SphinxBase  0.6
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 "sphinxbase/strfuncs.h"
00060 #include "sphinxbase/err.h"
00061 
00062 #include "fe_warp.h"
00063 #include "fe_warp_affine.h"
00064 
00065 #define N_PARAM         2
00066 #define YES             1
00067 #define NO              0
00068 
00069 /*
00070  * params[0] : a
00071  * params[1] : b
00072  */
00073 static float params[N_PARAM] = { 1.0f, 0.0f };
00074 static int32 is_neutral = YES;
00075 static char p_str[256] = "";
00076 static float nyquist_frequency = 0.0f;
00077 
00078 
00079 const char *
00080 fe_warp_affine_doc()
00081 {
00082     return "affine :== < w' = a * x + b >";
00083 }
00084 
00085 uint32
00086 fe_warp_affine_id()
00087 {
00088     return FE_WARP_ID_AFFINE;
00089 }
00090 
00091 uint32
00092 fe_warp_affine_n_param()
00093 {
00094     return N_PARAM;
00095 }
00096 
00097 void
00098 fe_warp_affine_set_parameters(char const *param_str, float sampling_rate)
00099 {
00100     char *tok;
00101     char *seps = " \t";
00102     char temp_param_str[256];
00103     int param_index = 0;
00104 
00105     nyquist_frequency = sampling_rate / 2;
00106     if (param_str == NULL) {
00107         is_neutral = YES;
00108         return;
00109     }
00110     /* The new parameters are the same as the current ones, so do nothing. */
00111     if (strcmp(param_str, p_str) == 0) {
00112         return;
00113     }
00114     is_neutral = NO;
00115     strcpy(temp_param_str, param_str);
00116     memset(params, 0, N_PARAM * sizeof(float));
00117     strcpy(p_str, param_str);
00118     /* FIXME: strtok() is not re-entrant... */
00119     tok = strtok(temp_param_str, seps);
00120     while (tok != NULL) {
00121         params[param_index++] = (float) atof_c(tok);
00122         tok = strtok(NULL, seps);
00123         if (param_index >= N_PARAM) {
00124             break;
00125         }
00126     }
00127     if (tok != NULL) {
00128         E_INFO
00129             ("Affine warping takes up to two arguments, %s ignored.\n",
00130              tok);
00131     }
00132     if (params[0] == 0) {
00133         is_neutral = YES;
00134         E_INFO
00135             ("Affine warping cannot have slope zero, warping not applied.\n");
00136     }
00137 }
00138 
00139 float
00140 fe_warp_affine_warped_to_unwarped(float nonlinear)
00141 {
00142     if (is_neutral) {
00143         return nonlinear;
00144     }
00145     else {
00146         /* linear = (nonlinear - b) / a */
00147         float temp = nonlinear - params[1];
00148         temp /= params[0];
00149         if (temp > nyquist_frequency) {
00150             E_WARN
00151                 ("Warp factor %g results in frequency (%.1f) higher than Nyquist (%.1f)\n",
00152                  params[0], temp, nyquist_frequency);
00153         }
00154         return temp;
00155     }
00156 }
00157 
00158 float
00159 fe_warp_affine_unwarped_to_warped(float linear)
00160 {
00161     if (is_neutral) {
00162         return linear;
00163     }
00164     else {
00165         /* nonlinear = a * linear - b */
00166         float temp = linear * params[0];
00167         temp += params[1];
00168         return temp;
00169     }
00170 }
00171 
00172 void
00173 fe_warp_affine_print(const char *label)
00174 {
00175     uint32 i;
00176 
00177     for (i = 0; i < N_PARAM; i++) {
00178         printf("%s[%04u]: %6.3f ", label, i, params[i]);
00179     }
00180     printf("\n");
00181 }
00182 
00183 /*
00184  * Log record.  Maintained by RCS.
00185  *
00186  * $Log: fe_warp_affine.c,v $
00187  * Revision 1.2  2006/02/17 00:31:34  egouvea
00188  * Removed switch -melwarp. Changed the default for window length to
00189  * 0.025625 from 0.256 (so that a window at 16kHz sampling rate has
00190  * exactly 410 samples). Cleaned up include's. Replaced some E_FATAL()
00191  * with E_WARN() and return.
00192  *
00193  * Revision 1.1  2006/02/16 00:18:26  egouvea
00194  * Implemented flexible warping function. The user can specify at run
00195  * time which of several shapes they want to use. Currently implemented
00196  * are an affine function (y = ax + b), an inverse linear (y = a/x) and a
00197  * piecewise linear (y = ax, up to a frequency F, and then it "breaks" so
00198  * Nyquist frequency matches in both scales.
00199  *
00200  * Added two switches, -warp_type and -warp_params. The first specifies
00201  * the type, which valid values:
00202  *
00203  * -inverse or inverse_linear
00204  * -linear or affine
00205  * -piecewise or piecewise_linear
00206  *
00207  * The inverse_linear is the same as implemented by EHT. The -mel_warp
00208  * switch was kept for compatibility (maybe remove it in the
00209  * future?). The code is compatible with EHT's changes: cepstra created
00210  * from code after his changes should be the same as now. Scripts that
00211  * worked with his changes should work now without changes. Tested a few
00212  * cases, same results.
00213  *
00214  */