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Diffstat (limited to 'libaudiofile/modules/adpcm.c')
| -rw-r--r-- | libaudiofile/modules/adpcm.c | 248 |
1 files changed, 248 insertions, 0 deletions
diff --git a/libaudiofile/modules/adpcm.c b/libaudiofile/modules/adpcm.c new file mode 100644 index 0000000..9ca7305 --- /dev/null +++ b/libaudiofile/modules/adpcm.c @@ -0,0 +1,248 @@ +/*********************************************************** +Copyright 1992 by Stichting Mathematisch Centrum, Amsterdam, The +Netherlands. + + All Rights Reserved + +Permission to use, copy, modify, and distribute this software and its +documentation for any purpose and without fee is hereby granted, +provided that the above copyright notice appear in all copies and that +both that copyright notice and this permission notice appear in +supporting documentation, and that the names of Stichting Mathematisch +Centrum or CWI not be used in advertising or publicity pertaining to +distribution of the software without specific, written prior permission. + +STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO +THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND +FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE +FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES +WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN +ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT +OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + +******************************************************************/ + +/* +** Intel/DVI ADPCM coder/decoder. +** +** The algorithm for this coder was taken from the IMA Compatability Project +** proceedings, Vol 2, Number 2; May 1992. +** +** Version 1.2, 18-Dec-92. +** +** Change log: +** - Fixed a stupid bug, where the delta was computed as +** stepsize*code/4 in stead of stepsize*(code+0.5)/4. +** - There was an off-by-one error causing it to pick +** an incorrect delta once in a blue moon. +** - The NODIVMUL define has been removed. Computations are now always done +** using shifts, adds and subtracts. It turned out that, because the standard +** is defined using shift/add/subtract, you needed bits of fixup code +** (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. +*/ + +#ifdef HAVE_CONFIG_H +#include <config.h> +#endif + +#include <sys/types.h> +#include <stdio.h> /*DBG*/ + +#include "adpcm.h" + +/* Intel ADPCM step variation table */ +static const int indexTable[16] = +{ + -1, -1, -1, -1, 2, 4, 6, 8, + -1, -1, -1, -1, 2, 4, 6, 8, +}; + +static const 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 _af_adpcm_coder (int16_t *indata, u_int8_t *outdata, int len, + struct adpcm_state *state) +{ + int16_t *inp; /* Input buffer pointer */ + u_int8_t *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 */ + + outp = 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 */ + if ( sign ) + valpred -= vpdiff; + else + 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 & 0x0f; + } else { + *outp++ = ((delta << 4) & 0xf0) | outputbuffer; + } + bufferstep = !bufferstep; + } + + /* Output last step, if needed */ + if ( !bufferstep ) + *outp++ = outputbuffer; + + state->valprev = valpred; + state->index = index; +} + +void _af_adpcm_decoder (u_int8_t *indata, int16_t *outdata, int len, + struct adpcm_state *state) +{ + u_int8_t *inp; /* Input buffer pointer */ + int16_t *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 */ + + outp = outdata; + inp = 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 >> 4) & 0xf; + } else { + inputbuffer = *inp++; + delta = inputbuffer & 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; + else if ( valpred < -32768 ) + valpred = -32768; + + /* Step 6 - Update step value */ + step = stepsizeTable[index]; + + /* Step 7 - Output value */ + *outp++ = valpred; + } + + state->valprev = valpred; + state->index = index; +} |