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rtl_fm: WBFM, AM, LSB and USB demod, raw IQ mode

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Signed-off-by: Steve Markgraf <steve@steve-m.de>
master
Kyle Keen 12 years ago committed by Steve Markgraf
parent 995a195f4d
commit b0b9e3d24f
1 changed files with 194 additions and 33 deletions
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  1. 227
      src/rtl_fm.c

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

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