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330 lines
8.6 KiB
C
330 lines
8.6 KiB
C
/***********************************************************
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Copyright 1992 by Stichting Mathematisch Centrum, Amsterdam, The
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Netherlands.
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and its
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documentation for any purpose and without fee is hereby granted,
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provided that the above copyright notice appear in all copies and that
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both that copyright notice and this permission notice appear in
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supporting documentation, and that the names of Stichting Mathematisch
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Centrum or CWI not be used in advertising or publicity pertaining to
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distribution of the software without specific, written prior permission.
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STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
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THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
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FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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******************************************************************/
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/*
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** Intel/DVI ADPCM coder/decoder.
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**
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** The algorithm for this coder was taken from the IMA Compatability Project
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** proceedings, Vol 2, Number 2; May 1992.
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**
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** Version 1.2, 18-Dec-92.
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*/
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#include "snd_local.h"
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/* Intel ADPCM step variation table */
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static int indexTable[16] = {
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-1, -1, -1, -1, 2, 4, 6, 8,
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-1, -1, -1, -1, 2, 4, 6, 8,
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};
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static int stepsizeTable[89] = {
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7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
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19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
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50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
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130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
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337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
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876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
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2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
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5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
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15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
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};
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void S_AdpcmEncode( short indata[], char outdata[], int len, struct adpcm_state *state ) {
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short *inp; /* Input buffer pointer */
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signed char *outp; /* output buffer pointer */
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int val; /* Current input sample value */
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int sign; /* Current adpcm sign bit */
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int delta; /* Current adpcm output value */
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int diff; /* Difference between val and sample */
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int step; /* Stepsize */
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int valpred; /* Predicted output value */
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int vpdiff; /* Current change to valpred */
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int index; /* Current step change index */
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int outputbuffer; /* place to keep previous 4-bit value */
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int bufferstep; /* toggle between outputbuffer/output */
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outp = (signed char *)outdata;
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inp = indata;
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valpred = state->sample;
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index = state->index;
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step = stepsizeTable[index];
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outputbuffer = 0; // quiet a compiler warning
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bufferstep = 1;
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for ( ; len > 0 ; len-- ) {
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val = *inp++;
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/* Step 1 - compute difference with previous value */
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diff = val - valpred;
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sign = (diff < 0) ? 8 : 0;
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if ( sign ) diff = (-diff);
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/* Step 2 - Divide and clamp */
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/* Note:
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** This code *approximately* computes:
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** delta = diff*4/step;
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** vpdiff = (delta+0.5)*step/4;
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** but in shift step bits are dropped. The net result of this is
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** that even if you have fast mul/div hardware you cannot put it to
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** good use since the fixup would be too expensive.
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*/
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delta = 0;
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vpdiff = (step >> 3);
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if ( diff >= step ) {
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delta = 4;
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diff -= step;
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vpdiff += step;
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}
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step >>= 1;
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if ( diff >= step ) {
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delta |= 2;
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diff -= step;
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vpdiff += step;
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}
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step >>= 1;
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if ( diff >= step ) {
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delta |= 1;
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vpdiff += step;
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}
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/* Step 3 - Update previous value */
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if ( sign )
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valpred -= vpdiff;
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else
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valpred += vpdiff;
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/* Step 4 - Clamp previous value to 16 bits */
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if ( valpred > 32767 )
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valpred = 32767;
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else if ( valpred < -32768 )
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valpred = -32768;
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/* Step 5 - Assemble value, update index and step values */
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delta |= sign;
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index += indexTable[delta];
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if ( index < 0 ) index = 0;
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if ( index > 88 ) index = 88;
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step = stepsizeTable[index];
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/* Step 6 - Output value */
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if ( bufferstep ) {
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outputbuffer = (delta << 4) & 0xf0;
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} else {
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*outp++ = (delta & 0x0f) | outputbuffer;
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}
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bufferstep = !bufferstep;
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}
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/* Output last step, if needed */
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if ( !bufferstep )
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*outp++ = outputbuffer;
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state->sample = valpred;
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state->index = index;
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}
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/* static */ void S_AdpcmDecode( const char indata[], short *outdata, int len, struct adpcm_state *state ) {
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signed char *inp; /* Input buffer pointer */
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int outp; /* output buffer pointer */
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int sign; /* Current adpcm sign bit */
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int delta; /* Current adpcm output value */
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int step; /* Stepsize */
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int valpred; /* Predicted value */
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int vpdiff; /* Current change to valpred */
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int index; /* Current step change index */
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int inputbuffer; /* place to keep next 4-bit value */
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int bufferstep; /* toggle between inputbuffer/input */
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outp = 0;
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inp = (signed char *)indata;
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valpred = state->sample;
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index = state->index;
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step = stepsizeTable[index];
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bufferstep = 0;
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inputbuffer = 0; // quiet a compiler warning
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for ( ; len > 0 ; len-- ) {
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/* Step 1 - get the delta value */
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if ( bufferstep ) {
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delta = inputbuffer & 0xf;
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} else {
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inputbuffer = *inp++;
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delta = (inputbuffer >> 4) & 0xf;
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}
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bufferstep = !bufferstep;
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/* Step 2 - Find new index value (for later) */
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index += indexTable[delta];
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if ( index < 0 ) index = 0;
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if ( index > 88 ) index = 88;
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/* Step 3 - Separate sign and magnitude */
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sign = delta & 8;
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delta = delta & 7;
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/* Step 4 - Compute difference and new predicted value */
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/*
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** Computes 'vpdiff = (delta+0.5)*step/4', but see comment
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** in adpcm_coder.
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*/
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vpdiff = step >> 3;
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if ( delta & 4 ) vpdiff += step;
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if ( delta & 2 ) vpdiff += step>>1;
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if ( delta & 1 ) vpdiff += step>>2;
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if ( sign )
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valpred -= vpdiff;
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else
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valpred += vpdiff;
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/* Step 5 - clamp output value */
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if ( valpred > 32767 )
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valpred = 32767;
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else if ( valpred < -32768 )
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valpred = -32768;
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/* Step 6 - Update step value */
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step = stepsizeTable[index];
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/* Step 7 - Output value */
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outdata[outp] = valpred;
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outp++;
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}
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state->sample = valpred;
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state->index = index;
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}
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/*
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====================
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S_AdpcmMemoryNeeded
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Returns the amount of memory (in bytes) needed to store the samples in out internal adpcm format
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====================
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*/
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int S_AdpcmMemoryNeeded( const wavinfo_t *info ) {
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float scale;
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int scaledSampleCount;
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int sampleMemory;
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int blockCount;
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int headerMemory;
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// determine scale to convert from input sampling rate to desired sampling rate
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scale = (float)info->rate / dma.speed;
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// calc number of samples at playback sampling rate
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scaledSampleCount = info->samples / scale;
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// calc memory need to store those samples using ADPCM at 4 bits per sample
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sampleMemory = scaledSampleCount / 2;
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// calc number of sample blocks needed of PAINTBUFFER_SIZE
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blockCount = scaledSampleCount / PAINTBUFFER_SIZE;
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if( scaledSampleCount % PAINTBUFFER_SIZE ) {
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blockCount++;
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}
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// calc memory needed to store the block headers
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headerMemory = blockCount * sizeof(adpcm_state_t);
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return sampleMemory + headerMemory;
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}
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/*
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====================
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S_AdpcmGetSamples
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====================
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*/
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void S_AdpcmGetSamples(sndBuffer *chunk, short *to) {
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adpcm_state_t state;
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byte *out;
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// get the starting state from the block header
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state.index = chunk->adpcm.index;
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state.sample = chunk->adpcm.sample;
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out = (byte *)chunk->sndChunk;
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// get samples
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S_AdpcmDecode((char *) out, to, SND_CHUNK_SIZE_BYTE*2, &state );
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}
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/*
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====================
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S_AdpcmEncodeSound
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====================
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*/
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void S_AdpcmEncodeSound( sfx_t *sfx, short *samples ) {
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adpcm_state_t state;
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int inOffset;
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int count;
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int n;
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sndBuffer *newchunk, *chunk;
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byte *out;
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inOffset = 0;
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count = sfx->soundLength;
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state.index = 0;
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state.sample = samples[0];
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chunk = NULL;
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while( count ) {
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n = count;
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if( n > SND_CHUNK_SIZE_BYTE*2 ) {
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n = SND_CHUNK_SIZE_BYTE*2;
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}
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newchunk = SND_malloc();
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if (sfx->soundData == NULL) {
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sfx->soundData = newchunk;
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} else {
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chunk->next = newchunk;
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}
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chunk = newchunk;
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// output the header
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chunk->adpcm.index = state.index;
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chunk->adpcm.sample = state.sample;
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out = (byte *)chunk->sndChunk;
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// encode the samples
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S_AdpcmEncode( samples + inOffset, (char *) out, n, &state );
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inOffset += n;
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count -= n;
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}
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}
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