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Diffstat (limited to 'gr-vocoder/include/vocoder/cvsd_encode_sb.h')
| -rw-r--r-- | gr-vocoder/include/vocoder/cvsd_encode_sb.h | 131 |
1 files changed, 0 insertions, 131 deletions
diff --git a/gr-vocoder/include/vocoder/cvsd_encode_sb.h b/gr-vocoder/include/vocoder/cvsd_encode_sb.h deleted file mode 100644 index 40f2eb2a6c..0000000000 --- a/gr-vocoder/include/vocoder/cvsd_encode_sb.h +++ /dev/null @@ -1,131 +0,0 @@ -/* -*- c++ -*- */ -/* - * Copyright 2007,2013 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_ENCODER_SB_H -#define INCLUDED_VOCODER_CVSD_ENCODER_SB_H - -#include <vocoder/api.h> -#include <gnuradio/sync_decimator.h> - -namespace gr { - namespace vocoder { - - /*! - * \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 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 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 VOCODER_API cvsd_encode_sb : virtual public sync_decimator - { - public: - // gr::vocoder::cvsd_encode_sb::sptr - typedef boost::shared_ptr<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 <= 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_ENCODE_SB_H */ |