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Re: quick and dirty way to play some data?

On Feb 16, 2005, at 8:58, Ben Dougall wrote:
hello,

what's the quickest and easiest way (either c or obj-c, not c++ if possible, preferably using coreaudio) to take some data (32bit floats who's values are all between -1.0 and 1.0), call that data a sound, probably have to provide some meta info details (probably Hz, number of channels, length amongst maybe others) along with it and play it?

#include <AudioUnit/AudioUnit.h>
#include <unistd.h>

#define kNumChannels 2 // how many channels to render

// AudioUnit rendering proc to generate a sine wave
// this is NOT an efficient way to do this but does illustrate very basic synthesis and
// how to use the render callback.
#include <math.h>

static const double kAmplitude = 0.25;
static const double kToneFrequency = 440.;
static double gFrameCount = 0.;
static Float64 gSampleRate = 44100.; // you might want to get this from the AU instead

static OSStatus MyRenderer( void *inRefCon,
AudioUnitRenderActionFlags *inActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumFrames,
AudioBufferList *ioData)
{
Float32 *p0 = (Float32 *)ioData->mBuffers[0].mData;
Float32 *p1 = (Float32 *)ioData->mBuffers[1].mData;
double j = gFrameCount;
double cycleLength = gSampleRate / kToneFrequency;
for (UInt32 i = 0; i < inNumFrames; ++i) {
*p0++ = *p1++ = sin(j / cycleLength * (M_PI * 2.0)) * kAmplitude;
j += 1.0;
if (j > cycleLength)
j -= cycleLength;
}
gFrameCount = j;
return noErr;
}


int main(int argc, char *argv[])
{
ComponentDescription compDesc;
Component comp;
AudioUnit outputAU;
AudioStreamBasicDescription streamDesc;

// open output unit
compDesc.componentType = kAudioUnitType_Output;
compDesc.componentSubType = kAudioUnitSubType_DefaultOutput;
compDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
compDesc.componentFlags = 0;
compDesc.componentFlagsMask = 0;
comp = FindNextComponent(NULL, &compDesc);
verify_noerr(OpenAComponent(comp, &outputAU));

// set stream format to stereo deinterleaved float32
streamDesc.mSampleRate = gSampleRate;
streamDesc.mFormatID = kAudioFormatLinearPCM;
streamDesc.mFormatFlags = kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved;
streamDesc.mFramesPerPacket = 1;
streamDesc.mBytesPerPacket = sizeof(Float32);
streamDesc.mBytesPerFrame = sizeof(Float32);
streamDesc.mChannelsPerFrame = kNumChannels;
streamDesc.mBitsPerChannel = 32;
verify_noerr(AudioUnitSetProperty(outputAU,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
0,
&streamDesc,
sizeof(streamDesc)));

// set input proc
AURenderCallbackStruct input;
input.inputProc = MyRenderer;
input.inputProcRefCon = NULL;
verify_noerr(AudioUnitSetProperty(outputAU,
kAudioUnitProperty_SetRenderCallback,
kAudioUnitScope_Global,
0,
&input,
sizeof(input)));

// initialize
verify_noerr(AudioUnitInitialize(outputAU));

// start playing
verify_noerr(AudioOutputUnitStart(outputAU));

// sleep forever
while (1)
sleep(1);
}

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 >quick and dirty way to play some data? (From: Ben Dougall <email@hidden>)



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