mirror of
https://github.com/rtlsdrblog/rtl-sdr-blog.git
synced 2025-01-27 02:14:55 +01:00
rtl_fm: WBFM, AM, LSB and USB demod, raw IQ mode
Signed-off-by: Steve Markgraf <steve@steve-m.de>
This commit is contained in:
Kyle Keen
Steve Markgraf
parent
995a195f4d
commit
b0b9e3d24f
227
src/rtl_fm.c
227
src/rtl_fm.c
@ -27,10 +27,11 @@
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* remove float math (disqualifies complex.h)
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* replace atan2 with a fast approximation
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* in-place array operations
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* wide band support
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* better wide band support
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* sanity checks
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* nicer FIR than square
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* scale squelch to other input parameters
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* test all the demodulations
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*/
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#include <errno.h>
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@ -56,8 +57,8 @@
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#define DEFAULT_SAMPLE_RATE 24000
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#define DEFAULT_ASYNC_BUF_NUMBER 32
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#define DEFAULT_BUF_LENGTH (1 * 16384)
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#define MINIMAL_BUF_LENGTH 512
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#define MAXIMAL_BUF_LENGTH (256 * 16384)
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#define MAXIMUM_OVERSAMPLE 16
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#define MAXIMUM_BUF_LENGTH (MAXIMUM_OVERSAMPLE * DEFAULT_BUF_LENGTH)
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#define CONSEQ_SQUELCH 20
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#define AUTO_GAIN -100
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@ -65,6 +66,7 @@ static pthread_t demod_thread;
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static sem_t data_ready;
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static int do_exit = 0;
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static rtlsdr_dev_t *dev = NULL;
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static int lcm_post[17] = {1,1,1,3,1,5,3,7,1,9,5,11,3,13,7,15,1};
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struct fm_state
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{
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@ -79,21 +81,28 @@ struct fm_state
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int squelch_level;
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int squelch_hits;
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int term_squelch_hits;
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uint8_t buf[DEFAULT_BUF_LENGTH];
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uint8_t buf[MAXIMUM_BUF_LENGTH];
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uint32_t buf_len;
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int signal[DEFAULT_BUF_LENGTH]; /* 16 bit signed i/q pairs */
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int16_t signal2[DEFAULT_BUF_LENGTH]; /* signal has lowpass, signal2 has demod */
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int signal[MAXIMUM_BUF_LENGTH]; /* 16 bit signed i/q pairs */
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int16_t signal2[MAXIMUM_BUF_LENGTH]; /* signal has lowpass, signal2 has demod */
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int signal_len;
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int signal2_len;
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FILE *file;
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int edge;
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uint32_t freqs[100];
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int freq_len;
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int freq_now;
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uint32_t sample_rate;
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int output_rate;
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int fir_enable;
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int fir[256]; /* fir_len == downsample */
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int fir_sum;
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int custom_atan;
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int deemph;
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int deemph_a;
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int now_lpr;
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int prev_lpr_index;
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void (*mode_demod)(struct fm_state*);
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};
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void usage(void)
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@ -107,13 +116,23 @@ void usage(void)
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"\t[-d device_index (default: 0)]\n"
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"\t[-g tuner_gain (default: automatic)]\n"
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"\t[-l squelch_level (default: 150)]\n"
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"\t[-E freq sets lower edge (default: center)]\n"
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"\t[-o oversampling (default: 1)]\n"
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"\t[-E sets lower edge tuning (default: center)]\n"
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"\t[-N enables NBFM mode (default: on)]\n"
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"\t[-W enables WBFM mode (default: off)]\n"
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"\t (-N -s 170e3 -o 4 -A -r 16e3 -l 0 -D)\n"
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"\tfilename (a '-' dumps samples to stdout)\n\n"
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"Experimental options:\n"
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"\t[-r output rate (default: same as -s)]\n"
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"\t[-t terminate_hits (default: 0/off)]\n"
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"\t (requires squelch on and scanning off)\n"
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"\t[-o oversampling (default: 1) !!BROKEN!!]\n"
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"\t[-M enables AM mode (default: off)]\n"
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"\t[-L enables LSB mode (default: off)]\n"
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"\t[-U enables USB mode (default: off)]\n"
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//"\t[-D enables DSB mode (default: off)]\n"
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"\t[-R enables raw mode (default: off, 2x16 bit output)]\n"
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"\t[-F enables high quality FIR (default: off/square)]\n"
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"\t[-D enables de-emphasis (default: off)]\n"
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"\t[-A enables high speed arctan (default: off)]\n\n"
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"Produces signed 16 bit ints, use Sox to hear them.\n"
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"\trtl_fm ... - | play -t raw -r 24k -e signed-integer -b 16 -c 1 -V1 -\n\n");
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@ -171,12 +190,12 @@ void low_pass(struct fm_state *fm, unsigned char *buf, uint32_t len)
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fm->now_j += ((int)buf[i+1] - 128);
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i += 2;
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fm->prev_index++;
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if (fm->prev_index < (fm->downsample)) {
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if (fm->prev_index < fm->downsample) {
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continue;
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}
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fm->signal[i2] = fm->now_r * fm->output_scale;
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fm->signal[i2+1] = fm->now_j * fm->output_scale;
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fm->prev_index = -1;
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fm->prev_index = 0;
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fm->now_r = 0;
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fm->now_j = 0;
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i2 += 2;
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@ -209,17 +228,17 @@ void low_pass_fir(struct fm_state *fm, unsigned char *buf, uint32_t len)
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{
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int i=0, i2=0, i3=0;
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while (i < (int)len) {
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fm->prev_index++;
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i3 = fm->prev_index;
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fm->now_r += ((int)buf[i] - 128) * fm->fir[i3] * fm->downsample / fm->fir_sum;
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fm->now_j += ((int)buf[i+1] - 128) * fm->fir[i3] * fm->downsample / fm->fir_sum;
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i += 2;
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if (fm->prev_index < (fm->downsample)) {
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fm->prev_index++;
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if (fm->prev_index < fm->downsample) {
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continue;
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}
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fm->signal[i2] = fm->now_r * fm->output_scale;
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fm->signal[i2+1] = fm->now_j * fm->output_scale;
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fm->prev_index = -1;
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fm->prev_index = 0;
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fm->now_r = 0;
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fm->now_j = 0;
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i2 += 2;
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@ -236,12 +255,35 @@ int low_pass_simple(int16_t *signal2, int len, int step)
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for(i2=0; i2<step; i2++) {
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sum += (int)signal2[i + i2];
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}
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signal2[i/step] = (int16_t)(sum / step);
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//signal2[i/step] = (int16_t)(sum / step);
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signal2[i/step] = (int16_t)(sum);
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}
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signal2[i/step + 1] = signal2[i/step];
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return len / step;
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}
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void low_pass_real(struct fm_state *fm)
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/* simple square window FIR */
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// add support for upsampling?
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{
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int i=0, i2=0;
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int fast = (int)fm->sample_rate / fm->post_downsample;
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int slow = fm->output_rate;
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while (i < fm->signal2_len) {
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fm->now_lpr += fm->signal2[i];
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i++;
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fm->prev_lpr_index += slow;
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if (fm->prev_lpr_index < fast) {
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continue;
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}
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fm->signal2[i2] = (int16_t)(fm->now_lpr / (fast/slow));
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fm->prev_lpr_index -= fast;
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fm->now_lpr = 0;
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i2 += 1;
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}
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fm->signal2_len = i2;
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}
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/* define our own complex math ops
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because ARMv5 has no hardware float */
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@ -257,8 +299,6 @@ int polar_discriminant(int ar, int aj, int br, int bj)
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double angle;
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multiply(ar, aj, br, -bj, &cr, &cj);
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angle = atan2((double)cj, (double)cr);
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//if (angle > (3.14159) || angle < (-3.14159))
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// {fprintf(stderr, "overflow %f\n", angle);}
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return (int)(angle / 3.14159 * (1<<14));
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}
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@ -310,6 +350,69 @@ void fm_demod(struct fm_state *fm)
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}
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fm->pre_r = fm->signal[fm->signal_len - 2];
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fm->pre_j = fm->signal[fm->signal_len - 1];
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fm->signal2_len = fm->signal_len/2;
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}
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void am_demod(struct fm_state *fm)
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// todo, fix this extreme laziness
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{
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int i, pcm;
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for (i = 0; i < (fm->signal_len); i += 2) {
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// hypot uses floats but won't overflow
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//pcm = (int)hypot(fm->signal[i], fm->signal[i+1]);
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pcm = fm->signal[i] * fm->signal[i];
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pcm += fm->signal[i+1] * fm->signal[i+1];
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fm->signal2[i/2] = (int16_t)sqrt(pcm); // * fm->output_scale;
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}
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fm->signal2_len = fm->signal_len/2;
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// lowpass? (3khz) highpass? (dc)
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}
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void usb_demod(struct fm_state *fm)
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{
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int i, pcm;
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for (i = 0; i < (fm->signal_len); i += 2) {
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pcm = fm->signal[i] + fm->signal[i+1];
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fm->signal2[i/2] = (int16_t)pcm; // * fm->output_scale;
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}
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fm->signal2_len = fm->signal_len/2;
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}
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void lsb_demod(struct fm_state *fm)
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{
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int i, pcm;
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for (i = 0; i < (fm->signal_len); i += 2) {
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pcm = fm->signal[i] - fm->signal[i+1];
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fm->signal2[i/2] = (int16_t)pcm; // * fm->output_scale;
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}
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fm->signal2_len = fm->signal_len/2;
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}
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void raw_demod(struct fm_state *fm)
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{
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/* hacky and pointless code */
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int i;
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for (i = 0; i < (fm->signal_len); i++) {
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fm->signal2[i] = (int16_t)fm->signal[i];
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}
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fm->signal2_len = fm->signal_len;
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}
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void deemph_filter(struct fm_state *fm)
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{
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static int avg; // cheating...
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int i, d;
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// de-emph IIR
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// avg = avg * (1 - alpha) + sample * alpha;
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for (i = 0; i < fm->signal2_len; i++) {
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d = fm->signal2[i] - avg;
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if (d > 0) {
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avg += (d + fm->deemph_a/2) / fm->deemph_a;
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} else {
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avg += (d - fm->deemph_a/2) / fm->deemph_a;
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}
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fm->signal2[i] = (int16_t)avg;
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}
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}
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int mad(int *samples, int len, int step)
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@ -371,7 +474,7 @@ static void optimal_settings(struct fm_state *fm, int freq, int hopping)
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fprintf(stderr, "Oversampling input by: %ix.\n", fm->downsample);
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fprintf(stderr, "Oversampling output by: %ix.\n", fm->post_downsample);
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fprintf(stderr, "Buffer size: %0.2fms\n",
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1000 * 0.5 * (float)DEFAULT_BUF_LENGTH / (float)capture_rate);
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1000 * 0.5 * lcm_post[fm->post_downsample] * (float)DEFAULT_BUF_LENGTH / (float)capture_rate);
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if (r < 0) {
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fprintf(stderr, "WARNING: Failed to set center freq.\n");}
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else {
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@ -379,27 +482,40 @@ static void optimal_settings(struct fm_state *fm, int freq, int hopping)
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/* Set the sample rate */
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fprintf(stderr, "Sampling at %u Hz.\n", capture_rate);
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if (fm->output_rate > 0) {
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fprintf(stderr, "Output at %u Hz.\n", fm->output_rate);
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} else {
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fprintf(stderr, "Output at %u Hz.\n", fm->sample_rate/fm->post_downsample);}
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r = rtlsdr_set_sample_rate(dev, (uint32_t)capture_rate);
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if (r < 0) {
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fprintf(stderr, "WARNING: Failed to set sample rate.\n");}
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}
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void full_demod(unsigned char *buf, uint32_t len, struct fm_state *fm)
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void full_demod(struct fm_state *fm)
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{
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int sr, freq_next;
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rotate_90(buf, len);
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rotate_90(fm->buf, fm->buf_len);
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if (fm->fir_enable) {
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low_pass_fir(fm, buf, len);
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low_pass_fir(fm, fm->buf, fm->buf_len);
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} else {
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low_pass(fm, buf, len);
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low_pass(fm, fm->buf, fm->buf_len);
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}
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fm->mode_demod(fm);
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if (fm->mode_demod == &raw_demod) {
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fwrite(fm->signal2, 2, fm->signal2_len, fm->file);
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return;
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}
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fm_demod(fm);
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sr = post_squelch(fm);
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if (fm->post_downsample > 1) {
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fm->signal_len = low_pass_simple(fm->signal2, fm->signal_len/2, fm->post_downsample)*2;}
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fm->signal2_len = low_pass_simple(fm->signal2, fm->signal2_len, fm->post_downsample);}
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if (fm->output_rate > 0) {
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low_pass_real(fm);
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}
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if (fm->deemph) {
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deemph_filter(fm);}
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/* ignore under runs for now */
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fwrite(fm->signal2, 2, fm->signal_len/2, fm->file);
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fwrite(fm->signal2, 2, fm->signal2_len, fm->file);
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if (fm->freq_len > 1 && !sr && fm->squelch_hits > CONSEQ_SQUELCH) {
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freq_next = (fm->freq_now + 1) % fm->freq_len;
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optimal_settings(fm, freq_next, 1);
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@ -418,10 +534,10 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
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return;}
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if (!ctx) {
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return;}
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/* single threaded uses 25% less CPU? */
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/* full_demod(buf, len, fm2); */
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memcpy(fm2->buf, buf, len);
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fm2->buf_len = len;
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/* single threaded uses 25% less CPU? */
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/* full_demod(fm2); */
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sem_getvalue(&data_ready, &dr_val);
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if (!dr_val) {
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sem_post(&data_ready);}
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@ -432,7 +548,7 @@ static void *demod_thread_fn(void *arg)
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struct fm_state *fm2 = arg;
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while (!do_exit) {
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sem_wait(&data_ready);
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full_demod(fm2->buf, fm2->buf_len, fm2);
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full_demod(fm2);
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if (!fm2->term_squelch_hits) {
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continue;}
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if (fm2->squelch_hits > fm2->term_squelch_hits) {
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@ -449,8 +565,7 @@ int main(int argc, char **argv)
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#endif
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struct fm_state fm;
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char *filename = NULL;
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int n_read;
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int r, opt;
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int n_read, r, opt, wb_mode = 0;
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int i, gain = AUTO_GAIN; // tenths of a dB
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uint8_t *buffer;
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uint32_t dev_index = 0;
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@ -463,12 +578,15 @@ int main(int argc, char **argv)
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fm.freq_len = 0;
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fm.edge = 0;
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fm.fir_enable = 0;
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fm.prev_index = -1;
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fm.prev_index = 0;
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fm.post_downsample = 1; // once this works, default = 4
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fm.custom_atan = 0;
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fm.deemph = 0;
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fm.output_rate = -1; // flag for disabled
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fm.mode_demod = &fm_demod;
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sem_init(&data_ready, 0, 0);
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while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:EFA")) != -1) {
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while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:EFANWMULRD")) != -1) {
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switch (opt) {
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case 'd':
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dev_index = atoi(optarg);
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@ -486,8 +604,13 @@ int main(int argc, char **argv)
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case 's':
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fm.sample_rate = (uint32_t)atof(optarg);
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break;
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case 'r':
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fm.output_rate = (int)atof(optarg);
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break;
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case 'o':
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fm.post_downsample = (int)atof(optarg);
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if (fm.post_downsample < 1 || fm.post_downsample > MAXIMUM_OVERSAMPLE) {
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fprintf(stderr, "Oversample must be between 1 and %i\n", MAXIMUM_OVERSAMPLE);}
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break;
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case 't':
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fm.term_squelch_hits = (int)atof(optarg);
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@ -501,6 +624,34 @@ int main(int argc, char **argv)
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case 'A':
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fm.custom_atan = 1;
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break;
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case 'D':
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fm.deemph = 1;
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break;
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case 'N':
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fm.mode_demod = &fm_demod;
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break;
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case 'W':
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wb_mode = 1;
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fm.mode_demod = &fm_demod;
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fm.sample_rate = 170000;
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fm.output_rate = 16000;
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fm.custom_atan = 1;
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fm.post_downsample = 4;
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fm.deemph = 1;
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fm.squelch_level = 0;
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break;
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case 'M':
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fm.mode_demod = &am_demod;
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break;
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case 'U':
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fm.mode_demod = &usb_demod;
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break;
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case 'L':
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fm.mode_demod = &lsb_demod;
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break;
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case 'R':
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fm.mode_demod = &raw_demod;
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break;
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default:
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usage();
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break;
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@ -515,7 +666,7 @@ int main(int argc, char **argv)
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filename = argv[optind];
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}
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buffer = malloc(DEFAULT_BUF_LENGTH * sizeof(uint8_t));
|
||||
buffer = malloc(lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH * sizeof(uint8_t));
|
||||
|
||||
device_count = rtlsdr_get_device_count();
|
||||
if (!device_count) {
|
||||
@ -550,6 +701,15 @@ int main(int argc, char **argv)
|
||||
SetConsoleCtrlHandler( (PHANDLER_ROUTINE) sighandler, TRUE );
|
||||
#endif
|
||||
|
||||
/* WBFM is special */
|
||||
if (wb_mode) {
|
||||
fm.freqs[0] += 15000;
|
||||
}
|
||||
|
||||
if (fm.deemph) {
|
||||
fm.deemph_a = (int)round(1.0/((1.0-exp(-1.0/(fm.output_rate * 75e-6)))));
|
||||
}
|
||||
|
||||
optimal_settings(&fm, 0, 0);
|
||||
build_fir(&fm);
|
||||
|
||||
@ -585,7 +745,8 @@ int main(int argc, char **argv)
|
||||
|
||||
pthread_create(&demod_thread, NULL, demod_thread_fn, (void *)(&fm));
|
||||
rtlsdr_read_async(dev, rtlsdr_callback, (void *)(&fm),
|
||||
DEFAULT_ASYNC_BUF_NUMBER, DEFAULT_BUF_LENGTH);
|
||||
DEFAULT_ASYNC_BUF_NUMBER,
|
||||
lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH);
|
||||
|
||||
if (do_exit) {
|
||||
fprintf(stderr, "\nUser cancel, exiting...\n");}
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user