HTK3.4程序员手册（2.3）--特征参数提取HParm.c

HTK3.4程序员手册（2.3）--特征参数提取HParm.c
by 云龙

HTK book中提到的参数有11种：
"LPC", "LPREFC", "LPCEPSTRA",   "LPDELCEP", "IREFC", "MFCC", "FBANK", "MELSPEC","DISCRETE", "PLP","ANON"



但HTK3.4中是否都支持呢？
请看ConvertFrame（）函数中的以下代码：
   switch(btgt){
   case LPC:
      Wave2LPC(cf->s,cf->a,cf->k,&re,&te);
      v = cf->a; bsize = cf->lpcOrder;
      break;
   case LPREFC:
      Wave2LPC(cf->s,cf->a,cf->k,&re,&te);
      v = cf->k; bsize = cf->lpcOrder;
      break;     
   case LPCEPSTRA:
      Wave2LPC(cf->s,cf->a,cf->k,&re,&te);
      LPC2Cepstrum(cf->a,cf->c);
      if (cf->cepLifter > 0)
         WeightCepstrum(cf->c, 1, cf->numCepCoef, cf->cepLifter);
      v = cf->c; bsize = cf->numCepCoef;
      break;
   case MELSPEC:
   case FBANK:
      Wave2FBank(cf->s, cf->fbank, rawE?NULL:&te, cf->fbInfo);
      v = cf->fbank; bsize = cf->numChans;
      break;
   case MFCC:
      Wave2FBank(cf->s, cf->fbank, rawE?NULL:&te, cf->fbInfo);
      FBank2MFCC(cf->fbank, cf->c, cf->numCepCoef);
      if (cf->cepLifter > 0)
         WeightCepstrum(cf->c, 1, cf->numCepCoef, cf->cepLifter);
      v = cf->c; bsize = cf->numCepCoef;
      break;
   case PLP:
      Wave2FBank(cf->s, cf->fbank, rawE ? NULL : &te, cf->fbInfo);
      FBank2ASpec(cf->fbank, cf->as, cf->eql, cf->compressFact, cf->fbInfo);
      ASpec2LPCep(cf->as, cf->ac, cf->lp, cf->c, cf->cm);
      if (cf->cepLifter > 0)
         WeightCepstrum(cf->c, 1, cf->numCepCoef, cf->cepLifter);
      v = cf->c;
      bsize = cf->numCepCoef;
      break;
   default:
      HError(6321,"ConvertFrame: target %s is not a parameterised form",
             ParmKind2Str(cf->tgtPK,buf));
   }
可以看出HTK3.4支持7中参数：LPC，LPREFC，LPCEPSTRA，MELSPEC，FBANK，MFCC，PLP。
参数转换顺序可以参照HTK book Fig.5.9：


IOConfigRec数据结构存放着很多参数，在特征提取中：

typedef struct {

   /* ------- Overrideable parameters ------- */

   ParmKind srcPK;            /* Source ParmKind */

   FileFormat srcFF;          /* Source File format */

   HTime srcSampRate;         /* Source Sample Rate */

   Boolean zMeanSrc;          /* Zero Mean the Source */

   ParmKind tgtPK;            /* Target ParmKind */

   FileFormat tgtFF;          /* Target File format */ 
...... 

}IOConfigRec;

 

ValidCodeParms（）函数检查analysis.conf的参数是否合理。

/* ValidCodeParms: check to ensure reasonable wave->parm code params */

static void ValidCodeParms(IOConfig cf)

 

/* SetUpForCoding: set style, sizes and  working storage */

static void SetUpForCoding(MemHeap *x, IOConfig cf, int frSize)

 

ValidConversion（）函数检查原格式到目标格式的转换是否 可能完成。

/* EXPORT->ValidConversion: checks that src -> tgt conversion is possible */

Boolean ValidConversion (ParmKind src, ParmKind tgt)

 

TotalComps（）函数返回 特征参数的 维度。

/* TotalComps: return the total number of components in a parameter vector

   with nStatic components and ParmKind pk */

static int TotalComps(int nStatic, ParmKind pk)

 

在OpenAsChannel（）函数中，计算特征参数所需的内存空间：

dBytes = cf->nCols * pbuf->main.maxRows * sizeof(float);

      = 39 * 243 * 4 = 37908

 

在提取特征参数FillBufFromChannel（）函数前，调用了StartBuffer（）函数，那么StartBuffer（）函数有什么作用呢？

/* EXPORT->StartBuffer: start audio and fill the buffer */

void StartBuffer(ParmBuf pbuf)