initialise();
void Shutdown();
bool Start();
bool Stop();
bool SetWave( int id, float frequency, float volume );
};
// Notes by name. Integer value is number of semitones above A.
enum Note
{
A = 0,
Asharp,
B,
C,
Csharp,
D,
Dsharp,
E,
F,
Fsharp,
G,
Gsharp,
Bflat = Asharp,
Dflat = Csharp,
Eflat = Dsharp,
Gflat = Fsharp,
Aflat = Gsharp,
};
// Helper function calculates fundamental frequency for a given note
float CalculateFrequencyFromNote( SInt32 semiTones, SInt32 octave=4 );
float CalculateFrequencyFromMIDINote( SInt32 midiNoteNumber );
Файл: BleepMachine.mm
//
// BleepMachine.mm
// WgHeroPrototype
//
// Created by Andy Buchanan on 05/01/2010.
// Copyright 2010 Andy Buchanan. All rights reserved.
//
#include "BleepMachine.h"
void BleepMachine::queueCallback( AudioQueueRef outAQ, AudioQueueBufferRef outBuffer )
{
// Render the wave
// AudioQueueBufferRef is considered "opaque", but it's a reference to
// an AudioQueueBuffer which is not.
// All the samples manipulate this, so I'm not quite sure what they mean by opaque
// saying....
SInt16* coreAudioBuffer = (SInt16*)outBuffer->mAudioData;
// Specify how many bytes we're providing
outBuffer->mAudioDataByteSize = kBufferSizeInFrames * m_outFormat.mBytesPerFrame;
// Generate the sine waves to Signed 16-Bit Stero interleaved ( Little Endian )
float volumeL = m_waves[kLeftWave].volume;
float volumeR = m_waves[kRightWave].volume;
float phaseL = m_waves[kLeftWave].phase;
float phaseR = m_waves[kRightWave].phase;
float fStepL = m_waves[kLeftWave].fStep;
float fStepR = m_waves[kRightWave].fStep;
for( int s=0; s<kBufferSizeInFrames*2; s+=2 )
{
float sampleL = ( volumeL * sinf( phaseL ) );
float sampleR = ( volumeR * sinf( phaseR ) );
short sampleIL = (int)(sampleL * 32767.0);
short sampleIR = (int)(sampleR * 32767.0);
coreAudioBuffer[s] = sampleIL;
coreAudioBuffer[s+1] = sampleIR;
phaseL += fStepL;
phaseR += fStepR;
}
m_waves[kLeftWave].phase = fmodf( phaseL, 2 * M_PI ); // Take modulus to preserve precision
m_waves[kRightWave].phase = fmodf( phaseR, 2 * M_PI );
// Enqueue the buffer
AudioQueueEnqueueBuffer( m_outAQ, outBuffer, 0, NULL );
}
bool BleepMachine::SetWave( int id, float frequency, float volume )
{
if ( ( id < kLeftWave ) || ( id >= kNumWaves ) ) return false;
Wave& wave = m_waves[ id ];
wave.volume = volume;
wave.frequency = frequency;
wave.fStep = 2 * M_PI * frequency / kSampleRate;
return true;
}
bool BleepMachine::Initialise()
{
m_outFormat.mSampleRate = kSampleRate;
m_outFormat.mFormatID = kAudioFormatLinearPCM;
m_outFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
m_outFormat.mFramesPerPacket = 1;
m_outFormat.mChannelsPerFrame = 2;
m_outFormat.mBytesPerPacket = m_outFormat.mBytesPerFrame = sizeof(UInt16) * 2;
m_outFormat.mBitsPerChannel = 16;
m_outFormat.mReserved = 0;
OSStatus result = AudioQueueNewOutput(
&m_outFormat,
BleepMachine::staticQueueCallback,
this,
NULL,
NULL,
0,
&m_outAQ
);
if ( result < 0 )
{
printf( "ERROR: %d\n", (int)result );
return false;
}
// Allocate buffers for the audio
UInt32 bufferSizeBytes = kBufferSizeInFrames * m_outFormat.mBytesPerFrame;
for ( int buf=0; buf<kNumBuffers; buf++ )
{
OSStatus result = AudioQueueAllocateBuffer( m_outAQ, bufferSizeBytes, &m_buffers[ buf ] );
if ( result )
{
printf( "ERROR: %d\n", (int)result );
return false;
}
// Prime the buffers
queueCallback( m_outAQ, m_buffers[ buf ] );
}
m_isInitialised = true;
return true;
}
void BleepMachine::Shutdown()
{
Stop();
if ( m_outAQ )
{
// AudioQueueDispose also chucks any audio buffers it has
AudioQueueDispose( m_outAQ, true );
}
m_isInitialised = false;
}
BleepMachine::BleepMachine()
: m_isInitialised(false), m_outAQ(0)
{
for ( int buf=0; buf<kNumBuffers; buf++ )
{
m_buffers[ buf ] = NULL;
}
}
BleepMachine::~BleepMachine()
{
Shutdown();
}
bool BleepMachine::Start()
{
OSStatus result = AudioQueueSetParameter( m_outAQ, kAudioQueueParam_Volume, 1.0 );
if ( result ) printf( "ERROR: %d\n", (int)result );
// Start the queue
result = AudioQueueStart( m_outAQ, NULL );
if ( result ) printf( "ERROR: %d\n", (int)result );
return true;
}
bool BleepMachine::Stop()
{
OSStatus result = AudioQueueStop( m_outAQ, true );
if ( result ) printf( "ERROR: %d\n", (int)result );
return true;
}
// A (A4=440)
// A# f(n)=2^(n/12) * r
// B where n = number of semitones
// C and r is the root frequency e.g. 440
// C#
// D frq -> MIDI note number
// D# p = 69 + 12 x log2(f/440)
// E
// F
// F#
// G
// G#
//
// MIDI Note ref: http://www.phys.unsw.edu.au/jw/notes.html
//
// MIDI Node numbers:
// A3 57
// A#3 58
// B3 59
// C4 60 <--
// C#4 61
// D4 62
// D#4 63
// E4 64
// F4 65
// F#4 66
// G4 67
// G#4 68
// A4 69 <--
// A#4 70
// B4 71
// C5 72
float CalculateFrequencyFromNote( SInt32 semiTones, SInt32 octave )
{
semiTones += ( 12 * (octave-4) );
float root = 440.f;
float fn = powf( 2.f, (float)semiTones/12.f ) * root;
return fn;
}
float CalculateFrequencyFromMIDINote( SInt32 midiNoteNumber )
{
SInt32 semiTones = midiNoteNumber - 69;
return CalculateFrequencyFromNote( semiTones, 4 );
}
//for ( SInt32 midiNote=21; midiNote<=108; ++midiNote )
//{
// printf( "MIDI Note %d: %f Hz \n",(int)midiNote,CalculateFrequencyFromMIDINote( midiNote ) );
//}
Обновление: основные сведения об использовании
Initialise. Где-то в начале, я использую initFromNib: в моем коде
m_bleepMachine = new BleepMachine;
m_bleepMachine->Initialise();
m_bleepMachine->Start();
Теперь воспроизводится звук, но генерируется тишина.
В своем коде вызывайте его, когда хотите изменить генерацию тона
m_bleepMachine->SetWave( ch, frq, vol );
- где ch - канал (0 или 1)
- где frq - частота, устанавливаемая в Гц
- где vol - объем (0 = -Inf дБ, 1 = -0 дБ)
При завершении программы
delete m_bleepMachine;