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src/libsphinxbase/fe/fe_warp_affine.c

00001 /* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */
00002 /* ====================================================================
00003  * Copyright (c) 2006 Carnegie Mellon University.  All rights 
00004  * reserved.
00005  *
00006  * Redistribution and use in source and binary forms, with or without
00007  * modification, are permitted provided that the following conditions
00008  * are met:
00009  *
00010  * 1. Redistributions of source code must retain the above copyright
00011  *    notice, this list of conditions and the following disclaimer. 
00012  *
00013  * 2. Redistributions in binary form must reproduce the above copyright
00014  *    notice, this list of conditions and the following disclaimer in
00015  *    the documentation and/or other materials provided with the
00016  *    distribution.
00017  *
00018  * This work was supported in part by funding from the Defense Advanced 
00019  * Research Projects Agency and the National Science Foundation of the 
00020  * United States of America, and the CMU Sphinx Speech Consortium.
00021  *
00022  * THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS'' AND 
00023  * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 
00024  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
00025  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY
00026  * NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00027  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
00028  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
00029  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 
00030  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
00031  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
00032  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00033  *
00034  * ====================================================================
00035  *
00036  */
00037 /*********************************************************************
00038  *
00039  * File: fe_warp_affine.c
00040  * 
00041  * Description: 
00042  *      Warp the frequency axis according to an affine function, i.e.:
00043  *
00044  *              w' = a * w + b
00045  *      
00046  *********************************************************************/
00047 
00048 /* static char rcsid[] = "@(#)$Id: fe_warp_affine.c,v 1.2 2006/02/17 00:31:34 egouvea Exp $"; */
00049 
00050 #include <stdio.h>
00051 #include <stdlib.h>
00052 #include <math.h>
00053 #include <string.h>
00054 
00055 #ifdef _MSC_VER
00056 #pragma warning (disable: 4996)
00057 #endif
00058 
00059 #include "strfuncs.h"
00060 #include "err.h"
00061 #include "fe_warp.h"
00062 #include "fe_warp_affine.h"
00063 
00064 #define N_PARAM         2
00065 #define YES             1
00066 #define NO              0
00067 
00068 /*
00069  * params[0] : a
00070  * params[1] : b
00071  */
00072 static float params[N_PARAM] = { 1.0f, 0.0f };
00073 static int32 is_neutral = YES;
00074 static char p_str[256] = "";
00075 static float nyquist_frequency = 0.0f;
00076 
00077 
00078 const char *
00079 fe_warp_affine_doc()
00080 {
00081     return "affine :== < w' = a * x + b >";
00082 }
00083 
00084 uint32
00085 fe_warp_affine_id()
00086 {
00087     return FE_WARP_ID_AFFINE;
00088 }
00089 
00090 uint32
00091 fe_warp_affine_n_param()
00092 {
00093     return N_PARAM;
00094 }
00095 
00096 void
00097 fe_warp_affine_set_parameters(char const *param_str, float sampling_rate)
00098 {
00099     char *tok;
00100     char *seps = " \t";
00101     char temp_param_str[256];
00102     int param_index = 0;
00103 
00104     nyquist_frequency = sampling_rate / 2;
00105     if (param_str == NULL) {
00106         is_neutral = YES;
00107         return;
00108     }
00109     /* The new parameters are the same as the current ones, so do nothing. */
00110     if (strcmp(param_str, p_str) == 0) {
00111         return;
00112     }
00113     is_neutral = NO;
00114     strcpy(temp_param_str, param_str);
00115     memset(params, 0, N_PARAM * sizeof(float));
00116     strcpy(p_str, param_str);
00117     /* FIXME: strtok() is not re-entrant... */
00118     tok = strtok(temp_param_str, seps);
00119     while (tok != NULL) {
00120         params[param_index++] = (float) atof_c(tok);
00121         tok = strtok(NULL, seps);
00122         if (param_index >= N_PARAM) {
00123             break;
00124         }
00125     }
00126     if (tok != NULL) {
00127         E_INFO
00128             ("Affine warping takes up to two arguments, %s ignored.\n",
00129              tok);
00130     }
00131     if (params[0] == 0) {
00132         is_neutral = YES;
00133         E_INFO
00134             ("Affine warping cannot have slope zero, warping not applied.\n");
00135     }
00136 }
00137 
00138 float
00139 fe_warp_affine_warped_to_unwarped(float nonlinear)
00140 {
00141     if (is_neutral) {
00142         return nonlinear;
00143     }
00144     else {
00145         /* linear = (nonlinear - b) / a */
00146         float temp = nonlinear - params[1];
00147         temp /= params[0];
00148         if (temp > nyquist_frequency) {
00149             E_WARN
00150                 ("Warp factor %g results in frequency (%.1f) higher than Nyquist (%.1f)\n",
00151                  params[0], temp, nyquist_frequency);
00152         }
00153         return temp;
00154     }
00155 }
00156 
00157 float
00158 fe_warp_affine_unwarped_to_warped(float linear)
00159 {
00160     if (is_neutral) {
00161         return linear;
00162     }
00163     else {
00164         /* nonlinear = a * linear - b */
00165         float temp = linear * params[0];
00166         temp += params[1];
00167         return temp;
00168     }
00169 }
00170 
00171 void
00172 fe_warp_affine_print(const char *label)
00173 {
00174     uint32 i;
00175 
00176     for (i = 0; i < N_PARAM; i++) {
00177         printf("%s[%04u]: %6.3f ", label, i, params[i]);
00178     }
00179     printf("\n");
00180 }
00181 
00182 /*
00183  * Log record.  Maintained by RCS.
00184  *
00185  * $Log: fe_warp_affine.c,v $
00186  * Revision 1.2  2006/02/17 00:31:34  egouvea
00187  * Removed switch -melwarp. Changed the default for window length to
00188  * 0.025625 from 0.256 (so that a window at 16kHz sampling rate has
00189  * exactly 410 samples). Cleaned up include's. Replaced some E_FATAL()
00190  * with E_WARN() and return.
00191  *
00192  * Revision 1.1  2006/02/16 00:18:26  egouvea
00193  * Implemented flexible warping function. The user can specify at run
00194  * time which of several shapes they want to use. Currently implemented
00195  * are an affine function (y = ax + b), an inverse linear (y = a/x) and a
00196  * piecewise linear (y = ax, up to a frequency F, and then it "breaks" so
00197  * Nyquist frequency matches in both scales.
00198  *
00199  * Added two switches, -warp_type and -warp_params. The first specifies
00200  * the type, which valid values:
00201  *
00202  * -inverse or inverse_linear
00203  * -linear or affine
00204  * -piecewise or piecewise_linear
00205  *
00206  * The inverse_linear is the same as implemented by EHT. The -mel_warp
00207  * switch was kept for compatibility (maybe remove it in the
00208  * future?). The code is compatible with EHT's changes: cepstra created
00209  * from code after his changes should be the same as now. Scripts that
00210  * worked with his changes should work now without changes. Tested a few
00211  * cases, same results.
00212  *
00213  */

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