| -rw-r--r-- | core/applets/vmemo/adpcm.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/core/applets/vmemo/adpcm.c b/core/applets/vmemo/adpcm.c index c4dfa50..a123249 100644 --- a/core/applets/vmemo/adpcm.c +++ b/core/applets/vmemo/adpcm.c @@ -41,98 +41,98 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. ** (because the div/mul simulation using shift/add/sub made some rounding ** errors that real div/mul don't make) and all together the resultant code ** ran slower than just using the shifts all the time. ** - Changed some of the variable names to be more meaningful. */ #include "adpcm.h" #include <stdio.h> /*DBG*/ #ifndef __STDC__ #define signed #endif /* Intel ADPCM step variation table */ static int indexTable[16] = { -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8, }; static int stepsizeTable[89] = { 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45, 50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230, 253, 279, 307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899, 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767 }; void adpcm_coder(indata, outdata, len, state) short indata[]; char outdata[]; int len; struct adpcm_state *state; { short *inp; /* Input buffer pointer */ signed char *outp; /* output buffer pointer */ int val; /* Current input sample value */ int sign; /* Current adpcm sign bit */ int delta; /* Current adpcm output value */ int diff; /* Difference between val and valprev */ int step; /* Stepsize */ int valpred; /* Predicted output value */ int vpdiff; /* Current change to valpred */ int index; /* Current step change index */ - int outputbuffer; /* place to keep previous 4-bit value */ - int bufferstep; /* toggle between outputbuffer/output */ + int outputbuffer = 0; /* place to keep previous 4-bit value */ + int bufferstep = 0; /* toggle between outputbuffer/output */ outp = (signed char *)outdata; inp = indata; valpred = state->valprev; index = state->index; step = stepsizeTable[index]; bufferstep = 1; for ( ; len > 0 ; len-- ) { val = *inp++; /* Step 1 - compute difference with previous value */ diff = val - valpred; sign = (diff < 0) ? 8 : 0; if ( sign ) diff = (-diff); /* Step 2 - Divide and clamp */ /* Note: ** This code *approximately* computes: ** delta = diff*4/step; ** vpdiff = (delta+0.5)*step/4; ** but in shift step bits are dropped. The net result of this is ** that even if you have fast mul/div hardware you cannot put it to ** good use since the fixup would be too expensive. */ delta = 0; vpdiff = (step >> 3); if ( diff >= step ) { delta = 4; diff -= step; vpdiff += step; } step >>= 1; if ( diff >= step ) { delta |= 2; diff -= step; vpdiff += step; } step >>= 1; if ( diff >= step ) { delta |= 1; vpdiff += step; } /* Step 3 - Update previous value */ @@ -142,98 +142,98 @@ adpcm_coder(indata, outdata, len, state) valpred += vpdiff; /* Step 4 - Clamp previous value to 16 bits */ if ( valpred > 32767 ) valpred = 32767; else if ( valpred < -32768 ) valpred = -32768; /* Step 5 - Assemble value, update index and step values */ delta |= sign; index += indexTable[delta]; if ( index < 0 ) index = 0; if ( index > 88 ) index = 88; step = stepsizeTable[index]; /* Step 6 - Output value */ if ( bufferstep ) { outputbuffer = (delta << 4) & 0xf0; } else { *outp++ = (delta & 0x0f) | outputbuffer; } bufferstep = !bufferstep; } /* Output last step, if needed */ if ( !bufferstep ) *outp++ = outputbuffer; state->valprev = valpred; state->index = index; } void adpcm_decoder(indata, outdata, len, state) char indata[]; short outdata[]; int len; struct adpcm_state *state; { signed char *inp; /* Input buffer pointer */ short *outp; /* output buffer pointer */ int sign; /* Current adpcm sign bit */ int delta; /* Current adpcm output value */ int step; /* Stepsize */ int valpred; /* Predicted value */ int vpdiff; /* Current change to valpred */ int index; /* Current step change index */ - int inputbuffer; /* place to keep next 4-bit value */ - int bufferstep; /* toggle between inputbuffer/input */ + int inputbuffer = 0; /* place to keep next 4-bit value */ + int bufferstep = 0; /* toggle between inputbuffer/input */ outp = outdata; inp = (signed char *)indata; valpred = state->valprev; index = state->index; step = stepsizeTable[index]; bufferstep = 0; for ( ; len > 0 ; len-- ) { /* Step 1 - get the delta value */ if ( bufferstep ) { delta = inputbuffer & 0xf; } else { inputbuffer = *inp++; delta = (inputbuffer >> 4) & 0xf; } bufferstep = !bufferstep; /* Step 2 - Find new index value (for later) */ index += indexTable[delta]; if ( index < 0 ) index = 0; if ( index > 88 ) index = 88; /* Step 3 - Separate sign and magnitude */ sign = delta & 8; delta = delta & 7; /* Step 4 - Compute difference and new predicted value */ /* ** Computes 'vpdiff = (delta+0.5)*step/4', but see comment ** in adpcm_coder. */ vpdiff = step >> 3; if ( delta & 4 ) vpdiff += step; if ( delta & 2 ) vpdiff += step>>1; if ( delta & 1 ) vpdiff += step>>2; if ( sign ) valpred -= vpdiff; else valpred += vpdiff; /* Step 5 - clamp output value */ if ( valpred > 32767 ) valpred = 32767; |