cabac.c

H.264编码实现

/*!
 *************************************************************************************
 * \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 "global.h"

#include "cabac.h"
#include "image.h"
#include "mb_access.h"

#if TRACE
  #define CABAC_TRACE if (dp->bitstream->trace_enabled) trace2out_cabac (se)
#else
  #define CABAC_TRACE
#endif

/***********************************************************************
 * L O C A L L Y   D E F I N E D   F U N C T I O N   P R O T O T Y P E S
 ***********************************************************************
 */


void unary_bin_encode(EncodingEnvironmentPtr eep_frame,
                      unsigned int symbol,
                      BiContextTypePtr ctx,
                      int ctx_offset);

void unary_bin_max_encode(EncodingEnvironmentPtr eep_frame,
                          unsigned int symbol,
                          BiContextTypePtr ctx,
                          int ctx_offset,
                          unsigned int max_symbol);

void unary_exp_golomb_level_encode( EncodingEnvironmentPtr eep_dp,
                                    unsigned int symbol,
                                    BiContextTypePtr ctx);

void unary_exp_golomb_mv_encode(EncodingEnvironmentPtr eep_dp,
                                unsigned int symbol,
                                BiContextTypePtr ctx,
                                unsigned int max_bin);



/*!
 ************************************************************************
 * \brief
 *    Check for available neighbouring blocks
 *    and set pointers in current macroblock
 ************************************************************************
 */
void CheckAvailabilityOfNeighborsCABAC(Macroblock *currMB)
{
  PixelPos up, left;
  int *mb_size = img->mb_size[IS_LUMA];

  getNeighbour(currMB, -1,  0, mb_size, &left);
  getNeighbour(currMB,  0, -1, mb_size, &up);

  if (up.available)
    currMB->mb_available_up = &img->mb_data[up.mb_addr];
  else
    currMB->mb_available_up = NULL;

  if (left.available)
    currMB->mb_available_left = &img->mb_data[left.mb_addr];
  else
    currMB->mb_available_left = NULL;
}

/*!
 ************************************************************************
 * \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 = (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 );
}

/*!
 ************************************************************************
 * \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 );
}


/*!
 ***************************************************************************
 * \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, DataPartition *dp)
{
  EncodingEnvironmentPtr eep_dp = &(dp->ee_cabac);
  int curr_len = arienco_bits_written(eep_dp);
  MotionInfoContexts *ctx     = (img->currentSlice)->mot_ctx;
  Macroblock         *currMB  = &img->mb_data[img->current_mb_nr];
  int                mb_field = se->value1;

  int a = currMB->mbAvailA ? img->mb_data[currMB->mbAddrA].mb_field : 0;
  int b = currMB->mbAvailB ? img->mb_data[currMB->mbAddrB].mb_field : 0;

  int act_ctx = a + b;

  biari_encode_symbol(eep_dp, (signed short) (mb_field != 0),&ctx->mb_aff_contexts[act_ctx]);

  se->context = act_ctx;

  dp->bitstream->write_flag = 1;
  se->len = (arienco_bits_written(eep_dp) - curr_len);
  CABAC_TRACE;
}

/*!
***************************************************************************
* \brief
*    This function is used to arithmetically encode the mb_skip_flag.
***************************************************************************
*/
void writeMB_skip_flagInfo_CABAC(Macroblock *currMB, SyntaxElement *se, DataPartition *dp)
{
  EncodingEnvironmentPtr eep_dp = &(dp->ee_cabac);
  int curr_len = arienco_bits_written(eep_dp);
  MotionInfoContexts *ctx = (img->currentSlice)->mot_ctx;
  int        curr_mb_type = se->value1;
  int a = (currMB->mb_available_left != NULL && (currMB->mb_available_left->skip_flag == 0)) ? 1 : 0;
  int b = (currMB->mb_available_up   != NULL && (currMB->mb_available_up  ->skip_flag == 0)) ? 1 : 0;
  int act_ctx = a + b;

  if (img->type == B_SLICE)
  {
    act_ctx += 7;

    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]);

    currMB->skip_flag = (se->value1==0 && se->value2==0) ? 1 : 0;
  }
  else
  {
    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]);

    currMB->skip_flag = (curr_mb_type==0) ? 1 : 0;
  }
  se->context = act_ctx;
  se->value1  = 1 - currMB->skip_flag;

  dp->bitstream->write_flag = 1;
  se->len = (arienco_bits_written(eep_dp) - curr_len);
  CABAC_TRACE;
}

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

void writeMB_transform_size_CABAC(SyntaxElement *se, DataPartition *dp)
{
  EncodingEnvironmentPtr eep_dp = &(dp->ee_cabac);
  MotionInfoContexts *ctx         = (img->currentSlice)->mot_ctx;
  Macroblock         *currMB      = &img->mb_data[img->current_mb_nr];

  int curr_len = arienco_bits_written(eep_dp);
  int act_sym = currMB->luma_transform_size_8x8_flag;


  int b = (currMB->mb_available_up == NULL) ? 0 : currMB->mb_available_up->luma_transform_size_8x8_flag;
  int a = (currMB->mb_available_left == NULL) ? 0 :currMB->mb_available_left->luma_transform_size_8x8_flag;
  int act_ctx     = a + b;

  se->context = act_ctx; // store context
  biari_encode_symbol(eep_dp, (signed short) (act_sym != 0), ctx->transform_size_contexts + act_ctx );

  dp->bitstream->write_flag = 1;
  se->len = (arienco_bits_written(eep_dp) - curr_len);
  CABAC_TRACE;
}

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

void writeMB_typeInfo_CABAC(SyntaxElement *se, DataPartition *dp)
{
  EncodingEnvironmentPtr eep_dp = &(dp->ee_cabac);
  int curr_len = arienco_bits_written(eep_dp);
  int a, b;
  int act_ctx = 0;
  int act_sym;
  signed short 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 &&  currMB->mb_available_up->mb_type != I8MB) ? 1 : 0 );

    if (currMB->mb_available_left == NULL)
      a = 0;
    else
      a = ((currMB->mb_available_left->mb_type != I4MB &&  currMB->mb_available_left->mb_type != I8MB) ? 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, (signed short) 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;
        biari_encode_symbol(eep_dp, (signed short) (act_sym!=1), ctx->mb_type_contexts[0] + act_ctx );
      }
      mode_sym = mode_sym & 0x03; // coding of I pred-mode: 0,1,2,3
      act_sym  = mode_sym >> 1;
      act_ctx  = 7;
      biari_encode_symbol(eep_dp, (signed short) act_sym, ctx->mb_type_contexts[0] + act_ctx );
      act_ctx  = 8;
      act_sym  = mode_sym & 0x01;
      biari_encode_symbol(eep_dp, (signed short) 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)