My immediate thought was: "This would make quite possibly the coolest iPhone application ever."
I think we spent about two weeks’ worth of nights reading documentation,
source code (Cocoa, iPhone, Java, C, and others), and plain outright
stabbing in the dark code-wise getting not much more than ugly pops and
crackles. Whenever we thought we had a clean note working, we’d change
the frequency to what should be another nice clean note, and would
instead get ear-shattering screeches.
Nonetheless we persevered and were even able to come up with a nifty
little piece of code that could take an array of frequencies and play
them together in what could be made to sound like a pleasant chord.
#import "TonePlayer.h"
typedef struct {
@defs(TonePlayer);
} SinewaveDef;
@implementation TonePlayer
static float gSampleRate = 44100.;
static float notes[111] = {
8.1758, 8.6620, 9.1770, 9.7227, 10.3009, 10.9134, 11.5623, 12.2499,
12.9783, 13.7500, 14.5676, 15.4339, 16.3516, 17.3239, 18.3540, 19.4454,
20.6017, 21.8268, 23.1247, 24.4997, 25.9565, 27.5000, 29.1352, 30.8677,
32.7032, 34.6478, 36.7081, 38.8909, 41.2034, 43.6535, 46.2493, 48.9994,
51.9131, 55.0000, 58.2705, 61.7354, 65.4064, 69.2957, 73.4162, 77.7817,
82.4069, 87.3071, 92.4986, 97.9989, 103.8262, 110.0000, 116.5409, 123.4708,
130.8128, 138.5913, 146.8324, 155.5635, 164.8138, 174.6141, 184.9972,
195.9977, 207.6523, 220.0000, 233.0819, 246.9417, 261.6256, 277.1826,
293.6648, 311.1270, 329.6276, 349.2282, 369.9944, 391.9954, 415.3047,
440.0000, 466.1638, 493.8833, 523.2511, 554.3653, 587.3295, 622.2540,
659.2551, 698.4565, 739.9888, 783.9909, 830.6094, 880.0000, 932.3275,
987.7666, 1046.5023, 1108.7305, 1174.6591, 1244.5079, 1318.5102, 1396.9129,
1479.9777, 1567.9817, 1661.2188, 1760.0000, 1864.6550, 1975.5332, 2093.0045,
2217.4610, 2349.3181, 2489.0159, 2637.0205, 2793.8259, 2959.9554, 3135.9635,
3322.4376, 3520.0000, 3729.3101, 3951.0664, 4186.0090, 4434.9221, 4698.6363
};
OSStatus RenderCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData)
{
SinewaveDef* def = inRefCon;
float *outL = ioData->mBuffers[0].mData;
float *outR = ioData->mBuffers[1].mData;
float wave, j;
float freqs[kTonesAvailable];
memset(freqs, 0.0f, sizeof(freqs));
for (int i=0; i< inNumberFrames; i++){
wave = 0.0f;
j = 0.0f;
for(int m = 0; m < kTonesAvailable; ++m) {
if(def->frequencies[m] != 0) {
if(freqs[m] == 0) freqs[m] = phaseOffsetFromFrequency(def->frequencies[m]);
wave += 0.5 * sinf(def->phase[m]);
def->phase[m] += freqs[m];
++j;
}
}
wave /= j;
*outL++ = wave;
*outR++ = wave;
}
return noErr;
}
float phaseOffsetFromFrequency(float frequency) {
return (float)(frequency * 2.0 * M_PI / gSampleRate);
}
-(void)resetFrequencies{
memset(frequencies, 0.0f, sizeof(frequencies));
memset(phase, 0.0f, sizeof(phase));
}
-(OSStatus)start{
[self resetFrequencies];
OSStatus status = AudioOutputUnitStart(audioUnit);
// See http://www.phys.unsw.edu.au/jw/notes.html for note numbers
frequencies[0] = notes[60]; // C
frequencies[1] = notes[64]; // E
frequencies[2] = notes[67]; // G
sleep(1);
frequencies[0] = notes[64];
frequencies[1] = notes[67];
frequencies[2] = notes[71];
sleep(1);
frequencies[0] = notes[74];
frequencies[1] = notes[67];
frequencies[2] = notes[70];
return status;
}
-(OSStatus)stop{
return AudioOutputUnitStop(audioUnit);
}
-(void)cleanUp{
AudioUnitUninitialize(audioUnit);
}
-(AudioStreamBasicDescription)audioFormat{
return audioFormat;
}
// Below code is a cut down version (for output only) of the code written by
// Micheal "Code Fighter" Tyson (punch on Mike)
// See http://michael.tyson.id.au/2008/11/04/using-remoteio-audio-unit/ for details
-(void)intialiseAudio{
OSStatus status;
// Describe audio component
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// Get component
AudioComponent inputComponent = AudioComponentFindNext(NULL, &desc);
// Get audio units
status = AudioComponentInstanceNew(inputComponent, &audioUnit);
UInt32 flag = 1;
// Enable IO for playback
status = AudioUnitSetProperty(audioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Output,
kOutputBus,
&flag,
sizeof(flag));
// Describe format
audioFormat.mSampleRate = gSampleRate;
audioFormat.mFormatID = kAudioFormatLinearPCM;
audioFormat.mFormatFlags = kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved;
audioFormat.mFramesPerPacket = 1;
audioFormat.mBytesPerPacket = sizeof(Float32);
audioFormat.mBytesPerFrame = sizeof(Float32);
audioFormat.mChannelsPerFrame = kNumChannels;
audioFormat.mBitsPerChannel = 32;
//Apply format
status = AudioUnitSetProperty(audioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
kOutputBus,
&audioFormat,
sizeof(audioFormat));
// Set up the playback callback
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = RenderCallback;
//set the reference to "self" this becomes *inRefCon in the playback callback
callbackStruct.inputProcRefCon = self;
status = AudioUnitSetProperty(audioUnit,
kAudioUnitProperty_SetRenderCallback,
kAudioUnitScope_Global,
kOutputBus,
&callbackStruct,
sizeof(callbackStruct));
// Initialise
status = AudioUnitInitialize(audioUnit);
}
@end
I really wish that I could remember how most of it worked, or, more
importantly, the multitude of projects whose code we had to look at to
get it working. If you recognise any of the code or can help add
references on how people can build up a nice list of references for
people to use if are following a similar pursuit.
If you are wondering what ever happened to the application we were
building, it seems we weren’t the only ones who recognised the potential
of ToneMatrix as an iPhone application. During the 2-3 weeks of us
developing the sound generation code, about 5-6 ToneMatrix clones were
added to the AppStore. While most were crap, there was one that we felt
left little to be improved upon and we therefore recommend everyone goes
and downloads
Melodica.
It’s just as addictive as the Flash version, only portable!
