/** * @file   strip_mfcc.c * * <JA> * @brief  MFCC誤からゼロサンプル誤を艱り近く * * エネルギ〖灌の猛からゼロサンプルのフレ〖ムを浮叫しますˉ * </JA> * <EN> * @brief  Strip zero frames from MFCC data * * Zero sample frames will be detected by the energy coefficient of MFCC. * </EN> * * The detection is done by setting valid range of log energy. *  * However, since HTK parameter file has no information for framesize or * frequency, defining precise upper bound of power is impossible. * * Guess the power that is in log scale as described below, * *   framesize  :      1    100    400   1000  10000(can't be!) *   upper bound: 20.794 25.400 26.786 27.702 30.005 *  * Thus it can be said that the range of [0..30] will work. * * When energy normalization was on, the parameters are normalized to: * *                 1.0 - (Emax - value) * ESCALE *                  * So the range becomes [1.0-Emax*ESCALE..1.0].  But * the engine cannot know whether the ENORMALIZE was on for given parameters. *  * As a conclusion, the safe bit is to set the range of log energy to *                   [-30..30] * hoping that escale is less than 1.0 (the HTK's default is 0.1). * * But remember, there are no guarantee that valid segments is not * misdetected.  When the misdetection frequently occurs on your MFCC file, * please try "-nostrip" option to turn off the stripping. * * @author Akinobu LEE * @date   Tue Feb 15 00:38:57 2005 * * $Revision: 1.3 $ *  *//* * Copyright (c) 1991-2007 Kawahara Lab., Kyoto University * Copyright (c) 2000-2005 Shikano Lab., Nara Institute of Science and Technology * Copyright (c) 2005-2007 Julius project team, Nagoya Institute of Technology * All rights reserved */#include <sent/stddefs.h>#include <sent/htk_param.h>#include <sent/mfcc.h>/// Invalid log value range to detect zero sample frame.#define IS_INVALID_FRAME_MFCC(A) ((A) < -30.0 || (A) > 30.0)/**  * Guess where the absolute energy coefficient is. *  * @param param [in] parameter data *  * @return the guessed dimension number of energy coefficient, -1 on failure. */static intguess_abs_e_location(HTK_Param *param){  short qualtype;  int basenum, abs_e_num;  qualtype = param->header.samptype & ~(F_COMPRESS | F_CHECKSUM);  qualtype &= ~(F_BASEMASK);  basenum = guess_basenum(param, qualtype);  if (qualtype & F_ENERGY) {    if (qualtype & F_ZEROTH) {      abs_e_num = basenum + 1;    } else {      abs_e_num = basenum;    }  } else {    /* absolute energy not included */    jlog("Stat: strip_mfcc: absolute energy coef. not exist, stripping disabled\n");    abs_e_num = -1;  }  return abs_e_num;}/**  * Strip zero frames from MFCC data. *  * @param param [in] parameter data *  * @return TRUE on success, FALSE on failure. */booleanparam_strip_zero(HTK_Param *param){  unsigned int src,dst;  int eloc;  /* guess where the absolute energy coefficient is */  eloc = guess_abs_e_location(param);  if ((eloc = guess_abs_e_location(param)) < 0) return FALSE;      /* guess the invalid range... */  dst = 0;  for(src=0;src<param->samplenum;src++) {    if (IS_INVALID_FRAME_MFCC(param->parvec[src][eloc])) {      jlog("Warning: strip_mfcc: frame %d has invalid energy, stripped\n", src);      continue;    }    if (src != dst) {      memcpy(param->parvec[dst], param->parvec[src], sizeof(VECT) * param->veclen);    }    dst++;  }  if (dst != param->samplenum) {    jlog("Warning: strip_mfcc: input shrinked from %d to %d frames\n", param->samplenum, dst);    param->header.samplenum = param->samplenum = dst;  }  return TRUE;}