/*---------------------------------------------------------------------------
 *
 *  Course:   Systems Design II
  *
 *  Module:   vlc.c
 *
 *  Purpose:  To encapsulate VLC coding tables for H.263 encoder
 *
 *  Notes:    Module required for slave CPUs. Codewords are taken from
 *            Telenor's H.263 encoder implementation.
 *
 *  Author:   Olli Lehtoranta and Tero Kangas
 *
 *  History:  23/09/2002: + Original version commented and ready
 *            31/10/2002: + TK: modified for Digital Systems Design II course
 **---------------------------------------------------------------------------
 */

#include "headers.h"


/*
* Intra picture coded block pattern for chrominance and macroblock mode
*
* Table element format = { Bit pattern value, codeword length }
*
* indexing with [mode][chroma block pattern]
*  mode 0 = INTRA
*  mode 1 = INTRA_Q
*
*/
const structVLC mcbpcIntraTable[2][4] =
{
   { {1,1},{1,3},{2,3},{3,3} },
   { {1,4},{1,6},{2,6},{6,6} }
};


/*
*
* Luminance block pattern table for Intra/Inter pictures
*
*/
const structVLC cbpyTable[16] =
{
   {3,4}, {5,5}, {4,5}, {9,4}, {3,5}, {7,4}, {2,6}, {11,4},
   {2,5}, {3,6}, {5,4}, {10,4}, {4,4}, {8,4}, {6,4}, {3,2}
};

/* First index is the run length, second is level-1.
   Zero bit length in the value means that there is no code for the combination. */
static const structVLC vlcCodes_notlast[41][12] = {
  /* run = 0 */
  {{0x02, 2}, {0x0f, 4}, {0x15, 6}, {0x17, 7}, {0x1f, 8}, {0x25, 9}, {0x24, 9}, {0x21,10}, {0x20,10}, {0x07,11}, {0x06,11}, {0x20,11}},
  /* run = 1 */
  {{0x06, 3}, {0x14, 6}, {0x1e, 8}, {0x0f,10}, {0x21,11}, {0x50,12}},
  /* run = 2 */
  {{0x0e, 4}, {0x1d, 8}, {0x0e,10}, {0x51,12}},
  /* run = 3 */
  {{0x0d, 5}, {0x23, 9}, {0x0d,10}},
  /* run = 4 */
  {{0x0c, 5}, {0x22, 9}, {0x52,12}},
  /* run = 5 */
  {{0x0b, 5}, {0x0c,10}, {0x53,12}},
  /* run = 6 */
  {{0x13, 6}, {0x0b,10}, {0x54,12}},
  /* run = 7 */
  {{0x12, 6}, {0x0a,10}},
  /* run = 8 */
  {{0x11, 6}, {0x09,10}},
  /* run = 9 */
  {{0x10, 6}, {0x08,10}},
  /* run = 10 */
  {{0x16, 7}, {0x55,12}},
  /* run = 11 */
  {{0x15, 7}},
  /* run = 12 */
  {{0x14, 7}},
  /* run = 13 */
  {{0x1c, 8}},
  /* run = 14 */
  {{0x1b, 8}},
  /* run = 15 */
  {{0x21, 9}},
  /* run = 16 */
  {{0x20, 9}},
  /* run = 17 */
  {{0x1f, 9}},
  /* run = 18 */
  {{0x1e, 9}},
  /* run = 19 */
  {{0x1d, 9}},
  /* run = 20 */
  {{0x1c, 9}},
  /* run = 21 */
  {{0x1b, 9}},
  /* run = 22 */
  {{0x1a, 9}},
  /* run = 23 */
  {{0x22,11}},
  /* run = 24 */
  {{0x23,11}},
  /* run = 25 */
  {{0x56,12}},
  /* run = 26 */
  {{0x57,12}}
};

static const structVLC vlcCodes_last[41][12] = {
  /* run = 0 */
  {{0x07, 4}, {0x19, 9}, {0x05,11}},
  /* run = 1 */
  {{0x0f, 6}, {0x04,11}},
  /* run = 2..40, level = 1 */
  {{0x0e, 6}}, {{0x0d, 6}}, {{0x0c, 6}},
  {{0x13, 7}}, {{0x12, 7}}, {{0x11, 7}}, {{0x10, 7}},
  {{0x1a, 8}}, {{0x19, 8}}, {{0x18, 8}}, {{0x17, 8}},
  {{0x16, 8}}, {{0x15, 8}}, {{0x14, 8}}, {{0x13, 8}},
  {{0x18, 9}}, {{0x17, 9}}, {{0x16, 9}}, {{0x15, 9}},
  {{0x14, 9}}, {{0x13, 9}}, {{0x12, 9}}, {{0x11, 9}},
  {{0x07,10}}, {{0x06,10}}, {{0x05,10}}, {{0x04,10}},
  {{0x24,11}}, {{0x25,11}}, {{0x26,11}}, {{0x27,11}},
  {{0x58,12}}, {{0x59,12}}, {{0x5a,12}}, {{0x5b,12}},
  {{0x5c,12}}, {{0x5d,12}}, {{0x5e,12}}, {{0x5f,12}}
};

/*---------------------------------------------------------------------------
*
*  Function: vlcCodeCoefficient
*
*  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
*            sign = positive / negative indication
*            stream = target bit buffer
*
*  Return:   V_TRUE if LAST,RUN,LEVEL combination can be encoded with
*            help of standard specified codes (optimal)
*
*  Purpose:  To provide look-up table based encoding for LAST,RUN,LEVEL
*            information
*
**---------------------------------------------------------------------------
*/
vbool vlcCodeCoefficient( const sint32 last,
                          const sint32 run,
                          const sint32 level,
                          const sint32 sign,
                          BitStreamType * const stream )
{
   sint32 value;
   sint32 bitCount;

  if (run > 40 || level > 12)
  {
    return V_FALSE;  
  }
  
  structVLC code;
  if (!last)
  {
    code = vlcCodes_notlast[run][level - 1];
  } else {
    code = vlcCodes_last[run][level - 1];
  }
  
  if (code.bitCount == 0)
  {
    return V_FALSE;
  }
  
  bitCount = code.bitCount + 1;
  value = (( code.bitPattern << 1 ) | sign);
  bitstreamPut(bitCount,value,stream);
  return V_TRUE;
}