SphinxBase 5prealpha
fe_warp_piecewise_linear.c
1/* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */
2/* ====================================================================
3 * Copyright (c) 2006 Carnegie Mellon University. All rights
4 * reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 *
18 * This work was supported in part by funding from the Defense Advanced
19 * Research Projects Agency and the National Science Foundation of the
20 * United States of America, and the CMU Sphinx Speech Consortium.
21 *
22 * THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS'' AND
23 * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
24 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
25 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY
26 * NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
27 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
28 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
32 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
33 *
34 * ====================================================================
35 *
36 */
37/*********************************************************************
38 *
39 * File: fe_warp_piecewise_linear.c
40 *
41 * Description:
42 *
43 * Warp the frequency axis according to an piecewise linear
44 * function. The function is linear up to a frequency F, where
45 * the slope changes so that the Nyquist frequency in the warped
46 * axis maps to the Nyquist frequency in the unwarped.
47 *
48 * w' = a * w, w < F
49 * w' = a' * w + b, W > F
50 * w'(0) = 0
51 * w'(F) = F
52 * w'(Nyq) = Nyq
53 *
54 *********************************************************************/
55
56/* static char rcsid[] = "@(#)$Id: fe_warp_piecewise_linear.c,v 1.2 2006/02/17 00:31:34 egouvea Exp $"; */
57
58#include <stdio.h>
59#include <stdlib.h>
60#include <math.h>
61#include <string.h>
62
63#ifdef _MSC_VER
64#pragma warning (disable: 4996)
65#endif
66
67#include "sphinxbase/strfuncs.h"
68#include "sphinxbase/err.h"
69
70#include "fe_warp.h"
71#include "fe_warp_piecewise_linear.h"
72
73#define N_PARAM 2
74#define YES 1
75#define NO 0
76
77/*
78 * params[0] : a
79 * params[1] : F (the non-differentiable point)
80 */
81static float params[N_PARAM] = { 1.0f, 6800.0f };
82static float final_piece[2];
83static int32 is_neutral = YES;
84static char p_str[256] = "";
85static float nyquist_frequency = 0.0f;
86
87
88const char *
89fe_warp_piecewise_linear_doc()
90{
91 return "piecewise_linear :== < w' = a * w, w < F >";
92}
93
94uint32
95fe_warp_piecewise_linear_id()
96{
97 return FE_WARP_ID_PIECEWISE_LINEAR;
98}
99
100uint32
101fe_warp_piecewise_linear_n_param()
102{
103 return N_PARAM;
104}
105
106void
107fe_warp_piecewise_linear_set_parameters(char const *param_str,
108 float sampling_rate)
109{
110 char *tok;
111 char *seps = " \t";
112 char temp_param_str[256];
113 int param_index = 0;
114
115 nyquist_frequency = sampling_rate / 2;
116 if (param_str == NULL) {
117 is_neutral = YES;
118 return;
119 }
120 /* The new parameters are the same as the current ones, so do nothing. */
121 if (strcmp(param_str, p_str) == 0) {
122 return;
123 }
124 is_neutral = NO;
125 strcpy(temp_param_str, param_str);
126 memset(params, 0, N_PARAM * sizeof(float));
127 memset(final_piece, 0, 2 * sizeof(float));
128 strcpy(p_str, param_str);
129 /* FIXME: strtok() is not re-entrant... */
130 tok = strtok(temp_param_str, seps);
131 while (tok != NULL) {
132 params[param_index++] = (float) atof_c(tok);
133 tok = strtok(NULL, seps);
134 if (param_index >= N_PARAM) {
135 break;
136 }
137 }
138 if (tok != NULL) {
139 E_INFO
140 ("Piecewise linear warping takes up to two arguments, %s ignored.\n",
141 tok);
142 }
143 if (params[1] < sampling_rate) {
144 /* Precompute these. These are the coefficients of a
145 * straight line that contains the points (F, aF) and (N,
146 * N), where a = params[0], F = params[1], N = Nyquist
147 * frequency.
148 */
149 if (params[1] == 0) {
150 params[1] = sampling_rate * 0.85f;
151 }
152 final_piece[0] =
153 (nyquist_frequency -
154 params[0] * params[1]) / (nyquist_frequency - params[1]);
155 final_piece[1] =
156 nyquist_frequency * params[1] * (params[0] -
157 1.0f) / (nyquist_frequency -
158 params[1]);
159 }
160 else {
161 memset(final_piece, 0, 2 * sizeof(float));
162 }
163 if (params[0] == 0) {
164 is_neutral = YES;
165 E_INFO
166 ("Piecewise linear warping cannot have slope zero, warping not applied.\n");
167 }
168}
169
170float
171fe_warp_piecewise_linear_warped_to_unwarped(float nonlinear)
172{
173 if (is_neutral) {
174 return nonlinear;
175 }
176 else {
177 /* linear = (nonlinear - b) / a */
178 float temp;
179 if (nonlinear < params[0] * params[1]) {
180 temp = nonlinear / params[0];
181 }
182 else {
183 temp = nonlinear - final_piece[1];
184 temp /= final_piece[0];
185 }
186 if (temp > nyquist_frequency) {
187 E_WARN
188 ("Warp factor %g results in frequency (%.1f) higher than Nyquist (%.1f)\n",
189 params[0], temp, nyquist_frequency);
190 }
191 return temp;
192 }
193}
194
195float
196fe_warp_piecewise_linear_unwarped_to_warped(float linear)
197{
198 if (is_neutral) {
199 return linear;
200 }
201 else {
202 float temp;
203 /* nonlinear = a * linear - b */
204 if (linear < params[1]) {
205 temp = linear * params[0];
206 }
207 else {
208 temp = final_piece[0] * linear + final_piece[1];
209 }
210 return temp;
211 }
212}
213
214void
215fe_warp_piecewise_linear_print(const char *label)
216{
217 uint32 i;
218
219 for (i = 0; i < N_PARAM; i++) {
220 printf("%s[%04u]: %6.3f ", label, i, params[i]);
221 }
222 printf("\n");
223}
Implementation of logging routines.
#define E_INFO(...)
Print logging information to standard error stream.
Definition err.h:114
#define E_WARN(...)
Print warning message to error log.
Definition err.h:109
Miscellaneous useful string functions.
SPHINXBASE_EXPORT double atof_c(char const *str)
Locale independent version of atof().
Definition strfuncs.c:55