multitone sine wave frequencies
I have a program that generates a sine wave. I wanted to know how to generate a multitone wave with 2 frequencies using this program.What has to be changed? Any help would be greatly appreciated.
Code:
static void generate_sine(const snd_pcm_channel_area_t *areas,
snd_pcm_uframes_t offset,
int count, double *_phase)
{
static double max_phase = 2. * M_PI;
double phase = *_phase;
double step = max_phase*freq/(double)rate;
unsigned char *samples[channels];
int steps[channels];
unsigned int chn;
int format_bits = snd_pcm_format_width(format);
unsigned int maxval = (1 << (format_bits - 1)) - 1;
int bps = format_bits / 8; // bytes per sample
int phys_bps = snd_pcm_format_physical_width(format) / 8;
int big_endian = snd_pcm_format_big_endian(format) == 1;
int to_unsigned = snd_pcm_format_unsigned(format) == 1;
int is_float = (format == SND_PCM_FORMAT_FLOAT_LE ||
format == SND_PCM_FORMAT_FLOAT_BE);
float amplitude_scale = amplitude/8.56;
// verify and prepare the contents of areas
for (chn = 0; chn < channels; chn++) {
if ((areas[chn].first % 8) != 0) {
printf("areas[%i].first == %i, aborting...", chn , areas[chn].first);
exit(EXIT_FAILURE);
}
samples[chn] = (((unsigned char *)areas[chn].addr) + (areas[chn].first / 8));
if ((areas[chn].step % 16) != 0) {
// printf("areas[%i].step == %i, aborting... ", chn areas[chn].step);
exit(EXIT_FAILURE);
}
steps[chn] = areas[chn].step / 8;
samples[chn] += offset * steps[chn];
}
// fill the channel areas
while (count-- > 0) {
union {
float f;
int i;
} fval;
int res, i;
if (is_float) {
fval.f = amplitude_scale * sin(phase) * maxval;
res = fval.i;
} else
res = amplitude_scale * sin(phase) * maxval;
if (to_unsigned)
res ^= 1U << (format_bits - 1);
for (chn = 0; chn < channels; chn++) {
// Generate data in native endian format
if (big_endian) {
for (i = 0; i < bps; i++)
*(samples[chn] + phys_bps - 1 - i) = (res >> i * 8) & 0xff;
} else {
// for (i = 0; i < bps; i++)
// *(samples[chn] + i) = (res >> i * 8) & 0xff;
}
samples[chn] += steps[chn];
}
phase += step;
if (phase >= max_phase)
phase -= max_phase;
}
*_phase = phase;
}
Code:
static int write_loop(snd_pcm_t *handle,
signed short *samples,
snd_pcm_channel_area_t *areas)
{
double phase = 0;
signed short *ptr;
int err, cptr;
while (1) {
generate_sine(areas, 0, period_size, &phase);
ptr = samples;
cptr = period_size;
while (cptr > 0) {
err = snd_pcm_writei(handle, ptr, cptr);
if (err == -EAGAIN)
continue;
if (err < 0) {
if (xrun_recovery(handle, err) < 0) {
printf("Write error: %s ", snd_strerror(err));
exit(EXIT_FAILURE);
}
break; /* skip one period */
}
ptr += err * channels;
cptr -= err;
}
}
}
Code:
int main(int argc, char *argv[])
{
snd_pcm_t *handle;
int err;
snd_pcm_hw_params_t *hwparams;
snd_pcm_sw_params_t *swparams;
int method = 0;
signed short *samples;
unsigned int chn;
snd_pcm_channel_area_t *areas;
snd_pcm_hw_params_alloca(&hwparams);
snd_pcm_sw_params_alloca(&swparams);
err = snd_output_stdio_attach(&output, stdout, 0);
printf( "snd_output_stdio_attach err=%d\n", err);
err = snd_pcm_open(&hspdif, device, SND_PCM_STREAM_PLAYBACK, 0);
printf( "snd_pcm_open err=%d\n", err);
err = set_hwparams(hspdif, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
printf( "set_hwparams err=%d\n", err);
err = set_swparams(hspdif, swparams);
printf( "set_swparams err=%d\n", err);
samples = new signed short [period_size * channels * snd_pcm_format_physical_width(format)];
printf( "samples array_size=%d\n", int( period_size * channels * snd_pcm_format_physical_width(format)) );
areas = new snd_pcm_channel_area_t [channels];
printf( "areas channels=%d\n", channels);
for (unsigned int chn = 0; chn < channels; chn++) {
areas[chn].addr = samples;
areas[chn].first = chn * snd_pcm_format_physical_width(format);
areas[chn].step = channels * snd_pcm_format_physical_width(format);
}
err = transfer_methods[method].transfer_loop(handle, samples, areas);
if (err < 0)
printf("Transfer failed: %s", snd_strerror(err));
delete [] areas;
delete []samples;
snd_pcm_close(handle);
return 0;
}
|
