/************************************************* * libr263: fast H.263 encoder library * * Copyright (C) 1996, Roalt Aalmoes, Twente University * SPA multimedia group * * Based on Telenor TMN 1.6 encoder (Copyright (C) 1995, Telenor R&D) * created by Karl Lillevold  * * Author encoder: Roalt Aalmoes, <aalmoes@huygens.nl> *  * Date: 31-07-96 **************************************************/#include"sim.h"/* For q=8, a "speedy" version is integrated */
// 量化,后系數存入qcoeff, 并找到CBP 63個AC系數(qcoeff有非零值時,CBP=CBP_Mask 32,16,8,4,2,1 分別對應6個8*8塊)
int QuantAndFindCBP(int *coeff, int *qcoeff, int QP, int Mode, int CBP_Mask){  int i;  int level;  int tempje;  int CBP = 0;  if (Mode == MODE_INTRA) /* Intra */
  {     qcoeff[0] = mmax(1,mmin(254,coeff[0] >> 3)); /* was: /8 *///DC ,除以8,  并限定到1到255    if(QP == 8) 
	{      for(i = 1; i < 64; i++) {	/* QP == 8 */	     level = (abs(coeff[i])) >> 4;                        //AC,除以16,	     qcoeff[i] = mmin(127, mmax(-127,sign(coeff[i]) * level));	     if(qcoeff[i])	        CBP = CBP_Mask; //32      }    } else 
	{			/* QP != 8 */      for(i = 1; i < 64; i++) {		level = (abs(coeff[i])) / (2*QP);		qcoeff[i] =  mmin(127,mmax(-127,sign(coeff[i]) * level));		if(qcoeff[i])	       CBP = CBP_Mask;      }    }	/* End intra QP == 8 */  }  else { /* non Intra */    if(QP == 8) {      for(i = 0; i < 64; i++) {	tempje = abs(coeff[i]) - 4;	if(tempje < 0) {	  *(qcoeff++) = 0;	} else {	  level = tempje >> 4; /* Note 2*QP == 2*8 = 2^4 == ">>4" */	  if((*(qcoeff++) = mmin(127,mmax(-127,(sign(coeff[i]) > 0) ?level :-level))) != 0)	    CBP = CBP_Mask;	}      }          } else {			/* QP != 8 */            for (i = 0; i < 64; i++) {	  level = (abs(coeff[i])-QP/2)  / (2*QP);	  if((*(qcoeff++) = mmin(127,mmax(-127,sign(coeff[i]) * level)))!= 0)	  CBP = CBP_Mask;      }          } /* End QP == 8 */      }    return CBP;}void Dequant(int *qcoeff, int *rcoeff, int QP, int Mode){  int i;    if (QP) {    for (i = 0; i < 64; i++) {      if (qcoeff[i]) {	if ((QP % 2) == 1)	  rcoeff[i] = QP * (2*abs(qcoeff[i]) + 1);	else	  rcoeff[i] = QP * (2*abs(qcoeff[i]) + 1) - 1;	rcoeff[i] = sign(qcoeff[i]) * rcoeff[i];      }      else	rcoeff[i] = 0;    }    if (Mode == MODE_INTRA) { /* Intra */      rcoeff[0] = qcoeff[0]*8;    }  }  else {    /* No quantizing at all */    for (i = 0; i < 64; i++) {      rcoeff[i] = qcoeff[i];    }  }  return;}