Merged r8195:8205 from jcorgan/ecc into trunk. Adds convolutional encoder

and decoder corresponding to the R=1/2, K=7 CCSDS standard ("Voyager").

This code is a GNU Radio wrapper around a 1995-era KA9Q portable-C 
implementation, and is designed for continuous streaming data, not packets.

The encoder takes MSB packed bytes and outputs channel symbols 0 or 1.

The decoder uses soft-decision Viterbi decoding on a floating point stream of
(possibly noise corrupted) [1.0, 1.0] symbols, and outputs MSB packed
decoded bytes.

Benchmarking on a 2.16 GHz Intel Core 2 Duo shows 4.7 Mbps decoding rate at 
100% CPU usage (single core).  (There is a newer KA9Q library that implements 
SIMD speed ups with correspondingly faster performance.)

The KA9Q library is placed into src/lib/viterbi.  It could use some cleanup,
file/function renaming, and refactoring, or even replacement with the newer
libfec code that is available.



git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@8206 221aa14e-8319-0410-a670-987f0aec2ac5

18 files changed, 1177 insertions, 4 deletions

diff --git a/gnuradio-core/src/lib/Makefile.am b/gnuradio-core/src/lib/Makefile.am
index f6693ddc2..66567048c 100644
--- a/gnuradio-core/src/lib/Makefile.am
+++ b/gnuradio-core/src/lib/Makefile.am
@@ -24,7 +24,7 @@ include $(top_srcdir)/Makefile.common
 ## Process this file with automake to produce Makefile.in
 
 # We've got to build . before swig
-SUBDIRS = missing runtime filter general gengen g72x reed-solomon io . swig
+SUBDIRS = missing runtime filter viterbi general gengen g72x reed-solomon io . swig
 
 # generate libgnuradio-core.la from the convenience libraries in subdirs
 
@@ -39,6 +39,7 @@ libgnuradio_core_qa_la_LDFLAGS = $(NO_UNDEFINED) -version-info 0:0:0 \
 libgnuradio_core_la_LIBADD  = 		\
 	filter/libfilter.la		\
 	g72x/libccitt.la		\
+	viterbi/libviterbi.la		\
 	general/libgeneral.la		\
 	gengen/libgengen.la		\
 	io/libio.la			\
diff --git a/gnuradio-core/src/lib/general/Makefile.am b/gnuradio-core/src/lib/general/Makefile.am
index 5a12a739a..b499ee670 100644
--- a/gnuradio-core/src/lib/general/Makefile.am
+++ b/gnuradio-core/src/lib/general/Makefile.am
@@ -59,12 +59,14 @@ libgeneral_la_SOURCES = 		\
 	gr_crc32.cc			\
 	gr_ctcss_squelch_ff.cc		\
 	gr_dd_mpsk_sync_cc.cc		\
+	gr_decode_ccsds_27_fb.cc	\
 	gr_deinterleave.cc		\
 	gr_delay.cc			\
 	gr_diff_decoder_bb.cc		\
 	gr_diff_encoder_bb.cc		\
 	gr_diff_phasor_cc.cc		\
 	gr_dpll_bb.cc			\
+	gr_encode_ccsds_27_bb.cc	\
 	gr_fake_channel_coder_pp.cc	\
 	gr_fast_atan2f.cc		\
 	gr_feedforward_agc_cc.cc	\
@@ -174,8 +176,6 @@ libgeneral_qa_la_SOURCES = 		\
 	qa_gr_fxpt_vco.cc		\
 	qa_gr_math.cc
 
-
-
 grinclude_HEADERS = 			\
 	gr_agc_cc.h                 	\
 	gr_agc_ff.h                 	\
@@ -199,15 +199,17 @@ grinclude_HEADERS = 			\
 	gr_costas_loop_cc.h		\
 	gr_count_bits.h			\
 	gr_cpfsk_bc.h			\
-    	gr_crc32.h			\
+	gr_crc32.h			\
 	gr_ctcss_squelch_ff.h		\
 	gr_dd_mpsk_sync_cc.h		\
+	gr_decode_ccsds_27_fb.h		\
 	gr_diff_decoder_bb.h		\
 	gr_diff_encoder_bb.h		\
 	gr_deinterleave.h		\
 	gr_delay.h			\
 	gr_diff_phasor_cc.h		\
 	gr_dpll_bb.h			\
+	gr_encode_ccsds_27_bb.h		\
 	gr_expj.h			\
 	gr_fake_channel_coder_pp.h	\
 	gr_feedforward_agc_cc.h		\
@@ -358,12 +360,14 @@ swiginclude_HEADERS =			\
 	gr_crc32.i			\
 	gr_ctcss_squelch_ff.i		\
 	gr_dd_mpsk_sync_cc.i		\
+	gr_decode_ccsds_27_fb.i		\
 	gr_diff_decoder_bb.i		\
 	gr_diff_encoder_bb.i		\
 	gr_diff_phasor_cc.i		\
 	gr_dpll_bb.i			\
 	gr_deinterleave.i		\
 	gr_delay.i			\
+	gr_encode_ccsds_27_bb.i		\
 	gr_fake_channel_coder_pp.i	\
 	gr_feedforward_agc_cc.i		\
 	gr_feval.i			\
diff --git a/gnuradio-core/src/lib/general/general.i b/gnuradio-core/src/lib/general/general.i
index 724ea0316..21bbdb2c5 100644
--- a/gnuradio-core/src/lib/general/general.i
+++ b/gnuradio-core/src/lib/general/general.i
@@ -131,6 +131,8 @@
 #include <gr_peak_detector2_fb.h>
 #include <gr_repeat.h>
 #include <gr_cpfsk_bc.h>
+#include <gr_encode_ccsds_27_bb.h>
+#include <gr_decode_ccsds_27_fb.h>
 %}
 
 %include "gr_nop.i"
@@ -242,3 +244,5 @@
 %include "gr_peak_detector2_fb.i"
 %include "gr_repeat.i"
 %include "gr_cpfsk_bc.i"
+%include "gr_encode_ccsds_27_bb.i"
+%include "gr_decode_ccsds_27_fb.i"
diff --git a/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.cc b/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.cc
new file mode 100644
index 000000000..add036f20
--- /dev/null
+++ b/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.cc
@@ -0,0 +1,86 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; 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 <gr_decode_ccsds_27_fb.h>
+#include <gr_io_signature.h>
+
+gr_decode_ccsds_27_fb_sptr 
+gr_make_decode_ccsds_27_fb()
+{
+  return gr_decode_ccsds_27_fb_sptr(new gr_decode_ccsds_27_fb());
+}
+
+gr_decode_ccsds_27_fb::gr_decode_ccsds_27_fb()
+  : gr_sync_decimator("decode_ccsds_27_fb",
+		      gr_make_io_signature(1, 1, sizeof(float)),
+		      gr_make_io_signature(1, 1, sizeof(char)),
+		      2*8)  // Rate 1/2 code, unpacked to packed translation
+{
+    float RATE = 0.5;
+    float ebn0 = 12.0;
+    float esn0 = RATE*pow(10.0, ebn0/10);
+
+    gen_met(d_mettab, 100, esn0, 0.0, 256);
+    viterbi_chunks_init(d_state0);
+}
+
+gr_decode_ccsds_27_fb::~gr_decode_ccsds_27_fb()
+{
+}
+
+int 
+gr_decode_ccsds_27_fb::work(int noutput_items,
+			    gr_vector_const_void_star &input_items,
+			    gr_vector_void_star &output_items)
+{
+  const float *in = (const float *)input_items[0];
+  unsigned char *out = (unsigned char *)output_items[0];
+
+  for (int i = 0; i < noutput_items*16; i++) {
+    // Translate and clip [-1.0..1.0] to [28..228]
+    float sample = in[i]*100.0+128.0;
+    if (sample > 255.0)
+	sample = 255.0;
+    else if (sample < 0.0)
+	sample = 0.0;
+    unsigned char sym = (unsigned char)(floor(sample));
+    
+    d_viterbi_in[d_count % 4] = sym;
+    if ((d_count % 4) == 3) {
+      // Every fourth symbol, perform butterfly operation
+      viterbi_butterfly2(d_viterbi_in, d_mettab, d_state0, d_state1);
+      
+      // Every sixteenth symbol, read out a byte
+      if (d_count % 16 == 11) {
+	// long metric = 
+	viterbi_get_output(d_state0, out++);
+	// printf("%li\n", *(out-1), metric);
+      }
+    }
+    
+    d_count++;
+  }
+
+  return noutput_items;
+}
diff --git a/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.h b/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.h
new file mode 100644
index 000000000..50a6c9d89
--- /dev/null
+++ b/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.h
@@ -0,0 +1,77 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+#ifndef INCLUDED_GR_DECODE_CCSDS_27_FB_H
+#define INCLUDED_GR_DECODE_CCSDS_27_FB_H
+
+#include <gr_sync_decimator.h>
+
+extern "C" {
+#include "../viterbi/viterbi.h"
+}
+
+class gr_decode_ccsds_27_fb;
+
+typedef boost::shared_ptr<gr_decode_ccsds_27_fb> gr_decode_ccsds_27_fb_sptr;
+
+gr_decode_ccsds_27_fb_sptr gr_make_decode_ccsds_27_fb();
+
+/*! \brief A rate 1/2, k=7 convolutional decoder for the CCSDS standard
+ * \ingroup ecc
+ *  
+ * This block performs soft-decision convolutional decoding using the Viterbi
+ * algorithm.
+ *  
+ * The input is a stream of (possibly noise corrupted) floating point values 
+ * nominally spanning [-1.0, 1.0], representing the encoded channel symbols 
+ * 0 (-1.0) and 1 (1.0), with erased symbols at 0.0.
+ *
+ * The output is MSB first packed bytes of decoded values.
+ *
+ * As a rate 1/2 code, there will be one output byte for every 16 input symbols.
+ *
+ * This block is designed for continuous data streaming, not packetized data.
+ * The first 32 bits out will be zeroes, with the output delayed four bytes
+ * from the corresponding inputs.
+ */
+
+class gr_decode_ccsds_27_fb : public gr_sync_decimator
+{
+private:
+  friend gr_decode_ccsds_27_fb_sptr gr_make_decode_ccsds_27_fb();
+
+  gr_decode_ccsds_27_fb();
+
+  // Viterbi state
+  int d_mettab[2][256];
+  struct viterbi_state d_state0[64];
+  struct viterbi_state d_state1[64];
+  unsigned char d_viterbi_in[16];
+
+  int d_count;
+      
+public:
+  ~gr_decode_ccsds_27_fb();
+
+  int work (int noutput_items,
+	    gr_vector_const_void_star &input_items,
+	    gr_vector_void_star &output_items);
+};
+
+#endif /* INCLUDED_GR_DECODE_CCSDS_27_FB_H */
diff --git a/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.i b/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.i
new file mode 100644
index 000000000..f05a0141b
--- /dev/null
+++ b/gnuradio-core/src/lib/general/gr_decode_ccsds_27_fb.i
@@ -0,0 +1,31 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+GR_SWIG_BLOCK_MAGIC(gr,decode_ccsds_27_fb);
+
+gr_decode_ccsds_27_fb_sptr gr_make_decode_ccsds_27_fb ();
+
+class gr_decode_ccsds_27_fb : public gr_sync_decimator
+{
+private:
+  gr_decode_ccsds_27_fb();
+};
diff --git a/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.cc b/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.cc
new file mode 100644
index 000000000..76b8091f7
--- /dev/null
+++ b/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.cc
@@ -0,0 +1,62 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2004,2008 Free Software Foundation, Inc.
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; 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 <gr_encode_ccsds_27_bb.h>
+#include <gr_io_signature.h>
+
+extern "C" {
+#include <../viterbi/viterbi.h>
+}
+
+gr_encode_ccsds_27_bb_sptr 
+gr_make_encode_ccsds_27_bb()
+{
+  return gr_encode_ccsds_27_bb_sptr(new gr_encode_ccsds_27_bb());
+}
+
+gr_encode_ccsds_27_bb::gr_encode_ccsds_27_bb()
+  : gr_sync_interpolator("encode_ccsds_27_bb",
+		         gr_make_io_signature(1, 1, sizeof(char)),
+		         gr_make_io_signature(1, 1, sizeof(char)),
+			 16)  // Rate 1/2 code, packed to unpacked conversion
+{
+  d_encstate = 0;
+}
+
+gr_encode_ccsds_27_bb::~gr_encode_ccsds_27_bb()
+{
+}
+
+int 
+gr_encode_ccsds_27_bb::work(int noutput_items,
+			    gr_vector_const_void_star &input_items,
+			    gr_vector_void_star &output_items)
+{
+  unsigned char *in = (unsigned char *)input_items[0];
+  unsigned char *out = (unsigned char *)output_items[0];
+
+  d_encstate = encode(out, in, noutput_items/16, d_encstate);
+
+  return noutput_items;
+}
diff --git a/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.h b/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.h
new file mode 100644
index 000000000..86832ee05
--- /dev/null
+++ b/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.h
@@ -0,0 +1,63 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+#ifndef INCLUDED_GR_ENCODE_CCSDS_27_BB_H
+#define INCLUDED_GR_ENCODE_CCSDS_27_BB_H
+
+#include <gr_sync_interpolator.h>
+
+class gr_encode_ccsds_27_bb;
+
+typedef boost::shared_ptr<gr_encode_ccsds_27_bb> gr_encode_ccsds_27_bb_sptr;
+
+gr_encode_ccsds_27_bb_sptr gr_make_encode_ccsds_27_bb();
+
+/*! \brief A rate 1/2, k=7 convolutional encoder for the CCSDS standard
+ * \ingroup ecc
+ *  
+ * This block performs convolutional encoding using the CCSDS standard
+ * polynomial ("Voyager").
+ *  
+ * The input is an MSB first packed stream of bits.
+ *
+ * The output is a stream of symbols 0 or 1 representing the encoded data.
+ *
+ * As a rate 1/2 code, there will be 16 output symbols for every input byte.
+ *
+ * This block is designed for continuous data streaming, not packetized data.
+ * There is no provision to "flush" the encoder.
+ */
+
+class gr_encode_ccsds_27_bb : public gr_sync_interpolator
+{
+private:
+  friend gr_encode_ccsds_27_bb_sptr gr_make_encode_ccsds_27_bb();
+
+  gr_encode_ccsds_27_bb();
+  unsigned char d_encstate;
+  
+ public:
+  ~gr_encode_ccsds_27_bb();
+
+  int work (int noutput_items,
+	    gr_vector_const_void_star &input_items,
+	    gr_vector_void_star &output_items);
+};
+
+#endif /* INCLUDED_GR_ENCODE_CCSDS_27_BB_H */
diff --git a/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.i b/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.i
new file mode 100644
index 000000000..d4bda41cc
--- /dev/null
+++ b/gnuradio-core/src/lib/general/gr_encode_ccsds_27_bb.i
@@ -0,0 +1,31 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+GR_SWIG_BLOCK_MAGIC(gr,encode_ccsds_27_bb);
+
+gr_encode_ccsds_27_bb_sptr gr_make_encode_ccsds_27_bb ();
+
+class gr_encode_ccsds_27_bb : public gr_sync_interpolator
+{
+private:
+  gr_encode_ccsds_27_bb();
+};
diff --git a/gnuradio-core/src/lib/viterbi/Makefile.am b/gnuradio-core/src/lib/viterbi/Makefile.am
new file mode 100644
index 000000000..3eb1502ba
--- /dev/null
+++ b/gnuradio-core/src/lib/viterbi/Makefile.am
@@ -0,0 +1,41 @@
+#
+# Copyright 2008 Free Software Foundation, Inc.
+# 
+# GNU Radio 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.
+# 
+# GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+# 
+
+INCLUDES = -Wall -Werror
+LIBS = -lm
+
+noinst_LTLIBRARIES = libviterbi.la
+
+libviterbi_la_SOURCES = \
+    metrics.c		\
+    tab.c		\
+    viterbi.c
+    
+noinst_HEADERS =	\
+    viterbi.h
+
+noinst_PROGRAMS = encode decode
+
+encode_SOURCES = encode.cc
+
+encode_LDADD = libviterbi.la
+
+decode_SOURCES = decode.cc
+
+decode_LDADD = libviterbi.la
diff --git a/gnuradio-core/src/lib/viterbi/decode.cc b/gnuradio-core/src/lib/viterbi/decode.cc
new file mode 100644
index 000000000..6580e4d66
--- /dev/null
+++ b/gnuradio-core/src/lib/viterbi/decode.cc
@@ -0,0 +1,88 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/*
+ * This is a minimal example demonstrating how to call the Viterbi decoder
+ * in continuous streaming mode.  It accepts data on stdin and writes to 
+ * stdout.
+ *
+ */
+
+extern "C" {
+#include "viterbi.h"
+}
+
+#include <cstdio>
+#include <cmath>
+
+#define MAXCHUNKSIZE 4096
+#define MAXENCSIZE MAXCHUNKSIZE*16
+
+int main()
+{
+  unsigned char data[MAXCHUNKSIZE];
+  signed char syms[MAXENCSIZE];
+  int count = 0;
+
+  // Initialize metric table
+  int mettab[2][256];
+  int amp = 100;
+  float RATE=0.5;
+  float ebn0 = 12.0;
+  float esn0 = RATE*pow(10.0, ebn0/10);
+  gen_met(mettab, amp, esn0, 0.0, 4);
+
+  // Initialize decoder state
+  struct viterbi_state state0[64];
+  struct viterbi_state state1[64];
+  unsigned char viterbi_in[16];
+  viterbi_chunks_init(state0);  
+
+  while (!feof(stdin)) {
+    unsigned int n = fread(syms, 1, MAXENCSIZE, stdin);
+    unsigned char *out = data;
+    
+    for (unsigned int i = 0; i < n; i++) {
+
+      // FIXME: This implements hard decoding by slicing the input stream
+      unsigned char sym = syms[i] > 0 ? -amp : amp;
+
+      // Write the symbol to the decoder input
+      viterbi_in[count % 4] = sym;
+
+      // Every four symbols, perform the butterfly2 operation
+      if ((count % 4) == 3) {
+        viterbi_butterfly2(viterbi_in, mettab, state0, state1);      
+
+	// Every sixteen symbols, perform the readback operation
+        if ((count > 64) && (count % 16) == 11) {
+          viterbi_get_output(state0, out);
+	  fwrite(out++, 1, 1, stdout);
+	}
+      }
+      
+      count++;
+    }    
+  }
+
+  return 0;
+}
diff --git a/gnuradio-core/src/lib/viterbi/encode.cc b/gnuradio-core/src/lib/viterbi/encode.cc
new file mode 100644
index 000000000..01acb3987
--- /dev/null
+++ b/gnuradio-core/src/lib/viterbi/encode.cc
@@ -0,0 +1,54 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/*
+ * This is a minimal example demonstrating how to call the ECC encoder
+ * in continuous streaming mode.  It accepts data on stdin and writes to 
+ * stdout.
+ * 
+ * FIXME: This does not flush the final bits out of the encoder.
+ *
+ */
+
+extern "C" {
+#include "viterbi.h"
+}
+
+#include <cstdio>
+
+#define MAXCHUNKSIZE 4096
+#define MAXENCSIZE MAXCHUNKSIZE*16
+
+int main()
+{
+  unsigned char encoder_state = 0;
+  unsigned char data[MAXCHUNKSIZE];
+  unsigned char syms[MAXENCSIZE];
+  
+  while (!feof(stdin)) {
+    unsigned int n = fread(data, 1, MAXCHUNKSIZE, stdin);
+    encoder_state = encode(syms, data, n, encoder_state);
+    fwrite(syms, 1, n*16, stdout);
+  }
+
+  return 0;
+}
diff --git a/gnuradio-core/src/lib/viterbi/metrics.c b/gnuradio-core/src/lib/viterbi/metrics.c
new file mode 100644
index 000000000..74f8ce09d
--- /dev/null
+++ b/gnuradio-core/src/lib/viterbi/metrics.c
@@ -0,0 +1,119 @@
+/*
+ * Copyright 1995 Phil Karn, KA9Q
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/* 
+ * Generate metric tables for a soft-decision convolutional decoder
+ * assuming gaussian noise on a PSK channel.
+ *
+ * Works from "first principles" by evaluating the normal probability
+ * function and then computing the log-likelihood function
+ * for every possible received symbol value
+ *
+ */
+
+/* Symbols are offset-binary, with 128 corresponding to an erased (no
+ * information) symbol
+ */
+#define	OFFSET	128
+
+#include <stdlib.h>
+#include <math.h>
+
+/* Normal function integrated from -Inf to x. Range: 0-1 */
+#define	normal(x)	(0.5 + 0.5*erf((x)/M_SQRT2))
+
+/* Logarithm base 2 */
+#define	log2(x)	(log(x)*M_LOG2E)
+
+/* Generate log-likelihood metrics for 8-bit soft quantized channel
+ * assuming AWGN and BPSK
+ */
+void
+gen_met(int mettab[2][256],	/* Metric table, [sent sym][rx symbol] */
+	int amp,		/* Signal amplitude, units */
+	double esn0,		/* Es/N0 ratio in dB */
+	double bias,		/* Metric bias; 0 for viterbi, rate for sequential */
+	int scale)		/* Scale factor */
+{
+  double noise;
+  int s,bit;
+  double metrics[2][256];
+  double p0,p1;
+  
+  /* Es/N0 as power ratio */
+  esn0 = pow(10.,esn0/10);
+  
+  noise = 0.5/esn0;	/* only half the noise for BPSK */
+  noise = sqrt(noise);	/* noise/signal Voltage ratio */
+  
+  /* Zero is a special value, since this sample includes all
+   * lower samples that were clipped to this value, i.e., it
+   * takes the whole lower tail of the curve 
+   */
+  p1 = normal(((0-OFFSET+0.5)/amp - 1)/noise);	/* P(s|1) */
+  
+  /* Prob of this value occurring for a 0-bit */	/* P(s|0) */
+  p0 = normal(((0-OFFSET+0.5)/amp + 1)/noise);
+  metrics[0][0] = log2(2*p0/(p1+p0)) - bias;
+  metrics[1][0] = log2(2*p1/(p1+p0)) - bias;
+  
+  for(s=1;s<255;s++){
+    /* P(s|1), prob of receiving s given 1 transmitted */
+    p1 = normal(((s-OFFSET+0.5)/amp - 1)/noise) -
+      normal(((s-OFFSET-0.5)/amp - 1)/noise);
+    
+    /* P(s|0), prob of receiving s given 0 transmitted */
+    p0 = normal(((s-OFFSET+0.5)/amp + 1)/noise) -
+      normal(((s-OFFSET-0.5)/amp + 1)/noise);
+    
+#ifdef notdef
+    printf("P(%d|1) = %lg, P(%d|0) = %lg\n",s,p1,s,p0);
+#endif
+    metrics[0][s] = log2(2*p0/(p1+p0)) - bias;
+    metrics[1][s] = log2(2*p1/(p1+p0)) - bias;
+  }
+  /* 255 is also a special value */
+  /* P(s|1) */
+  p1 = 1 - normal(((255-OFFSET-0.5)/amp - 1)/noise);
+  /* P(s|0) */
+  p0 = 1 - normal(((255-OFFSET-0.5)/amp + 1)/noise);
+  
+  metrics[0][255] = log2(2*p0/(p1+p0)) - bias;
+  metrics[1][255] = log2(2*p1/(p1+p0)) - bias;
+#ifdef	notdef
+  /* The probability of a raw symbol error is the probability
+   * that a 1-bit would be received as a sample with value
+   * 0-128. This is the offset normal curve integrated from -Inf to 0.
+   */
+  printf("symbol Pe = %lg\n",normal(-1/noise));
+#endif
+  for(bit=0;bit<2;bit++){
+    for(s=0;s<256;s++){
+      /* Scale and round to nearest integer */
+      mettab[bit][s] = floor(metrics[bit][s] * scale + 0.5);
+#ifdef	notdef
+      printf("metrics[%d][%d] = %lg, mettab = %d\n",
+	     bit,s,metrics[bit][s],mettab[bit][s]);
+#endif
+    }
+  }
+}
diff --git a/gnuradio-core/src/lib/viterbi/tab.c b/gnuradio-core/src/lib/viterbi/tab.c
new file mode 100644
index 000000000..1133c6308
--- /dev/null
+++ b/gnuradio-core/src/lib/viterbi/tab.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright 1995 Phil Karn, KA9Q
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/* 8-bit parity lookup table, generated by partab.c */
+unsigned char Partab[] = {
+ 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,
+ 1, 0, 0, 1, 0, 1, 1, 0,
+ 0, 1, 1, 0, 1, 0, 0, 1,
+ 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,
+ 0, 1, 1, 0, 1, 0, 0, 1,
+ 1, 0, 0, 1, 0, 1, 1, 0,
+ 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,
+ 1, 0, 0, 1, 0, 1, 1, 0,
+ 0, 1, 1, 0, 1, 0, 0, 1,
+ 0, 1, 1, 0, 1, 0, 0, 1,
+ 1, 0, 0, 1, 0, 1, 1, 0,
+ 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,
+ 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,
+ 1, 0, 0, 1, 0, 1, 1, 0,
+ 0, 1, 1, 0, 1, 0, 0, 1,
+ 0, 1, 1, 0, 1, 0, 0, 1,
+ 1, 0, 0, 1, 0, 1, 1, 0,
+};
diff --git a/gnuradio-core/src/lib/viterbi/viterbi.c b/gnuradio-core/src/lib/viterbi/viterbi.c
new file mode 100644
index 000000000..9f5c1e72a
--- /dev/null
+++ b/gnuradio-core/src/lib/viterbi/viterbi.c
@@ -0,0 +1,355 @@
+/*
+ * Copyright 1995 Phil Karn, KA9Q
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/* 
+ * Viterbi decoder for K=7 rate=1/2 convolutional code
+ * Some modifications from original Karn code by Matt Ettus
+ */
+
+#include "viterbi.h"
+
+/* The two generator polynomials for the NASA Standard K=7 code.
+ * Since these polynomials are known to be optimal for this constraint
+ * length there is not much point in changing them. But if you do, you
+ * will have to regenerate the BUTTERFLY macro calls in viterbi()
+ */
+#define	POLYA	0x6d
+#define	POLYB	0x4f
+
+/* The basic Viterbi decoder operation, called a "butterfly"
+ * operation because of the way it looks on a trellis diagram. Each
+ * butterfly involves an Add-Compare-Select (ACS) operation on the two nodes
+ * where the 0 and 1 paths from the current node merge at the next step of
+ * the trellis.
+ *
+ * The code polynomials are assumed to have 1's on both ends. Given a
+ * function encode_state() that returns the two symbols for a given
+ * encoder state in the low two bits, such a code will have the following
+ * identities for even 'n' < 64:
+ *
+ * 	encode_state(n) = encode_state(n+65)
+ *	encode_state(n+1) = encode_state(n+64) = (3 ^ encode_state(n))
+ *
+ * Any convolutional code you would actually want to use will have
+ * these properties, so these assumptions aren't too limiting.
+ *
+ * Doing this as a macro lets the compiler evaluate at compile time the
+ * many expressions that depend on the loop index and encoder state and
+ * emit them as immediate arguments.
+ * This makes an enormous difference on register-starved machines such
+ * as the Intel x86 family where evaluating these expressions at runtime
+ * would spill over into memory.
+ */
+#define	BUTTERFLY(i,sym) { \
+	int m0,m1;\
+\
+	/* ACS for 0 branch */\
+	m0 = state[i].metric + mets[sym];	/* 2*i */\
+	m1 = state[i+32].metric + mets[3^sym];	/* 2*i + 64 */\
+	if(m0 > m1){\
+		next[2*i].metric = m0;\
+		next[2*i].path = state[i].path << 1;\
+	} else {\
+		next[2*i].metric = m1;\
+		next[2*i].path = (state[i+32].path << 1)|1;\
+	}\
+	/* ACS for 1 branch */\
+	m0 = state[i].metric + mets[3^sym];	/* 2*i + 1 */\
+	m1 = state[i+32].metric + mets[sym];	/* 2*i + 65 */\
+	if(m0 > m1){\
+		next[2*i+1].metric = m0;\
+		next[2*i+1].path = state[i].path << 1;\
+	} else {\
+		next[2*i+1].metric = m1;\
+		next[2*i+1].path = (state[i+32].path << 1)|1;\
+	}\
+}
+
+extern unsigned char Partab[];	/* Parity lookup table */
+
+/* Convolutionally encode data into binary symbols */
+unsigned char
+encode(unsigned char *symbols,
+       unsigned char *data,
+       unsigned int nbytes,
+       unsigned char encstate)
+{
+  int i;
+  
+  while(nbytes-- != 0){
+    for(i=7;i>=0;i--){
+      encstate = (encstate << 1) | ((*data >> i) & 1);
+      *symbols++ = Partab[encstate & POLYA];
+      *symbols++ = Partab[encstate & POLYB];
+    }
+    data++;
+  }
+  
+  return encstate;
+}
+
+/* Viterbi decoder */
+int
+viterbi(unsigned long *metric,	/* Final path metric (returned value) */
+	unsigned char *data,	/* Decoded output data */
+	unsigned char *symbols,	/* Raw deinterleaved input symbols */
+	unsigned int nbits,	/* Number of output bits */
+	int mettab[2][256]	/* Metric table, [sent sym][rx symbol] */
+	){
+  unsigned int bitcnt = 0;
+  int mets[4];
+  long bestmetric;
+  int beststate,i;
+  struct viterbi_state state0[64],state1[64],*state,*next;
+  
+  state = state0;
+  next = state1;
+  
+  /* Initialize starting metrics to prefer 0 state */
+  state[0].metric = 0;
+  for(i=1;i<64;i++)
+    state[i].metric = -999999;
+  state[0].path = 0;
+  
+  for(bitcnt = 0;bitcnt < nbits;bitcnt++){
+    /* Read input symbol pair and compute all possible branch
+     * metrics
+     */
+    mets[0] = mettab[0][symbols[0]] + mettab[0][symbols[1]];
+    mets[1] = mettab[0][symbols[0]] + mettab[1][symbols[1]];
+    mets[2] = mettab[1][symbols[0]] + mettab[0][symbols[1]];
+    mets[3] = mettab[1][symbols[0]] + mettab[1][symbols[1]];
+    symbols += 2;
+
+    /* These macro calls were generated by genbut.c */
+    BUTTERFLY(0,0);
+    BUTTERFLY(1,1);
+    BUTTERFLY(2,3);
+    BUTTERFLY(3,2);
+    BUTTERFLY(4,3);
+    BUTTERFLY(5,2);
+    BUTTERFLY(6,0);
+    BUTTERFLY(7,1);
+    BUTTERFLY(8,0);
+    BUTTERFLY(9,1);
+    BUTTERFLY(10,3);
+    BUTTERFLY(11,2);
+    BUTTERFLY(12,3);
+    BUTTERFLY(13,2);
+    BUTTERFLY(14,0);
+    BUTTERFLY(15,1);
+    BUTTERFLY(16,2);
+    BUTTERFLY(17,3);
+    BUTTERFLY(18,1);
+    BUTTERFLY(19,0);
+    BUTTERFLY(20,1);
+    BUTTERFLY(21,0);
+    BUTTERFLY(22,2);
+    BUTTERFLY(23,3);
+    BUTTERFLY(24,2);
+    BUTTERFLY(25,3);
+    BUTTERFLY(26,1);
+    BUTTERFLY(27,0);
+    BUTTERFLY(28,1);
+    BUTTERFLY(29,0);
+    BUTTERFLY(30,2);
+    BUTTERFLY(31,3);
+    
+    /* Swap current and next states */
+    if(bitcnt & 1){
+      state = state0;
+      next = state1;
+    } else {
+      state = state1;
+      next = state0;
+    }
+    // ETTUS
+    //if(bitcnt > nbits-7){
+    /* In tail, poison non-zero nodes */
+    //for(i=1;i<64;i += 2)
+    //	state[i].metric = -9999999;
+    //}
+    /* Produce output every 8 bits once path memory is full */
+    if((bitcnt % 8) == 5 && bitcnt > 32){
+      /* Find current best path */
+      bestmetric = state[0].metric;
+      beststate = 0;
+      for(i=1;i<64;i++){
+	if(state[i].metric > bestmetric){
+	  bestmetric = state[i].metric;
+	  beststate = i;
+	}
+      }
+#ifdef	notdef
+      printf("metrics[%d] = %d state = %lx\n",beststate,
+	     state[beststate].metric,state[beststate].path);
+#endif
+      *data++ = state[beststate].path >> 24;
+    }
+    
+  }
+  /* Output remaining bits from 0 state */
+  // ETTUS  Find best state instead
+  bestmetric = state[0].metric;
+  beststate = 0;
+  for(i=1;i<64;i++){
+    if(state[i].metric > bestmetric){
+      bestmetric = state[i].metric;
+      beststate = i;
+    }
+  }
+  if((i = bitcnt % 8) != 6)
+    state[beststate].path <<= 6-i;
+  
+  *data++ = state[beststate].path >> 24;
+  *data++ = state[beststate].path >> 16;
+  *data++ = state[beststate].path >> 8;
+  *data = state[beststate].path;
+  //printf ("BS = %d\tBSM = %d\tM0 = %d\n",beststate,state[beststate].metric,state[0].metric);
+  *metric = state[beststate].metric;
+  return 0;
+}
+
+
+void
+viterbi_chunks_init(struct viterbi_state* state) {
+  // Initialize starting metrics to prefer 0 state
+  int i;
+  state[0].metric = 0;
+  state[0].path = 0;
+  for(i=1;i<64;i++)
+    state[i].metric = -999999;
+}
+
+void
+viterbi_butterfly8(unsigned char *symbols, int mettab[2][256], struct viterbi_state *state0, struct viterbi_state *state1)
+{
+  unsigned int bitcnt;
+  int mets[4];
+  
+  struct viterbi_state *state, *next;
+  state = state0;
+  next = state1;
+  // Operate on 16 symbols (8 bits) at a time
+  for(bitcnt = 0;bitcnt < 8;bitcnt++){
+    // Read input symbol pair and compute all possible branch metrics
+    mets[0] = mettab[0][symbols[0]] + mettab[0][symbols[1]];
+    mets[1] = mettab[0][symbols[0]] + mettab[1][symbols[1]];
+    mets[2] = mettab[1][symbols[0]] + mettab[0][symbols[1]];
+    mets[3] = mettab[1][symbols[0]] + mettab[1][symbols[1]];
+    symbols += 2;
+    
+    // These macro calls were generated by genbut.c 
+    BUTTERFLY(0,0);BUTTERFLY(1,1);BUTTERFLY(2,3);BUTTERFLY(3,2);
+    BUTTERFLY(4,3);BUTTERFLY(5,2);BUTTERFLY(6,0);BUTTERFLY(7,1);
+    BUTTERFLY(8,0);BUTTERFLY(9,1);BUTTERFLY(10,3);BUTTERFLY(11,2);
+    BUTTERFLY(12,3);BUTTERFLY(13,2);BUTTERFLY(14,0);BUTTERFLY(15,1);
+    BUTTERFLY(16,2);BUTTERFLY(17,3);BUTTERFLY(18,1);BUTTERFLY(19,0);
+    BUTTERFLY(20,1);BUTTERFLY(21,0);BUTTERFLY(22,2);BUTTERFLY(23,3);
+    BUTTERFLY(24,2);BUTTERFLY(25,3);BUTTERFLY(26,1);BUTTERFLY(27,0);
+    BUTTERFLY(28,1);BUTTERFLY(29,0);BUTTERFLY(30,2);BUTTERFLY(31,3);
+    
+    // Swap current and next states
+    if(bitcnt & 1){
+      state = state0;
+      next = state1;
+    } else {
+      state = state1;
+      next = state0;
+    }
+  }
+}
+
+void
+viterbi_butterfly2(unsigned char *symbols, int mettab[2][256], struct viterbi_state *state0, struct viterbi_state *state1)
+{
+  //unsigned int bitcnt;
+  int mets[4];
+  
+  struct viterbi_state *state, *next;
+  state = state0;
+  next = state1;
+  // Operate on 4 symbols (2 bits) at a time
+  
+  // Read input symbol pair and compute all possible branch metrics
+  mets[0] = mettab[0][symbols[0]] + mettab[0][symbols[1]];
+  mets[1] = mettab[0][symbols[0]] + mettab[1][symbols[1]];
+  mets[2] = mettab[1][symbols[0]] + mettab[0][symbols[1]];
+  mets[3] = mettab[1][symbols[0]] + mettab[1][symbols[1]];
+  
+  // These macro calls were generated by genbut.c 
+  BUTTERFLY(0,0);BUTTERFLY(1,1);BUTTERFLY(2,3);BUTTERFLY(3,2);
+  BUTTERFLY(4,3);BUTTERFLY(5,2);BUTTERFLY(6,0);BUTTERFLY(7,1);
+  BUTTERFLY(8,0);BUTTERFLY(9,1);BUTTERFLY(10,3);BUTTERFLY(11,2);
+  BUTTERFLY(12,3);BUTTERFLY(13,2);BUTTERFLY(14,0);BUTTERFLY(15,1);
+  BUTTERFLY(16,2);BUTTERFLY(17,3);BUTTERFLY(18,1);BUTTERFLY(19,0);
+  BUTTERFLY(20,1);BUTTERFLY(21,0);BUTTERFLY(22,2);BUTTERFLY(23,3);
+  BUTTERFLY(24,2);BUTTERFLY(25,3);BUTTERFLY(26,1);BUTTERFLY(27,0);
+  BUTTERFLY(28,1);BUTTERFLY(29,0);BUTTERFLY(30,2);BUTTERFLY(31,3);
+  
+  state = state1;
+  next = state0;
+  
+  // Read input symbol pair and compute all possible branch metrics
+  mets[0] = mettab[0][symbols[2]] + mettab[0][symbols[3]];
+  mets[1] = mettab[0][symbols[2]] + mettab[1][symbols[3]];
+  mets[2] = mettab[1][symbols[2]] + mettab[0][symbols[3]];
+  mets[3] = mettab[1][symbols[2]] + mettab[1][symbols[3]];
+  
+  // These macro calls were generated by genbut.c 
+  BUTTERFLY(0,0);BUTTERFLY(1,1);BUTTERFLY(2,3);BUTTERFLY(3,2);
+  BUTTERFLY(4,3);BUTTERFLY(5,2);BUTTERFLY(6,0);BUTTERFLY(7,1);
+  BUTTERFLY(8,0);BUTTERFLY(9,1);BUTTERFLY(10,3);BUTTERFLY(11,2);
+  BUTTERFLY(12,3);BUTTERFLY(13,2);BUTTERFLY(14,0);BUTTERFLY(15,1);
+  BUTTERFLY(16,2);BUTTERFLY(17,3);BUTTERFLY(18,1);BUTTERFLY(19,0);
+  BUTTERFLY(20,1);BUTTERFLY(21,0);BUTTERFLY(22,2);BUTTERFLY(23,3);
+  BUTTERFLY(24,2);BUTTERFLY(25,3);BUTTERFLY(26,1);BUTTERFLY(27,0);
+  BUTTERFLY(28,1);BUTTERFLY(29,0);BUTTERFLY(30,2);BUTTERFLY(31,3);
+}
+
+unsigned char
+viterbi_get_output(struct viterbi_state *state, unsigned char *outbuf) {
+  // Produce output every 8 bits once path memory is full 
+  //  if((bitcnt % 8) == 5 && bitcnt > 32) {
+  
+  //  Find current best path
+  unsigned int i,beststate;
+  int bestmetric;
+  
+  bestmetric = state[0].metric;
+  beststate = 0;
+  for(i=1;i<64;i++)
+    if(state[i].metric > bestmetric) {
+      bestmetric = state[i].metric;
+      beststate = i;
+    }
+  *outbuf =  state[beststate].path >> 24;
+  return bestmetric;
+}
+
+
+//printf ("BS = %d\tBSM = %d\tM0 = %d\n",beststate,state[beststate].metric,state[0].metric);
+// In tail, poison non-zero nodes
+//if(bits_out > packet_size-7)
+//  for(i=1;i<64;i += 2)
+//    state[i].metric = -9999999;
+
diff --git a/gnuradio-core/src/lib/viterbi/viterbi.h b/gnuradio-core/src/lib/viterbi/viterbi.h
new file mode 100644
index 000000000..155b0d93a
--- /dev/null
+++ b/gnuradio-core/src/lib/viterbi/viterbi.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2008 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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.
+ * 
+ * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/* The path memory for each state is 32 bits. This is slightly shorter
+ * than we'd like for K=7, especially since we chain back every 8 bits.
+ * But it fits so nicely into a 32-bit machine word...
+ */
+struct viterbi_state {
+  unsigned long path;	/* Decoded path to this state */
+  long metric;		/* Cumulative metric to this state */
+};
+
+int gen_met(int mettab[2][256],	/* Metric table */
+	    int amp,		/* Signal amplitude */
+	    double esn0,	/* Es/N0 ratio in dB */
+	    double bias, 	/* Metric bias */
+	    int scale);		/* Scale factor */
+
+unsigned char
+encode(unsigned char *symbols, unsigned char *data,
+       unsigned int nbytes,unsigned char encstate);
+
+void 
+viterbi_chunks_init(struct viterbi_state* state);
+
+void 
+viterbi_butterfly2(unsigned char *symbols, int mettab[2][256], 
+		   struct viterbi_state *state0, struct viterbi_state *state1);
+
+unsigned char
+viterbi_get_output(struct viterbi_state *state, unsigned char *outbuf);
diff --git a/gnuradio-core/src/python/gnuradio/gr/Makefile.am b/gnuradio-core/src/python/gnuradio/gr/Makefile.am
index 5aaef2540..7a317a1a3 100644
--- a/gnuradio-core/src/python/gnuradio/gr/Makefile.am
+++ b/gnuradio-core/src/python/gnuradio/gr/Makefile.am
@@ -49,6 +49,7 @@ noinst_PYTHON = 			\
 	qa_agc.py			\
 	qa_argmax.py			\
 	qa_bin_statistics.py		\
+	qa_ecc_ccsds27.py		\
 	qa_cma_equalizer.py		\
 	qa_complex_to_xxx.py		\
 	qa_constellation_decoder_cb.py  \
diff --git a/gnuradio-core/src/python/gnuradio/gr/qa_ecc_ccsds_27.py b/gnuradio-core/src/python/gnuradio/gr/qa_ecc_ccsds_27.py
new file mode 100755
index 000000000..f02c1a323
--- /dev/null
+++ b/gnuradio-core/src/python/gnuradio/gr/qa_ecc_ccsds_27.py
@@ -0,0 +1,50 @@
+#!/usr/bin/env python
+#
+# Copyright 2004,2007 Free Software Foundation, Inc.
+# 
+# This file is part of GNU Radio
+# 
+# GNU Radio 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.
+# 
+# GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+# 
+
+from gnuradio import gr, gr_unittest
+
+class test_ccsds_27 (gr_unittest.TestCase):
+
+    def setUp (self):
+        self.tb = gr.top_block ()
+
+    def tearDown (self):
+        self.tb = None
+
+    def test_ccsds_27 (self):
+        src_data = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+	expected = (0, 0, 0, 0, 1, 2, 3, 4, 5, 6)
+        src = gr.vector_source_b(src_data)
+	enc = gr.encode_ccsds_27_bb()
+	b2f = gr.char_to_float()
+	add = gr.add_const_ff(-0.5)
+	mul = gr.multiply_const_ff(2.0)
+	dec = gr.decode_ccsds_27_fb()
+	dst = gr.vector_sink_b()
+	self.tb.connect(src, enc, b2f, add, mul, dec, dst)
+	self.tb.run()
+	dst_data = dst.data()
+        self.assertEqual(expected, dst_data)
+    
+
+if __name__ == '__main__':
+    gr_unittest.main ()