--- /dev/null
+/* -*- c++ -*- */
+/*
+ * Copyright 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.
+ */
+#ifndef INCLUDED_CVSD_ENCODER_SB_H
+#define INCLUDED_CVSD_ENCODER_SB_H
+
+#include <gr_sync_decimator.h>
+
+class cvsd_encode_sb;
+
+typedef boost::shared_ptr<cvsd_encode_sb> cvsd_encode_sb_sptr;
+
+ /*!
+ * \brief Constructor parameters to initialize the CVSD encoder. 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 less or equal 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)
+ *
+ */
+
+cvsd_encode_sb_sptr cvsd_make_encode_sb (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);
+
+/*!
+ * \brief This block performs CVSD audio encoding. Its design and implementation
+ * is modeled after the CVSD encoder/decoder specifications defined in the
+ * Bluetooth standard.
+ *
+ * \ingroup vocoder_blk
+ *
+ * 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 encoder effectively provides 8-to-1 compression. More
+ * specifically, each incoming audio sample is compared to an internal
+ * reference value. If the input is greater or equal to the reference,
+ * the encoder outputs a "1" bit. If the input is less than the reference,
+ * the encoder outputs a "0" bit. The reference value is then updated
+ * accordingly based on the frequency of outputted "1" or "0" bits. By
+ * grouping 8 outputs bits together, the encoder essentially produce one
+ * output byte for every 8 input audio samples.
+ *
+ * This encoder requires that input audio samples are 2-byte short signed
+ * integers. The result bandwidth conversion, therefore, is 16 input bytes
+ * of raw audio data to 1 output byte of encoded audio data.
+ *
+ * The CVSD encoder module must be prefixed by an up-converter to over-sample
+ * the audio data prior to encoding. The Bluetooth standard specifically
+ * calls for a 1-to-8 interpolating up-converter. While this reduces the
+ * overall compression of the codec, this is required so that the encoder
+ * can accurately compute the slope between adjacent audio samples and
+ * correctly update its internal reference value.
+ *
+ * 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 cvsd_encode_sb : public gr_sync_decimator
+{
+private:
+ friend cvsd_encode_sb_sptr cvsd_make_encode_sb (short min_step,
+ short max_step,
+ double step_decay,
+ double accum_decay,
+ int K,
+ int J,
+ short pos_accum_max,
+ short neg_accum_max);
+
+ cvsd_encode_sb (short min_step, short max_step, double step_decay,
+ double accum_decay, int K, int J,
+ short pos_accum_max, short neg_accum_max);
+
+ //! Member functions required by the encoder/decoder
+ //! \brief Rounding function specific to CVSD
+ //! \return the input value rounded to the nearest integer
+ int cvsd_round(double input);
+
+ //! \brief A power function specific to CVSD data formats
+ //! \return (radix)^power, where radix and power are short integers
+ unsigned int cvsd_pow (short radix, short power);
+
+ //! \brief Sums number of 1's in the input
+ //! \return the number of 1s in the four bytes of an input unsigned integer
+ unsigned char cvsd_bitwise_sum (unsigned int input);
+
+ // Members variables related to the CVSD encoder use to update interal reference value
+ short d_min_step;
+ short d_max_step;
+ double d_step_decay;
+ double d_accum_decay;
+
+ int d_K; //!< \brief Size of shift register; the number of output bits remembered in shift register
+ int d_J; //!< \brief Number of bits in the shift register that are equal; size of run of 1s, 0s
+
+ short d_pos_accum_max;
+ short d_neg_accum_max;
+
+ int d_accum; //!< \brief Current value of internal reference
+ int d_loop_counter; //!< \brief Current value of the loop counter
+ unsigned int d_runner; //!< \brief Current value of the shift register
+ short d_stepsize; //!< \brief Current value of the step sizer
+
+ public:
+ ~cvsd_encode_sb (); // public destructor
+
+ short min_step() { return d_min_step; }
+ short max_step() { return d_max_step; }
+ double step_decay() { return d_step_decay; }
+ double accum_decay() { return d_accum_decay; }
+ int K() { return d_K; }
+ int J() { return d_J; }
+ short pos_accum_max() { return d_pos_accum_max; }
+ short neg_accum_max() { return d_neg_accum_max; }
+
+ int work (int noutput_items,
+ gr_vector_const_void_star &input_items,
+ gr_vector_void_star &output_items);
+};
+
+#endif /* INCLUDED_CVSD_ENCODE_SB_H */
projects / debian / gnuradio / blobdiff