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/*---------------------------------------------------------------------------

*

*  Course:   System Design II

*

*  Module:   code.c

*

*  Purpose:  Run-Length Encoding functions for H.263 encoder

*

*  Notes:    Only INTRA MB:s supported

*

*  Author:   Tero Kangas and Olli Lehtoranta

*

*  History:  31/10/2002: + Original version ready

*

**---------------------------------------------------------------------------

*/

#include "headers.h"

const uint16 zigzagScan[64] =

{

  0,1,8,16,9,2,3,10,17,24,32,25,18,11,4,5,

  12,19,26,33,40,48,41,34,27,20,13,6,7,14,21,28,

  35,42,49,56,57,50,43,36,29,22,15,23,30,37,44,51,

  58,59,52,45,38,31,39,46,53,60,61,54,47,55,62,63

};

/*---------------------------------------------------------------------------

*

*  Function: codePictureHeader

*

*  Input:    pic = pointer to picture information structure

*

*  Return:   none

*

*  Purpose:  To encode H.263 picture header

*

**---------------------------------------------------------------------------

*/

void codePictureHeader( const PictureType * const pic, BitStreamType * const stream ){

  /* Picture start code */

  bitstreamPut(22,0x20,stream);

  /* Temporal reference */

  bitstreamPut(8,pic->TR,stream);

  /* PTYPE */

  /* bit 1 always 1 to avoid start code emulation:              1 */

  /* bit 2 always zero for distinction with H.261:              0 */

  /* bit 3 no support for split-screen in this software:        0 */

  /* bit 4 document_camera indicator:                           0 */

  /* bit 5 freeze_picture_release:                              0 */

  /* bit 6-8 QCIF source format:                            0b010 */

  /* bit 9 Picture coding type is INTRA always:                 0 */

  /* bit 10 no support for Unrestricted Motion Vector mode:     0 */

  /* bit 11 no support for Syntax-based Arithmetic Coding mode: 0 */

  /* bit 12 no support for Advanced Prediction mode:            0 */

  /* bit 13 no support for PB-mode:                             0 */

  bitstreamPut(13,0x1040,stream);

  /* PQUANT */

  bitstreamPut(5,pic->QUANT,stream);

  /* Continuous Presence Multipoint (CPM) */

  bitstreamPut(1,0,stream);  /* CPM is not supported  */

  /* Picture Sub Bitstream Indicator (PSBI) */

  /* not needed */

  /* TRB and DBQUANT: extra information for PB-frames */

  /* PB not needed */

  /* PEI (extra information) */

  /* "Encoders shall not insert PSPARE until specified by the ITU" */

  bitstreamPut(1,0,stream);

  /* PSPARE */

  /* not supported */

}

/*---------------------------------------------------------------------------

*

*  Function: codeLastRunLevel

*

*  Input:    last = indication, if this is the last coefficient to be coded

*            run = number of zeros after previously coded coefficient

*            level = absolute value of coefficient to be coded

*

*  Return:   none

*

*  Purpose:  Uses H.263 escape coding or standard given codes to encode

*            given data

*

**---------------------------------------------------------------------------

*/

static void codeLastRunLevel( const sint32 last,

                              const sint32 run,

                              const sint32 level,

                              BitStreamType * const stream ) {

  sint32 sign = 0;

  if( level < 0 ){

    sign = 1;

  }

  /* Is escape coding necessary?   */

  if( vlcCodeCoefficient(last,run,abs(level),sign,stream) == V_FALSE ) {

    /* 7-bit H.263 escape code */

    bitstreamPut(7,3,stream);

    /* 1-bit last coefficient indication  */

    bitstreamPut(1,last,stream);

    /* 6-bit run count */

    bitstreamPut(6,run,stream);

    /* 8-bit level */

    bitstreamPut(8,(level & 0xff),stream);

    /* printf("Last %4i Run %4i Level %4i\n",last,run,level); */

  }

}

/*---------------------------------------------------------------------------

*

*  Function: codeIntraBlocks

*

*  Input:    MB = pointer to macroblock data

*            stream = encoding parameters and buffers

*

*  Return:   none

*

*  Purpose:  Encodes all six 8 x 8 blocks belonging to the macroblock

*            with last, run, level coding. Intra macroblocks will

*            always include the DC coefficient.

*

**---------------------------------------------------------------------------

*/

void codeIntraBlocks(const MBType * const MB,

                    BitStreamType * const stream){

  sint16 value;

  sint32 index;

  sint32 run;

  sint32 block;

  sint32 previous_run;

  sint32 level;

  sint32 mask = 32;

  const sint16 * coeffs;

  /* Loop through all 8 x 8 blocks  */

  for( block = 0; block < 6; block++ ) {

    coeffs = MB->data + block*64;

    /* DC coefficient */

    if( coeffs[0] == 128 )

      bitstreamPut(8,255,stream);

    else

      bitstreamPut(8,coeffs[0],stream);

    /* AC coefficients */

    /* Last, run, level scanning part  */

    if( ( MB->cbp & mask ) != 0 ) {

      /* Init the scanning system  */

      index = 1;

      run = 0;

      previous_run = 0;

      level = 0;

      /* Pre-scan because of LAST must be known  */

      while( index < 64 ) {

        /* Notice how zigzag scan is taken in the account */

        value = coeffs[ zigzagScan[index++] ];

        if( value != 0 ) {

          level = value;

          previous_run = run;

          run = 0;

          break;

        }

        run++;

      }

      /* Scan possible remaining coefficients  */

      while( index < 64 ) {

        value = coeffs[ zigzagScan[index++] ];

        if( value != 0 ) {

          codeLastRunLevel(0,previous_run,level,stream);

          level = value;

          previous_run = run;

          run = 0;

        }

        else {

          run++;

        }

      }

      /* Put the last coefficient into the bitstream  */

      codeLastRunLevel(1,previous_run,level,stream);

    }

     /* Move to next block */

      mask = mask >> 1;

  }

}

/*---------------------------------------------------------------------------

*

*  Function: codeIntraMB

*

*  Input:    MB = pointer to macroblock data

*            stream = encoding parameters and buffers

*

*  Return:   none

*

*  Purpose:  To manage VLC encoding of Intra macroblocks (headers + blocks)

*

**---------------------------------------------------------------------------

*/

void codeIntraMB(const MBType * const MB, BitStreamType * const stream){

  sint32 bitCount;

  sint32 bitPattern;

  sint32 chromaCbp;

  sint32 lumaCbp;

  /* COD, MODB, CBPB, DQUANT, MVD, MVD(2-4) and MVDB not needed */

  /* CBPCM */

  chromaCbp = MB->cbp & 3;

  bitCount = mcbpcIntraTable[0][chromaCbp].bitCount;

  bitPattern = mcbpcIntraTable[0][chromaCbp].bitPattern;

  bitstreamPut(bitCount,bitPattern,stream);

  /* CBPY */

  lumaCbp = MB->cbp >> 2;

  bitCount = cbpyTable[lumaCbp].bitCount;

  bitPattern = cbpyTable[lumaCbp].bitPattern;

  bitstreamPut(bitCount,bitPattern,stream);

  /* Block layer encoding */

  codeIntraBlocks(MB,stream);

}