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diff --git a/blocks/src/lib/imbe_decoder.h b/blocks/src/lib/imbe_decoder.h
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+++ b/blocks/src/lib/imbe_decoder.h
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+/* -*- C++ -*- */
+
+/*
+ * Copyright 2008 Steve Glass
+ * 
+ * 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_IMBE_DECODER_H 
+#define INCLUDED_IMBE_DECODER_H 
+
+#include <boost/noncopyable.hpp>
+#include <boost/shared_ptr.hpp>
+#include <deque>
+#include <vector>
+
+typedef std::deque<float> audio_samples;
+typedef std::vector<bool> voice_codeword;
+
+typedef boost::shared_ptr<class imbe_decoder> imbe_decoder_sptr;
+
+/**
+ * imbe_decoder is the interface to the various mechanisms for
+ * translating P25 voice codewords into audio samples.
+ */
+class imbe_decoder : public boost::noncopyable {
+public:
+
+   /**
+    * imbe_decoder (virtual) constructor. The exact subclass
+    * instantiated depends on some yet-to-be-decided magic.
+    *
+    * \return A shared_ptr to an imbe_decoder.
+    */
+   static imbe_decoder_sptr make();
+
+   /**
+    * imbe_decoder (virtual) destructor.
+    */
+   virtual ~imbe_decoder();
+
+   /**
+    * Decode the compressed IMBE audio.
+    *
+    * \param cw IMBE codeword (including parity check bits).
+    */
+   virtual void decode(const voice_codeword& cw) = 0;
+
+   /**
+    * Returns the audio_samples samples. These are mono samples at
+    * 8KS/s represented as a float in the range -1.0 .. +1.0.
+    *
+    * \return A non-null pointer to a deque<float> of audio samples.
+    */
+   audio_samples *audio();
+
+protected:
+
+   /**
+    * Construct an instance of imbe_decoder. Access is protected
+    * because this is an abstract class and users should call
+    * make_imbe_decoder to construct  concrete instances.
+    */
+   imbe_decoder();
+
+private:
+
+   /**
+    * The audio samples produced by the IMBE decoder.
+    */
+   audio_samples d_audio;
+   
+};
+
+#endif /* INCLUDED_IMBE_DECODER_H */