vlc.c

This program can encode the YUV vdieo format to H.264 and decode it.

    return -1;

  // make infoword
  inf = 0;                          // shortest possible code is 1, then info is always 0    

  while (len--)
  {
    bitcounter++;
    bitoffset --;
    bitoffset &= 0x07;
    cur_byte  += (bitoffset == 7);
    inf <<= 1;
    inf |= ((*cur_byte)>> (bitoffset)) & 0x01;
  }

  *info = inf;
  return bitcounter;           // return absolute offset in bit from start of frame
}


/*!
 ************************************************************************
 * \brief
 *    test if bit buffer contains only stop bit
 *
 * \param buffer
 *    buffer containing VLC-coded data bits
 * \param totbitoffset
 *    bit offset from start of partition
 * \param bytecount
 *    buffer length
 * \return
 *    true if more bits available
 ************************************************************************
 */
int more_rbsp_data (byte buffer[],int totbitoffset,int bytecount)
{
  int bitoffset   = (7 - (totbitoffset & 0x07));      // bit from start of byte
  long byteoffset = (totbitoffset >> 3);      // byte from start of buffer
  byte *cur_byte  = &(buffer[byteoffset]);
  int ctr_bit     = 0;      // control bit for current bit posision
  int cnt         = 0;

  assert (byteoffset<bytecount);

  // there is more until we're in the last byte
  if (byteoffset < (bytecount - 1)) return TRUE;

  // read one bit
  ctr_bit = ((*cur_byte)>> (bitoffset--)) & 0x01;

  // a stop bit has to be one
  if (ctr_bit==0) return TRUE;  

  while (bitoffset>=0 && !cnt)
  {
    cnt |= ((*cur_byte)>> (bitoffset--)) & 0x01;   // set up control bit
  }

  return (cnt);
}


/*!
 ************************************************************************
 * \brief
 *    Check if there are symbols for the next MB
 ************************************************************************
 */
int uvlc_startcode_follows(struct img_par *img, int dummy)
{
  int dp_Nr = assignSE2partition[img->currentSlice->dp_mode][SE_MBTYPE];
  DataPartition *dP = &(img->currentSlice->partArr[dp_Nr]);
  Bitstream   *currStream = dP->bitstream;
  byte *buf  = currStream->streamBuffer;

  //KS: new function test for End of Buffer
  return (!(more_rbsp_data(buf, currStream->frame_bitoffset,currStream->bitstream_length)));
}



/*!
 ************************************************************************
 * \brief
 *  read one exp-golomb VLC symbol
 *
 * \param buffer
 *    containing VLC-coded data bits
 * \param totbitoffset
 *    bit offset from start of partition
 * \param  info
 *    returns the value of the symbol
 * \param bytecount
 *    buffer length
 * \return
 *    bits read
 ************************************************************************
 */
int GetVLCSymbol (byte buffer[],int totbitoffset,int *info, int bytecount)
{

  register int inf;
  long byteoffset = (totbitoffset >> 3);         // byte from start of buffer
  int  bitoffset  = (7 - (totbitoffset & 0x07)); // bit from start of byte
  int  bitcounter = 1;
  int  len        = 0;
  byte *cur_byte = &(buffer[byteoffset]);
  int  ctr_bit    = ((*cur_byte) >> (bitoffset)) & 0x01;  // control bit for current bit posision

  while (ctr_bit == 0)
  {                 // find leading 1 bit
    len++;
    bitcounter++;
    bitoffset--;
    bitoffset &= 0x07;
    cur_byte  += (bitoffset == 7);
    byteoffset+= (bitoffset == 7);      
    ctr_bit    = ((*cur_byte) >> (bitoffset)) & 0x01;
  }

  if (byteoffset + ((len + 7) >> 3) > bytecount)
    return -1;

  // make infoword
  inf = 0;                          // shortest possible code is 1, then info is always 0    

  while (len--)
  {
    bitoffset --;    
    bitoffset &= 0x07;
    cur_byte  += (bitoffset == 7);
    bitcounter++;
    inf <<= 1;    
    inf |= ((*cur_byte) >> (bitoffset)) & 0x01;
  }

  *info = inf;
  return bitcounter;           // return absolute offset in bit from start of frame
}

extern void tracebits2(const char *trace_str,  int len,  int info) ;

/*!
 ************************************************************************
 * \brief
 *    code from bitstream (2d tables)
 ************************************************************************
 */

int code_from_bitstream_2d(SyntaxElement *sym,
                           Bitstream *currStream,
                           const int *lentab,
                           const int *codtab,
                           int tabwidth,
                           int tabheight,
                           int *code)
{
  int frame_bitoffset        = currStream->frame_bitoffset;
  int BitstreamLengthInBytes = currStream->bitstream_length - (frame_bitoffset >> 3);
  byte *buf                  = &currStream->streamBuffer[frame_bitoffset>>3];
  int current_bit_pos        = 7 - (frame_bitoffset & 0x07);

  int i, j;
  const int *len = &lentab[0], *cod = &codtab[0];

  // this VLC decoding method is not optimized for speed
  for (j = 0; j < tabheight; j++) 
  {
    for (i = 0; i < tabwidth; i++)
    {
      //if ((*len == 0) || (ShowBits(buf, frame_bitoffset, BitstreamLengthInBytes, *len) != *cod))
      if ((*len == 0) || (ShowBitsThres(buf, current_bit_pos, BitstreamLengthInBytes, *len, *cod) != *cod))
      {
        len++;
        cod++;
      }
      else
      {
        sym->value1 = i;
        sym->value2 = j;        
        sym->len = *len;
        currStream->frame_bitoffset += *len; // move bitstream pointer
        *code = *cod;                        // found code and return
        return 0;
      }
    }
  }
  return -1;  // failed to find code
}


/*!
 ************************************************************************
 * \brief
 *    read FLC codeword from UVLC-partition
 ************************************************************************
 */
int readSyntaxElement_FLC(SyntaxElement *sym, Bitstream *currStream)
{
  int frame_bitoffset        = currStream->frame_bitoffset;
  int BitstreamLengthInBytes = currStream->bitstream_length;
  byte *buf                  = currStream->streamBuffer;

  if ((GetBits(buf, frame_bitoffset, &(sym->inf), BitstreamLengthInBytes, sym->len)) < 0)
    return -1;

  sym->value1 = sym->inf;
  currStream->frame_bitoffset += sym->len; // move bitstream pointer

#if TRACE
  tracebits2(sym->tracestring, sym->len, sym->inf);
#endif

  return 1;
}



/*!
 ************************************************************************
 * \brief
 *    read NumCoeff/TrailingOnes codeword from UVLC-partition
 ************************************************************************
 */

int readSyntaxElement_NumCoeffTrailingOnes(SyntaxElement *sym,  
                                           Bitstream *currStream,
                                           char *type)
{
  int frame_bitoffset        = currStream->frame_bitoffset;
  int BitstreamLengthInBytes = currStream->bitstream_length;
  byte *buf                  = currStream->streamBuffer;

  static const int lentab[3][4][17] =
  {
    {   // 0702
      { 1, 6, 8, 9,10,11,13,13,13,14,14,15,15,16,16,16,16},
      { 0, 2, 6, 8, 9,10,11,13,13,14,14,15,15,15,16,16,16},
      { 0, 0, 3, 7, 8, 9,10,11,13,13,14,14,15,15,16,16,16},
      { 0, 0, 0, 5, 6, 7, 8, 9,10,11,13,14,14,15,15,16,16},
    },
    {
      { 2, 6, 6, 7, 8, 8, 9,11,11,12,12,12,13,13,13,14,14},
      { 0, 2, 5, 6, 6, 7, 8, 9,11,11,12,12,13,13,14,14,14},
      { 0, 0, 3, 6, 6, 7, 8, 9,11,11,12,12,13,13,13,14,14},
      { 0, 0, 0, 4, 4, 5, 6, 6, 7, 9,11,11,12,13,13,13,14},
    },
    {
      { 4, 6, 6, 6, 7, 7, 7, 7, 8, 8, 9, 9, 9,10,10,10,10},
      { 0, 4, 5, 5, 5, 5, 6, 6, 7, 8, 8, 9, 9, 9,10,10,10},
      { 0, 0, 4, 5, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9,10,10,10},
      { 0, 0, 0, 4, 4, 4, 4, 4, 5, 6, 7, 8, 8, 9,10,10,10},
    },
  };

  static const int codtab[3][4][17] =
  {
    {
      { 1, 5, 7, 7, 7, 7,15,11, 8,15,11,15,11,15,11, 7,4},
      { 0, 1, 4, 6, 6, 6, 6,14,10,14,10,14,10, 1,14,10,6},
      { 0, 0, 1, 5, 5, 5, 5, 5,13, 9,13, 9,13, 9,13, 9,5},
      { 0, 0, 0, 3, 3, 4, 4, 4, 4, 4,12,12, 8,12, 8,12,8},
    },
    {
      { 3,11, 7, 7, 7, 4, 7,15,11,15,11, 8,15,11, 7, 9,7},
      { 0, 2, 7,10, 6, 6, 6, 6,14,10,14,10,14,10,11, 8,6},
      { 0, 0, 3, 9, 5, 5, 5, 5,13, 9,13, 9,13, 9, 6,10,5},
      { 0, 0, 0, 5, 4, 6, 8, 4, 4, 4,12, 8,12,12, 8, 1,4},
    },
    {
      {15,15,11, 8,15,11, 9, 8,15,11,15,11, 8,13, 9, 5,1},
      { 0,14,15,12,10, 8,14,10,14,14,10,14,10, 7,12, 8,4},
      { 0, 0,13,14,11, 9,13, 9,13,10,13, 9,13, 9,11, 7,3},
      { 0, 0, 0,12,11,10, 9, 8,13,12,12,12, 8,12,10, 6,2},
    },
  };

  int retval = 0, code;
  int vlcnum = sym->value1;
  // vlcnum is the index of Table used to code coeff_token
  // vlcnum==3 means (8<=nC) which uses 6bit FLC

  if (vlcnum == 3)
  {
    // read 6 bit FLC
    code = ShowBits(buf, frame_bitoffset, BitstreamLengthInBytes, 6);
    currStream->frame_bitoffset += 6;
    sym->value2 = (code & 3);
    sym->value1 = (code >> 2);

    if (!sym->value1 && sym->value2 == 3)
    {
      // #c = 0, #t1 = 3 =>  #c = 0
      sym->value2 = 0;
    }
    else
      sym->value1++;

    sym->len = 6;
  }
  else
  {
    //retval = code_from_bitstream_2d(sym, currStream, &lentab[vlcnum][0][0], &codtab[vlcnum][0][0], 17, 4, &code);    
    retval = code_from_bitstream_2d(sym, currStream, lentab[vlcnum][0], codtab[vlcnum][0], 17, 4, &code);
    if (retval)
    {
      printf("ERROR: failed to find NumCoeff/TrailingOnes\n");
      exit(-1);
    }
  }

#if TRACE
  snprintf(sym->tracestring,
    TRACESTRING_SIZE, "%s # c & tr.1s vlc=%d #c=%d #t1=%d",
           type, vlcnum, sym->value1, sym->value2);
  tracebits2(sym->tracestring, sym->len, code);
#endif

  return retval;
}


/*!
 ************************************************************************
 * \brief
 *    read NumCoeff/TrailingOnes codeword from UVLC-partition ChromaDC
 ************************************************************************
 */
int readSyntaxElement_NumCoeffTrailingOnesChromaDC(SyntaxElement *sym,  Bitstream *currStream)
{
  static const int lentab[3][4][17] =
  {
    //YUV420
   {{ 2, 6, 6, 6, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 1, 6, 7, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 3, 7, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 0, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
    //YUV422
   {{ 1, 7, 7, 9, 9,10,11,12,13, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 2, 7, 7, 9,10,11,12,12, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 3, 7, 7, 9,10,11,12, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 0, 5, 6, 7, 7,10,11, 0, 0, 0, 0, 0, 0, 0, 0}},
    //YUV444
   {{ 1, 6, 8, 9,10,11,13,13,13,14,14,15,15,16,16,16,16},
    { 0, 2, 6, 8, 9,10,11,13,13,14,14,15,15,15,16,16,16},
    { 0, 0, 3, 7, 8, 9,10,11,13,13,14,14,15,15,16,16,16},
    { 0, 0, 0, 5, 6, 7, 8, 9,10,11,13,14,14,15,15,16,16}}
  };

  static const int codtab[3][4][17] =
  {
    //YUV420
   {{ 1, 7, 4, 3, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 1, 6, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 1, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
    //YUV422
   {{ 1,15,14, 7, 6, 7, 7, 7, 7, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 1,13,12, 5, 6, 6, 6, 5, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 1,11,10, 4, 5, 5, 4, 0, 0, 0, 0, 0, 0, 0, 0},
    { 0, 0, 0, 1, 1, 9, 8, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0}},
    //YUV444
   {{ 1, 5, 7, 7, 7, 7,15,11, 8,15,11,15,11,15,11, 7, 4},
    { 0, 1, 4, 6, 6, 6, 6,14,10,14,10,14,10, 1,14,10, 6},
    { 0, 0, 1, 5, 5, 5, 5, 5,13, 9,13, 9,13, 9,13, 9, 5},
    { 0, 0, 0, 3, 3, 4, 4, 4, 4, 4,12,12, 8,12, 8,12, 8}}

  };
   
  int code;
  int yuv = active_sps->chroma_format_idc - 1;
  int retval = code_from_bitstream_2d(sym, currStream, &lentab[yuv][0][0], &codtab[yuv][0][0], 17, 4, &code);

  if (retval)
  {
    printf("ERROR: failed to find NumCoeff/TrailingOnes ChromaDC\n");
    exit(-1);
  }

#if TRACE
    snprintf(sym->tracestring,
      TRACESTRING_SIZE, "ChrDC # c & tr.1s  #c=%d #t1=%d",
              sym->value1, sym->value2);
    tracebits2(sym->tracestring, sym->len, code);

#endif

  return retval;
}




/*!
 ************************************************************************
 * \brief
 *    read Level VLC0 codeword from UVLC-partition
 ************************************************************************
 */
int readSyntaxElement_Level_VLC0(SyntaxElement *sym, Bitstream *currStream)
{
  int frame_bitoffset        = currStream->frame_bitoffset;
  int BitstreamLengthInBytes = currStream->bitstream_length;
  byte *buf                  = currStream->streamBuffer;
  int len = 0, sign=0, level=0, code = 1;
  int offset, addbit;

  while (!ShowBits(buf, frame_bitoffset+len, BitstreamLengthInBytes, 1))
    len++;

  len++;
  frame_bitoffset += len;

  if (len < 15)
  {
    sign  = (len - 1) & 1;
    level = ((len - 1) >> 1) + 1;
  }
  else if (len == 15)
  {
    // escape code
    code <<= 4;
    code |= ShowBits(buf, frame_bitoffset, BitstreamLengthInBytes, 4);
    len  += 4;
    frame_bitoffset += 4;
    sign = (code & 0x01);
    level = ((code >> 1) & 0x07) + 8;
  }
  else if (len >= 16)
  {
    // escape code
    addbit = (len - 16);
    len   -= 4;
    code   = ShowBits(buf, frame_bitoffset, BitstreamLengthInBytes, len);
    sign   =  (code & 0x01);
    frame_bitoffset += len;    

    offset=(2048<<addbit) - 2032;
    level = (code >> 1) + offset;
    code |= (1 << (len)); // for display purpose only
    len += addbit + 16;
 }

  sym->inf = (sign) ? -level : level ;
  sym->len = len;

#if TRACE
  tracebits2(sym->tracestring, sym->len, code);
#endif
  currStream->frame_bitoffset = frame_bitoffset;
  return 0;

}

/*!
 ************************************************************************
 * \brief
 *    read Level VLC codeword from UVLC-partition
 ************************************************************************
 */
int readSyntaxElement_Level_VLCN(SyntaxElement *sym, int vlc, Bitstream *currStream)
{