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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * time_scale.h - Time scaling for linear speech data
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2004 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: time_scale.h,v 1.7 2006/10/24 13:45:28 steveu Exp $
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26 */
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27
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28 #if !defined(_TIME_SCALE_H_)
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29 #define _TIME_SCALE_H_
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30
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31 /*! \page time_scale_page Time scaling speech
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32 \section time_scale_page_sec_1 What does it do?
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33 The time scaling module allows speech files to be played back at a
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34 different speed, from the speed at which they were recorded. If this
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35 were done by simply speeding up or slowing down replay, the pitch of
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36 the voice would change, and sound very odd. This modules keeps the pitch
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37 of the voice normal.
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38
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39 \section time_scale_page_sec_2 How does it work?
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40 The time scaling module is based on the Pointer Interval Controlled
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41 OverLap and Add (PICOLA) method, developed by Morita Naotaka.
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42 Mikio Ikeda has an excellent web page on this subject at
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43 http://keizai.yokkaichi-u.ac.jp/~ikeda/research/picola.html
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44 There is also working code there. This implementation uses
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45 exactly the same algorithms, but the code is a complete rewrite.
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46 Mikio's code batch processes files. This version works incrementally
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47 on streams, and allows multiple streams to be processed concurrently.
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48 */
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49
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50 #define TIME_SCALE_MIN_PITCH 60
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51 #define TIME_SCALE_MAX_PITCH 250
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52 #define TIME_SCALE_BUF_LEN (2*SAMPLE_RATE/TIME_SCALE_MIN_PITCH)
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53
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54 typedef struct
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55 {
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56 double rate;
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57 double rcomp;
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58 double rate_nudge;
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59 int fill;
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60 int lcp;
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61 int16_t buf[TIME_SCALE_BUF_LEN];
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62 } time_scale_t;
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63
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64 #ifdef __cplusplus
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65 extern "C" {
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66 #endif
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67
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68 /*! Initialise a time scale context. This must be called before the first
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69 use of the context, to initialise its contents.
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70 \brief Initialise a time scale context.
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71 \param s The time scale context.
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72 \param rate The ratio between the output speed and the input speed.
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73 \return 0 if initialised OK, else -1. */
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74 int time_scale_init(time_scale_t *s, float rate);
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75
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76 /*! Change the time scale rate.
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77 \brief Change the time scale rate.
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78 \param s The time scale context.
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79 \param rate The ratio between the output speed and the input speed.
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80 \return 0 if changed OK, else -1. */
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81 int time_scale_rate(time_scale_t *s, float rate);
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82
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83 /*! Time scale a chunk of audio samples.
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84 \brief Time scale a chunk of audio samples.
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85 \param s The time sclae context.
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86 \param out The output audio sample buffer.
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87 \param in The input audio sample buffer.
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88 \param len The number of input samples.
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89 \return The number of output samples.
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90 */
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91 int time_scale(time_scale_t *s, int16_t out[], int16_t in[], int len);
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92
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93 #ifdef __cplusplus
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94 }
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95 #endif
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96
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97 #endif
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98 /*- End of file ------------------------------------------------------------*/
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