WDL/adpcm_encode.h

   1 #ifndef _WDL_ADPCM_ENCODE_H_
   2 #define _WDL_ADPCM_ENCODE_H_
   3
   4
   5 #include "pcmfmtcvt.h"
   6
   7 void WDL_adpcm_encode_IMA(PCMFMTCVT_DBL_TYPE *samples, int numsamples, int nch, int bps,
   8                           unsigned char *bufout, int *bufout_used, short **predState);
   9
  10 #define WDL_adpcm_encode_IMA_samplesneededbytes(bytes,bps) ((((bytes)-4)*8)/(bps)+1)
  11
  12
  13 // untested. also probably slow.
  14 #ifdef WDL_ADPCM_ENCODE_IMPL
  15
  16
  17 static signed char ima_adpcm_index_table[8] = { -1, -1, -1, -1, 2, 4, 6, 8, };
  18 static short ima_adpcm_step_table[89] = {
  19   7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
  20   19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
  21   50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
  22   130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
  23   337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
  24   876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
  25   2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
  26   5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
  27   15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
  28 };
  29
  30 static char calcBestNibble(int *initial_step_index, int lastSpl, int thisSpl, short *lastsplout, int bps)
  31 {
  32
  33   int step=ima_adpcm_step_table[*initial_step_index];
  34
  35   char sign=0;
  36   int adiff = thisSpl - lastSpl;
  37   if (adiff<0) { adiff=-adiff; sign=8; }
  38
  39   // adiff == (nib*step)/4 + step/8
  40   // adiff - step/8 = nib*step/4
  41   // nib = 4*(adiff-step/8)/step = 4*adiff/step - 0.5
  42   int nib =  step ? ((4 * adiff - step/2) / step) : 0;
  43   if (nib<0) nib=0;
  44   else if(nib>7) nib=7;
  45
  46   if (bps==2) nib&=4;
  47
  48   int diff = (nib*step)/4 + step/8;
  49   *lastsplout = lastSpl + (sign?-diff:diff);
  50
  51
  52   *initial_step_index += ima_adpcm_index_table[nib];
  53
  54   if (*initial_step_index<0)*initial_step_index=0;
  55   else if (*initial_step_index>88)*initial_step_index=88;
  56
  57   return (char)nib|sign;
  58 }
  59
  60
  61
  62 void WDL_adpcm_encode_IMA(PCMFMTCVT_DBL_TYPE *samples, int numsamples, int nch, int bps,
  63                           unsigned char *bufout, int *bufout_used, short **predState)
  64 {
  65   int x;
  66   if (!*predState) *predState=(short *)calloc(nch,sizeof(short));
  67
  68   short *pstate = *predState;
  69   for(x=0;x<nch;x++)
  70   {
  71     int left=numsamples;
  72     PCMFMTCVT_DBL_TYPE *spl = samples+x;
  73     unsigned char *wrptr = bufout + x*4;
  74
  75     int step_index=pstate[x];
  76
  77     short last_out;
  78     double_TO_INT16(last_out,*spl);
  79     left--;
  80
  81     *wrptr++ = last_out&0xff; *wrptr++ = last_out>>8;
  82     spl+=nch;
  83
  84     *wrptr++ = step_index&0xff; *wrptr++ = step_index>>8;
  85
  86     wrptr += (nch-1)*4;
  87
  88
  89     int outpos=0;
  90     const int outblocklen = bps == 2 ? 16 : 8;
  91     unsigned char buildchar=0;
  92
  93     while (left-->0)
  94     {
  95       short this_spl;
  96       double_TO_INT16(this_spl,*spl);
  97       char nib = calcBestNibble(&step_index,last_out,this_spl,&last_out,bps);
  98
  99       spl+=nch;
 100
 101       // update output
 102       if (bps == 2)
 103       {
 104         nib>>=2;
 105         switch (outpos&3)
 106         {
 107           case 0: buildchar = nib; break;
 108           case 1: buildchar |= nib<<2; break;
 109           case 2: buildchar |= nib<<4; break;
 110           case 3: *wrptr++ = buildchar | (nib<<6);  break;
 111         }
 112       }
 113       else
 114       {
 115         if (!(outpos&1)) buildchar = nib;
 116         else *wrptr++ = buildchar | (nib<<4);
 117       }
 118
 119       // skip other channels
 120       if (++outpos == outblocklen)
 121       {
 122         wrptr += ((nch-1)*outblocklen*bps)/8;
 123         outpos=0;
 124       }
 125     }
 126     pstate[x] = step_index;
 127
 128   }
 129   *bufout_used = (((numsamples-1)*bps)/8 + 4)*nch;
 130
 131
 132 }
 133
 134 #endif
 135
 136
 137 #endif//_WDL_ADPCM_ENCODE_H_