diff --git a/op25/gr-op25_repeater/include/op25_repeater/CMakeLists.txt b/op25/gr-op25_repeater/include/op25_repeater/CMakeLists.txt
index 0fbd32c..b93833a 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/CMakeLists.txt
+++ b/op25/gr-op25_repeater/include/op25_repeater/CMakeLists.txt
@@ -25,6 +25,7 @@ install(FILES
     vocoder.h
     gardner_costas_cc.h
     p25_frame_assembler.h
+    frame_assembler.h
     ambe_encoder_sb.h
     fsk4_slicer_fb.h DESTINATION include/op25_repeater
 )
diff --git a/op25/gr-op25_repeater/include/op25_repeater/frame_assembler.h b/op25/gr-op25_repeater/include/op25_repeater/frame_assembler.h
new file mode 100644
index 0000000..086a1ba
--- /dev/null
+++ b/op25/gr-op25_repeater/include/op25_repeater/frame_assembler.h
@@ -0,0 +1,59 @@
+/* -*- c++ -*- */
+/* 
+ * Copyright 2017 Max H. Parke KA1RBI
+ * 
+ * This 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 3, or (at your option)
+ * any later version.
+ * 
+ * This software 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 software; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+
+#ifndef INCLUDED_OP25_REPEATER_FRAME_ASSEMBLER_H
+#define INCLUDED_OP25_REPEATER_FRAME_ASSEMBLER_H
+
+#include <op25_repeater/api.h>
+#include <gnuradio/block.h>
+#include <gnuradio/msg_queue.h>
+
+namespace gr {
+  namespace op25_repeater {
+
+    /*!
+     * \brief <+description of block+>
+     * \ingroup op25_repeater
+     *
+     */
+    class OP25_REPEATER_API frame_assembler : virtual public gr::block
+    {
+     public:
+      typedef boost::shared_ptr<frame_assembler> sptr;
+
+      /*!
+       * \brief Return a shared_ptr to a new instance of op25_repeater::frame_assembler.
+       *
+       * To avoid accidental use of raw pointers, op25_repeater::frame_assembler's
+       * constructor is in a private implementation
+       * class. op25_repeater::frame_assembler::make is the public interface for
+       * creating new instances.
+       */
+      static sptr make(const char* options, int debug, gr::msg_queue::sptr queue);
+      virtual void set_xormask(const char*p) {}
+      virtual void set_slotid(int slotid) {}
+    };
+
+  } // namespace op25_repeater
+} // namespace gr
+
+#endif /* INCLUDED_OP25_REPEATER_FRAME_ASSEMBLER_H */
+
diff --git a/op25/gr-op25_repeater/lib/CMakeLists.txt b/op25/gr-op25_repeater/lib/CMakeLists.txt
index 361f266..8e73154 100644
--- a/op25/gr-op25_repeater/lib/CMakeLists.txt
+++ b/op25/gr-op25_repeater/lib/CMakeLists.txt
@@ -32,6 +32,7 @@ list(APPEND op25_repeater_sources
     vocoder_impl.cc
     gardner_costas_cc_impl.cc
     p25_frame_assembler_impl.cc
+    frame_assembler_impl.cc
     fsk4_slicer_fb_impl.cc )
 
 list(APPEND op25_repeater_sources
@@ -52,6 +53,9 @@ list(APPEND op25_repeater_sources
     ambe.c
     mbelib.c
     ambe_encoder.cc
+    rx_sync.cc
+    op25_audio.cc
+    CCITTChecksumReverse.cpp
 )
 
 add_library(gnuradio-op25_repeater SHARED ${op25_repeater_sources})
diff --git a/op25/gr-op25_repeater/lib/frame_assembler_impl.cc b/op25/gr-op25_repeater/lib/frame_assembler_impl.cc
new file mode 100644
index 0000000..8760a1f
--- /dev/null
+++ b/op25/gr-op25_repeater/lib/frame_assembler_impl.cc
@@ -0,0 +1,96 @@
+/* -*- c++ -*- */
+/* 
+ * Copyright 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Max H. Parke KA1RBI 
+ * 
+ * This 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 3, or (at your option)
+ * any later version.
+ * 
+ * This software 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 software; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gnuradio/io_signature.h>
+#include "frame_assembler_impl.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <vector>
+#include <sys/time.h>
+
+namespace gr {
+  namespace op25_repeater {
+
+    void frame_assembler_impl::set_xormask(const char*p) {
+    }
+
+    void frame_assembler_impl::set_slotid(int slotid) {
+    }
+
+    frame_assembler::sptr
+    frame_assembler::make(const char* options, int debug, gr::msg_queue::sptr queue)
+    {
+      return gnuradio::get_initial_sptr
+        (new frame_assembler_impl(options, debug, queue));
+    }
+
+    /*
+     * The private constructor
+     */
+
+    /*
+     * Our virtual destructor.
+     */
+    frame_assembler_impl::~frame_assembler_impl()
+    {
+    }
+
+static const int MIN_IN = 1;	// mininum number of input streams
+static const int MAX_IN = 1;	// maximum number of input streams
+
+/*
+ * The private constructor
+ */
+    frame_assembler_impl::frame_assembler_impl(const char* options, int debug, gr::msg_queue::sptr queue)
+      : gr::block("frame_assembler",
+		   gr::io_signature::make (MIN_IN, MAX_IN, sizeof (char)),
+		   gr::io_signature::make (0, 0, 0)),
+	d_msg_queue(queue),
+	d_sync(options, debug)
+{
+}
+
+int 
+frame_assembler_impl::general_work (int noutput_items,
+                               gr_vector_int &ninput_items,
+                               gr_vector_const_void_star &input_items,
+                               gr_vector_void_star &output_items)
+{
+
+  const uint8_t *in = (const uint8_t *) input_items[0];
+
+  for (int i=0; i<ninput_items[0]; i++)
+      d_sync.rx_sym(in[i]);
+  consume_each(ninput_items[0]);
+  // Tell runtime system how many output items we produced.
+  return 0;
+}
+
+  } /* namespace op25_repeater */
+} /* namespace gr */
diff --git a/op25/gr-op25_repeater/lib/frame_assembler_impl.h b/op25/gr-op25_repeater/lib/frame_assembler_impl.h
new file mode 100644
index 0000000..a869c5e
--- /dev/null
+++ b/op25/gr-op25_repeater/lib/frame_assembler_impl.h
@@ -0,0 +1,70 @@
+/* -*- c++ -*- */
+/* 
+ * Copyright 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Max H. Parke KA1RBI
+ * 
+ * This 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 3, or (at your option)
+ * any later version.
+ * 
+ * This software 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 software; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef INCLUDED_OP25_REPEATER_FRAME_ASSEMBLER_IMPL_H
+#define INCLUDED_OP25_REPEATER_FRAME_ASSEMBLER_IMPL_H
+
+#include <op25_repeater/frame_assembler.h>
+
+#include <gnuradio/msg_queue.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <deque>
+
+#include "rx_sync.h"
+
+typedef std::deque<uint8_t> dibit_queue;
+
+namespace gr {
+  namespace op25_repeater {
+
+    class frame_assembler_impl : public frame_assembler
+    {
+     private:
+        int d_debug;
+	gr::msg_queue::sptr d_msg_queue;
+        rx_sync d_sync;
+
+  // internal functions
+
+    void queue_msg(int duid);
+    void set_xormask(const char*p) ;
+    void set_slotid(int slotid) ;
+
+ public:
+
+     public:
+      frame_assembler_impl(const char* options, int debug, gr::msg_queue::sptr queue);
+      ~frame_assembler_impl();
+
+      // Where all the action really happens
+
+      int general_work(int noutput_items,
+		       gr_vector_int &ninput_items,
+		       gr_vector_const_void_star &input_items,
+		       gr_vector_void_star &output_items);
+    };
+
+  } // namespace op25_repeater
+} // namespace gr
+
+#endif /* INCLUDED_OP25_REPEATER_FRAME_ASSEMBLER_IMPL_H */
diff --git a/op25/gr-op25_repeater/lib/rx_sync.cc b/op25/gr-op25_repeater/lib/rx_sync.cc
new file mode 100644
index 0000000..1ca7f8e
--- /dev/null
+++ b/op25/gr-op25_repeater/lib/rx_sync.cc
@@ -0,0 +1,377 @@
+// P25 Decoder (C) Copyright 2013, 2014, 2015, 2016, 2017 Max H. Parke KA1RBI
+// 
+// This file is part of OP25
+// 
+// OP25 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 3, or (at your option)
+// any later version.
+// 
+// OP25 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 OP25; see the file COPYING. If not, write to the Free
+// Software Foundation, Inc., 51 Franklin Street, Boston, MA
+// 02110-1301, USA.
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <string>
+#include <iostream>
+#include <deque>
+#include <assert.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include "rx_sync.h"
+
+#include "bit_utils.h"
+
+#include "check_frame_sync.h"
+
+#include "p25p2_vf.h"
+#include "mbelib.h"
+#include "ambe.h"
+#include "rs.h"
+#include "crc16.h"
+
+#include "ysf_const.h"
+#include "dmr_const.h"
+#include "p25_frame.h"
+#include "op25_imbe_frame.h"
+#include "software_imbe_decoder.h"
+#include "op25_audio.h"
+
+namespace gr{
+    namespace op25_repeater{
+
+void rx_sync::cbuf_insert(const uint8_t c) {
+	d_cbuf[d_cbuf_idx] = c;
+	d_cbuf[d_cbuf_idx + CBUF_SIZE] = c;
+	d_cbuf_idx = (d_cbuf_idx + 1) % CBUF_SIZE;
+}
+
+void rx_sync::sync_reset(void) {
+	d_threshold = 0;
+	d_shift_reg = 0;
+	d_unmute_until[0] = 0;
+	d_unmute_until[1] = 0;
+}
+
+static int ysf_decode_fich(const uint8_t src[100], uint8_t dest[32]) {   // input is 100 dibits, result is 32 bits
+// return -1 on decode error, else 0
+	static const int pc[] = {0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1};
+	uint8_t buf[100];
+	for (int i=0; i<20; i++) {
+		for (int j=0; j<5; j++) {
+			buf[j+i*5] = src[i+j*20];
+		}
+	}
+	uint8_t dr = 0;
+	uint8_t ans[100];
+	/* fake trellis decode */
+	/* TODO: make less fake */
+	for (int i=0; i<100; i++) {
+		uint8_t sym = buf[i];
+		uint8_t d0  = ((dr << 1) | 0) & 0x1f;
+		uint8_t r0 = (pc[ d0 & 0x19 ] << 1) + pc[ d0 & 0x17];
+		uint8_t d1  = ((dr << 1) | 1) & 0x1f;
+		uint8_t r1 = (pc[ d1 & 0x19 ] << 1) + pc[ d1 & 0x17];
+		if (sym == r0) {
+			ans[i] = 0;
+			dr = d0;
+		} else if (sym == r1) {
+			ans[i] = 1;
+			dr = d1;
+		} else {
+			return -1;  /* decode error */
+		}
+	}
+	uint8_t fich_bits[12*4];
+	store_i(gly24128Dec(load_i(ans+24*0, 24)), fich_bits+12*0, 12);
+	store_i(gly24128Dec(load_i(ans+24*1, 24)), fich_bits+12*1, 12);
+	store_i(gly24128Dec(load_i(ans+24*2, 24)), fich_bits+12*2, 12);
+	store_i(gly24128Dec(load_i(ans+24*3, 24)), fich_bits+12*3, 12);
+	uint16_t crc_result = crc16(fich_bits, 48);
+	if (crc_result != 0)
+		return -1;	// crc failure
+	memcpy(dest, fich_bits, 32);
+	return 0;
+}
+
+void rx_sync::ysf_sync(const uint8_t dibitbuf[], bool& ysf_fullrate, bool& unmute) {
+	uint8_t fich_buf[32];
+	int rc = ysf_decode_fich(dibitbuf+20, fich_buf);
+	if (rc == 0) {
+		uint32_t fich = load_i(fich_buf, 32);
+		uint32_t dt = (fich >> 8) & 3;
+		d_shift_reg = dt;
+	}
+	switch(d_shift_reg) {
+	case 0:		// voice/data mode 1
+		unmute = false;
+		break;
+	case 1:		// data mode
+		unmute = false;
+		break;
+	case 2:		// voice/data mode 2
+		unmute = true;
+		ysf_fullrate = false;
+		break;
+	case 3:		// voice fr mode
+		unmute = true;
+		ysf_fullrate = true;
+		break;
+	}
+	if (d_debug > 5 && !unmute)
+		fprintf(stderr, "ysf_sync: muting audio: dt: %d, rc: %d\n", d_shift_reg, rc);
+}
+
+void rx_sync::dmr_sync(const uint8_t bitbuf[], int& current_slot, bool& unmute) {
+	static const int slot_ids[] = {0, 1, 0, 0, 1, 1, 0, 1};
+	int tact;
+	int chan;
+	int fstype;
+	uint8_t tactbuf[sizeof(cach_tact_bits)];
+
+	for (size_t i=0; i<sizeof(cach_tact_bits); i++)
+		tactbuf[i] = bitbuf[cach_tact_bits[i]];
+	tact = hamming_7_4_decode[load_i(tactbuf, 7)];
+	chan = (tact>>2) & 1;
+	d_shift_reg = (d_shift_reg << 1) + chan;
+	current_slot = slot_ids[d_shift_reg & 7];
+
+	uint64_t sync = load_reg64(bitbuf + (MODE_DATA[RX_TYPE_DMR].sync_offset << 1), MODE_DATA[RX_TYPE_DMR].sync_len);
+	if (check_frame_sync(DMR_VOICE_SYNC_MAGIC ^ sync, d_threshold, MODE_DATA[RX_TYPE_DMR].sync_len))
+		fstype = 1;
+	else if (check_frame_sync(DMR_IDLE_SYNC_MAGIC ^ sync, d_threshold, MODE_DATA[RX_TYPE_DMR].sync_len))
+		fstype = 2;
+	else
+		fstype = 0;
+	if (fstype > 0)
+		d_expires = d_symbol_count + MODE_DATA[d_current_type].expiration;
+	if (fstype == 1) {
+		if (!d_unmute_until[current_slot] && d_debug > 5)
+			fprintf(stderr, "unmute slot %d\n", current_slot);
+		d_unmute_until[current_slot] = d_symbol_count + MODE_DATA[d_current_type].expiration;
+	} else if (fstype == 2) {
+		if (d_unmute_until[current_slot] && d_debug > 5)
+			fprintf(stderr, "mute slot %d\n", current_slot);
+		d_unmute_until[current_slot] = 0;
+	}
+	if (d_unmute_until[current_slot] <= d_symbol_count) {
+		d_unmute_until[current_slot] = 0;
+	}
+	unmute = d_unmute_until[current_slot] > 0;
+}
+
+rx_sync::rx_sync(const char * options, int debug) :	// constructor
+	d_symbol_count(0),
+	d_sync_reg(0),
+	d_cbuf_idx(0),
+	d_current_type(RX_TYPE_NONE),
+	d_rx_count(0),
+	d_expires(0),
+	d_stereo(false),
+	d_debug(debug),
+	d_audio(options, debug)
+{
+	mbe_initMbeParms (&cur_mp[0], &prev_mp[0], &enh_mp[0]);
+	mbe_initMbeParms (&cur_mp[1], &prev_mp[1], &enh_mp[1]);
+	sync_reset();
+}
+
+rx_sync::~rx_sync()	// destructor
+{
+}
+
+
+void rx_sync::codeword(const uint8_t* cw, const enum codeword_types codeword_type, int slot_id) {
+	static const int x=4;
+	static const int y=26;
+	static const uint8_t majority[8] = {0,0,0,1,0,1,1,1};
+
+	int b[9];
+	uint8_t buf[4*26];
+	uint8_t tmp_codeword [144];
+	uint32_t E0, ET;
+	uint32_t u[8];
+	bool do_fullrate = false;
+	bool do_silence = false;
+	voice_codeword fullrate_cw(voice_codeword_sz);
+
+	switch(codeword_type) {
+	case CODEWORD_DMR:
+		interleaver.process_vcw(cw, b);
+		if (b[0] < 120)
+			mbe_dequantizeAmbe2250Parms(&cur_mp[slot_id], &prev_mp[slot_id], b);
+		break;
+	case CODEWORD_DSTAR:
+		interleaver.decode_dstar(cw, b, false);
+		if (b[0] < 120)
+			mbe_dequantizeAmbe2400Parms(&cur_mp[slot_id], &prev_mp[slot_id], b);
+		break;
+	case CODEWORD_YSF_HALFRATE:	// 104 bits
+		for (int i=0; i<x; i++) {
+			for (int j=0; j<y; j++) 
+				buf[j+i*y] = cw[i+j*x];
+		}
+		ysf_scramble(buf, 104);
+		for (int i=0; i<27; i++)
+			tmp_codeword[i] = majority[ (buf[0+i*3] << 2) | (buf[1+i*3] << 1) | buf[2+i*3] ];
+
+		memcpy(tmp_codeword+27, buf+81, 22);
+		decode_49bit(b, tmp_codeword);
+		if (b[0] < 120)
+			mbe_dequantizeAmbe2250Parms(&cur_mp[slot_id], &prev_mp[slot_id], b);
+		break;
+	case CODEWORD_P25P2:
+		break;
+	case CODEWORD_P25P1:	// 144 bits
+		for (int i=0; i<144; i++)
+			fullrate_cw[i] = cw[i];
+		imbe_header_decode(fullrate_cw, u[0], u[1], u[2], u[3], u[4], u[5], u[6], u[7], E0, ET);
+		do_fullrate = true;
+		break;
+	case CODEWORD_YSF_FULLRATE:	// 144 bits
+		for (int i=0; i<144; i++)
+			fullrate_cw[i] = cw[ysf_permutation[i]];
+		imbe_header_decode(fullrate_cw, u[0], u[1], u[2], u[3], u[4], u[5], u[6], u[7], E0, ET);
+		do_fullrate = true;
+		break;
+	}
+	mbe_moveMbeParms (&cur_mp[slot_id], &prev_mp[slot_id]);
+	if (do_fullrate) {
+		d_software_decoder[slot_id].decode(fullrate_cw);
+	} else {	/* halfrate */
+		if (b[0] >= 120) {
+			do_silence = true;
+		} else {
+			d_software_decoder[slot_id].decode_tap(cur_mp[slot_id].L, 0, cur_mp[slot_id].w0, &cur_mp[slot_id].Vl[1], &cur_mp[slot_id].Ml[1]);
+		}
+	}
+	audio_samples *samples = d_software_decoder[slot_id].audio();
+	float snd;
+	int16_t samp_buf[NSAMP_OUTPUT];
+	for (int i=0; i < NSAMP_OUTPUT; i++) {
+		if ((!do_silence) && samples->size() > 0) {
+			snd = samples->front();
+			samples->pop_front();
+		} else {
+			snd = 0;
+		}
+		if (do_fullrate)
+			snd *= 32768.0;
+		samp_buf[i] = snd;
+	}
+	output(samp_buf, slot_id);
+}
+
+void rx_sync::output(int16_t * samp_buf, const ssize_t slot_id) {
+	if (!d_stereo) {
+		d_audio.send_audio_channel(samp_buf, NSAMP_OUTPUT * sizeof(int16_t), slot_id);
+		return;
+	}
+}
+
+void rx_sync::rx_sym(const uint8_t sym)
+{
+	uint8_t bitbuf[864*2];
+	enum rx_types sync_detected = RX_TYPE_NONE;
+	int current_slot;
+	bool unmute;
+	uint8_t tmpcw[144];
+	bool ysf_fullrate;
+
+	d_symbol_count ++;
+	d_sync_reg = (d_sync_reg << 2) | (sym & 3);
+	for (int i = 1; i < RX_N_TYPES; i++) {
+		if (check_frame_sync(MODE_DATA[i].sync ^ d_sync_reg, (i == d_current_type) ? d_threshold : 0, MODE_DATA[i].sync_len)) {
+			sync_detected = (enum rx_types) i;
+			break;
+		}
+	}
+	cbuf_insert(sym);
+	if (d_current_type == RX_TYPE_NONE && sync_detected == RX_TYPE_NONE)
+		return;
+	d_rx_count ++;
+	if (sync_detected != RX_TYPE_NONE) {
+		if (d_current_type != sync_detected) {
+			d_current_type = sync_detected;
+			d_expires = d_symbol_count + MODE_DATA[d_current_type].expiration;
+			d_rx_count = 0;
+		}
+		if (d_rx_count != MODE_DATA[d_current_type].sync_offset + (MODE_DATA[d_current_type].sync_len >> 1)) {
+			if (d_debug)
+				fprintf(stderr, "resync at count %d for protocol %s\n", d_rx_count, MODE_DATA[d_current_type].type);
+			sync_reset();
+			d_rx_count = MODE_DATA[d_current_type].sync_offset + (MODE_DATA[d_current_type].sync_len >> 1);
+		} else {
+			d_threshold = std::min(d_threshold + 1, 2);
+		}
+		d_expires = d_symbol_count + MODE_DATA[d_current_type].expiration;
+	}
+	if (d_symbol_count >= d_expires) {
+		if (d_debug)
+			fprintf(stderr, "%s: timeout, symbol %d\n", MODE_DATA[d_current_type].type, d_symbol_count);
+		d_current_type = RX_TYPE_NONE;
+		return;
+	}
+	if (d_rx_count < MODE_DATA[d_current_type].fragment_len)
+		return;
+	d_rx_count = 0;
+	int start_idx = d_cbuf_idx + CBUF_SIZE - MODE_DATA[d_current_type].fragment_len;
+	assert (start_idx >= 0);
+	uint8_t * symbol_ptr = d_cbuf+start_idx;
+	uint8_t * bit_ptr = symbol_ptr;
+	if (d_current_type != RX_TYPE_DSTAR) {
+		dibits_to_bits(bitbuf, symbol_ptr, MODE_DATA[d_current_type].fragment_len);
+		bit_ptr = bitbuf;
+	}
+	switch (d_current_type) {
+	case RX_TYPE_NONE:
+		break;
+	case RX_TYPE_P25:
+		for (unsigned int codeword_ct=0; codeword_ct < nof_voice_codewords; codeword_ct++) {
+			for (unsigned int i=0; i<voice_codeword_sz; i++)
+				tmpcw[i] = bit_ptr[voice_codeword_bits[codeword_ct][i]];
+			codeword(tmpcw, CODEWORD_P25P1, 0);  // 144 bits
+		}
+		break;
+	case RX_TYPE_DMR:
+		dmr_sync(bit_ptr, current_slot, unmute);
+		if (!unmute)
+			break;
+		codeword(symbol_ptr+12, CODEWORD_DMR, current_slot);
+		memcpy(tmpcw, symbol_ptr+48, 18);
+		memcpy(tmpcw+18, symbol_ptr+90, 18);
+		codeword(tmpcw, CODEWORD_DMR, current_slot);
+		codeword(symbol_ptr+108, CODEWORD_DMR, current_slot);
+		break;
+	case RX_TYPE_DSTAR:
+		codeword(bit_ptr, CODEWORD_DSTAR, 0);   // 72 bits = 72 symbols
+		break;
+	case RX_TYPE_YSF:
+		ysf_sync(symbol_ptr, ysf_fullrate, unmute);
+		if (!unmute)
+			break;
+		for (int vcw = 0; vcw < 5; vcw++) {
+			if (ysf_fullrate) {
+				codeword(bit_ptr + 2*(vcw*72 + 120), CODEWORD_YSF_FULLRATE, 0);  // 144 bits
+			} else {	/* halfrate */
+				codeword(bit_ptr + 2*(vcw*72 + 120 + 20), CODEWORD_YSF_HALFRATE, 0);   // 104 bits
+			}
+		}
+		break;
+	case RX_N_TYPES:
+		assert(0==1);     /* should not occur */
+		break;
+	}
+}
+    } // end namespace op25_repeater
+} // end namespace gr
diff --git a/op25/gr-op25_repeater/lib/rx_sync.h b/op25/gr-op25_repeater/lib/rx_sync.h
new file mode 100644
index 0000000..bbad158
--- /dev/null
+++ b/op25/gr-op25_repeater/lib/rx_sync.h
@@ -0,0 +1,122 @@
+// P25 Decoder (C) Copyright 2013, 2014, 2015, 2016, 2017 Max H. Parke KA1RBI
+// 
+// This file is part of OP25
+// 
+// OP25 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 3, or (at your option)
+// any later version.
+// 
+// OP25 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 OP25; see the file COPYING. If not, write to the Free
+// Software Foundation, Inc., 51 Franklin Street, Boston, MA
+// 02110-1301, USA.
+
+#ifndef INCLUDED_RX_SYNC_H
+#define INCLUDED_RX_SYNC_H
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <string>
+#include <iostream>
+#include <deque>
+#include <assert.h>
+
+#include "bit_utils.h"
+#include "check_frame_sync.h"
+
+#include "p25p2_vf.h"
+#include "mbelib.h"
+#include "ambe.h"
+
+#include "ysf_const.h"
+#include "dmr_const.h"
+#include "p25_frame.h"
+#include "op25_imbe_frame.h"
+#include "software_imbe_decoder.h"
+#include "op25_audio.h"
+
+namespace gr{
+    namespace op25_repeater{
+
+static const uint64_t DSTAR_FRAME_SYNC_MAGIC = 0x444445101440LL;  // expanded into dibits
+
+enum rx_types {
+	RX_TYPE_NONE=0,
+	RX_TYPE_P25,
+	RX_TYPE_DMR,
+	RX_TYPE_DSTAR,
+	RX_TYPE_YSF,
+	RX_N_TYPES
+};   // also used as array index
+
+static const struct _mode_data {
+	const char * type;
+	int sync_len;
+	int sync_offset;
+	int fragment_len;   // symbols
+	int expiration;
+	uint64_t sync;
+} MODE_DATA[RX_N_TYPES] = {
+	{"NONE",   0,0,0,0,0},
+	{"P25",    48,0,864,1728,   P25_FRAME_SYNC_MAGIC},
+	{"DMR",    48,66,144,1728,  DMR_VOICE_SYNC_MAGIC},
+	{"DSTAR",  48,72,96,2016*2, DSTAR_FRAME_SYNC_MAGIC},
+	{"YSF",    40,0,480,480*2,  YSF_FRAME_SYNC_MAGIC}
+};   // index order must match rx_types enum
+
+enum codeword_types {
+	CODEWORD_P25P1,
+	CODEWORD_P25P2,
+	CODEWORD_DMR,
+	CODEWORD_DSTAR,
+	CODEWORD_YSF_FULLRATE,
+	CODEWORD_YSF_HALFRATE
+};
+
+class rx_sync {
+public:
+	void rx_sym(const uint8_t sym);
+	void sync_reset(void);
+	rx_sync(const char * options, int debug);
+	~rx_sync();
+private:
+	void cbuf_insert(const uint8_t c);
+	void dmr_sync(const uint8_t bitbuf[], int& current_slot, bool& unmute);
+	void ysf_sync(const uint8_t dibitbuf[], bool& ysf_fullrate, bool& unmute);
+	void codeword(const uint8_t* cw, const enum codeword_types codeword_type, int slot_id);
+	void output(int16_t * samp_buf, const ssize_t slot_id);
+	static const int CBUF_SIZE=864;
+	static const int NSAMP_OUTPUT = 160;
+
+	unsigned int d_symbol_count;
+	uint64_t d_sync_reg;
+	uint8_t d_cbuf[CBUF_SIZE*2];
+	unsigned int d_cbuf_idx;
+	enum rx_types d_current_type;
+	int d_threshold;
+	int d_rx_count;
+	unsigned int d_expires;
+	int d_shift_reg;
+	unsigned int d_unmute_until[2];
+	p25p2_vf interleaver;
+	mbe_parms cur_mp[2];
+	mbe_parms prev_mp[2];
+	mbe_parms enh_mp[2];
+	software_imbe_decoder d_software_decoder[2];
+	std::deque<int16_t> d_output_queue[2];
+	bool d_stereo;
+	int d_debug;
+	op25_audio d_audio;
+};
+
+    } // end namespace op25_repeater
+} // end namespace gr
+#endif // INCLUDED_RX_SYNC_H