fe_warp_piecewise_linear.c
/* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* ====================================================================
* Copyright (c) 2006 Carnegie Mellon University. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
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*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* This work was supported in part by funding from the Defense Advanced
* Research Projects Agency and the National Science Foundation of the
* United States of America, and the CMU Sphinx Speech Consortium.
*
* THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS'' AND
* ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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* ====================================================================
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*/
/*********************************************************************
*
* File: fe_warp_piecewise_linear.c
*
* Description:
*
* Warp the frequency axis according to an piecewise linear
* function. The function is linear up to a frequency F, where
* the slope changes so that the Nyquist frequency in the warped
* axis maps to the Nyquist frequency in the unwarped.
*
* w' = a * w, w < F
* w' = a' * w + b, W > F
* w'(0) = 0
* w'(F) = F
* w'(Nyq) = Nyq
*
*********************************************************************/
/* static char rcsid[] = "@(#)$Id: fe_warp_piecewise_linear.c,v 1.2 2006/02/17 00:31:34 egouvea Exp $"; */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#ifdef _MSC_VER
#pragma warning (disable: 4996)
#endif
#include "sphinxbase/strfuncs.h"
#include "sphinxbase/err.h"
#include "fe_warp.h"
#include "fe_warp_piecewise_linear.h"
#define N_PARAM 2
#define YES 1
#define NO 0
/*
* params[0] : a
* params[1] : F (the non-differentiable point)
*/
static float params[N_PARAM] = { 1.0f, 6800.0f };
static float final_piece[2];
static int32 is_neutral = YES;
static char p_str[256] = "";
static float nyquist_frequency = 0.0f;
const char *
fe_warp_piecewise_linear_doc()
{
return "piecewise_linear :== < w' = a * w, w < F >";
}
uint32
fe_warp_piecewise_linear_id()
{
return FE_WARP_ID_PIECEWISE_LINEAR;
}
uint32
fe_warp_piecewise_linear_n_param()
{
return N_PARAM;
}
void
fe_warp_piecewise_linear_set_parameters(char const *param_str,
float sampling_rate)
{
char *tok;
char *seps = " \t";
char temp_param_str[256];
int param_index = 0;
nyquist_frequency = sampling_rate / 2;
if (param_str == NULL) {
is_neutral = YES;
return;
}
/* The new parameters are the same as the current ones, so do nothing. */
if (strcmp(param_str, p_str) == 0) {
return;
}
is_neutral = NO;
strcpy(temp_param_str, param_str);
memset(params, 0, N_PARAM * sizeof(float));
memset(final_piece, 0, 2 * sizeof(float));
strcpy(p_str, param_str);
/* FIXME: strtok() is not re-entrant... */
tok = strtok(temp_param_str, seps);
while (tok != NULL) {
params[param_index++] = (float) atof_c(tok);
tok = strtok(NULL, seps);
if (param_index >= N_PARAM) {
break;
}
}
if (tok != NULL) {
E_INFO
("Piecewise linear warping takes up to two arguments, %s ignored.\n",
tok);
}
if (params[1] < sampling_rate) {
/* Precompute these. These are the coefficients of a
* straight line that contains the points (F, aF) and (N,
* N), where a = params[0], F = params[1], N = Nyquist
* frequency.
*/
if (params[1] == 0) {
params[1] = sampling_rate * 0.85f;
}
final_piece[0] =
(nyquist_frequency -
params[0] * params[1]) / (nyquist_frequency - params[1]);
final_piece[1] =
nyquist_frequency * params[1] * (params[0] -
1.0f) / (nyquist_frequency -
params[1]);
}
else {
memset(final_piece, 0, 2 * sizeof(float));
}
if (params[0] == 0) {
is_neutral = YES;
E_INFO
("Piecewise linear warping cannot have slope zero, warping not applied.\n");
}
}
float
fe_warp_piecewise_linear_warped_to_unwarped(float nonlinear)
{
if (is_neutral) {
return nonlinear;
}
else {
/* linear = (nonlinear - b) / a */
float temp;
if (nonlinear < params[0] * params[1]) {
temp = nonlinear / params[0];
}
else {
temp = nonlinear - final_piece[1];
temp /= final_piece[0];
}
if (temp > nyquist_frequency) {
E_WARN
("Warp factor %g results in frequency (%.1f) higher than Nyquist (%.1f)\n",
params[0], temp, nyquist_frequency);
}
return temp;
}
}
float
fe_warp_piecewise_linear_unwarped_to_warped(float linear)
{
if (is_neutral) {
return linear;
}
else {
float temp;
/* nonlinear = a * linear - b */
if (linear < params[1]) {
temp = linear * params[0];
}
else {
temp = final_piece[0] * linear + final_piece[1];
}
return temp;
}
}
void
fe_warp_piecewise_linear_print(const char *label)
{
uint32 i;
for (i = 0; i < N_PARAM; i++) {
printf("%s[%04u]: %6.3f ", label, i, params[i]);
}
printf("\n");
}
/*
* Log record. Maintained by RCS.
*
* $Log: fe_warp_piecewise_linear.c,v $
* Revision 1.2 2006/02/17 00:31:34 egouvea
* Removed switch -melwarp. Changed the default for window length to
* 0.025625 from 0.256 (so that a window at 16kHz sampling rate has
* exactly 410 samples). Cleaned up include's. Replaced some E_FATAL()
* with E_WARN() and return.
*
* Revision 1.1 2006/02/16 00:18:26 egouvea
* Implemented flexible warping function. The user can specify at run
* time which of several shapes they want to use. Currently implemented
* are an affine function (y = ax + b), an inverse linear (y = a/x) and a
* piecewise linear (y = ax, up to a frequency F, and then it "breaks" so
* Nyquist frequency matches in both scales.
*
* Added two switches, -warp_type and -warp_params. The first specifies
* the type, which valid values:
*
* -inverse or inverse_linear
* -linear or affine
* -piecewise or piecewise_linear
*
* The inverse_linear is the same as implemented by EHT. The -mel_warp
* switch was kept for compatibility (maybe remove it in the
* future?). The code is compatible with EHT's changes: cepstra created
* from code after his changes should be the same as now. Scripts that
* worked with his changes should work now without changes. Tested a few
* cases, same results.
*
*/
strfuncs.h
Miscellaneous useful string functions.
E_INFO
#define E_INFO
Print logging information to standard error stream.
Definition: err.h:147
E_WARN
#define E_WARN
Print warning information to standard error stream.
Definition: err.h:164
atof_c
SPHINXBASE_EXPORT double atof_c(char const *str)
Locale independent version of atof().
Definition: strfuncs.c:56
err.h
Implementation of logging routines.