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1 files changed, 1289 insertions, 0 deletions

diff --git a/src/rtl_fm.c b/src/rtl_fm.c
new file mode 100644
index 0000000..7c84332
--- /dev/null
+++ b/src/rtl_fm.c
@@ -0,0 +1,1289 @@
+/*
+ * rtl-sdr, turns your Realtek RTL2832 based DVB dongle into a SDR receiver
+ * Copyright (C) 2012 by Steve Markgraf <steve@steve-m.de>
+ * Copyright (C) 2012 by Hoernchen <la@tfc-server.de>
+ * Copyright (C) 2012 by Kyle Keen <keenerd@gmail.com>
+ * Copyright (C) 2013 by Elias Oenal <EliasOenal@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+/*
+ * written because people could not do real time
+ * FM demod on Atom hardware with GNU radio
+ * based on rtl_sdr.c and rtl_tcp.c
+ *
+ * lots of locks, but that is okay
+ * (no many-to-many locks)
+ *
+ * todo:
+ *       sanity checks
+ *       scale squelch to other input parameters
+ *       test all the demodulations
+ *       pad output on hop
+ *       frequency ranges could be stored better
+ *       scaled AM demod amplification
+ *       auto-hop after time limit
+ *       peak detector to tune onto stronger signals
+ *       fifo for active hop frequency
+ *       clips
+ *       noise squelch
+ *       merge stereo patch
+ *       merge soft agc patch
+ *       merge udp patch
+ *       testmode to detect overruns
+ *       watchdog to reset bad dongle
+ *       fix oversampling
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#ifndef _WIN32
+#include <unistd.h>
+#else
+#include <windows.h>
+#include <fcntl.h>
+#include <io.h>
+#include "getopt/getopt.h"
+#define usleep(x) Sleep(x/1000)
+#if defined(_MSC_VER) && (_MSC_VER < 1800)
+#define round(x) (x > 0.0 ? floor(x + 0.5): ceil(x - 0.5))
+#endif
+#define _USE_MATH_DEFINES
+#endif
+
+#include <math.h>
+#include <pthread.h>
+#include <libusb.h>
+
+#include "rtl-sdr.h"
+#include "convenience/convenience.h"
+
+#define DEFAULT_SAMPLE_RATE		24000
+#define DEFAULT_BUF_LENGTH		(1 * 16384)
+#define MAXIMUM_OVERSAMPLE		16
+#define MAXIMUM_BUF_LENGTH		(MAXIMUM_OVERSAMPLE * DEFAULT_BUF_LENGTH)
+#define AUTO_GAIN			-100
+#define BUFFER_DUMP			4096
+
+#define FREQUENCIES_LIMIT		1000
+
+static volatile int do_exit = 0;
+static int lcm_post[17] = {1,1,1,3,1,5,3,7,1,9,5,11,3,13,7,15,1};
+static int ACTUAL_BUF_LENGTH;
+
+static int *atan_lut = NULL;
+static int atan_lut_size = 131072; /* 512 KB */
+static int atan_lut_coef = 8;
+
+struct dongle_state
+{
+	int      exit_flag;
+	pthread_t thread;
+	rtlsdr_dev_t *dev;
+	int      dev_index;
+	uint32_t freq;
+	uint32_t rate;
+	int      gain;
+	uint16_t buf16[MAXIMUM_BUF_LENGTH];
+	uint32_t buf_len;
+	int      ppm_error;
+	int      offset_tuning;
+	int      direct_sampling;
+	int      mute;
+	struct demod_state *demod_target;
+};
+
+struct demod_state
+{
+	int      exit_flag;
+	pthread_t thread;
+	int16_t  lowpassed[MAXIMUM_BUF_LENGTH];
+	int      lp_len;
+	int16_t  lp_i_hist[10][6];
+	int16_t  lp_q_hist[10][6];
+	int16_t  result[MAXIMUM_BUF_LENGTH];
+	int16_t  droop_i_hist[9];
+	int16_t  droop_q_hist[9];
+	int      result_len;
+	int      rate_in;
+	int      rate_out;
+	int      rate_out2;
+	int      now_r, now_j;
+	int      pre_r, pre_j;
+	int      prev_index;
+	int      downsample;    /* min 1, max 256 */
+	int      post_downsample;
+	int      output_scale;
+	int      squelch_level, conseq_squelch, squelch_hits, terminate_on_squelch;
+	int      downsample_passes;
+	int      comp_fir_size;
+	int      custom_atan;
+	int      deemph, deemph_a;
+	int      now_lpr;
+	int      prev_lpr_index;
+	int      dc_block, dc_avg;
+	void     (*mode_demod)(struct demod_state*);
+	pthread_rwlock_t rw;
+	pthread_cond_t ready;
+	pthread_mutex_t ready_m;
+	struct output_state *output_target;
+};
+
+struct output_state
+{
+	int      exit_flag;
+	pthread_t thread;
+	FILE     *file;
+	char     *filename;
+	int16_t  result[MAXIMUM_BUF_LENGTH];
+	int      result_len;
+	int      rate;
+	pthread_rwlock_t rw;
+	pthread_cond_t ready;
+	pthread_mutex_t ready_m;
+};
+
+struct controller_state
+{
+	int      exit_flag;
+	pthread_t thread;
+	uint32_t freqs[FREQUENCIES_LIMIT];
+	int      freq_len;
+	int      freq_now;
+	int      edge;
+	int      wb_mode;
+	pthread_cond_t hop;
+	pthread_mutex_t hop_m;
+};
+
+// multiple of these, eventually
+struct dongle_state dongle;
+struct demod_state demod;
+struct output_state output;
+struct controller_state controller;
+
+void usage(void)
+{
+	fprintf(stderr,
+		"rtl_fm, a simple narrow band FM demodulator for RTL2832 based DVB-T receivers\n\n"
+		"Use:\trtl_fm -f freq [-options] [filename]\n"
+		"\t-f frequency_to_tune_to [Hz]\n"
+		"\t    use multiple -f for scanning (requires squelch)\n"
+		"\t    ranges supported, -f 118M:137M:25k\n"
+		"\t[-M modulation (default: fm)]\n"
+		"\t    fm, wbfm, raw, am, usb, lsb\n"
+		"\t    wbfm == -M fm -s 170k -o 4 -A fast -r 32k -l 0 -E deemp\n"
+		"\t    raw mode outputs 2x16 bit IQ pairs\n"
+		"\t[-s sample_rate (default: 24k)]\n"
+		"\t[-d device_index (default: 0)]\n"
+		"\t[-T enable bias-T on GPIO PIN 0 (works for rtl-sdr.com v3 dongles)]\n"
+		"\t[-g tuner_gain (default: automatic)]\n"
+		"\t[-l squelch_level (default: 0/off)]\n"
+		//"\t    for fm squelch is inverted\n"
+		//"\t[-o oversampling (default: 1, 4 recommended)]\n"
+		"\t[-p ppm_error (default: 0)]\n"
+		"\t[-E enable_option (default: none)]\n"
+		"\t    use multiple -E to enable multiple options\n"
+		"\t    edge:    enable lower edge tuning\n"
+		"\t    dc:      enable dc blocking filter\n"
+		"\t    deemp:   enable de-emphasis filter\n"
+		"\t    direct:  enable direct sampling 1 (usually I)\n"
+		"\t    direct2: enable direct sampling 2 (usually Q)\n"
+		"\t    offset:  enable offset tuning\n"
+		"\tfilename ('-' means stdout)\n"
+		"\t    omitting the filename also uses stdout\n\n"
+		"Experimental options:\n"
+		"\t[-r resample_rate (default: none / same as -s)]\n"
+		"\t[-t squelch_delay (default: 10)]\n"
+		"\t    +values will mute/scan, -values will exit\n"
+		"\t[-F fir_size (default: off)]\n"
+		"\t    enables low-leakage downsample filter\n"
+		"\t    size can be 0 or 9.  0 has bad roll off\n"
+		"\t[-A std/fast/lut choose atan math (default: std)]\n"
+		//"\t[-C clip_path (default: off)\n"
+		//"\t (create time stamped raw clips, requires squelch)\n"
+		//"\t (path must have '\%s' and will expand to date_time_freq)\n"
+		//"\t[-H hop_fifo (default: off)\n"
+		//"\t (fifo will contain the active frequency)\n"
+		"\n"
+		"Produces signed 16 bit ints, use Sox or aplay to hear them.\n"
+		"\trtl_fm ... | play -t raw -r 24k -es -b 16 -c 1 -V1 -\n"
+		"\t           | aplay -r 24k -f S16_LE -t raw -c 1\n"
+		"\t  -M wbfm  | play -r 32k ... \n"
+		"\t  -s 22050 | multimon -t raw /dev/stdin\n\n");
+	exit(1);
+}
+
+#ifdef _WIN32
+BOOL WINAPI
+sighandler(int signum)
+{
+	if (CTRL_C_EVENT == signum) {
+		fprintf(stderr, "Signal caught, exiting!\n");
+		do_exit = 1;
+		rtlsdr_cancel_async(dongle.dev);
+		return TRUE;
+	}
+	return FALSE;
+}
+#else
+static void sighandler(int signum)
+{
+	fprintf(stderr, "Signal caught, exiting!\n");
+	do_exit = 1;
+	rtlsdr_cancel_async(dongle.dev);
+}
+#endif
+
+/* more cond dumbness */
+#define safe_cond_signal(n, m) pthread_mutex_lock(m); pthread_cond_signal(n); pthread_mutex_unlock(m)
+#define safe_cond_wait(n, m) pthread_mutex_lock(m); pthread_cond_wait(n, m); pthread_mutex_unlock(m)
+
+/* {length, coef, coef, coef}  and scaled by 2^15
+   for now, only length 9, optimal way to get +85% bandwidth */
+#define CIC_TABLE_MAX 10
+int cic_9_tables[][10] = {
+	{0,},
+	{9, -156,  -97, 2798, -15489, 61019, -15489, 2798,  -97, -156},
+	{9, -128, -568, 5593, -24125, 74126, -24125, 5593, -568, -128},
+	{9, -129, -639, 6187, -26281, 77511, -26281, 6187, -639, -129},
+	{9, -122, -612, 6082, -26353, 77818, -26353, 6082, -612, -122},
+	{9, -120, -602, 6015, -26269, 77757, -26269, 6015, -602, -120},
+	{9, -120, -582, 5951, -26128, 77542, -26128, 5951, -582, -120},
+	{9, -119, -580, 5931, -26094, 77505, -26094, 5931, -580, -119},
+	{9, -119, -578, 5921, -26077, 77484, -26077, 5921, -578, -119},
+	{9, -119, -577, 5917, -26067, 77473, -26067, 5917, -577, -119},
+	{9, -199, -362, 5303, -25505, 77489, -25505, 5303, -362, -199},
+};
+
+#if defined(_MSC_VER) && (_MSC_VER < 1800)
+double log2(double n)
+{
+	return log(n) / log(2.0);
+}
+#endif
+
+void rotate_90(unsigned char *buf, uint32_t len)
+/* 90 rotation is 1+0j, 0+1j, -1+0j, 0-1j
+   or [0, 1, -3, 2, -4, -5, 7, -6] */
+{
+	uint32_t i;
+	unsigned char tmp;
+	for (i=0; i<len; i+=8) {
+		/* uint8_t negation = 255 - x */
+		tmp = 255 - buf[i+3];
+		buf[i+3] = buf[i+2];
+		buf[i+2] = tmp;
+
+		buf[i+4] = 255 - buf[i+4];
+		buf[i+5] = 255 - buf[i+5];
+
+		tmp = 255 - buf[i+6];
+		buf[i+6] = buf[i+7];
+		buf[i+7] = tmp;
+	}
+}
+
+void low_pass(struct demod_state *d)
+/* simple square window FIR */
+{
+	int i=0, i2=0;
+	while (i < d->lp_len) {
+		d->now_r += d->lowpassed[i];
+		d->now_j += d->lowpassed[i+1];
+		i += 2;
+		d->prev_index++;
+		if (d->prev_index < d->downsample) {
+			continue;
+		}
+		d->lowpassed[i2]   = d->now_r; // * d->output_scale;
+		d->lowpassed[i2+1] = d->now_j; // * d->output_scale;
+		d->prev_index = 0;
+		d->now_r = 0;
+		d->now_j = 0;
+		i2 += 2;
+	}
+	d->lp_len = i2;
+}
+
+int low_pass_simple(int16_t *signal2, int len, int step)
+// no wrap around, length must be multiple of step
+{
+	int i, i2, sum;
+	for(i=0; i < len; i+=step) {
+		sum = 0;
+		for(i2=0; i2<step; i2++) {
+			sum += (int)signal2[i + i2];
+		}
+		//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 demod_state *s)
+/* simple square window FIR */
+// add support for upsampling?
+{
+	int i=0, i2=0;
+	int fast = (int)s->rate_out;
+	int slow = s->rate_out2;
+	while (i < s->result_len) {
+		s->now_lpr += s->result[i];
+		i++;
+		s->prev_lpr_index += slow;
+		if (s->prev_lpr_index < fast) {
+			continue;
+		}
+		s->result[i2] = (int16_t)(s->now_lpr / (fast/slow));
+		s->prev_lpr_index -= fast;
+		s->now_lpr = 0;
+		i2 += 1;
+	}
+	s->result_len = i2;
+}
+
+void fifth_order(int16_t *data, int length, int16_t *hist)
+/* for half of interleaved data */
+{
+	int i;
+	int16_t a, b, c, d, e, f;
+	a = hist[1];
+	b = hist[2];
+	c = hist[3];
+	d = hist[4];
+	e = hist[5];
+	f = data[0];
+	/* a downsample should improve resolution, so don't fully shift */
+	data[0] = (a + (b+e)*5 + (c+d)*10 + f) >> 4;
+	for (i=4; i<length; i+=4) {
+		a = c;
+		b = d;
+		c = e;
+		d = f;
+		e = data[i-2];
+		f = data[i];
+		data[i/2] = (a + (b+e)*5 + (c+d)*10 + f) >> 4;
+	}
+	/* archive */
+	hist[0] = a;
+	hist[1] = b;
+	hist[2] = c;
+	hist[3] = d;
+	hist[4] = e;
+	hist[5] = f;
+}
+
+void generic_fir(int16_t *data, int length, int *fir, int16_t *hist)
+/* Okay, not at all generic.  Assumes length 9, fix that eventually. */
+{
+	int d, temp, sum;
+	for (d=0; d<length; d+=2) {
+		temp = data[d];
+		sum = 0;
+		sum += (hist[0] + hist[8]) * fir[1];
+		sum += (hist[1] + hist[7]) * fir[2];
+		sum += (hist[2] + hist[6]) * fir[3];
+		sum += (hist[3] + hist[5]) * fir[4];
+		sum +=            hist[4]  * fir[5];
+		data[d] = sum >> 15 ;
+		hist[0] = hist[1];
+		hist[1] = hist[2];
+		hist[2] = hist[3];
+		hist[3] = hist[4];
+		hist[4] = hist[5];
+		hist[5] = hist[6];
+		hist[6] = hist[7];
+		hist[7] = hist[8];
+		hist[8] = temp;
+	}
+}
+
+/* define our own complex math ops
+   because ARMv5 has no hardware float */
+
+void multiply(int ar, int aj, int br, int bj, int *cr, int *cj)
+{
+	*cr = ar*br - aj*bj;
+	*cj = aj*br + ar*bj;
+}
+
+int polar_discriminant(int ar, int aj, int br, int bj)
+{
+	int cr, cj;
+	double angle;
+	multiply(ar, aj, br, -bj, &cr, &cj);
+	angle = atan2((double)cj, (double)cr);
+	return (int)(angle / 3.14159 * (1<<14));
+}
+
+int fast_atan2(int y, int x)
+/* pre scaled for int16 */
+{
+	int yabs, angle;
+	int pi4=(1<<12), pi34=3*(1<<12);  // note pi = 1<<14
+	if (x==0 && y==0) {
+		return 0;
+	}
+	yabs = y;
+	if (yabs < 0) {
+		yabs = -yabs;
+	}
+	if (x >= 0) {
+		angle = pi4  - pi4 * (x-yabs) / (x+yabs);
+	} else {
+		angle = pi34 - pi4 * (x+yabs) / (yabs-x);
+	}
+	if (y < 0) {
+		return -angle;
+	}
+	return angle;
+}
+
+int polar_disc_fast(int ar, int aj, int br, int bj)
+{
+	int cr, cj;
+	multiply(ar, aj, br, -bj, &cr, &cj);
+	return fast_atan2(cj, cr);
+}
+
+int atan_lut_init(void)
+{
+	int i = 0;
+
+	atan_lut = malloc(atan_lut_size * sizeof(int));
+
+	for (i = 0; i < atan_lut_size; i++) {
+		atan_lut[i] = (int) (atan((double) i / (1<<atan_lut_coef)) / 3.14159 * (1<<14));
+	}
+
+	return 0;
+}
+
+int polar_disc_lut(int ar, int aj, int br, int bj)
+{
+	int cr, cj, x, x_abs;
+
+	multiply(ar, aj, br, -bj, &cr, &cj);
+
+	/* special cases */
+	if (cr == 0 || cj == 0) {
+		if (cr == 0 && cj == 0)
+			{return 0;}
+		if (cr == 0 && cj > 0)
+			{return 1 << 13;}
+		if (cr == 0 && cj < 0)
+			{return -(1 << 13);}
+		if (cj == 0 && cr > 0)
+			{return 0;}
+		if (cj == 0 && cr < 0)
+			{return 1 << 14;}
+	}
+
+	/* real range -32768 - 32768 use 64x range -> absolute maximum: 2097152 */
+	x = (cj << atan_lut_coef) / cr;
+	x_abs = abs(x);
+
+	if (x_abs >= atan_lut_size) {
+		/* we can use linear range, but it is not necessary */
+		return (cj > 0) ? 1<<13 : -(1<<13);
+	}
+
+	if (x > 0) {
+		return (cj > 0) ? atan_lut[x] : atan_lut[x] - (1<<14);
+	} else {
+		return (cj > 0) ? (1<<14) - atan_lut[-x] : -atan_lut[-x];
+	}
+
+	return 0;
+}
+
+void fm_demod(struct demod_state *fm)
+{
+	int i, pcm;
+	int16_t *lp = fm->lowpassed;
+	pcm = polar_discriminant(lp[0], lp[1],
+		fm->pre_r, fm->pre_j);
+	fm->result[0] = (int16_t)pcm;
+	for (i = 2; i < (fm->lp_len-1); i += 2) {
+		switch (fm->custom_atan) {
+		case 0:
+			pcm = polar_discriminant(lp[i], lp[i+1],
+				lp[i-2], lp[i-1]);
+			break;
+		case 1:
+			pcm = polar_disc_fast(lp[i], lp[i+1],
+				lp[i-2], lp[i-1]);
+			break;
+		case 2:
+			pcm = polar_disc_lut(lp[i], lp[i+1],
+				lp[i-2], lp[i-1]);
+			break;
+		}
+		fm->result[i/2] = (int16_t)pcm;
+	}
+	fm->pre_r = lp[fm->lp_len - 2];
+	fm->pre_j = lp[fm->lp_len - 1];
+	fm->result_len = fm->lp_len/2;
+}
+
+void am_demod(struct demod_state *fm)
+// todo, fix this extreme laziness
+{
+	int i, pcm;
+	int16_t *lp = fm->lowpassed;
+	int16_t *r  = fm->result;
+	for (i = 0; i < fm->lp_len; i += 2) {
+		// hypot uses floats but won't overflow
+		//r[i/2] = (int16_t)hypot(lp[i], lp[i+1]);
+		pcm = lp[i] * lp[i];
+		pcm += lp[i+1] * lp[i+1];
+		r[i/2] = (int16_t)sqrt(pcm) * fm->output_scale;
+	}
+	fm->result_len = fm->lp_len/2;
+	// lowpass? (3khz)  highpass?  (dc)
+}
+
+void usb_demod(struct demod_state *fm)
+{
+	int i, pcm;
+	int16_t *lp = fm->lowpassed;
+	int16_t *r  = fm->result;
+	for (i = 0; i < fm->lp_len; i += 2) {
+		pcm = lp[i] + lp[i+1];
+		r[i/2] = (int16_t)pcm * fm->output_scale;
+	}
+	fm->result_len = fm->lp_len/2;
+}
+
+void lsb_demod(struct demod_state *fm)
+{
+	int i, pcm;
+	int16_t *lp = fm->lowpassed;
+	int16_t *r  = fm->result;
+	for (i = 0; i < fm->lp_len; i += 2) {
+		pcm = lp[i] - lp[i+1];
+		r[i/2] = (int16_t)pcm * fm->output_scale;
+	}
+	fm->result_len = fm->lp_len/2;
+}
+
+void raw_demod(struct demod_state *fm)
+{
+	int i;
+	for (i = 0; i < fm->lp_len; i++) {
+		fm->result[i] = (int16_t)fm->lowpassed[i];
+	}
+	fm->result_len = fm->lp_len;
+}
+
+void deemph_filter(struct demod_state *fm)
+{
+	static int avg;  // cheating...
+	int i, d;
+	// de-emph IIR
+	// avg = avg * (1 - alpha) + sample * alpha;
+	for (i = 0; i < fm->result_len; i++) {
+		d = fm->result[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->result[i] = (int16_t)avg;
+	}
+}
+
+void dc_block_filter(struct demod_state *fm)
+{
+	int i, avg;
+	int64_t sum = 0;
+	for (i=0; i < fm->result_len; i++) {
+		sum += fm->result[i];
+	}
+	avg = sum / fm->result_len;
+	avg = (avg + fm->dc_avg * 9) / 10;
+	for (i=0; i < fm->result_len; i++) {
+		fm->result[i] -= avg;
+	}
+	fm->dc_avg = avg;
+}
+
+int mad(int16_t *samples, int len, int step)
+/* mean average deviation */
+{
+	int i=0, sum=0, ave=0;
+	if (len == 0)
+		{return 0;}
+	for (i=0; i<len; i+=step) {
+		sum += samples[i];
+	}
+	ave = sum / (len * step);
+	sum = 0;
+	for (i=0; i<len; i+=step) {
+		sum += abs(samples[i] - ave);
+	}
+	return sum / (len / step);
+}
+
+int rms(int16_t *samples, int len, int step)
+/* largely lifted from rtl_power */
+{
+	int i;
+	long p, t, s;
+	double dc, err;
+
+	p = t = 0L;
+	for (i=0; i<len; i+=step) {
+		s = (long)samples[i];
+		t += s;
+		p += s * s;
+	}
+	/* correct for dc offset in squares */
+	dc = (double)(t*step) / (double)len;
+	err = t * 2 * dc - dc * dc * len;
+
+	return (int)sqrt((p-err) / len);
+}
+
+void arbitrary_upsample(int16_t *buf1, int16_t *buf2, int len1, int len2)
+/* linear interpolation, len1 < len2 */
+{
+	int i = 1;
+	int j = 0;
+	int tick = 0;
+	double frac;  // use integers...
+	while (j < len2) {
+		frac = (double)tick / (double)len2;
+		buf2[j] = (int16_t)(buf1[i-1]*(1-frac) + buf1[i]*frac);
+		j++;
+		tick += len1;
+		if (tick > len2) {
+			tick -= len2;
+			i++;
+		}
+		if (i >= len1) {
+			i = len1 - 1;
+			tick = len2;
+		}
+	}
+}
+
+void arbitrary_downsample(int16_t *buf1, int16_t *buf2, int len1, int len2)
+/* fractional boxcar lowpass, len1 > len2 */
+{
+	int i = 1;
+	int j = 0;
+	int tick = 0;
+	double remainder = 0;
+	double frac;  // use integers...
+	buf2[0] = 0;
+	while (j < len2) {
+		frac = 1.0;
+		if ((tick + len2) > len1) {
+			frac = (double)(len1 - tick) / (double)len2;}
+		buf2[j] += (int16_t)((double)buf1[i] * frac + remainder);
+		remainder = (double)buf1[i] * (1.0-frac);
+		tick += len2;
+		i++;
+		if (tick > len1) {
+			j++;
+			buf2[j] = 0;
+			tick -= len1;
+		}
+		if (i >= len1) {
+			i = len1 - 1;
+			tick = len1;
+		}
+	}
+	for (j=0; j<len2; j++) {
+		buf2[j] = buf2[j] * len2 / len1;}
+}
+
+void arbitrary_resample(int16_t *buf1, int16_t *buf2, int len1, int len2)
+/* up to you to calculate lengths and make sure it does not go OOB
+ * okay for buffers to overlap, if you are downsampling */
+{
+	if (len1 < len2) {
+		arbitrary_upsample(buf1, buf2, len1, len2);
+	} else {
+		arbitrary_downsample(buf1, buf2, len1, len2);
+	}
+}
+
+void full_demod(struct demod_state *d)
+{
+	int i, ds_p;
+	int sr = 0;
+	ds_p = d->downsample_passes;
+	if (ds_p) {
+		for (i=0; i < ds_p; i++) {
+			fifth_order(d->lowpassed,   (d->lp_len >> i), d->lp_i_hist[i]);
+			fifth_order(d->lowpassed+1, (d->lp_len >> i) - 1, d->lp_q_hist[i]);
+		}
+		d->lp_len = d->lp_len >> ds_p;
+		/* droop compensation */
+		if (d->comp_fir_size == 9 && ds_p <= CIC_TABLE_MAX) {
+			generic_fir(d->lowpassed, d->lp_len,
+				cic_9_tables[ds_p], d->droop_i_hist);
+			generic_fir(d->lowpassed+1, d->lp_len-1,
+				cic_9_tables[ds_p], d->droop_q_hist);
+		}
+	} else {
+		low_pass(d);
+	}
+	/* power squelch */
+	if (d->squelch_level) {
+		sr = rms(d->lowpassed, d->lp_len, 1);
+		if (sr < d->squelch_level) {
+			d->squelch_hits++;
+			for (i=0; i<d->lp_len; i++) {
+				d->lowpassed[i] = 0;
+			}
+		} else {
+			d->squelch_hits = 0;}
+	}
+	d->mode_demod(d);  /* lowpassed -> result */
+	if (d->mode_demod == &raw_demod) {
+		return;
+	}
+	/* todo, fm noise squelch */
+	// use nicer filter here too?
+	if (d->post_downsample > 1) {
+		d->result_len = low_pass_simple(d->result, d->result_len, d->post_downsample);}
+	if (d->deemph) {
+		deemph_filter(d);}
+	if (d->dc_block) {
+		dc_block_filter(d);}
+	if (d->rate_out2 > 0) {
+		low_pass_real(d);
+		//arbitrary_resample(d->result, d->result, d->result_len, d->result_len * d->rate_out2 / d->rate_out);
+	}
+}
+
+static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
+{
+	int i;
+	struct dongle_state *s = ctx;
+	struct demod_state *d = s->demod_target;
+
+	if (do_exit) {
+		return;}
+	if (!ctx) {
+		return;}
+	if (s->mute) {
+		for (i=0; i<s->mute; i++) {
+			buf[i] = 127;}
+		s->mute = 0;
+	}
+	if (!s->offset_tuning) {
+		rotate_90(buf, len);}
+	for (i=0; i<(int)len; i++) {
+		s->buf16[i] = (int16_t)buf[i] - 127;}
+	pthread_rwlock_wrlock(&d->rw);
+	memcpy(d->lowpassed, s->buf16, 2*len);
+	d->lp_len = len;
+	pthread_rwlock_unlock(&d->rw);
+	safe_cond_signal(&d->ready, &d->ready_m);
+}
+
+static void *dongle_thread_fn(void *arg)
+{
+	struct dongle_state *s = arg;
+	rtlsdr_read_async(s->dev, rtlsdr_callback, s, 0, s->buf_len);
+	return 0;
+}
+
+static void *demod_thread_fn(void *arg)
+{
+	struct demod_state *d = arg;
+	struct output_state *o = d->output_target;
+	while (!do_exit) {
+		safe_cond_wait(&d->ready, &d->ready_m);
+		pthread_rwlock_wrlock(&d->rw);
+		full_demod(d);
+		pthread_rwlock_unlock(&d->rw);
+		if (d->exit_flag) {
+			do_exit = 1;
+		}
+		if (d->squelch_level && d->squelch_hits > d->conseq_squelch) {
+			d->squelch_hits = d->conseq_squelch + 1;  /* hair trigger */
+			safe_cond_signal(&controller.hop, &controller.hop_m);
+			continue;
+		}
+		pthread_rwlock_wrlock(&o->rw);
+		memcpy(o->result, d->result, 2*d->result_len);
+		o->result_len = d->result_len;
+		pthread_rwlock_unlock(&o->rw);
+		safe_cond_signal(&o->ready, &o->ready_m);
+	}
+	return 0;
+}
+
+static void *output_thread_fn(void *arg)
+{
+	struct output_state *s = arg;
+	while (!do_exit) {
+		// use timedwait and pad out under runs
+		safe_cond_wait(&s->ready, &s->ready_m);
+		pthread_rwlock_rdlock(&s->rw);
+		fwrite(s->result, 2, s->result_len, s->file);
+		pthread_rwlock_unlock(&s->rw);
+	}
+	return 0;
+}
+
+static void optimal_settings(int freq, int rate)
+{
+	// giant ball of hacks
+	// seems unable to do a single pass, 2:1
+	int capture_freq, capture_rate;
+	struct dongle_state *d = &dongle;
+	struct demod_state *dm = &demod;
+	struct controller_state *cs = &controller;
+	dm->downsample = (1000000 / dm->rate_in) + 1;
+	if (dm->downsample_passes) {
+		dm->downsample_passes = (int)log2(dm->downsample) + 1;
+		dm->downsample = 1 << dm->downsample_passes;
+	}
+	capture_freq = freq;
+	capture_rate = dm->downsample * dm->rate_in;
+	if (!d->offset_tuning) {
+		capture_freq = freq + capture_rate/4;}
+	capture_freq += cs->edge * dm->rate_in / 2;
+	dm->output_scale = (1<<15) / (128 * dm->downsample);
+	if (dm->output_scale < 1) {
+		dm->output_scale = 1;}
+	if (dm->mode_demod == &fm_demod) {
+		dm->output_scale = 1;}
+	d->freq = (uint32_t)capture_freq;
+	d->rate = (uint32_t)capture_rate;
+}
+
+static void *controller_thread_fn(void *arg)
+{
+	// thoughts for multiple dongles
+	// might be no good using a controller thread if retune/rate blocks
+	int i;
+	struct controller_state *s = arg;
+
+	if (s->wb_mode) {
+		for (i=0; i < s->freq_len; i++) {
+			s->freqs[i] += 16000;}
+	}
+
+	/* set up primary channel */
+	optimal_settings(s->freqs[0], demod.rate_in);
+	if (dongle.direct_sampling) {
+		verbose_direct_sampling(dongle.dev, dongle.direct_sampling);}
+	if (dongle.offset_tuning) {
+		verbose_offset_tuning(dongle.dev);}
+
+	/* Set the frequency */
+	verbose_set_frequency(dongle.dev, dongle.freq);
+	fprintf(stderr, "Oversampling input by: %ix.\n", demod.downsample);
+	fprintf(stderr, "Oversampling output by: %ix.\n", demod.post_downsample);
+	fprintf(stderr, "Buffer size: %0.2fms\n",
+		1000 * 0.5 * (float)ACTUAL_BUF_LENGTH / (float)dongle.rate);
+
+	/* Set the sample rate */
+	verbose_set_sample_rate(dongle.dev, dongle.rate);
+	fprintf(stderr, "Output at %u Hz.\n", demod.rate_in/demod.post_downsample);
+
+	while (!do_exit) {
+		safe_cond_wait(&s->hop, &s->hop_m);
+		if (s->freq_len <= 1) {
+			continue;}
+		/* hacky hopping */
+		s->freq_now = (s->freq_now + 1) % s->freq_len;
+		optimal_settings(s->freqs[s->freq_now], demod.rate_in);
+		rtlsdr_set_center_freq(dongle.dev, dongle.freq);
+		dongle.mute = BUFFER_DUMP;
+	}
+	return 0;
+}
+
+void frequency_range(struct controller_state *s, char *arg)
+{
+	char *start, *stop, *step;
+	int i;
+	start = arg;
+	stop = strchr(start, ':') + 1;
+	if (stop == (char *)1) { // no stop or step given
+		s->freqs[s->freq_len] = (uint32_t) atofs(start);
+		s->freq_len++;
+		return;
+	}
+	stop[-1] = '\0';
+	step = strchr(stop, ':') + 1;
+	if (step == (char *)1) { // no step given
+		s->freqs[s->freq_len] = (uint32_t) atofs(start);
+		s->freq_len++;
+		s->freqs[s->freq_len] = (uint32_t) atofs(stop);
+		s->freq_len++;
+		stop[-1] = ':';
+		return;
+	}
+	step[-1] = '\0';
+	for(i=(int)atofs(start); i<=(int)atofs(stop); i+=(int)atofs(step))
+	{
+		s->freqs[s->freq_len] = (uint32_t)i;
+		s->freq_len++;
+		if (s->freq_len >= FREQUENCIES_LIMIT) {
+			break;}
+	}
+	stop[-1] = ':';
+	step[-1] = ':';
+}
+
+void dongle_init(struct dongle_state *s)
+{
+	s->rate = DEFAULT_SAMPLE_RATE;
+	s->gain = AUTO_GAIN; // tenths of a dB
+	s->mute = 0;
+	s->direct_sampling = 0;
+	s->offset_tuning = 0;
+	s->demod_target = &demod;
+}
+
+void demod_init(struct demod_state *s)
+{
+	s->rate_in = DEFAULT_SAMPLE_RATE;
+	s->rate_out = DEFAULT_SAMPLE_RATE;
+	s->squelch_level = 0;
+	s->conseq_squelch = 10;
+	s->terminate_on_squelch = 0;
+	s->squelch_hits = 11;
+	s->downsample_passes = 0;
+	s->comp_fir_size = 0;
+	s->prev_index = 0;
+	s->post_downsample = 1;  // once this works, default = 4
+	s->custom_atan = 0;
+	s->deemph = 0;
+	s->rate_out2 = -1;  // flag for disabled
+	s->mode_demod = &fm_demod;
+	s->pre_j = s->pre_r = s->now_r = s->now_j = 0;
+	s->prev_lpr_index = 0;
+	s->deemph_a = 0;
+	s->now_lpr = 0;
+	s->dc_block = 0;
+	s->dc_avg = 0;
+	pthread_rwlock_init(&s->rw, NULL);
+	pthread_cond_init(&s->ready, NULL);
+	pthread_mutex_init(&s->ready_m, NULL);
+	s->output_target = &output;
+}
+
+void demod_cleanup(struct demod_state *s)
+{
+	pthread_rwlock_destroy(&s->rw);
+	pthread_cond_destroy(&s->ready);
+	pthread_mutex_destroy(&s->ready_m);
+}
+
+void output_init(struct output_state *s)
+{
+	s->rate = DEFAULT_SAMPLE_RATE;
+	pthread_rwlock_init(&s->rw, NULL);
+	pthread_cond_init(&s->ready, NULL);
+	pthread_mutex_init(&s->ready_m, NULL);
+}
+
+void output_cleanup(struct output_state *s)
+{
+	pthread_rwlock_destroy(&s->rw);
+	pthread_cond_destroy(&s->ready);
+	pthread_mutex_destroy(&s->ready_m);
+}
+
+void controller_init(struct controller_state *s)
+{
+	s->freqs[0] = 100000000;
+	s->freq_len = 0;
+	s->edge = 0;
+	s->wb_mode = 0;
+	pthread_cond_init(&s->hop, NULL);
+	pthread_mutex_init(&s->hop_m, NULL);
+}
+
+void controller_cleanup(struct controller_state *s)
+{
+	pthread_cond_destroy(&s->hop);
+	pthread_mutex_destroy(&s->hop_m);
+}
+
+void sanity_checks(void)
+{
+	if (controller.freq_len == 0) {
+		fprintf(stderr, "Please specify a frequency.\n");
+		exit(1);
+	}
+
+	if (controller.freq_len >= FREQUENCIES_LIMIT) {
+		fprintf(stderr, "Too many channels, maximum %i.\n", FREQUENCIES_LIMIT);
+		exit(1);
+	}
+
+	if (controller.freq_len > 1 && demod.squelch_level == 0) {
+		fprintf(stderr, "Please specify a squelch level.  Required for scanning multiple frequencies.\n");
+		exit(1);
+	}
+
+}
+
+int main(int argc, char **argv)
+{
+#ifndef _WIN32
+	struct sigaction sigact;
+#endif
+	int r, opt;
+	int dev_given = 0;
+	int custom_ppm = 0;
+    int enable_biastee = 0;
+	dongle_init(&dongle);
+	demod_init(&demod);
+	output_init(&output);
+	controller_init(&controller);
+
+	while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:p:E:F:A:M:hT")) != -1) {
+		switch (opt) {
+		case 'd':
+			dongle.dev_index = verbose_device_search(optarg);
+			dev_given = 1;
+			break;
+		case 'f':
+			if (controller.freq_len >= FREQUENCIES_LIMIT) {
+				break;}
+			if (strchr(optarg, ':'))
+				{frequency_range(&controller, optarg);}
+			else
+			{
+				controller.freqs[controller.freq_len] = (uint32_t)atofs(optarg);
+				controller.freq_len++;
+			}
+			break;
+		case 'g':
+			dongle.gain = (int)(atof(optarg) * 10);
+			break;
+		case 'l':
+			demod.squelch_level = (int)atof(optarg);
+			break;
+		case 's':
+			demod.rate_in = (uint32_t)atofs(optarg);
+			demod.rate_out = (uint32_t)atofs(optarg);
+			break;
+		case 'r':
+			output.rate = (int)atofs(optarg);
+			demod.rate_out2 = (int)atofs(optarg);
+			break;
+		case 'o':
+			fprintf(stderr, "Warning: -o is very buggy\n");
+			demod.post_downsample = (int)atof(optarg);
+			if (demod.post_downsample < 1 || demod.post_downsample > MAXIMUM_OVERSAMPLE) {
+				fprintf(stderr, "Oversample must be between 1 and %i\n", MAXIMUM_OVERSAMPLE);}
+			break;
+		case 't':
+			demod.conseq_squelch = (int)atof(optarg);
+			if (demod.conseq_squelch < 0) {
+				demod.conseq_squelch = -demod.conseq_squelch;
+				demod.terminate_on_squelch = 1;
+			}
+			break;
+		case 'p':
+			dongle.ppm_error = atoi(optarg);
+			custom_ppm = 1;
+			break;
+		case 'E':
+			if (strcmp("edge",  optarg) == 0) {
+				controller.edge = 1;}
+			if (strcmp("dc", optarg) == 0) {
+				demod.dc_block = 1;}
+			if (strcmp("deemp",  optarg) == 0) {
+				demod.deemph = 1;}
+			if (strcmp("direct",  optarg) == 0) {
+				dongle.direct_sampling = 1;}
+			if (strcmp("direct2", optarg) == 0) {
+				dongle.direct_sampling = 2;}
+			if (strcmp("offset",  optarg) == 0) {
+				dongle.offset_tuning = 1;}
+			break;
+		case 'F':
+			demod.downsample_passes = 1;  /* truthy placeholder */
+			demod.comp_fir_size = atoi(optarg);
+			break;
+		case 'A':
+			if (strcmp("std",  optarg) == 0) {
+				demod.custom_atan = 0;}
+			if (strcmp("fast", optarg) == 0) {
+				demod.custom_atan = 1;}
+			if (strcmp("lut",  optarg) == 0) {
+				atan_lut_init();
+				demod.custom_atan = 2;}
+			break;
+		case 'M':
+			if (strcmp("fm",  optarg) == 0) {
+				demod.mode_demod = &fm_demod;}
+			if (strcmp("raw",  optarg) == 0) {
+				demod.mode_demod = &raw_demod;}
+			if (strcmp("am",  optarg) == 0) {
+				demod.mode_demod = &am_demod;}
+			if (strcmp("usb", optarg) == 0) {
+				demod.mode_demod = &usb_demod;}
+			if (strcmp("lsb", optarg) == 0) {
+				demod.mode_demod = &lsb_demod;}
+			if (strcmp("wbfm",  optarg) == 0) {
+				controller.wb_mode = 1;
+				demod.mode_demod = &fm_demod;
+				demod.rate_in = 170000;
+				demod.rate_out = 170000;
+				demod.rate_out2 = 32000;
+				demod.custom_atan = 1;
+				//demod.post_downsample = 4;
+				demod.deemph = 1;
+				demod.squelch_level = 0;}
+			break;
+		case 'T':
+			enable_biastee = 1;
+			break;
+		case 'h':
+		default:
+			usage();
+			break;
+		}
+	}
+
+	/* quadruple sample_rate to limit to Δθ to ±π/2 */
+	demod.rate_in *= demod.post_downsample;
+
+	if (!output.rate) {
+		output.rate = demod.rate_out;}
+
+	sanity_checks();
+
+	if (controller.freq_len > 1) {
+		demod.terminate_on_squelch = 0;}
+
+	if (argc <= optind) {
+		output.filename = "-";
+	} else {
+		output.filename = argv[optind];
+	}
+
+	ACTUAL_BUF_LENGTH = lcm_post[demod.post_downsample] * DEFAULT_BUF_LENGTH;
+
+	if (!dev_given) {
+		dongle.dev_index = verbose_device_search("0");
+	}
+
+	if (dongle.dev_index < 0) {
+		exit(1);
+	}
+
+	r = rtlsdr_open(&dongle.dev, (uint32_t)dongle.dev_index);
+	if (r < 0) {
+		fprintf(stderr, "Failed to open rtlsdr device #%d.\n", dongle.dev_index);
+		exit(1);
+	}
+#ifndef _WIN32
+	sigact.sa_handler = sighandler;
+	sigemptyset(&sigact.sa_mask);
+	sigact.sa_flags = 0;
+	sigaction(SIGINT, &sigact, NULL);
+	sigaction(SIGTERM, &sigact, NULL);
+	sigaction(SIGQUIT, &sigact, NULL);
+	sigaction(SIGPIPE, &sigact, NULL);
+#else
+	SetConsoleCtrlHandler( (PHANDLER_ROUTINE) sighandler, TRUE );
+#endif
+
+	if (demod.deemph) {
+		demod.deemph_a = (int)round(1.0/((1.0-exp(-1.0/(demod.rate_out * 75e-6)))));
+	}
+
+	/* Set the tuner gain */
+	if (dongle.gain == AUTO_GAIN) {
+		verbose_auto_gain(dongle.dev);
+	} else {
+		dongle.gain = nearest_gain(dongle.dev, dongle.gain);
+		verbose_gain_set(dongle.dev, dongle.gain);
+	}
+
+	rtlsdr_set_bias_tee(dongle.dev, enable_biastee);
+	if (enable_biastee)
+		fprintf(stderr, "activated bias-T on GPIO PIN 0\n");
+
+	verbose_ppm_set(dongle.dev, dongle.ppm_error);
+
+	if (strcmp(output.filename, "-") == 0) { /* Write samples to stdout */
+		output.file = stdout;
+#ifdef _WIN32
+		_setmode(_fileno(output.file), _O_BINARY);
+#endif
+	} else {
+		output.file = fopen(output.filename, "wb");
+		if (!output.file) {
+			fprintf(stderr, "Failed to open %s\n", output.filename);
+			exit(1);
+		}
+	}
+
+	//r = rtlsdr_set_testmode(dongle.dev, 1);
+
+	/* Reset endpoint before we start reading from it (mandatory) */
+	verbose_reset_buffer(dongle.dev);
+
+	pthread_create(&controller.thread, NULL, controller_thread_fn, (void *)(&controller));
+	usleep(100000);
+	pthread_create(&output.thread, NULL, output_thread_fn, (void *)(&output));
+	pthread_create(&demod.thread, NULL, demod_thread_fn, (void *)(&demod));
+	pthread_create(&dongle.thread, NULL, dongle_thread_fn, (void *)(&dongle));
+
+	while (!do_exit) {
+		usleep(100000);
+	}
+
+	if (do_exit) {
+		fprintf(stderr, "\nUser cancel, exiting...\n");}
+	else {
+		fprintf(stderr, "\nLibrary error %d, exiting...\n", r);}
+
+	rtlsdr_cancel_async(dongle.dev);
+	pthread_join(dongle.thread, NULL);
+	safe_cond_signal(&demod.ready, &demod.ready_m);
+	pthread_join(demod.thread, NULL);
+	safe_cond_signal(&output.ready, &output.ready_m);
+	pthread_join(output.thread, NULL);
+	safe_cond_signal(&controller.hop, &controller.hop_m);
+	pthread_join(controller.thread, NULL);
+
+	//dongle_cleanup(&dongle);
+	demod_cleanup(&demod);
+	output_cleanup(&output);
+	controller_cleanup(&controller);
+
+	if (output.file != stdout) {
+		fclose(output.file);}
+
+	rtlsdr_close(dongle.dev);
+	return r >= 0 ? r : -r;
+}
+
+// vim: tabstop=8:softtabstop=8:shiftwidth=8:noexpandtab