countbit.c

h.263 c编码源码。目录下有input。qcif原始未压缩文件

/*************************************************
 * 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, <[e-mail]>
 * 
 * Date: 31-07-96
 **************************************************/

#include"sim.h"
#include"huffman.h"
#include"indices.h"
 
/**********************************************************************
 *
 *	Name:		CountBitsMB
 *	Description:    counts bits used for MB info
 *	
 *	Input:	        Mode, COD, CBP, Picture and Bits structures
 *	Returns:       
 *	Side effects:
 *
 *	Date: 941129	Author: [e-mail]
 *
 ***********************************************************************/

// 计算宏块信息需要的bit数
// COD skip此宏块时为1 ,no skip 为0
// 对宏块的COD,CBPCM,CBPY 编码

void CountBitsMB(int Mode, int COD, int CBP, int CBPB, Pict *pic, Bits *bits)
{
  extern EHUFF *vlc_cbpy, *vlc_cbpcm, *vlc_cbpcm_intra;
  int cbpy, cbpcm, length;

  /* COD */
  if (trace) {
    fprintf(tf,"MB-nr: %d",pic->MB);
    if (pic->picture_coding_type == PCT_INTER)
      fprintf(tf,"  COD: %d\n",COD);
  }

  if (pic->picture_coding_type == PCT_INTER) {
    mputv(1,COD);
    bits->COD++;
  }

  if (COD) 
    return;    /* not coded */

  /* CBPCM */// 对CBP编码
  cbpcm = Mode | ((CBP&3)<<4);   // mode intra时3,inter时0  CBP的后两位,表示U和V块是否需要编码  cbp为60时,UV处为00,则cbpc为3, 编码时 3,1,1,编1位的1
                                  // uv处00,cbpcm 3(1,1);  10 , 35(3,2);   01 ,  19(3,1) ;   11, 51(3,3);
  if (trace) {
    fprintf(tf,"CBPCM (CBP=%d) (cbpcm=%d): ",CBP,cbpcm);
  }
  
  // 对cbpcm编码,返回编码长度
  if (pic->picture_coding_type == PCT_INTRA) {  
    length = Encode(cbpcm,vlc_cbpcm_intra);   // 对cbpcm编码,写入
  } else {
    length = Encode(cbpcm,vlc_cbpcm);
  }
  bits->CBPCM += length;

    
  /* CBPY */
  cbpy = CBP>>2;                             //亮度块Y1～Y4是否编码的标志位, 
  if (Mode == MODE_INTRA || Mode == MODE_INTRA_Q) /* Intra */
    cbpy = cbpy^15;  //帧内  异或(相减)
  if (trace) {
    fprintf(tf,"CBPY (CBP=%d) (cbpy=%d): ",CBP,cbpy);
  }
  // cbpy编码
  length = Encode(cbpy, vlc_cbpy);
  bits->CBPY += length;
  

  return;
}


/**********************************************************************
 *
 *	Name:		CountBitsSlice
 *	Description:    couonts bits used for slice (GOB) info
 *	
 *	Input:	        slice no., quantizer
 *
 *	Date: 94????	Author: [e-mail]
 *
 ***********************************************************************/

int CountBitsSlice(int slice, int quant)
{
  int bits = 0;


  /* Picture Start Code */
  if (trace)
    fprintf(tf,"GOB sync (GBSC): ");
  mputv(PSC_LENGTH,PSC); /* PSC */
  bits += PSC_LENGTH;

  /* Group Number */
  if (trace)
    fprintf(tf,"GN: ");
  mputv(5,slice);
  bits += 5;

  /* GOB Sub Bitstream Indicator */
  /* if CPM == 1: read 2 bits GSBI */
  /* not supported in this version */

  /* GOB Frame ID */
  if (trace)
    fprintf(tf,"GFID: ");
  mputv(2, 0);  
  /* NB: in error-prone environments this value should change if 
     PTYPE in picture header changes. In this version of the encoder
     PTYPE only changes when PB-frames are used in the following cases:
     (i) after the first intra frame
     (ii) if the distance between two P-frames is very large 
     Therefore I haven't implemented this GFID change */
  /* GFID is not allowed to change unless PTYPE changes */
  bits += 2;

  /* Gquant */
  if (trace)
    fprintf(tf,"GQUANT: ");
  mputv(5,quant);
  bits += 5;

  return bits;
}


/**********************************************************************
 *
 *	Name:		CountBitsCoeff
 *	Description:	counts bits used for coeffs
 *	
 *	Input:		qcoeff, coding mode CBP, bits structure, no. of 
 *                      coeffs
 *			
 *	Returns:	struct with no. of bits used
 *	Side effects:	
 *
 *	Date: 940111	Author:	[e-mail]
 *
 ***********************************************************************/
//16*16宏块, 对qcoeff编码,写入bit流,并将写入bit数加入到 bits->Y,和 bits->U中
// ncoeffs 取值为64 
void CountBitsCoeff(int *qcoeff, int Mode, int CBP, Bits *bits, int ncoeffs)

{
  
  int i;
   //intra 
  if (Mode == MODE_INTRA) {
    for (i = 0; i < 4; i++) {//对qcoeff编码,写入比特流, 返回写入bit的个数
      bits->Y += CodeCoeff(Mode, qcoeff,i,ncoeffs);
    }
    for (i = 4; i < 6; i++) {
      bits->C += CodeCoeff(Mode, qcoeff,i,ncoeffs);  //uv处为0时,只编码DC值,8位
    }
  }   
  else {//inter
    for (i = 0; i < 4; i++) {
      if ((i==0 && CBP&32) || 
	  (i==1 && CBP&16) ||
	  (i==2 && CBP&8) || 
	  (i==3 && CBP&4) || 
	  (i==4 && CBP&2) ||
	  (i==5 && CBP&1)) {
	bits->Y += CodeCoeff(Mode, qcoeff, i, ncoeffs);
      }
    }
    for (i = 4; i < 6; i++) {
      if ((i==0 && CBP&32) || 
	  (i==1 && CBP&16) ||
	  (i==2 && CBP&8) || 
	  (i==3 && CBP&4) || 
	  (i==4 && CBP&2) ||
	  (i==5 && CBP&1)) {
	bits->C += CodeCoeff(Mode, qcoeff, i, ncoeffs);
      }
    }
  }
  return;
}

  
// 对dct变换的系数编码
// mode 区分帧内帧间模式,qcoeff dct变换量化后系数, block 第block个8*8小块, 共ncoeffs个系数,取值为64 
// 编码后写入码流,返回写入的bit数目
//????????????????????
int CodeCoeff(int Mode, int *qcoeff, int block, int ncoeffs)   //prev_level 上一个不为0的值
{
  int j, bits;
  int prev_run, run, prev_level, level, first;
  int prev_ind, ind, prev_s, s, length;

  extern EHUFF *vlc_3d;

  run = bits = 0;
  first = 1;
  prev_run = prev_level = prev_ind = level = s = prev_s = ind = 0;
  
  for (j = block*ncoeffs; j< (block + 1)*ncoeffs; j++)// 8*8 的小块的64个值
  {   
    /* DC */
    if (!(j%ncoeffs) && (Mode == MODE_INTRA))
	{
      /* DC coeff */  
      if (qcoeff[block*ncoeffs] != 128)
	       mputv(8,qcoeff[block*ncoeffs]);   // 写入DC的值
      else
	       mputv(8,255);
      bits += 8;
    }
    else 
	{
      /* AC coeff */
      s = 0;
      /* Increment run if coeff is zero */
      if ((level = qcoeff[j]) == 0)
	  {
	          run++;                              // run 当前位置到前一个非零值中,0的个数
      }
      else 
	  {
	     /* code run & level and count bits */
	     if (level < 0) 
		 {
	        s = 1;                                //qcoeff[j]值为负, s符号位, s=1
	        level = -level;
		 }
		ind = level | run<<4;                     // ind值为level的?????????????????(一般为level)  // ind 为level值加run左4位,
		ind = ind | 0<<12; /* Not last coeff */

	    if (!first)
		{
	        /* Encode the previous ind */
	        if (prev_level  < 13 && prev_run < 64) // level值小于13,length=0;
			{
				//!!!!!!!!
	        length = Encode(prev_ind,vlc_3d);   //编码为0时
			} 
			else
	        length = 0;           
	        if (length == 0) /* Escape coding *///length为0时   ,64个AC的最后一个系数
			{  
				if (prev_s == 1) {prev_level = (prev_level^0xff)+1;} // ?????????
				// 最后一位
				Encode(ESCAPE,vlc_3d); // 7167时, 写入7位,3值
				mputv(1,0);
				mputv(6,prev_run);
				mputv(8,prev_level);
				bits += 22;          //共22位
			}
			else 
			{
				mputv(1,prev_s);     //1位,系数>0, 为0;  系数<0,为1
				bits += length + 1;
			}
		} 

		prev_run = run; prev_s = s;
		prev_level = level; prev_ind = ind; // level为实际值,ind为level加上前面0个数(run<<4)的值 编码为prev_ind,为0时重新编
		run = first = 0;
    }//end of   level = qcoeff[j]) == 0
   }//end of if intra
  } // end of for 


  /* Encode the last coeff *///编码最后一位
  if (!first)
  {
   
    prev_ind = prev_ind | 1<<12;   /* last coeff */
    if (prev_level  < 13 && prev_run < 64)
	{ 
      length = Encode(prev_ind,vlc_3d);
    } 
	else
      length = 0;
    if (length == 0) 
	{  /* Escape coding */
      
      if (prev_s == 1) 
	  {
		  prev_level = (prev_level^0xff)+1;}
      Encode(ESCAPE,vlc_3d);  // 7167为vlc_3d表中最大值
      mputv(1,1);
      mputv(6,prev_run);
      mputv(8,prev_level);
      bits += 22;
    }
    else 
	{
      mputv(1,prev_s);
      bits += length + 1;
    }
  }
  return bits;
}

 
/**********************************************************************
 *
 *	Name:		FindCBP
 *	Description:	Finds the CBP for a macroblock
 *	
 *	Input:		qcoeff and mode
 *			
 *	Returns:	CBP
 *	Side effects:	
 *
 *	Date: 940829	Author:	[e-mail]
 *
 ***********************************************************************/

//整个宏块中,从量化系数中,得到CBP的值
int FindCBP(int *qcoeff, int Mode, int ncoeffs)
{
  
  int i,j;
  int CBP = 0;

				/* IF INTRABLOCK then intra =1 else 0 */
  int intra = (Mode == MODE_INTRA);

  /* Set CBP for this Macroblock */
  for (i = 0; i < 6; i++) 
  {
				
    /* First time i = 0: j = 0 ..64-1  set bit 5 if coeff != 0
       Sec. time  i = 1; j = 64..128-1 set bit 4 if coeff != 0
       */
    /* OPTIMIZE: I think for i can be removed 
       and only values i=0 must be proessed */
    for (j = i*ncoeffs + intra; j < (i+1)*ncoeffs; j++) 
	{
      if (qcoeff[j]) 
	  {
	    if (i == 0) {CBP |= 32;}
		else if (i == 1) {CBP |= 16;}
		else if (i == 2) {CBP |= 8;}
		else if (i == 3) {CBP |= 4;}
		else if (i == 4) {CBP |= 2;}
		else if (i == 5) {CBP |= 1;}
		else {
		fprintf(stderr,"Error in CBP assignment\n");
		exit(-1);
		} 
	    break;	  
	  
	  }
    }
  }

  return CBP;
}

//MV_ptr整帧图像宏块的mv, 当前为x,y宏块, newgob是否为新片,
void CountBitsVectors(MotionVector *MV_ptr, Bits *bits, int x, int y, int Mode, int newgob, Pict *pic)
{
  int y_vec, x_vec;
  extern EHUFF *vlc_mv;
  int pmv0, pmv1;
  int start,stop,block;
  MotionVector *MV_xy;

  start = 0; stop = 0;
  MV_xy = MV_ptr + y*mbc + x;

  for (block = start; block <= stop;  block++) 
  {

    FindPMV(MV_ptr,x,y,&pmv0,&pmv1, block, newgob, 1);//1,使用半象素

    x_vec = (2*(*MV_xy).x + (*MV_xy).x_half) - pmv0;
    y_vec = (2*(*MV_xy).y + (*MV_xy).y_half) - pmv1;

    if (!long_vectors) 
	{