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1580 lines
43 KiB
C
1580 lines
43 KiB
C
/*
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* The simplest AC3 encoder
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* Copyright (c) 2000 Fabrice Bellard.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/**
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* @file ac3enc.c
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* The simplest AC3 encoder.
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*/
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//#define DEBUG
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//#define DEBUG_BITALLOC
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#include "avcodec.h"
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#include "ac3.h"
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typedef struct AC3EncodeContext {
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PutBitContext pb;
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int nb_channels;
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int nb_all_channels;
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int lfe_channel;
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int bit_rate;
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unsigned int sample_rate;
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unsigned int bsid;
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unsigned int frame_size_min; /* minimum frame size in case rounding is necessary */
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unsigned int frame_size; /* current frame size in words */
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int halfratecod;
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unsigned int frmsizecod;
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unsigned int fscod; /* frequency */
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unsigned int acmod;
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int lfe;
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unsigned int bsmod;
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short last_samples[AC3_MAX_CHANNELS][256];
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unsigned int chbwcod[AC3_MAX_CHANNELS];
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int nb_coefs[AC3_MAX_CHANNELS];
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/* bitrate allocation control */
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int sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;
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AC3BitAllocParameters bit_alloc;
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int csnroffst;
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int fgaincod[AC3_MAX_CHANNELS];
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int fsnroffst[AC3_MAX_CHANNELS];
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/* mantissa encoding */
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int mant1_cnt, mant2_cnt, mant4_cnt;
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} AC3EncodeContext;
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#include "ac3tab.h"
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#define MDCT_NBITS 9
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#define N (1 << MDCT_NBITS)
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/* new exponents are sent if their Norm 1 exceed this number */
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#define EXP_DIFF_THRESHOLD 1000
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static void fft_init(int ln);
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static void ac3_crc_init(void);
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static inline int16_t fix15(float a)
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{
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int v;
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v = (int)(a * (float)(1 << 15));
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if (v < -32767)
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v = -32767;
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else if (v > 32767)
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v = 32767;
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return v;
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}
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static inline int calc_lowcomp1(int a, int b0, int b1)
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{
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if ((b0 + 256) == b1) {
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a = 384 ;
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} else if (b0 > b1) {
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a = a - 64;
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if (a < 0) a=0;
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}
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return a;
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}
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static inline int calc_lowcomp(int a, int b0, int b1, int bin)
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{
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if (bin < 7) {
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if ((b0 + 256) == b1) {
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a = 384 ;
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} else if (b0 > b1) {
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a = a - 64;
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if (a < 0) a=0;
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}
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} else if (bin < 20) {
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if ((b0 + 256) == b1) {
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a = 320 ;
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} else if (b0 > b1) {
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a= a - 64;
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if (a < 0) a=0;
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}
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} else {
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a = a - 128;
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if (a < 0) a=0;
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}
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return a;
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}
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/* AC3 bit allocation. The algorithm is the one described in the AC3
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spec. */
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void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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int8_t *exp, int start, int end,
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int snroffset, int fgain, int is_lfe,
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int deltbae,int deltnseg,
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uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
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{
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int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
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int fastleak,slowleak,address,tmp;
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int16_t psd[256]; /* scaled exponents */
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int16_t bndpsd[50]; /* interpolated exponents */
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int16_t excite[50]; /* excitation */
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int16_t mask[50]; /* masking value */
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/* exponent mapping to PSD */
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for(bin=start;bin<end;bin++) {
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psd[bin]=(3072 - (exp[bin] << 7));
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}
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/* PSD integration */
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j=start;
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k=masktab[start];
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do {
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v=psd[j];
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j++;
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end1=bndtab[k+1];
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if (end1 > end) end1=end;
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for(i=j;i<end1;i++) {
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int c,adr;
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/* logadd */
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v1=psd[j];
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c=v-v1;
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if (c >= 0) {
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adr=c >> 1;
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if (adr > 255) adr=255;
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v=v + latab[adr];
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} else {
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adr=(-c) >> 1;
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if (adr > 255) adr=255;
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v=v1 + latab[adr];
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}
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j++;
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}
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bndpsd[k]=v;
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k++;
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} while (end > bndtab[k]);
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/* excitation function */
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bndstrt = masktab[start];
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bndend = masktab[end-1] + 1;
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if (bndstrt == 0) {
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lowcomp = 0;
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lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;
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excite[0] = bndpsd[0] - fgain - lowcomp ;
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lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;
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excite[1] = bndpsd[1] - fgain - lowcomp ;
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begin = 7 ;
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for (bin = 2; bin < 7; bin++) {
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if (!(is_lfe && bin == 6))
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lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1]) ;
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fastleak = bndpsd[bin] - fgain ;
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slowleak = bndpsd[bin] - s->sgain ;
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excite[bin] = fastleak - lowcomp ;
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if (!(is_lfe && bin == 6)) {
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if (bndpsd[bin] <= bndpsd[bin+1]) {
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begin = bin + 1 ;
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break ;
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}
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}
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}
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end1=bndend;
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if (end1 > 22) end1=22;
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for (bin = begin; bin < end1; bin++) {
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if (!(is_lfe && bin == 6))
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lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
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fastleak -= s->fdecay ;
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v = bndpsd[bin] - fgain;
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if (fastleak < v) fastleak = v;
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slowleak -= s->sdecay ;
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v = bndpsd[bin] - s->sgain;
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if (slowleak < v) slowleak = v;
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v=fastleak - lowcomp;
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if (slowleak > v) v=slowleak;
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excite[bin] = v;
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}
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begin = 22;
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} else {
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/* coupling channel */
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begin = bndstrt;
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fastleak = (s->cplfleak << 8) + 768;
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slowleak = (s->cplsleak << 8) + 768;
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}
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for (bin = begin; bin < bndend; bin++) {
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fastleak -= s->fdecay ;
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v = bndpsd[bin] - fgain;
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if (fastleak < v) fastleak = v;
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slowleak -= s->sdecay ;
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v = bndpsd[bin] - s->sgain;
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if (slowleak < v) slowleak = v;
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v=fastleak;
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if (slowleak > v) v = slowleak;
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excite[bin] = v;
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}
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/* compute masking curve */
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for (bin = bndstrt; bin < bndend; bin++) {
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v1 = excite[bin];
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tmp = s->dbknee - bndpsd[bin];
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if (tmp > 0) {
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v1 += tmp >> 2;
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}
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v=hth[bin >> s->halfratecod][s->fscod];
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if (v1 > v) v=v1;
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mask[bin] = v;
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}
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/* delta bit allocation */
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if (deltbae == 0 || deltbae == 1) {
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int band, seg, delta;
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band = 0 ;
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for (seg = 0; seg < deltnseg; seg++) {
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band += deltoffst[seg] ;
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if (deltba[seg] >= 4) {
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delta = (deltba[seg] - 3) << 7;
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} else {
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delta = (deltba[seg] - 4) << 7;
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}
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for (k = 0; k < deltlen[seg]; k++) {
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mask[band] += delta ;
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band++ ;
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}
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}
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}
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/* compute bit allocation */
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i = start ;
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j = masktab[start] ;
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do {
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v=mask[j];
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v -= snroffset ;
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v -= s->floor ;
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if (v < 0) v = 0;
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v &= 0x1fe0 ;
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v += s->floor ;
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end1=bndtab[j] + bndsz[j];
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if (end1 > end) end1=end;
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for (k = i; k < end1; k++) {
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address = (psd[i] - v) >> 5 ;
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if (address < 0) address=0;
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else if (address > 63) address=63;
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bap[i] = baptab[address];
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i++;
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}
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} while (end > bndtab[j++]) ;
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}
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typedef struct IComplex {
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short re,im;
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} IComplex;
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static void fft_init(int ln)
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{
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int i, j, m, n;
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float alpha;
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n = 1 << ln;
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for(i=0;i<(n/2);i++) {
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alpha = 2 * M_PI * (float)i / (float)n;
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costab[i] = fix15(cos(alpha));
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sintab[i] = fix15(sin(alpha));
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}
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for(i=0;i<n;i++) {
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m=0;
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for(j=0;j<ln;j++) {
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m |= ((i >> j) & 1) << (ln-j-1);
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}
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fft_rev[i]=m;
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}
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}
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/* butter fly op */
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#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
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{\
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int ax, ay, bx, by;\
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bx=pre1;\
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by=pim1;\
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ax=qre1;\
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ay=qim1;\
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pre = (bx + ax) >> 1;\
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pim = (by + ay) >> 1;\
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qre = (bx - ax) >> 1;\
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qim = (by - ay) >> 1;\
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}
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#define MUL16(a,b) ((a) * (b))
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#define CMUL(pre, pim, are, aim, bre, bim) \
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{\
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pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
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pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
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}
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/* do a 2^n point complex fft on 2^ln points. */
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static void fft(IComplex *z, int ln)
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{
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int j, l, np, np2;
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int nblocks, nloops;
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register IComplex *p,*q;
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int tmp_re, tmp_im;
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np = 1 << ln;
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/* reverse */
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for(j=0;j<np;j++) {
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int k;
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IComplex tmp;
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k = fft_rev[j];
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if (k < j) {
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tmp = z[k];
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z[k] = z[j];
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z[j] = tmp;
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}
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}
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/* pass 0 */
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p=&z[0];
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j=(np >> 1);
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do {
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BF(p[0].re, p[0].im, p[1].re, p[1].im,
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p[0].re, p[0].im, p[1].re, p[1].im);
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p+=2;
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} while (--j != 0);
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/* pass 1 */
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p=&z[0];
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j=np >> 2;
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do {
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BF(p[0].re, p[0].im, p[2].re, p[2].im,
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p[0].re, p[0].im, p[2].re, p[2].im);
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BF(p[1].re, p[1].im, p[3].re, p[3].im,
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p[1].re, p[1].im, p[3].im, -p[3].re);
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p+=4;
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} while (--j != 0);
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/* pass 2 .. ln-1 */
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nblocks = np >> 3;
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nloops = 1 << 2;
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np2 = np >> 1;
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do {
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p = z;
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q = z + nloops;
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for (j = 0; j < nblocks; ++j) {
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BF(p->re, p->im, q->re, q->im,
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p->re, p->im, q->re, q->im);
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p++;
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q++;
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for(l = nblocks; l < np2; l += nblocks) {
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CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
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BF(p->re, p->im, q->re, q->im,
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p->re, p->im, tmp_re, tmp_im);
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p++;
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q++;
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}
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p += nloops;
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q += nloops;
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}
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nblocks = nblocks >> 1;
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nloops = nloops << 1;
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} while (nblocks != 0);
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}
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/* do a 512 point mdct */
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static void mdct512(int32_t *out, int16_t *in)
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{
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int i, re, im, re1, im1;
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int16_t rot[N];
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IComplex x[N/4];
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/* shift to simplify computations */
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for(i=0;i<N/4;i++)
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rot[i] = -in[i + 3*N/4];
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for(i=N/4;i<N;i++)
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rot[i] = in[i - N/4];
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/* pre rotation */
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for(i=0;i<N/4;i++) {
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re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
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im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
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CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
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}
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fft(x, MDCT_NBITS - 2);
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/* post rotation */
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for(i=0;i<N/4;i++) {
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re = x[i].re;
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im = x[i].im;
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CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
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out[2*i] = im1;
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out[N/2-1-2*i] = re1;
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}
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}
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/* XXX: use another norm ? */
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static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
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{
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int sum, i;
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sum = 0;
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for(i=0;i<n;i++) {
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sum += abs(exp1[i] - exp2[i]);
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}
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return sum;
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}
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static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
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uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
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int ch, int is_lfe)
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{
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int i, j;
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int exp_diff;
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/* estimate if the exponent variation & decide if they should be
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reused in the next frame */
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exp_strategy[0][ch] = EXP_NEW;
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for(i=1;i<NB_BLOCKS;i++) {
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exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
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#ifdef DEBUG
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printf("exp_diff=%d\n", exp_diff);
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#endif
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if (exp_diff > EXP_DIFF_THRESHOLD)
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exp_strategy[i][ch] = EXP_NEW;
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else
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exp_strategy[i][ch] = EXP_REUSE;
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}
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if (is_lfe)
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return;
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|
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/* now select the encoding strategy type : if exponents are often
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recoded, we use a coarse encoding */
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i = 0;
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while (i < NB_BLOCKS) {
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j = i + 1;
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while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
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j++;
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switch(j - i) {
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case 1:
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exp_strategy[i][ch] = EXP_D45;
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break;
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case 2:
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case 3:
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exp_strategy[i][ch] = EXP_D25;
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break;
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default:
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exp_strategy[i][ch] = EXP_D15;
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break;
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}
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i = j;
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}
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}
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|
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/* set exp[i] to min(exp[i], exp1[i]) */
|
|
static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
|
|
{
|
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int i;
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|
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for(i=0;i<n;i++) {
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if (exp1[i] < exp[i])
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exp[i] = exp1[i];
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}
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|
}
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|
|
/* update the exponents so that they are the ones the decoder will
|
|
decode. Return the number of bits used to code the exponents */
|
|
static int encode_exp(uint8_t encoded_exp[N/2],
|
|
uint8_t exp[N/2],
|
|
int nb_exps,
|
|
int exp_strategy)
|
|
{
|
|
int group_size, nb_groups, i, j, k, recurse, exp_min, delta;
|
|
uint8_t exp1[N/2];
|
|
|
|
switch(exp_strategy) {
|
|
case EXP_D15:
|
|
group_size = 1;
|
|
break;
|
|
case EXP_D25:
|
|
group_size = 2;
|
|
break;
|
|
default:
|
|
case EXP_D45:
|
|
group_size = 4;
|
|
break;
|
|
}
|
|
nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
|
|
|
|
/* for each group, compute the minimum exponent */
|
|
exp1[0] = exp[0]; /* DC exponent is handled separately */
|
|
k = 1;
|
|
for(i=1;i<=nb_groups;i++) {
|
|
exp_min = exp[k];
|
|
assert(exp_min >= 0 && exp_min <= 24);
|
|
for(j=1;j<group_size;j++) {
|
|
if (exp[k+j] < exp_min)
|
|
exp_min = exp[k+j];
|
|
}
|
|
exp1[i] = exp_min;
|
|
k += group_size;
|
|
}
|
|
|
|
/* constraint for DC exponent */
|
|
if (exp1[0] > 15)
|
|
exp1[0] = 15;
|
|
|
|
/* Iterate until the delta constraints between each groups are
|
|
satisfyed. I'm sure it is possible to find a better algorithm,
|
|
but I am lazy */
|
|
do {
|
|
recurse = 0;
|
|
for(i=1;i<=nb_groups;i++) {
|
|
delta = exp1[i] - exp1[i-1];
|
|
if (delta > 2) {
|
|
/* if delta too big, we encode a smaller exponent */
|
|
exp1[i] = exp1[i-1] + 2;
|
|
} else if (delta < -2) {
|
|
/* if delta is too small, we must decrease the previous
|
|
exponent, which means we must recurse */
|
|
recurse = 1;
|
|
exp1[i-1] = exp1[i] + 2;
|
|
}
|
|
}
|
|
} while (recurse);
|
|
|
|
/* now we have the exponent values the decoder will see */
|
|
encoded_exp[0] = exp1[0];
|
|
k = 1;
|
|
for(i=1;i<=nb_groups;i++) {
|
|
for(j=0;j<group_size;j++) {
|
|
encoded_exp[k+j] = exp1[i];
|
|
}
|
|
k += group_size;
|
|
}
|
|
|
|
#if defined(DEBUG)
|
|
printf("exponents: strategy=%d\n", exp_strategy);
|
|
for(i=0;i<=nb_groups * group_size;i++) {
|
|
printf("%d ", encoded_exp[i]);
|
|
}
|
|
printf("\n");
|
|
#endif
|
|
|
|
return 4 + (nb_groups / 3) * 7;
|
|
}
|
|
|
|
/* return the size in bits taken by the mantissa */
|
|
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
|
|
{
|
|
int bits, mant, i;
|
|
|
|
bits = 0;
|
|
for(i=0;i<nb_coefs;i++) {
|
|
mant = m[i];
|
|
switch(mant) {
|
|
case 0:
|
|
/* nothing */
|
|
break;
|
|
case 1:
|
|
/* 3 mantissa in 5 bits */
|
|
if (s->mant1_cnt == 0)
|
|
bits += 5;
|
|
if (++s->mant1_cnt == 3)
|
|
s->mant1_cnt = 0;
|
|
break;
|
|
case 2:
|
|
/* 3 mantissa in 7 bits */
|
|
if (s->mant2_cnt == 0)
|
|
bits += 7;
|
|
if (++s->mant2_cnt == 3)
|
|
s->mant2_cnt = 0;
|
|
break;
|
|
case 3:
|
|
bits += 3;
|
|
break;
|
|
case 4:
|
|
/* 2 mantissa in 7 bits */
|
|
if (s->mant4_cnt == 0)
|
|
bits += 7;
|
|
if (++s->mant4_cnt == 2)
|
|
s->mant4_cnt = 0;
|
|
break;
|
|
case 14:
|
|
bits += 14;
|
|
break;
|
|
case 15:
|
|
bits += 16;
|
|
break;
|
|
default:
|
|
bits += mant - 1;
|
|
break;
|
|
}
|
|
}
|
|
return bits;
|
|
}
|
|
|
|
|
|
static int bit_alloc(AC3EncodeContext *s,
|
|
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
|
|
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
|
|
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
|
|
int frame_bits, int csnroffst, int fsnroffst)
|
|
{
|
|
int i, ch;
|
|
|
|
/* compute size */
|
|
for(i=0;i<NB_BLOCKS;i++) {
|
|
s->mant1_cnt = 0;
|
|
s->mant2_cnt = 0;
|
|
s->mant4_cnt = 0;
|
|
for(ch=0;ch<s->nb_all_channels;ch++) {
|
|
ac3_parametric_bit_allocation(&s->bit_alloc,
|
|
bap[i][ch], (int8_t *)encoded_exp[i][ch],
|
|
0, s->nb_coefs[ch],
|
|
(((csnroffst-15) << 4) +
|
|
fsnroffst) << 2,
|
|
fgaintab[s->fgaincod[ch]],
|
|
ch == s->lfe_channel,
|
|
2, 0, NULL, NULL, NULL);
|
|
frame_bits += compute_mantissa_size(s, bap[i][ch],
|
|
s->nb_coefs[ch]);
|
|
}
|
|
}
|
|
#if 0
|
|
printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
|
|
csnroffst, fsnroffst, frame_bits,
|
|
16 * s->frame_size - ((frame_bits + 7) & ~7));
|
|
#endif
|
|
return 16 * s->frame_size - frame_bits;
|
|
}
|
|
|
|
#define SNR_INC1 4
|
|
|
|
static int compute_bit_allocation(AC3EncodeContext *s,
|
|
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
|
|
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
|
|
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
|
|
int frame_bits)
|
|
{
|
|
int i, ch;
|
|
int csnroffst, fsnroffst;
|
|
uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
|
|
static int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
|
|
|
|
/* init default parameters */
|
|
s->sdecaycod = 2;
|
|
s->fdecaycod = 1;
|
|
s->sgaincod = 1;
|
|
s->dbkneecod = 2;
|
|
s->floorcod = 4;
|
|
for(ch=0;ch<s->nb_all_channels;ch++)
|
|
s->fgaincod[ch] = 4;
|
|
|
|
/* compute real values */
|
|
s->bit_alloc.fscod = s->fscod;
|
|
s->bit_alloc.halfratecod = s->halfratecod;
|
|
s->bit_alloc.sdecay = sdecaytab[s->sdecaycod] >> s->halfratecod;
|
|
s->bit_alloc.fdecay = fdecaytab[s->fdecaycod] >> s->halfratecod;
|
|
s->bit_alloc.sgain = sgaintab[s->sgaincod];
|
|
s->bit_alloc.dbknee = dbkneetab[s->dbkneecod];
|
|
s->bit_alloc.floor = floortab[s->floorcod];
|
|
|
|
/* header size */
|
|
frame_bits += 65;
|
|
// if (s->acmod == 2)
|
|
// frame_bits += 2;
|
|
frame_bits += frame_bits_inc[s->acmod];
|
|
|
|
/* audio blocks */
|
|
for(i=0;i<NB_BLOCKS;i++) {
|
|
frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
|
|
if (s->acmod == 2)
|
|
frame_bits++; /* rematstr */
|
|
frame_bits += 2 * s->nb_channels; /* chexpstr[2] * c */
|
|
if (s->lfe)
|
|
frame_bits++; /* lfeexpstr */
|
|
for(ch=0;ch<s->nb_channels;ch++) {
|
|
if (exp_strategy[i][ch] != EXP_REUSE)
|
|
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
|
|
}
|
|
frame_bits++; /* baie */
|
|
frame_bits++; /* snr */
|
|
frame_bits += 2; /* delta / skip */
|
|
}
|
|
frame_bits++; /* cplinu for block 0 */
|
|
/* bit alloc info */
|
|
/* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
|
|
/* csnroffset[6] */
|
|
/* (fsnoffset[4] + fgaincod[4]) * c */
|
|
frame_bits += 2*4 + 3 + 6 + s->nb_all_channels * (4 + 3);
|
|
|
|
/* CRC */
|
|
frame_bits += 16;
|
|
|
|
/* now the big work begins : do the bit allocation. Modify the snr
|
|
offset until we can pack everything in the requested frame size */
|
|
|
|
csnroffst = s->csnroffst;
|
|
while (csnroffst >= 0 &&
|
|
bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)
|
|
csnroffst -= SNR_INC1;
|
|
if (csnroffst < 0) {
|
|
fprintf(stderr, "Yack, Error !!!\n");
|
|
return -1;
|
|
}
|
|
while ((csnroffst + SNR_INC1) <= 63 &&
|
|
bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
|
|
csnroffst + SNR_INC1, 0) >= 0) {
|
|
csnroffst += SNR_INC1;
|
|
memcpy(bap, bap1, sizeof(bap1));
|
|
}
|
|
while ((csnroffst + 1) <= 63 &&
|
|
bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits, csnroffst + 1, 0) >= 0) {
|
|
csnroffst++;
|
|
memcpy(bap, bap1, sizeof(bap1));
|
|
}
|
|
|
|
fsnroffst = 0;
|
|
while ((fsnroffst + SNR_INC1) <= 15 &&
|
|
bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
|
|
csnroffst, fsnroffst + SNR_INC1) >= 0) {
|
|
fsnroffst += SNR_INC1;
|
|
memcpy(bap, bap1, sizeof(bap1));
|
|
}
|
|
while ((fsnroffst + 1) <= 15 &&
|
|
bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
|
|
csnroffst, fsnroffst + 1) >= 0) {
|
|
fsnroffst++;
|
|
memcpy(bap, bap1, sizeof(bap1));
|
|
}
|
|
|
|
s->csnroffst = csnroffst;
|
|
for(ch=0;ch<s->nb_all_channels;ch++)
|
|
s->fsnroffst[ch] = fsnroffst;
|
|
#if defined(DEBUG_BITALLOC)
|
|
{
|
|
int j;
|
|
|
|
for(i=0;i<6;i++) {
|
|
for(ch=0;ch<s->nb_all_channels;ch++) {
|
|
printf("Block #%d Ch%d:\n", i, ch);
|
|
printf("bap=");
|
|
for(j=0;j<s->nb_coefs[ch];j++) {
|
|
printf("%d ",bap[i][ch][j]);
|
|
}
|
|
printf("\n");
|
|
}
|
|
}
|
|
}
|
|
#endif
|
|
return 0;
|
|
}
|
|
|
|
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] = 0;
|
|
}
|
|
|
|
|
|
static int AC3_encode_init(AVCodecContext *avctx)
|
|
{
|
|
int freq = avctx->sample_rate;
|
|
int bitrate = avctx->bit_rate;
|
|
int channels = avctx->channels;
|
|
AC3EncodeContext *s = avctx->priv_data;
|
|
int i, j, ch;
|
|
float alpha;
|
|
static const uint8_t acmod_defs[6] = {
|
|
0x01, /* C */
|
|
0x02, /* L R */
|
|
0x03, /* L C R */
|
|
0x06, /* L R SL SR */
|
|
0x07, /* L C R SL SR */
|
|
0x07, /* L C R SL SR (+LFE) */
|
|
};
|
|
|
|
avctx->frame_size = AC3_FRAME_SIZE;
|
|
|
|
/* number of channels */
|
|
if (channels < 1 || channels > 6)
|
|
return -1;
|
|
s->acmod = acmod_defs[channels - 1];
|
|
s->lfe = (channels == 6) ? 1 : 0;
|
|
s->nb_all_channels = channels;
|
|
s->nb_channels = channels > 5 ? 5 : channels;
|
|
s->lfe_channel = s->lfe ? 5 : -1;
|
|
|
|
/* frequency */
|
|
for(i=0;i<3;i++) {
|
|
for(j=0;j<3;j++)
|
|
if ((ac3_freqs[j] >> i) == freq)
|
|
goto found;
|
|
}
|
|
return -1;
|
|
found:
|
|
s->sample_rate = freq;
|
|
s->halfratecod = i;
|
|
s->fscod = j;
|
|
s->bsid = 8 + s->halfratecod;
|
|
s->bsmod = 0; /* complete main audio service */
|
|
|
|
/* bitrate & frame size */
|
|
bitrate /= 1000;
|
|
for(i=0;i<19;i++) {
|
|
if ((ac3_bitratetab[i] >> s->halfratecod) == bitrate)
|
|
break;
|
|
}
|
|
if (i == 19)
|
|
return -1;
|
|
s->bit_rate = bitrate;
|
|
s->frmsizecod = i << 1;
|
|
s->frame_size_min = (bitrate * 1000 * AC3_FRAME_SIZE) / (freq * 16);
|
|
/* for now we do not handle fractional sizes */
|
|
s->frame_size = s->frame_size_min;
|
|
|
|
/* bit allocation init */
|
|
for(ch=0;ch<s->nb_channels;ch++) {
|
|
/* bandwidth for each channel */
|
|
/* XXX: should compute the bandwidth according to the frame
|
|
size, so that we avoid anoying high freq artefacts */
|
|
s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */
|
|
s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37;
|
|
}
|
|
if (s->lfe) {
|
|
s->nb_coefs[s->lfe_channel] = 7; /* fixed */
|
|
}
|
|
/* initial snr offset */
|
|
s->csnroffst = 40;
|
|
|
|
ac3_common_init();
|
|
|
|
/* mdct init */
|
|
fft_init(MDCT_NBITS - 2);
|
|
for(i=0;i<N/4;i++) {
|
|
alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
|
|
xcos1[i] = fix15(-cos(alpha));
|
|
xsin1[i] = fix15(-sin(alpha));
|
|
}
|
|
|
|
ac3_crc_init();
|
|
|
|
avctx->coded_frame= avcodec_alloc_frame();
|
|
avctx->coded_frame->key_frame= 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* output the AC3 frame header */
|
|
static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
|
|
{
|
|
init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
|
|
|
|
put_bits(&s->pb, 16, 0x0b77); /* frame header */
|
|
put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
|
|
put_bits(&s->pb, 2, s->fscod);
|
|
put_bits(&s->pb, 6, s->frmsizecod + (s->frame_size - s->frame_size_min));
|
|
put_bits(&s->pb, 5, s->bsid);
|
|
put_bits(&s->pb, 3, s->bsmod);
|
|
put_bits(&s->pb, 3, s->acmod);
|
|
if ((s->acmod & 0x01) && s->acmod != 0x01)
|
|
put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
|
|
if (s->acmod & 0x04)
|
|
put_bits(&s->pb, 2, 1); /* XXX -6 dB */
|
|
if (s->acmod == 0x02)
|
|
put_bits(&s->pb, 2, 0); /* surround not indicated */
|
|
put_bits(&s->pb, 1, s->lfe); /* LFE */
|
|
put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
|
|
put_bits(&s->pb, 1, 0); /* no compression control word */
|
|
put_bits(&s->pb, 1, 0); /* no lang code */
|
|
put_bits(&s->pb, 1, 0); /* no audio production info */
|
|
put_bits(&s->pb, 1, 0); /* no copyright */
|
|
put_bits(&s->pb, 1, 1); /* original bitstream */
|
|
put_bits(&s->pb, 1, 0); /* no time code 1 */
|
|
put_bits(&s->pb, 1, 0); /* no time code 2 */
|
|
put_bits(&s->pb, 1, 0); /* no addtional bit stream info */
|
|
}
|
|
|
|
/* symetric quantization on 'levels' levels */
|
|
static inline int sym_quant(int c, int e, int levels)
|
|
{
|
|
int v;
|
|
|
|
if (c >= 0) {
|
|
v = (levels * (c << e)) >> 24;
|
|
v = (v + 1) >> 1;
|
|
v = (levels >> 1) + v;
|
|
} else {
|
|
v = (levels * ((-c) << e)) >> 24;
|
|
v = (v + 1) >> 1;
|
|
v = (levels >> 1) - v;
|
|
}
|
|
assert (v >= 0 && v < levels);
|
|
return v;
|
|
}
|
|
|
|
/* asymetric quantization on 2^qbits levels */
|
|
static inline int asym_quant(int c, int e, int qbits)
|
|
{
|
|
int lshift, m, v;
|
|
|
|
lshift = e + qbits - 24;
|
|
if (lshift >= 0)
|
|
v = c << lshift;
|
|
else
|
|
v = c >> (-lshift);
|
|
/* rounding */
|
|
v = (v + 1) >> 1;
|
|
m = (1 << (qbits-1));
|
|
if (v >= m)
|
|
v = m - 1;
|
|
assert(v >= -m);
|
|
return v & ((1 << qbits)-1);
|
|
}
|
|
|
|
/* Output one audio block. There are NB_BLOCKS audio blocks in one AC3
|
|
frame */
|
|
static void output_audio_block(AC3EncodeContext *s,
|
|
uint8_t exp_strategy[AC3_MAX_CHANNELS],
|
|
uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
|
|
uint8_t bap[AC3_MAX_CHANNELS][N/2],
|
|
int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
|
|
int8_t global_exp[AC3_MAX_CHANNELS],
|
|
int block_num)
|
|
{
|
|
int ch, nb_groups, group_size, i, baie, rbnd;
|
|
uint8_t *p;
|
|
uint16_t qmant[AC3_MAX_CHANNELS][N/2];
|
|
int exp0, exp1;
|
|
int mant1_cnt, mant2_cnt, mant4_cnt;
|
|
uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
|
|
int delta0, delta1, delta2;
|
|
|
|
for(ch=0;ch<s->nb_channels;ch++)
|
|
put_bits(&s->pb, 1, 0); /* 512 point MDCT */
|
|
for(ch=0;ch<s->nb_channels;ch++)
|
|
put_bits(&s->pb, 1, 1); /* no dither */
|
|
put_bits(&s->pb, 1, 0); /* no dynamic range */
|
|
if (block_num == 0) {
|
|
/* for block 0, even if no coupling, we must say it. This is a
|
|
waste of bit :-) */
|
|
put_bits(&s->pb, 1, 1); /* coupling strategy present */
|
|
put_bits(&s->pb, 1, 0); /* no coupling strategy */
|
|
} else {
|
|
put_bits(&s->pb, 1, 0); /* no new coupling strategy */
|
|
}
|
|
|
|
if (s->acmod == 2)
|
|
{
|
|
if(block_num==0)
|
|
{
|
|
/* first block must define rematrixing (rematstr) */
|
|
put_bits(&s->pb, 1, 1);
|
|
|
|
/* dummy rematrixing rematflg(1:4)=0 */
|
|
for (rbnd=0;rbnd<4;rbnd++)
|
|
put_bits(&s->pb, 1, 0);
|
|
}
|
|
else
|
|
{
|
|
/* no matrixing (but should be used in the future) */
|
|
put_bits(&s->pb, 1, 0);
|
|
}
|
|
}
|
|
|
|
#if defined(DEBUG)
|
|
{
|
|
static int count = 0;
|
|
printf("Block #%d (%d)\n", block_num, count++);
|
|
}
|
|
#endif
|
|
/* exponent strategy */
|
|
for(ch=0;ch<s->nb_channels;ch++) {
|
|
put_bits(&s->pb, 2, exp_strategy[ch]);
|
|
}
|
|
|
|
if (s->lfe) {
|
|
put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
|
|
}
|
|
|
|
for(ch=0;ch<s->nb_channels;ch++) {
|
|
if (exp_strategy[ch] != EXP_REUSE)
|
|
put_bits(&s->pb, 6, s->chbwcod[ch]);
|
|
}
|
|
|
|
/* exponents */
|
|
for (ch = 0; ch < s->nb_all_channels; ch++) {
|
|
switch(exp_strategy[ch]) {
|
|
case EXP_REUSE:
|
|
continue;
|
|
case EXP_D15:
|
|
group_size = 1;
|
|
break;
|
|
case EXP_D25:
|
|
group_size = 2;
|
|
break;
|
|
default:
|
|
case EXP_D45:
|
|
group_size = 4;
|
|
break;
|
|
}
|
|
nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
|
|
p = encoded_exp[ch];
|
|
|
|
/* first exponent */
|
|
exp1 = *p++;
|
|
put_bits(&s->pb, 4, exp1);
|
|
|
|
/* next ones are delta encoded */
|
|
for(i=0;i<nb_groups;i++) {
|
|
/* merge three delta in one code */
|
|
exp0 = exp1;
|
|
exp1 = p[0];
|
|
p += group_size;
|
|
delta0 = exp1 - exp0 + 2;
|
|
|
|
exp0 = exp1;
|
|
exp1 = p[0];
|
|
p += group_size;
|
|
delta1 = exp1 - exp0 + 2;
|
|
|
|
exp0 = exp1;
|
|
exp1 = p[0];
|
|
p += group_size;
|
|
delta2 = exp1 - exp0 + 2;
|
|
|
|
put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
|
|
}
|
|
|
|
if (ch != s->lfe_channel)
|
|
put_bits(&s->pb, 2, 0); /* no gain range info */
|
|
}
|
|
|
|
/* bit allocation info */
|
|
baie = (block_num == 0);
|
|
put_bits(&s->pb, 1, baie);
|
|
if (baie) {
|
|
put_bits(&s->pb, 2, s->sdecaycod);
|
|
put_bits(&s->pb, 2, s->fdecaycod);
|
|
put_bits(&s->pb, 2, s->sgaincod);
|
|
put_bits(&s->pb, 2, s->dbkneecod);
|
|
put_bits(&s->pb, 3, s->floorcod);
|
|
}
|
|
|
|
/* snr offset */
|
|
put_bits(&s->pb, 1, baie); /* always present with bai */
|
|
if (baie) {
|
|
put_bits(&s->pb, 6, s->csnroffst);
|
|
for(ch=0;ch<s->nb_all_channels;ch++) {
|
|
put_bits(&s->pb, 4, s->fsnroffst[ch]);
|
|
put_bits(&s->pb, 3, s->fgaincod[ch]);
|
|
}
|
|
}
|
|
|
|
put_bits(&s->pb, 1, 0); /* no delta bit allocation */
|
|
put_bits(&s->pb, 1, 0); /* no data to skip */
|
|
|
|
/* mantissa encoding : we use two passes to handle the grouping. A
|
|
one pass method may be faster, but it would necessitate to
|
|
modify the output stream. */
|
|
|
|
/* first pass: quantize */
|
|
mant1_cnt = mant2_cnt = mant4_cnt = 0;
|
|
qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
|
|
|
|
for (ch = 0; ch < s->nb_all_channels; ch++) {
|
|
int b, c, e, v;
|
|
|
|
for(i=0;i<s->nb_coefs[ch];i++) {
|
|
c = mdct_coefs[ch][i];
|
|
e = encoded_exp[ch][i] - global_exp[ch];
|
|
b = bap[ch][i];
|
|
switch(b) {
|
|
case 0:
|
|
v = 0;
|
|
break;
|
|
case 1:
|
|
v = sym_quant(c, e, 3);
|
|
switch(mant1_cnt) {
|
|
case 0:
|
|
qmant1_ptr = &qmant[ch][i];
|
|
v = 9 * v;
|
|
mant1_cnt = 1;
|
|
break;
|
|
case 1:
|
|
*qmant1_ptr += 3 * v;
|
|
mant1_cnt = 2;
|
|
v = 128;
|
|
break;
|
|
default:
|
|
*qmant1_ptr += v;
|
|
mant1_cnt = 0;
|
|
v = 128;
|
|
break;
|
|
}
|
|
break;
|
|
case 2:
|
|
v = sym_quant(c, e, 5);
|
|
switch(mant2_cnt) {
|
|
case 0:
|
|
qmant2_ptr = &qmant[ch][i];
|
|
v = 25 * v;
|
|
mant2_cnt = 1;
|
|
break;
|
|
case 1:
|
|
*qmant2_ptr += 5 * v;
|
|
mant2_cnt = 2;
|
|
v = 128;
|
|
break;
|
|
default:
|
|
*qmant2_ptr += v;
|
|
mant2_cnt = 0;
|
|
v = 128;
|
|
break;
|
|
}
|
|
break;
|
|
case 3:
|
|
v = sym_quant(c, e, 7);
|
|
break;
|
|
case 4:
|
|
v = sym_quant(c, e, 11);
|
|
switch(mant4_cnt) {
|
|
case 0:
|
|
qmant4_ptr = &qmant[ch][i];
|
|
v = 11 * v;
|
|
mant4_cnt = 1;
|
|
break;
|
|
default:
|
|
*qmant4_ptr += v;
|
|
mant4_cnt = 0;
|
|
v = 128;
|
|
break;
|
|
}
|
|
break;
|
|
case 5:
|
|
v = sym_quant(c, e, 15);
|
|
break;
|
|
case 14:
|
|
v = asym_quant(c, e, 14);
|
|
break;
|
|
case 15:
|
|
v = asym_quant(c, e, 16);
|
|
break;
|
|
default:
|
|
v = asym_quant(c, e, b - 1);
|
|
break;
|
|
}
|
|
qmant[ch][i] = v;
|
|
}
|
|
}
|
|
|
|
/* second pass : output the values */
|
|
for (ch = 0; ch < s->nb_all_channels; ch++) {
|
|
int b, q;
|
|
|
|
for(i=0;i<s->nb_coefs[ch];i++) {
|
|
q = qmant[ch][i];
|
|
b = bap[ch][i];
|
|
switch(b) {
|
|
case 0:
|
|
break;
|
|
case 1:
|
|
if (q != 128)
|
|
put_bits(&s->pb, 5, q);
|
|
break;
|
|
case 2:
|
|
if (q != 128)
|
|
put_bits(&s->pb, 7, q);
|
|
break;
|
|
case 3:
|
|
put_bits(&s->pb, 3, q);
|
|
break;
|
|
case 4:
|
|
if (q != 128)
|
|
put_bits(&s->pb, 7, q);
|
|
break;
|
|
case 14:
|
|
put_bits(&s->pb, 14, q);
|
|
break;
|
|
case 15:
|
|
put_bits(&s->pb, 16, q);
|
|
break;
|
|
default:
|
|
put_bits(&s->pb, b - 1, q);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* compute the ac3 crc */
|
|
|
|
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
|
|
|
|
static void ac3_crc_init(void)
|
|
{
|
|
unsigned int c, n, k;
|
|
|
|
for(n=0;n<256;n++) {
|
|
c = n << 8;
|
|
for (k = 0; k < 8; k++) {
|
|
if (c & (1 << 15))
|
|
c = ((c << 1) & 0xffff) ^ (CRC16_POLY & 0xffff);
|
|
else
|
|
c = c << 1;
|
|
}
|
|
crc_table[n] = c;
|
|
}
|
|
}
|
|
|
|
static unsigned int ac3_crc(uint8_t *data, int n, unsigned int crc)
|
|
{
|
|
int i;
|
|
for(i=0;i<n;i++) {
|
|
crc = (crc_table[data[i] ^ (crc >> 8)] ^ (crc << 8)) & 0xffff;
|
|
}
|
|
return crc;
|
|
}
|
|
|
|
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
|
|
{
|
|
unsigned int c;
|
|
|
|
c = 0;
|
|
while (a) {
|
|
if (a & 1)
|
|
c ^= b;
|
|
a = a >> 1;
|
|
b = b << 1;
|
|
if (b & (1 << 16))
|
|
b ^= poly;
|
|
}
|
|
return c;
|
|
}
|
|
|
|
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
|
|
{
|
|
unsigned int r;
|
|
r = 1;
|
|
while (n) {
|
|
if (n & 1)
|
|
r = mul_poly(r, a, poly);
|
|
a = mul_poly(a, a, poly);
|
|
n >>= 1;
|
|
}
|
|
return r;
|
|
}
|
|
|
|
|
|
/* compute log2(max(abs(tab[]))) */
|
|
static int log2_tab(int16_t *tab, int n)
|
|
{
|
|
int i, v;
|
|
|
|
v = 0;
|
|
for(i=0;i<n;i++) {
|
|
v |= abs(tab[i]);
|
|
}
|
|
return av_log2(v);
|
|
}
|
|
|
|
static void lshift_tab(int16_t *tab, int n, int lshift)
|
|
{
|
|
int i;
|
|
|
|
if (lshift > 0) {
|
|
for(i=0;i<n;i++) {
|
|
tab[i] <<= lshift;
|
|
}
|
|
} else if (lshift < 0) {
|
|
lshift = -lshift;
|
|
for(i=0;i<n;i++) {
|
|
tab[i] >>= lshift;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* fill the end of the frame and compute the two crcs */
|
|
static int output_frame_end(AC3EncodeContext *s)
|
|
{
|
|
int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
|
|
uint8_t *frame;
|
|
|
|
frame_size = s->frame_size; /* frame size in words */
|
|
/* align to 8 bits */
|
|
flush_put_bits(&s->pb);
|
|
/* add zero bytes to reach the frame size */
|
|
frame = s->pb.buf;
|
|
n = 2 * s->frame_size - (pbBufPtr(&s->pb) - frame) - 2;
|
|
assert(n >= 0);
|
|
if(n>0)
|
|
memset(pbBufPtr(&s->pb), 0, n);
|
|
|
|
/* Now we must compute both crcs : this is not so easy for crc1
|
|
because it is at the beginning of the data... */
|
|
frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
|
|
crc1 = ac3_crc(frame + 4, (2 * frame_size_58) - 4, 0);
|
|
/* XXX: could precompute crc_inv */
|
|
crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
|
|
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
|
|
frame[2] = crc1 >> 8;
|
|
frame[3] = crc1;
|
|
|
|
crc2 = ac3_crc(frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2, 0);
|
|
frame[2*frame_size - 2] = crc2 >> 8;
|
|
frame[2*frame_size - 1] = crc2;
|
|
|
|
// printf("n=%d frame_size=%d\n", n, frame_size);
|
|
return frame_size * 2;
|
|
}
|
|
|
|
static int AC3_encode_frame(AVCodecContext *avctx,
|
|
unsigned char *frame, int buf_size, void *data)
|
|
{
|
|
AC3EncodeContext *s = avctx->priv_data;
|
|
short *samples = data;
|
|
int i, j, k, v, ch;
|
|
int16_t input_samples[N];
|
|
int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
|
|
uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
|
|
uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
|
|
uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
|
|
uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
|
|
int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
|
|
int frame_bits;
|
|
|
|
frame_bits = 0;
|
|
for(ch=0;ch<s->nb_all_channels;ch++) {
|
|
/* fixed mdct to the six sub blocks & exponent computation */
|
|
for(i=0;i<NB_BLOCKS;i++) {
|
|
int16_t *sptr;
|
|
int sinc;
|
|
|
|
/* compute input samples */
|
|
memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(int16_t));
|
|
sinc = s->nb_all_channels;
|
|
sptr = samples + (sinc * (N/2) * i) + ch;
|
|
for(j=0;j<N/2;j++) {
|
|
v = *sptr;
|
|
input_samples[j + N/2] = v;
|
|
s->last_samples[ch][j] = v;
|
|
sptr += sinc;
|
|
}
|
|
|
|
/* apply the MDCT window */
|
|
for(j=0;j<N/2;j++) {
|
|
input_samples[j] = MUL16(input_samples[j],
|
|
ac3_window[j]) >> 15;
|
|
input_samples[N-j-1] = MUL16(input_samples[N-j-1],
|
|
ac3_window[j]) >> 15;
|
|
}
|
|
|
|
/* Normalize the samples to use the maximum available
|
|
precision */
|
|
v = 14 - log2_tab(input_samples, N);
|
|
if (v < 0)
|
|
v = 0;
|
|
exp_samples[i][ch] = v - 8;
|
|
lshift_tab(input_samples, N, v);
|
|
|
|
/* do the MDCT */
|
|
mdct512(mdct_coef[i][ch], input_samples);
|
|
|
|
/* compute "exponents". We take into account the
|
|
normalization there */
|
|
for(j=0;j<N/2;j++) {
|
|
int e;
|
|
v = abs(mdct_coef[i][ch][j]);
|
|
if (v == 0)
|
|
e = 24;
|
|
else {
|
|
e = 23 - av_log2(v) + exp_samples[i][ch];
|
|
if (e >= 24) {
|
|
e = 24;
|
|
mdct_coef[i][ch][j] = 0;
|
|
}
|
|
}
|
|
exp[i][ch][j] = e;
|
|
}
|
|
}
|
|
|
|
compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
|
|
|
|
/* compute the exponents as the decoder will see them. The
|
|
EXP_REUSE case must be handled carefully : we select the
|
|
min of the exponents */
|
|
i = 0;
|
|
while (i < NB_BLOCKS) {
|
|
j = i + 1;
|
|
while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
|
|
exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
|
|
j++;
|
|
}
|
|
frame_bits += encode_exp(encoded_exp[i][ch],
|
|
exp[i][ch], s->nb_coefs[ch],
|
|
exp_strategy[i][ch]);
|
|
/* copy encoded exponents for reuse case */
|
|
for(k=i+1;k<j;k++) {
|
|
memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
|
|
s->nb_coefs[ch] * sizeof(uint8_t));
|
|
}
|
|
i = j;
|
|
}
|
|
}
|
|
|
|
compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
|
|
/* everything is known... let's output the frame */
|
|
output_frame_header(s, frame);
|
|
|
|
for(i=0;i<NB_BLOCKS;i++) {
|
|
output_audio_block(s, exp_strategy[i], encoded_exp[i],
|
|
bap[i], mdct_coef[i], exp_samples[i], i);
|
|
}
|
|
return output_frame_end(s);
|
|
}
|
|
|
|
static int AC3_encode_close(AVCodecContext *avctx)
|
|
{
|
|
av_freep(&avctx->coded_frame);
|
|
return 0;
|
|
}
|
|
|
|
#if 0
|
|
/*************************************************************************/
|
|
/* TEST */
|
|
|
|
#define FN (N/4)
|
|
|
|
void fft_test(void)
|
|
{
|
|
IComplex in[FN], in1[FN];
|
|
int k, n, i;
|
|
float sum_re, sum_im, a;
|
|
|
|
/* FFT test */
|
|
|
|
for(i=0;i<FN;i++) {
|
|
in[i].re = random() % 65535 - 32767;
|
|
in[i].im = random() % 65535 - 32767;
|
|
in1[i] = in[i];
|
|
}
|
|
fft(in, 7);
|
|
|
|
/* do it by hand */
|
|
for(k=0;k<FN;k++) {
|
|
sum_re = 0;
|
|
sum_im = 0;
|
|
for(n=0;n<FN;n++) {
|
|
a = -2 * M_PI * (n * k) / FN;
|
|
sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
|
|
sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
|
|
}
|
|
printf("%3d: %6d,%6d %6.0f,%6.0f\n",
|
|
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
|
|
}
|
|
}
|
|
|
|
void mdct_test(void)
|
|
{
|
|
int16_t input[N];
|
|
int32_t output[N/2];
|
|
float input1[N];
|
|
float output1[N/2];
|
|
float s, a, err, e, emax;
|
|
int i, k, n;
|
|
|
|
for(i=0;i<N;i++) {
|
|
input[i] = (random() % 65535 - 32767) * 9 / 10;
|
|
input1[i] = input[i];
|
|
}
|
|
|
|
mdct512(output, input);
|
|
|
|
/* do it by hand */
|
|
for(k=0;k<N/2;k++) {
|
|
s = 0;
|
|
for(n=0;n<N;n++) {
|
|
a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
|
|
s += input1[n] * cos(a);
|
|
}
|
|
output1[k] = -2 * s / N;
|
|
}
|
|
|
|
err = 0;
|
|
emax = 0;
|
|
for(i=0;i<N/2;i++) {
|
|
printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
|
|
e = output[i] - output1[i];
|
|
if (e > emax)
|
|
emax = e;
|
|
err += e * e;
|
|
}
|
|
printf("err2=%f emax=%f\n", err / (N/2), emax);
|
|
}
|
|
|
|
void test_ac3(void)
|
|
{
|
|
AC3EncodeContext ctx;
|
|
unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
|
|
short samples[AC3_FRAME_SIZE];
|
|
int ret, i;
|
|
|
|
AC3_encode_init(&ctx, 44100, 64000, 1);
|
|
|
|
fft_test();
|
|
mdct_test();
|
|
|
|
for(i=0;i<AC3_FRAME_SIZE;i++)
|
|
samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
|
|
ret = AC3_encode_frame(&ctx, frame, samples);
|
|
printf("ret=%d\n", ret);
|
|
}
|
|
#endif
|
|
|
|
AVCodec ac3_encoder = {
|
|
"ac3",
|
|
CODEC_TYPE_AUDIO,
|
|
CODEC_ID_AC3,
|
|
sizeof(AC3EncodeContext),
|
|
AC3_encode_init,
|
|
AC3_encode_frame,
|
|
AC3_encode_close,
|
|
NULL,
|
|
};
|