From c6acabb7df67983a3a4ebd4a34a7655a431bdeb7 Mon Sep 17 00:00:00 2001
From: Johnathan Corgan <johnathan@corganlabs.com>
Date: Tue, 30 Apr 2013 13:22:52 -0700
Subject: vocoder: moved include dir to gnuradio/vocoder
---
.../include/gnuradio/vocoder/cvsd_decode_bs.h | 132 +++++++++++++++++++++
1 file changed, 132 insertions(+)
create mode 100644 gr-vocoder/include/gnuradio/vocoder/cvsd_decode_bs.h
(limited to 'gr-vocoder/include/gnuradio/vocoder/cvsd_decode_bs.h')
diff --git a/gr-vocoder/include/gnuradio/vocoder/cvsd_decode_bs.h b/gr-vocoder/include/gnuradio/vocoder/cvsd_decode_bs.h
new file mode 100644
index 0000000000..324dcea1a1
--- /dev/null
+++ b/gr-vocoder/include/gnuradio/vocoder/cvsd_decode_bs.h
@@ -0,0 +1,132 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2007,2011,2013 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.
+ */
+
+#ifndef INCLUDED_VOCODER_CVSD_DECODE_BS_H
+#define INCLUDED_VOCODER_CVSD_DECODE_BS_H
+
+#include <gnuradio/vocoder/api.h>
+#include <gnuradio/sync_interpolator.h>
+
+namespace gr {
+ namespace vocoder {
+
+ /*!
+ * \brief This block performs CVSD audio decoding. Its design and
+ * implementation is modeled after the CVSD encoder/decoder
+ * specifications defined in the Bluetooth standard.
+ * \ingroup audio_blk
+ *
+ * \details
+ * CVSD is a method for encoding speech that seeks to reduce the
+ * bandwidth required for digital voice transmission. CVSD takes
+ * advantage of strong correlation between samples, quantizing the
+ * difference in amplitude between two consecutive samples. This
+ * difference requires fewer quantization levels as compared to
+ * other methods that quantize the actual amplitude level,
+ * reducing the bandwidth. CVSD employs a two level quantizer
+ * (one bit) and an adaptive algorithm that allows for continuous
+ * step size adjustment.
+ *
+ * The coder can represent low amplitude signals with accuracy
+ * without sacrificing performance on large amplitude signals, a
+ * trade off that occurs in some non-adaptive modulations.
+ *
+ * The CVSD decoder effectively provides 1-to-8 decompression.
+ * More specifically, for each incoming input bit, the decoder
+ * outputs one audio sample. If the input is a "1" bit, the
+ * internal reference is increased appropriately and then
+ * outputted as the next estimated audio sample. If the input is
+ * a "0" bit, the internal reference is decreased appropriately
+ * and then likewise outputted as the next estimated audio sample.
+ * Grouping 8 input bits together, the encoder essentially
+ * produces 8 output audio samples for everyone one input byte.
+ *
+ * This decoder requires that output audio samples are 2-byte
+ * short signed integers. The result bandwidth conversion,
+ * therefore, is 1 byte of encoded audio data to 16 output bytes
+ * of raw audio data.
+ *
+ * The CVSD decoder module must be post-fixed by a down-converter
+ * to under-sample the audio data after decoding. The Bluetooth
+ * standard specifically calls for a 8-to-1 decimating
+ * down-converter. This is required so that so that output
+ * sampling rate equals the original input sampling rate present
+ * before the encoder. In all cases, the output down-converter
+ * rate must be the inverse of the input up-converter rate before
+ * the CVSD encoder.
+ *
+ * References:
+ * 1. Continuously Variable Slope Delta Modulation (CVSD) A Tutorial,
+ * Available: http://www.eetkorea.com/ARTICLES/2003AUG/A/2003AUG29_NTEK_RFD_AN02.PDF.
+ * 2. Specification of The Bluetooth System
+ * Available: http://grouper.ieee.org/groups/802/15/Bluetooth/core_10_b.pdf.
+ * 3. McGarrity, S., Bluetooth Full Duplex Voice and Data Transmission. 2002.
+ * Bluetooth Voice Simulink� Model, Available:
+ * http://www.mathworks.com/company/newsletters/digest/nov01/bluetooth.html
+ */
+ class VOCODER_API cvsd_decode_bs : virtual public sync_interpolator
+ {
+ public:
+ // gr::vocoder::cvsd_decode_bs::sptr
+ typedef boost::shared_ptr<cvsd_decode_bs> sptr;
+
+ /*!
+ * \brief Constructor parameters to initialize the CVSD decoder.
+ * The default values are modeled after the Bluetooth standard
+ * and should not be changed, except by an advanced user
+ *
+ * \param min_step Minimum step size used to update the internal reference.
+ * Default: "10"
+ * \param max_step Maximum step size used to update the internal reference.
+ * Default: "1280"
+ * \param step_decay Decay factor applied to step size when there is not a run of J output 1s or 0s.
+ * Default: "0.9990234375" (i.e. 1-1/1024)
+ * \param accum_decay Decay factor applied to the internal reference during every interation of the codec.
+ * Default: "0.96875" (i.e. 1-1/32)
+ * \param K; Size of shift register; the number of output bits remembered by codec (must be <= to 32).
+ * Default: "32"
+ * \param J; Number of bits in the shift register that are equal; i.e. the size of a run of 1s, 0s.
+ * Default: "4"
+ * \param pos_accum_max Maximum integer value allowed for the internal reference.
+ * Default: "32767" (2^15 - 1 or MAXSHORT)
+ * \param neg_accum_max Minimum integer value allowed for the internal reference.
+ * Default: "-32767" (-2^15 + 1 or MINSHORT+1)
+ */
+ static sptr make(short min_step=10, short max_step=1280,
+ double step_decay=0.9990234375, double accum_decay= 0.96875,
+ int K=32, int J=4,
+ short pos_accum_max=32767, short neg_accum_max=-32767);
+
+ virtual short min_step() = 0;
+ virtual short max_step() = 0;
+ virtual double step_decay() = 0;
+ virtual double accum_decay() = 0;
+ virtual int K() = 0;
+ virtual int J() = 0;
+ virtual short pos_accum_max() = 0;
+ virtual short neg_accum_max() = 0;
+ };
+
+ } /* namespace vocoder */
+} /* namespace gr */
+
+#endif /* INCLUDED_VOCODER_CVSD_DECODE_BS_H */
--
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