cabac.c

此源码是关于h264图像编解码的工程

/*!
 *************************************************************************************
 * \file cabac.c
 *
 * \brief
 *    CABAC entropy coding routines
 *
 * \author
 *    Main contributors (see contributors.h for copyright, address and affiliation details)
 *    - Detlev Marpe                    <[e-mail]>
 **************************************************************************************
 */

#include <stdlib.h>
#include <math.h>
#include <memory.h>
#include <assert.h>
#include "cabac.h"
#include "image.h"
#include "mb_access.h"

/*!
 ************************************************************************
 * \brief
 *    Allocation of contexts models for the motion info
 *    used for arithmetic encoding
 ************************************************************************
 */
MotionInfoContexts* create_contexts_MotionInfo(void)
{
  MotionInfoContexts* enco_ctx;

  enco_ctx = (MotionInfoContexts*) calloc(1, sizeof(MotionInfoContexts) );
  if( enco_ctx == NULL )
    no_mem_exit("create_contexts_MotionInfo: enco_ctx");

  return enco_ctx;
}


/*!
 ************************************************************************
 * \brief
 *    Allocates of contexts models for the texture info
 *    used for arithmetic encoding
 ************************************************************************
 */
TextureInfoContexts* create_contexts_TextureInfo(void)
{
  TextureInfoContexts*  enco_ctx;

  enco_ctx = (TextureInfoContexts*) calloc(1, sizeof(TextureInfoContexts) );
  if( enco_ctx == NULL )
    no_mem_exit("create_contexts_TextureInfo: enco_ctx");

  return enco_ctx;
}




/*!
 ************************************************************************
 * \brief
 *    Frees the memory of the contexts models
 *    used for arithmetic encoding of the motion info.
 ************************************************************************
 */
void delete_contexts_MotionInfo(MotionInfoContexts *enco_ctx)
{
  if( enco_ctx == NULL )
    return;

  free( enco_ctx );

  return;
}

/*!
 ************************************************************************
 * \brief
 *    Frees the memory of the contexts models
 *    used for arithmetic encoding of the texture info.
 ************************************************************************
 */
void delete_contexts_TextureInfo(TextureInfoContexts *enco_ctx)
{
  if( enco_ctx == NULL )
    return;

  free( enco_ctx );

  return;
}


/*!
 **************************************************************************
 * \brief
 *    generates arithmetic code and passes the code to the buffer
 **************************************************************************
 */
int writeSyntaxElement_CABAC(SyntaxElement *se, DataPartition *this_dataPart)
{
  int curr_len;
  EncodingEnvironmentPtr eep_dp = &(this_dataPart->ee_cabac);

  curr_len = arienco_bits_written(eep_dp);

  // perform the actual coding by calling the appropriate method
  se->writing(se, eep_dp);

  if(se->type != SE_HEADER)
    this_dataPart->bitstream->write_flag = 1;

  return (se->len = (arienco_bits_written(eep_dp) - curr_len));
}

/*!
 ***************************************************************************
 * \brief
 *    This function is used to arithmetically encode the field
 *    mode info of a given MB  in the case of mb-based frame/field decision
 ***************************************************************************
 */
void writeFieldModeInfo_CABAC(SyntaxElement *se, EncodingEnvironmentPtr eep_dp)
{
  int a,b,act_ctx;
  MotionInfoContexts *ctx         = (img->currentSlice)->mot_ctx;
  Macroblock         *currMB      = &img->mb_data[img->current_mb_nr];
  int                mb_field = se->value1;
  
  if (currMB->mbAvailA)
    a = img->mb_data[currMB->mbAddrA].mb_field;
  else
    a = 0;
  if (currMB->mbAvailB)
    b = img->mb_data[currMB->mbAddrB].mb_field;
  else
    b=0;

  act_ctx = a + b;

  if (mb_field==0) // frame
    biari_encode_symbol(eep_dp, 0,&ctx->mb_aff_contexts[act_ctx]);
  else
    biari_encode_symbol(eep_dp, 1,&ctx->mb_aff_contexts[act_ctx]);
  
  se->context = act_ctx;
  
  return;
}

/*!
 ***************************************************************************
 * \brief
 *    This function is used to arithmetically encode the mb_skip_flag.
 ***************************************************************************
 */
void writeMB_skip_flagInfo_CABAC(SyntaxElement *se, EncodingEnvironmentPtr eep_dp)
{
  int a,b,act_ctx;
  int bframe   = (img->type==B_SLICE);
  MotionInfoContexts *ctx         = (img->currentSlice)->mot_ctx;
  Macroblock         *currMB      = &img->mb_data[img->current_mb_nr];
  int                curr_mb_type = se->value1;

  if (bframe)
  {
    if (currMB->mb_available_up == NULL)
      b = 0;
    else
      b = (currMB->mb_available_up->mb_type==0 && currMB->mb_available_up->cbp==0 ? 0 : 1);
    if (currMB->mb_available_left == NULL)
      a = 0;
    else
      a = (currMB->mb_available_left->mb_type==0 && currMB->mb_available_left->cbp==0 ? 0 : 1);
    
    act_ctx = 7 + a + b;

    if (se->value1==0 && se->value2==0) // DIRECT mode, no coefficients
      biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][act_ctx]);
    else
      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][act_ctx]);   
  }
  else
  {
    if (currMB->mb_available_up == NULL)
      b = 0;
    else
      b = (( (currMB->mb_available_up)->mb_type != 0) ? 1 : 0 );
    if (currMB->mb_available_left == NULL)
      a = 0;
    else
      a = (( (currMB->mb_available_left)->mb_type != 0) ? 1 : 0 );

    act_ctx = a + b;

    if (curr_mb_type==0) // SKIP
      biari_encode_symbol(eep_dp, 1,&ctx->mb_type_contexts[1][act_ctx]);
    else
      biari_encode_symbol(eep_dp, 0,&ctx->mb_type_contexts[1][act_ctx]);
  }
  se->context = act_ctx;
  return;
}

/*!
 ***************************************************************************
 * \brief
 *    This function is used to arithmetically encode the macroblock
 *    type info of a given MB.
 ***************************************************************************
 */

void writeMB_typeInfo_CABAC(SyntaxElement *se, EncodingEnvironmentPtr eep_dp)
{
  int a, b;
  int act_ctx = 0;
  int act_sym;
  int csym;
  int bframe   = (img->type==B_SLICE);
  int mode_sym = 0;
  int mode16x16;


  MotionInfoContexts *ctx         = (img->currentSlice)->mot_ctx;
  Macroblock         *currMB      = &img->mb_data[img->current_mb_nr];
  int                curr_mb_type = se->value1;

  if(img->type == I_SLICE)  // INTRA-frame
  {
    if (currMB->mb_available_up == NULL)
      b = 0;
    else 
      b = (( currMB->mb_available_up->mb_type != I4MB) ? 1 : 0 );
    if (currMB->mb_available_left == NULL)
      a = 0;
    else 
      a = (( currMB->mb_available_left->mb_type != I4MB) ? 1 : 0 );

    act_ctx     = a + b;
    act_sym     = curr_mb_type;
    se->context = act_ctx; // store context

    if (act_sym==0) // 4x4 Intra
    {
      biari_encode_symbol(eep_dp, 0, ctx->mb_type_contexts[0] + act_ctx );
    }
    else if( act_sym == 25 ) // PCM-MODE
    {
      biari_encode_symbol(eep_dp, 1, ctx->mb_type_contexts[0] + act_ctx );

      biari_encode_symbol_final(eep_dp, 1);
    }
    else // 16x16 Intra
    {
      biari_encode_symbol(eep_dp, 1, ctx->mb_type_contexts[0] + act_ctx );

      biari_encode_symbol_final(eep_dp, 0);

      mode_sym = act_sym-1; // Values in the range of 0...23
      act_ctx  = 4;
      act_sym  = mode_sym/12;
      biari_encode_symbol(eep_dp, (unsigned char) act_sym, ctx->mb_type_contexts[0] + act_ctx ); // coding of AC/no AC
      mode_sym = mode_sym % 12;
      act_sym  = mode_sym / 4; // coding of cbp: 0,1,2
      act_ctx  = 5;
      if (act_sym==0)
      {
        biari_encode_symbol(eep_dp, 0, ctx->mb_type_contexts[0] + act_ctx );
      }
      else
      {
        biari_encode_symbol(eep_dp, 1, ctx->mb_type_contexts[0] + act_ctx );
        act_ctx=6;
        if (act_sym==1)
        {
          biari_encode_symbol(eep_dp, 0, ctx->mb_type_contexts[0] + act_ctx );
        }
        else
        {
          biari_encode_symbol(eep_dp, 1, ctx->mb_type_contexts[0] + act_ctx );
        }
      }
      mode_sym = mode_sym % 4; // coding of I pred-mode: 0,1,2,3
      act_sym  = mode_sym/2;
      act_ctx  = 7;
      biari_encode_symbol(eep_dp, (unsigned char) act_sym, ctx->mb_type_contexts[0] + act_ctx );
      act_ctx  = 8;
      act_sym  = mode_sym%2;
      biari_encode_symbol(eep_dp, (unsigned char) act_sym, ctx->mb_type_contexts[0] + act_ctx );
    }
  }
  else // INTER
  {
    
    if (bframe)
    {
      if (currMB->mb_available_up == NULL)
        b = 0;
      else
        b = (( currMB->mb_available_up->mb_type != 0) ? 1 : 0 );
      if (currMB->mb_available_left == NULL)
        a = 0;
      else
        a = (( currMB->mb_available_left->mb_type != 0) ? 1 : 0 );
      act_ctx = a + b;
      se->context = act_ctx; // store context
    }
    act_sym = curr_mb_type;

    if (act_sym>=(mode16x16=(bframe?24:7)))
    {
      mode_sym = act_sym-mode16x16;
      act_sym  = mode16x16; // 16x16 mode info
    }



    if (!bframe)
    {
      switch (act_sym)
      {
      case 0:
        break;
      case 1:
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][4]);
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][5]);
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][6]);
        break;
      case 2:
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][4]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[1][5]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[1][7]);
        break;
      case 3:
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][4]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[1][5]);
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][7]);
        break;
      case 4:
      case 5:
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][4]);
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][5]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[1][6]);
        break;
      case 6:
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[1][4]);
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[1][7]);
        break;
      case 7:
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[1][4]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[1][7]);
        break;
      default:
        printf ("Unsupported MB-MODE in writeMB_typeInfo_CABAC!\n");
        exit (1);
      }
    }
    else //===== B-FRAMES =====
    {
      if (act_sym==0)
      {
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][act_ctx]);
      }
      else if (act_sym<=2)
      {
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][act_ctx]);
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][4]);
        csym=act_sym-1;
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
      }
      else if (act_sym<=10)
      {
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][act_ctx]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][4]);
        biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][5]);
        csym=(((act_sym-3)>>2)&0x01);
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
        csym=(((act_sym-3)>>1)&0x01);
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
        csym=((act_sym-3)&0x01);
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
      }
      else if (act_sym==11 || act_sym==22)
      {
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][act_ctx]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][4]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][5]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        if (act_sym==11)  biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
        else              biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
      }
      else
      {
        if (act_sym > 22) act_sym--;
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][act_ctx]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][4]);
        biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][5]);
        csym=(((act_sym-12)>>3)&0x01);
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
        csym=(((act_sym-12)>>2)&0x01);
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
        csym=(((act_sym-12)>>1)&0x01);
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]);
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
        csym=((act_sym-12)&0x01);
        if (csym) biari_encode_symbol (eep_dp, 1, &ctx->mb_type_contexts[2][6]); 
        else      biari_encode_symbol (eep_dp, 0, &ctx->mb_type_contexts[2][6]);
        if (act_sym >=22) act_sym++;
      }
    }

    if(act_sym==mode16x16) // additional info for 16x16 Intra-mode
    {
      if( mode_sym==25 )
      {
        biari_encode_symbol_final(eep_dp, 1 );
        return;
      }
      biari_encode_symbol_final(eep_dp, 0 );

      act_ctx = 8;
      act_sym = mode_sym/12;
      biari_encode_symbol(eep_dp, (unsigned char) act_sym, ctx->mb_type_contexts[1] + act_ctx ); // coding of AC/no AC
      mode_sym = mode_sym % 12;

      act_sym = mode_sym / 4; // coding of cbp: 0,1,2
      act_ctx = 9;
      if (act_sym==0)
      {
        biari_encode_symbol(eep_dp, 0, ctx->mb_type_contexts[1] + act_ctx );
      }
      else
      {
        biari_encode_symbol(eep_dp, 1, ctx->mb_type_contexts[1] + act_ctx );
        if (act_sym==1)
        {
          biari_encode_symbol(eep_dp, 0, ctx->mb_type_contexts[1] + act_ctx );
        }
        else
        {
          biari_encode_symbol(eep_dp, 1, ctx->mb_type_contexts[1] + act_ctx );
        }
      }