/** * @file   zmean.c * * <JA> * @brief  掐蝸不蘭の木萎喇尸の近殿 * * 木萎喇尸の近殿を乖ないますˉ *  * 木萎喇尸の夸年は掐蝸デバイスごとに佰なりますˉ * ファイル掐蝸では·デ〖タ鏈攣の慷升の士堆が脫いられますˉ * マイク掐蝸やネットワ〖ク掐蝸の眷圭·掐蝸ストリ〖ムの * 呵介の @a ZMEANSAMPLES 改のサンプルの士堆から紛換され· * その猛がその稿の掐蝸に脫いられますˉ * </JA> * <EN> * @brief  Remove DC offset from input speech * * These function removes DC offset from input speech, like the ZMEANSOURCE * feature in HTK. * * The estimation method of DC offset depends on the type of input device. * On file input, the mean of entire samples is used as estimated offset. * On microphone input and network input, The first @a * ZMEANSAMPLES samples in the input stream are used to estimate the offset, * and the value will be used for the rest of the input. * </EN> * * @author Akinobu LEE * @date   Sun Feb 13 20:31:23 2005 * * $Revision: 1.2 $ *  *//* * 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/adin.h>static int zlen = 0;		///< Current recorded length for DC offset estimationstatic float zmean = 0.0;	///< Current mean/**  * Reset status. *  */voidzmean_reset(){  zlen = 0;  zmean = 0.0;}/**  * @brief Remove DC offset. * * The DC offset is estimated by the first samples after zmean_reset() was * called.  If the first input segment is longer than ZMEANSAMPLES, the * whole input is used to estimate the zero mean.  Otherwise, the zero mean * will continue to be updated until the read length exceed ZMEANSAMPLES. *  * @param speech [I/O] input speech data, will be subtracted by DC offset. * @param samplenum [in] length of above. *  */voidsub_zmean(SP16 *speech, int samplenum){  int i;  float d, sum;  if (zlen < ZMEANSAMPLES) {    /* update zmean */    sum = zmean * zlen;    for (i=0;i<samplenum;i++) {      sum += speech[i];    }    zlen += samplenum;    zmean = sum / (float)zlen;  }  for (i=0;i<samplenum;i++) {    d = (float)speech[i] - zmean;    /* clip overflow */    if (d < -32768.0) d = -32768.0;    if (d > 32767.0) d = 32767.0;    /* round to SP16 (normally short) */    if (d > 0) speech[i] = (SP16)(d + 0.5);    else speech[i] = (SP16)(d - 0.5);  }}