78 lines
2.5 KiB
C
78 lines
2.5 KiB
C
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#include "ac108_help.h"
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void generate_sine(const snd_pcm_channel_area_t *areas,
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snd_pcm_uframes_t offset,
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int count, double *_phase)
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{
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snd_pcm_format_t format = SND_PCM_FORMAT_S32; /* sample format */
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unsigned int rate = 16000; /* stream rate */
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unsigned int channels = 4; /* count of channels */
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unsigned int buffer_time = 500000; /* ring buffer length in us */
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unsigned int period_time = 100000; /* period time in us */
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double freq = 160; /* sinusoidal wave frequency in Hz */
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int verbose = 0; /* verbose flag */
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int resample = 1; /* enable alsa-lib resampling */
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int period_event = 0; /* produce poll event after each period */
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static double max_phase = 2. * M_PI;
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double phase = *_phase;
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double step = max_phase*freq/(double)rate;
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unsigned char *samples[channels];
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int steps[channels];
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unsigned int chn;
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int format_bits = snd_pcm_format_width(format);
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unsigned int maxval = (1 << (format_bits - 1)) - 1;
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int bps = format_bits / 8; /* bytes per sample */
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int phys_bps = snd_pcm_format_physical_width(format) / 8;
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int big_endian = snd_pcm_format_big_endian(format) == 1;
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int to_unsigned = snd_pcm_format_unsigned(format) == 1;
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int is_float = (format == SND_PCM_FORMAT_FLOAT_LE ||
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format == SND_PCM_FORMAT_FLOAT_BE);
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/* verify and prepare the contents of areas */
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for (chn = 0; chn < channels; chn++) {
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if ((areas[chn].first % 8) != 0) {
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printf("areas[%i].first == %i, aborting...\n", chn, areas[chn].first);
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exit(EXIT_FAILURE);
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}
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samples[chn] = /*(signed short *)*/(((unsigned char *)areas[chn].addr) + (areas[chn].first / 8));
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if ((areas[chn].step % 16) != 0) {
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printf("areas[%i].step == %i, aborting...\n", chn, areas[chn].step);
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exit(EXIT_FAILURE);
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}
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steps[chn] = areas[chn].step / 8;
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samples[chn] += offset * steps[chn];
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}
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/* fill the channel areas */
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while (count-- > 0) {
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union {
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float f;
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int i;
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} fval;
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int res, i;
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if (is_float) {
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fval.f = sin(phase);
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res = fval.i;
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} else
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res = sin(phase) * maxval;
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if (to_unsigned)
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res ^= 1U << (format_bits - 1);
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for (chn = 0; chn < channels; chn++) {
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/* Generate data in native endian format */
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if (big_endian) {
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for (i = 0; i < bps; i++)
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*(samples[chn] + phys_bps - 1 - i) = (res >> i * 8) & 0xff;
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} else {
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for (i = 0; i < bps; i++)
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*(samples[chn] + i) = (res >> i * 8) & 0xff;
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}
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samples[chn] += steps[chn];
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}
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phase += step;
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if (phase >= max_phase)
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phase -= max_phase;
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}
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*_phase = phase;
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}
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