[SCM] libav/experimental: Create ac3.c which will be used for AC-3 common code.
siretart at users.alioth.debian.org
siretart at users.alioth.debian.org
Sun Jun 30 15:57:31 UTC 2013
The following commit has been merged in the experimental branch:
commit 96ae7f11e7c8a2e379f9c79451926e217dd65653
Author: Justin Ruggles <justin.ruggles at gmail.com>
Date: Fri Mar 9 13:54:44 2007 +0000
Create ac3.c which will be used for AC-3 common code.
Originally committed as revision 8305 to svn://svn.ffmpeg.org/ffmpeg/trunk
diff --git a/libavcodec/ac3.c b/libavcodec/ac3.c
new file mode 100644
index 0000000..019c776
--- /dev/null
+++ b/libavcodec/ac3.c
@@ -0,0 +1,197 @@
+/*
+ * Common code between AC3 encoder and decoder
+ * Copyright (c) 2000 Fabrice Bellard.
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file ac3.c
+ * Common code between AC3 encoder and decoder.
+ */
+
+#include "avcodec.h"
+#include "ac3.h"
+#include "ac3tab.h"
+
+static inline int calc_lowcomp1(int a, int b0, int b1, int c)
+{
+ if ((b0 + 256) == b1) {
+ a = c;
+ } else if (b0 > b1) {
+ a = FFMAX(a - 64, 0);
+ }
+ return a;
+}
+
+static inline int calc_lowcomp(int a, int b0, int b1, int bin)
+{
+ if (bin < 7) {
+ return calc_lowcomp1(a, b0, b1, 384);
+ } else if (bin < 20) {
+ return calc_lowcomp1(a, b0, b1, 320);
+ } else {
+ return FFMAX(a - 128, 0);
+ }
+}
+
+/* AC3 bit allocation. The algorithm is the one described in the AC3
+ spec. */
+void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
+ int8_t *exp, int start, int end,
+ int snroffset, int fgain, int is_lfe,
+ int deltbae,int deltnseg,
+ uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
+{
+ int bin,i,j,k,end1,v,bndstrt,bndend,lowcomp,begin;
+ int fastleak,slowleak,address,tmp;
+ int16_t psd[256]; /* scaled exponents */
+ int16_t bndpsd[50]; /* interpolated exponents */
+ int16_t excite[50]; /* excitation */
+ int16_t mask[50]; /* masking value */
+
+ /* exponent mapping to PSD */
+ for(bin=start;bin<end;bin++) {
+ psd[bin]=(3072 - (exp[bin] << 7));
+ }
+
+ /* PSD integration */
+ j=start;
+ k=masktab[start];
+ do {
+ v=psd[j];
+ j++;
+ end1 = FFMIN(bndtab[k+1], end);
+ for(i=j;i<end1;i++) {
+ /* logadd */
+ int adr = FFMIN(FFABS(v - psd[j]) >> 1, 255);
+ v = FFMAX(v, psd[j]) + latab[adr];
+ j++;
+ }
+ bndpsd[k]=v;
+ k++;
+ } while (end > bndtab[k]);
+
+ /* excitation function */
+ bndstrt = masktab[start];
+ bndend = masktab[end-1] + 1;
+
+ if (bndstrt == 0) {
+ lowcomp = 0;
+ lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1], 384);
+ excite[0] = bndpsd[0] - fgain - lowcomp;
+ lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2], 384);
+ excite[1] = bndpsd[1] - fgain - lowcomp;
+ begin = 7;
+ for (bin = 2; bin < 7; bin++) {
+ if (!(is_lfe && bin == 6))
+ lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1], 384);
+ fastleak = bndpsd[bin] - fgain;
+ slowleak = bndpsd[bin] - s->sgain;
+ excite[bin] = fastleak - lowcomp;
+ if (!(is_lfe && bin == 6)) {
+ if (bndpsd[bin] <= bndpsd[bin+1]) {
+ begin = bin + 1;
+ break;
+ }
+ }
+ }
+
+ end1=bndend;
+ if (end1 > 22) end1=22;
+
+ for (bin = begin; bin < end1; bin++) {
+ if (!(is_lfe && bin == 6))
+ lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin);
+
+ fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
+ slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
+ excite[bin] = FFMAX(fastleak - lowcomp, slowleak);
+ }
+ begin = 22;
+ } else {
+ /* coupling channel */
+ begin = bndstrt;
+
+ fastleak = (s->cplfleak << 8) + 768;
+ slowleak = (s->cplsleak << 8) + 768;
+ }
+
+ for (bin = begin; bin < bndend; bin++) {
+ fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
+ slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
+ excite[bin] = FFMAX(fastleak, slowleak);
+ }
+
+ /* compute masking curve */
+
+ for (bin = bndstrt; bin < bndend; bin++) {
+ tmp = s->dbknee - bndpsd[bin];
+ if (tmp > 0) {
+ excite[bin] += tmp >> 2;
+ }
+ mask[bin] = FFMAX(hth[bin >> s->halfratecod][s->fscod], excite[bin]);
+ }
+
+ /* delta bit allocation */
+
+ if (deltbae == 0 || deltbae == 1) {
+ int band, seg, delta;
+ band = 0;
+ for (seg = 0; seg < deltnseg; seg++) {
+ band += deltoffst[seg];
+ if (deltba[seg] >= 4) {
+ delta = (deltba[seg] - 3) << 7;
+ } else {
+ delta = (deltba[seg] - 4) << 7;
+ }
+ for (k = 0; k < deltlen[seg]; k++) {
+ mask[band] += delta;
+ band++;
+ }
+ }
+ }
+
+ /* compute bit allocation */
+
+ i = start;
+ j = masktab[start];
+ do {
+ v = (FFMAX(mask[j] - snroffset - s->floor, 0) & 0x1FE0) + s->floor;
+ end1 = FFMIN(bndtab[j] + bndsz[j], end);
+ for (k = i; k < end1; k++) {
+ address = av_clip((psd[i] - v) >> 5, 0, 63);
+ bap[i] = baptab[address];
+ i++;
+ }
+ } while (end > bndtab[j++]);
+}
+
+void ac3_common_init(void)
+{
+ int i, j, k, l, v;
+ /* compute bndtab and masktab from bandsz */
+ k = 0;
+ l = 0;
+ for(i=0;i<50;i++) {
+ bndtab[i] = l;
+ v = bndsz[i];
+ for(j=0;j<v;j++) masktab[k++]=i;
+ l += v;
+ }
+ bndtab[50] = l;
+}
--
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