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qudarature

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This commit is contained in:
kuba
2024-12-30 12:44:22 +01:00
parent 77643571e3
commit 8314299abb
1 changed files with 20 additions and 9 deletions
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stereo_coder_rds.c
+20 -9
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@@ -37,23 +37,34 @@ void float_array_to_s16le(const float *input, int16_t *output, size_t num_sample
} }
#define M_2PI (3.14159265358979323846 * 2.0) #define M_2PI (3.14159265358979323846 * 2.0)
#define M_PI_2 (3.14159265358979323846 / 2.0)
// Track phase continuously to maintain frequency accuracy
typedef struct { typedef struct {
float phase; float phase;
float phase_increment; float phase_increment;
float quadrature_phase;
} Oscillator; } Oscillator;
void init_oscillator(Oscillator *osc, float frequency, float sample_rate) { void init_oscillator(Oscillator *osc, float frequency, float sample_rate) {
osc->phase = 0.0f; osc->phase = 0.0f;
osc->quadrature_phase = M_PI_2; // 90 degrees phase shift
osc->phase_increment = (M_2PI * frequency) / sample_rate; osc->phase_increment = (M_2PI * frequency) / sample_rate;
} }
float get_next_sample(Oscillator *osc) { float get_next_sample(Oscillator *osc, int quadrature) {
float sample = sinf(osc->phase); float sample;
osc->phase += osc->phase_increment; if (quadrature) {
if (osc->phase >= M_2PI) { sample = sinf(osc->quadrature_phase);
osc->phase -= M_2PI; osc->quadrature_phase += osc->phase_increment;
if (osc->quadrature_phase >= M_2PI) {
osc->quadrature_phase -= M_2PI;
}
} else {
sample = sinf(osc->phase);
osc->phase += osc->phase_increment;
if (osc->phase >= M_2PI) {
osc->phase -= M_2PI;
}
} }
return sample; return sample;
} }
@@ -174,9 +185,9 @@ int main() {
mono_s16le_to_float(input_rds, rds_data, BUFFER_SIZE); mono_s16le_to_float(input_rds, rds_data, BUFFER_SIZE);
for (int i = 0; i < BUFFER_SIZE; i++) { for (int i = 0; i < BUFFER_SIZE; i++) {
float pilot = get_next_sample(&pilot_osc); float pilot = get_next_sample(&pilot_osc, 0);
float stereo_carrier = get_next_sample(&stereo_osc); float stereo_carrier = get_next_sample(&stereo_osc, 0);
float rds_carrier = get_next_sample(&rds_osc); float rds_carrier = get_next_sample(&rds_osc, 1);
float mono = (left[i] + right[i]) / 2.0f; float mono = (left[i] + right[i]) / 2.0f;
float stereo = (left[i] - right[i]) / 2.0f; float stereo = (left[i] - right[i]) / 2.0f;