How do I synthesize sounds with CoreAudio on iPhone/Mac

Question

I\'d like to play a synthesised sound in an iPhone. Instead of using a pre-recorded sound and using SystemSoundID to play an existing binary, I\'d like to synthesise it. Partial

Answer 1

Davide Vosti's link to http://lists.apple.com/archives/coreaudio-api/2008/Dec/msg00173.html no longer works, since Apple lists seem to be unresponsive. Here is Google's cache for completeness.

//
//  AudioUnitTestAppDelegate.m
//  AudioUnitTest
//
//  Created by Marc Vaillant on 11/25/08.
//  Copyright __MyCompanyName__ 2008. All rights reserved.
//

#import "AudioUnitTestAppDelegate.h"
#include 
//#include "MachTimer.hpp"
#include 
#include 

using namespace std;

#define kOutputBus 0
#define kInputBus 1
#define SAMPLE_RATE 44100

vector _pcm;
int _index;

@implementation AudioUnitTestAppDelegate

@synthesize window;

void generateTone(
                vector& pcm, 
                int freq, 
                double lengthMS, 
                int sampleRate, 
                double riseTimeMS, 
                double gain)
{
  int numSamples = ((double) sampleRate) * lengthMS / 1000.;
  int riseTimeSamples = ((double) sampleRate) * riseTimeMS / 1000.;

  if(gain > 1.)
    gain = 1.;
  if(gain < 0.)
    gain = 0.;

  pcm.resize(numSamples);

  for(int i = 0; i < numSamples; ++i)
  {
    double value = sin(2. * M_PI * freq * i / sampleRate);
    if(i < riseTimeSamples)
      value *= sin(i * M_PI / (2.0 * riseTimeSamples));
    if(i > numSamples - riseTimeSamples - 1)
      value *= sin(2. * M_PI * (i - (numSamples - riseTimeSamples) + riseTimeSamples)/ (4. * riseTimeSamples));

    pcm[i] = (int) (value * 32500.0 * gain);
    pcm[i] += (pcm[i]<<16);
  }

}

static OSStatus playbackCallback(void *inRefCon, 
                                  AudioUnitRenderActionFlags *ioActionFlags, 
                                  const AudioTimeStamp *inTimeStamp, 
                                  UInt32 inBusNumber, 
                                  UInt32 inNumberFrames, 
                                  AudioBufferList *ioData) 
{    
    cout<<"index = "<<_index<