ref: 19144759ff0bc03f470689c61a15fac88caacd7d
dir: /src/adpcm.c/
/* * adpcm.c codex functions for MS_ADPCM data * (hopefully) provides interoperability with * Microsoft's ADPCM format, but, as usual, * see LACK-OF-WARRANTY information below. * * Copyright (C) 1999 Stanley J. Brooks <stabro@megsinet.net> * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * */ /* * November 22, 1999 * specs I've seen are unclear about ADPCM supporting more than 2 channels, * but these routines support more channels in a manner which looks (IMHO) * like the most natural extension. * * Remark: code still turbulent, encoding very new. * */ #include <sys/types.h> #include <math.h> #include <stdio.h> #include "st_i.h" #include "adpcm.h" typedef struct MsState { st_sample_t step; /* step size */ short iCoef[2]; } MsState_t; #define lsbshortldi(x,p) { (x)=((short)((int)(p)[0] + ((int)(p)[1]<<8))); (p) += 2; } /* * Lookup tables for MS ADPCM format */ /* these are step-size adjust factors, where * 1.0 is scaled to 0x100 */ static const st_sample_t stepAdjustTable[] = { 230, 230, 230, 230, 307, 409, 512, 614, 768, 614, 512, 409, 307, 230, 230, 230 }; /* TODO : The first 7 iCoef sets are always hardcoded and must appear in the actual WAVE file. They should be read in in case a sound program added extras to the list. */ const short iCoef[7][2] = { { 256, 0}, { 512,-256}, { 0, 0}, { 192, 64}, { 240, 0}, { 460,-208}, { 392,-232} }; static inline st_sample_t AdpcmDecode(st_sample_t c, MsState_t *state, st_sample_t sample1, st_sample_t sample2) { st_sample_t vlin; st_sample_t sample; st_sample_t step; /** Compute next step value **/ step = state->step; { st_sample_t nstep; nstep = (stepAdjustTable[c] * step) >> 8; state->step = (nstep < 16)? 16:nstep; } /** make linear prediction for next sample **/ vlin = ((sample1 * state->iCoef[0]) + (sample2 * state->iCoef[1])) >> 8; /** then add the code*step adjustment **/ c -= (c & 0x08) << 1; sample = (c * step) + vlin; if (sample > 0x7fff) sample = 0x7fff; else if (sample < -0x8000) sample = -0x8000; return (sample); } /* AdpcmBlockExpandI() outputs interleaved samples into one output buffer */ const char *AdpcmBlockExpandI( int chans, /* total channels */ int nCoef, const short *iCoef, const unsigned char *ibuff,/* input buffer[blockAlign] */ SAMPL *obuff, /* output samples, n*chans */ int n /* samples to decode PER channel */ ) { const unsigned char *ip; int ch; const char *errmsg = NULL; MsState_t state[4]; /* One decompressor state for each channel */ /* Read the four-byte header for each channel */ ip = ibuff; for (ch = 0; ch < chans; ch++) { unsigned char bpred = *ip++; if (bpred >= nCoef) { errmsg = "MSADPCM bpred >= nCoef, arbitrarily using 0\n"; bpred = 0; } state[ch].iCoef[0] = iCoef[(int)bpred*2+0]; state[ch].iCoef[1] = iCoef[(int)bpred*2+1]; } for (ch = 0; ch < chans; ch++) lsbshortldi(state[ch].step, ip); /* sample1's directly into obuff */ for (ch = 0; ch < chans; ch++) lsbshortldi(obuff[chans+ch], ip); /* sample2's directly into obuff */ for (ch = 0; ch < chans; ch++) lsbshortldi(obuff[ch], ip); { int ch; unsigned char b; short *op, *top, *tmp; /* already have 1st 2 samples from block-header */ op = obuff + 2*chans; top = obuff + n*chans; ch = 0; while (op < top) { b = *ip++; tmp = op; *op++ = AdpcmDecode(b >> 4, state+ch, tmp[-chans], tmp[-2*chans]); if (++ch == chans) ch = 0; /* ch = ++ch % chans; */ tmp = op; *op++ = AdpcmDecode(b&0x0f, state+ch, tmp[-chans], tmp[-2*chans]); if (++ch == chans) ch = 0; /* ch = ++ch % chans; */ } } return errmsg; } static int AdpcmMashS( int ch, /* channel number to encode, REQUIRE 0 <= ch < chans */ int chans, /* total channels */ SAMPL v[2], /* values to use as starting 2 */ const short iCoef[2],/* lin predictor coeffs */ const SAMPL *ibuff, /* ibuff[] is interleaved input samples */ int n, /* samples to encode PER channel */ int *iostep, /* input/output step, REQUIRE 16 <= *st <= 0x7fff */ unsigned char *obuff /* output buffer[blockAlign], or NULL for no output */ ) { const SAMPL *ip, *itop; unsigned char *op; int ox = 0; /* */ int i, d, v0, v1, step; double d2; /* long long is okay also, speed abt the same */ ip = ibuff + ch; /* point ip to 1st input sample for this channel */ itop = ibuff + n*chans; v0 = v[0]; v1 = v[1]; d = *ip - v1; ip += chans; /* 1st input sample for this channel */ d2 = d*d; /* d2 will be sum of squares of errors, given input v0 and *st */ d = *ip - v0; ip += chans; /* 2nd input sample for this channel */ d2 += d*d; step = *iostep; op = obuff; /* output pointer (or NULL) */ if (op) { /* NULL means don't output, just compute the rms error */ op += chans; /* skip bpred indices */ op += 2*ch; /* channel's stepsize */ op[0] = step; op[1] = step>>8; op += 2*chans; /* skip to v0 */ op[0] = v0; op[1] = v0>>8; op += 2*chans; /* skip to v1 */ op[0] = v1; op[1] = v1>>8; op = obuff+7*chans; /* point to base of output nibbles */ ox = 4*ch; } for (i = 0; ip < itop; ip+=chans) { int vlin,d,dp,c; /* make linear prediction for next sample */ vlin = (v0 * iCoef[0] + v1 * iCoef[1]) >> 8; d = *ip - vlin; /* difference between linear prediction and current sample */ dp = d + (step<<3) + (step>>1); c = 0; if (dp>0) { c = dp/step; if (c>15) c = 15; } c -= 8; dp = c * step; /* quantized estimate of samp - vlin */ c &= 0x0f; /* mask to 4 bits */ v1 = v0; /* shift history */ v0 = vlin + dp; if (v0<-0x8000) v0 = -0x8000; else if (v0>0x7fff) v0 = 0x7fff; d = *ip - v0; d2 += d*d; /* update square-error */ if (op) { /* if we want output, put it in proper place */ op[ox>>3] |= (ox&4)? c:(c<<4); ox += 4*chans; st_debug_more("%.1x",c); } /* Update the step for the next sample */ step = (stepAdjustTable[c] * step) >> 8; if (step < 16) step = 16; } if (op) st_debug_more("\n"); d2 /= n; /* be sure it's non-negative */ st_debug_more("ch%d: st %d->%d, d %.1f\n", ch, *iostep, step, sqrt(d2)); *iostep = step; return (int) sqrt(d2); } static inline void AdpcmMashChannel( int ch, /* channel number to encode, REQUIRE 0 <= ch < chans */ int chans, /* total channels */ const SAMPL *ip, /* ip[] is interleaved input samples */ int n, /* samples to encode PER channel, REQUIRE */ int *st, /* input/output steps, 16<=st[i] */ unsigned char *obuff /* output buffer[blockAlign] */ ) { SAMPL v[2]; int n0,s0,s1,ss,smin; int d,dmin,k,kmin; n0 = n/2; if (n0>32) n0=32; if (*st<16) *st = 16; v[1] = ip[ch]; v[0] = ip[ch+chans]; dmin = 0; kmin = 0; smin = 0; /* for each of 7 standard coeff sets, we try compression * beginning with last step-value, and with slightly * forward-adjusted step-value, taking best of the 14 */ for (k=0; k<7; k++) { int d0,d1; ss = s0 = *st; d0=AdpcmMashS(ch, chans, v, iCoef[k], ip, n, &ss, NULL); /* with step s0 */ s1 = s0; AdpcmMashS(ch, chans, v, iCoef[k], ip, n0, &s1, NULL); st_debug_more(" s32 %d\n",s1); ss = s1 = (3*s0+s1)/4; d1=AdpcmMashS(ch, chans, v, iCoef[k], ip, n, &ss, NULL); /* with step s1 */ if (!k || d0<dmin || d1<dmin) { kmin = k; if (d0<=d1) { dmin = d0; smin = s0; }else{ dmin = d1; smin = s1; } } } *st = smin; st_debug_more("kmin %d, smin %5d, ",kmin,smin); d=AdpcmMashS(ch, chans, v, iCoef[kmin], ip, n, st, obuff); obuff[ch] = kmin; } void AdpcmBlockMashI( int chans, /* total channels */ const SAMPL *ip, /* ip[n*chans] is interleaved input samples */ int n, /* samples to encode PER channel */ int *st, /* input/output steps, 16<=st[i] */ unsigned char *obuff, /* output buffer[blockAlign] */ int blockAlign /* >= 7*chans + chans*(n-2)/2.0 */ ) { int ch; unsigned char *p; st_debug("AdpcmMashI(chans %d, ip %p, n %d, st %p, obuff %p, bA %d)\n", chans, ip, n, st, obuff, blockAlign); for (p=obuff+7*chans; p<obuff+blockAlign; p++) *p=0; for (ch=0; ch<chans; ch++) AdpcmMashChannel(ch, chans, ip, n, st+ch, obuff); } /* * AdpcmSamplesIn(dataLen, chans, blockAlign, samplesPerBlock) * returns the number of samples/channel which would be * in the dataLen, given the other parameters ... * if input samplesPerBlock is 0, then returns the max * samplesPerBlock which would go into a block of size blockAlign * Yes, it is confusing usage. */ st_size_t AdpcmSamplesIn( st_size_t dataLen, unsigned short chans, unsigned short blockAlign, unsigned short samplesPerBlock ){ st_size_t m, n; if (samplesPerBlock) { n = (dataLen / blockAlign) * samplesPerBlock; m = (dataLen % blockAlign); } else { n = 0; m = blockAlign; } if (m >= (size_t)(7*chans)) { m -= 7*chans; /* bytes beyond block-header */ m = (2*m)/chans + 2; /* nibbles/chans + 2 in header */ if (samplesPerBlock && m > samplesPerBlock) m = samplesPerBlock; n += m; } return n; } st_size_t AdpcmBytesPerBlock( unsigned short chans, unsigned short samplesPerBlock ) { st_size_t n; n = 7*chans; /* header */ if (samplesPerBlock > 2) n += (((st_size_t)samplesPerBlock-2)*chans + 1)/2; return n; }