RtAudio example - Sine Wave Tone (440Hz)

sine.cpp

// RtAudio exsample - Sine Wave (440Hz)

#include <math.h>

#include <RtAudio/RtAudio.h>

#if defined(__cplusplus)
extern "C" {
#endif

typedef struct {
    unsigned int	nRate;		/* Sampling Rate (sample/sec) */
    unsigned int	nChannel;	/* Channel Number */
    unsigned int	nFrame;		/* Frame Number of Wave Table */
    float		*wftable;	/* Wave Form Table(interleaved) */
    unsigned int	cur;		/* current index of WaveFormTable(in Frame) */
} CallbackData;

static int
rtaudio_callback(
	void			*outbuf,
	void			*inbuf,
	unsigned int		nFrames,
	double			streamtime,
	RtAudioStreamStatus	status,
	void			*userdata)
{
	(void)inbuf;
	float	*buf = (float*)outbuf;
	unsigned int remainFrames;
	CallbackData	*data = (CallbackData*)userdata;

	remainFrames = nFrames;
	while (remainFrames > 0) {
	    unsigned int sz = data->nFrame - data->cur;
	    if (sz > remainFrames)
		sz = remainFrames;
	    memcpy(buf, data->wftable+(data->cur*data->nChannel),
		   sz * data->nChannel * sizeof(float));
	    data->cur = (data->cur + sz) % data->nFrame;
	    buf += sz * data->nChannel;
	    remainFrames -= sz;
	}
	return 0;
}

int
main(void)
{
    RtAudio *audio;
    unsigned int bufsize = 4096;
    CallbackData data;

    try {
	audio = new RtAudio(RtAudio::MACOSX_CORE);
    }catch  (RtError e){
	fprintf(stderr, "fail to create RtAudio: %s¥n", e.what());
	return 1;
    }
    if (!audio){
	fprintf(stderr, "fail to allocate RtAudio¥n");
	return 1;
    }
    /* probe audio devices */
    unsigned int devId = audio->getDefaultOutputDevice();

    /* Setup output stream parameters */
    RtAudio::StreamParameters *outParam = new RtAudio::StreamParameters();

    outParam->deviceId = devId;
    outParam->nChannels = 2;

    audio->openStream(outParam, NULL, RTAUDIO_FLOAT32, 44100,
     		      &bufsize, rtaudio_callback, &data);

    /* Create Wave Form Table */
    data.nRate = 44100;
    /* Frame Number is based on Freq(440Hz) and Sampling Rate(44100) */
    /* hmm... nFrame = 44100 is enough approximation, maybe... */
    data.nFrame = 44100;
    data.nChannel = outParam->nChannels;
    data.cur = 0;
    data.wftable = (float *)calloc(data.nChannel * data.nFrame, sizeof(float));
    if (!data.wftable)
    {
	delete audio;
	fprintf(stderr, "fail to allocate memory¥n");
	return 1;
    }
    for(unsigned int i = 0; i < data.nFrame; i++) {
      float v = sin(i * M_PI * 2 * 440 / data.nRate);
      for(unsigned int j = 0; j < data.nChannel; j++) {
	  data.wftable[i*data.nChannel+j] = v;
      }
    }

    audio->startStream();
    sleep(10);
    audio->stopStream();
    audio->closeStream();
    delete audio;

    return 0;
}

#if defined(__cplusplus)
}
#endif