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04ac5cada1
FFmpeg/libavcodec/ac3dec.c
Justin Ruggles 04ac5cada1 cosmetics: indentation 
Originally committed as revision 9887 to svn://svn.ffmpeg.org/ffmpeg/trunk
2007-08-04 01:14:14 +00:00

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/*
* AC-3 Audio Decoder
* This code is developed as part of Google Summer of Code 2006 Program.
*
* Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com).
* Copyright (c) 2007 Justin Ruggles
*
* Portions of this code are derived from liba52
* http://liba52.sourceforge.net
* Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 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
* General Public License for more details.
*
* You should have received a copy of the GNU 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
*/
#include <stdio.h>
#include <stddef.h>
#include <math.h>
#include <string.h>
#include "avcodec.h"
#include "ac3_parser.h"
#include "bitstream.h"
#include "dsputil.h"
#include "random.h"
/**
* Table of bin locations for rematrixing bands
* reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
*/
static const uint8_t rematrix_band_tbl[5] = { 13, 25, 37, 61, 253 };
/* table for exponent to scale_factor mapping
* scale_factor[i] = 2 ^ -(i + 15)
*/
static float scale_factors[25];
/** table for grouping exponents */
static uint8_t exp_ungroup_tbl[128][3];
static int16_t l3_quantizers_1[32];
static int16_t l3_quantizers_2[32];
static int16_t l3_quantizers_3[32];
static int16_t l5_quantizers_1[128];
static int16_t l5_quantizers_2[128];
static int16_t l5_quantizers_3[128];
static int16_t l7_quantizers[7];
static int16_t l11_quantizers_1[128];
static int16_t l11_quantizers_2[128];
static int16_t l15_quantizers[15];
static const uint8_t qntztab[16] = { 0, 5, 7, 3, 7, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16 };
/* Adjustmens in dB gain */
#define LEVEL_MINUS_3DB 0.7071067811865476
#define LEVEL_MINUS_4POINT5DB 0.5946035575013605
#define LEVEL_MINUS_6DB 0.5000000000000000
#define LEVEL_PLUS_3DB 1.4142135623730951
#define LEVEL_PLUS_6DB 2.0000000000000000
#define LEVEL_ZERO 0.0000000000000000
static const float clevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB,
LEVEL_MINUS_6DB, LEVEL_MINUS_4POINT5DB };
static const float slevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO, LEVEL_MINUS_6DB };
#define AC3_OUTPUT_LFEON 8
typedef struct {
int acmod;
int cmixlev;
int surmixlev;
int dsurmod;
int blksw[AC3_MAX_CHANNELS];
int dithflag[AC3_MAX_CHANNELS];
int dither_all;
int cplinu;
int chincpl[AC3_MAX_CHANNELS];
int phsflginu;
int cplcoe;
uint32_t cplbndstrc;
int rematstr;
int nrematbnd;
int rematflg[AC3_MAX_CHANNELS];
int cplexpstr;
int lfeexpstr;
int chexpstr[5];
int cplsnroffst;
int cplfgain;
int snroffst[5];
int fgain[5];
int lfesnroffst;
int lfefgain;
int cpldeltbae;
int deltbae[5];
int cpldeltnseg;
uint8_t cpldeltoffst[8];
uint8_t cpldeltlen[8];
uint8_t cpldeltba[8];
int deltnseg[5];
uint8_t deltoffst[5][8];
uint8_t deltlen[5][8];
uint8_t deltba[5][8];
/* Derived Attributes. */
int sampling_rate;
int bit_rate;
int frame_size;
int nchans; //number of total channels
int nfchans; //number of full-bandwidth channels
int lfeon; //lfe channel in use
int output_mode; ///< output channel configuration
int out_channels; ///< number of output channels
float dynrng; //dynamic range gain
float dynrng2; //dynamic range gain for 1+1 mode
float cplco[5][18]; //coupling coordinates
int ncplbnd; //number of coupling bands
int ncplsubnd; //number of coupling sub bands
int cplstrtmant; //coupling start mantissa
int cplendmant; //coupling end mantissa
int endmant[5]; //channel end mantissas
AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
int8_t dcplexps[256]; //decoded coupling exponents
int8_t dexps[5][256]; //decoded fbw channel exponents
int8_t dlfeexps[256]; //decoded lfe channel exponents
uint8_t cplbap[256]; //coupling bit allocation pointers
uint8_t bap[5][256]; //fbw channel bit allocation pointers
uint8_t lfebap[256]; //lfe channel bit allocation pointers
float transform_coeffs_cpl[256];
DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); //transform coefficients
/* For IMDCT. */
MDCTContext imdct_512; //for 512 sample imdct transform
MDCTContext imdct_256; //for 256 sample imdct transform
DSPContext dsp; //for optimization
DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][256]); //output after imdct transform and windowing
DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][256]); //delay - added to the next block
DECLARE_ALIGNED_16(float, tmp_imdct[256]); //temporary storage for imdct transform
DECLARE_ALIGNED_16(float, tmp_output[512]); //temporary storage for output before windowing
DECLARE_ALIGNED_16(float, window[256]); //window coefficients
/* Miscellaneous. */
GetBitContext gb;
AVRandomState dith_state; //for dither generation
} AC3DecodeContext;
/*********** BEGIN INIT HELPER FUNCTIONS ***********/
/**
* Generate a Kaiser-Bessel Derived Window.
*/
static void ac3_window_init(float *window)
{
int i, j;
double sum = 0.0, bessel, tmp;
double local_window[256];
double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
for (i = 0; i < 256; i++) {
tmp = i * (256 - i) * alpha2;
bessel = 1.0;
for (j = 100; j > 0; j--) /* defaul to 100 iterations */
bessel = bessel * tmp / (j * j) + 1;
sum += bessel;
local_window[i] = sum;
}
sum++;
for (i = 0; i < 256; i++)
window[i] = sqrt(local_window[i] / sum);
}
/*
* Generate quantizer tables.
*/
static void generate_quantizers_table(int16_t quantizers[], int level, int length)
{
int i;
for (i = 0; i < length; i++)
quantizers[i] = ((2 * i - level + 1) << 15) / level;
}
static void generate_quantizers_table_1(int16_t quantizers[], int level, int length1, int length2, int size)
{
int i, j;
int16_t v;
for (i = 0; i < length1; i++) {
v = ((2 * i - level + 1) << 15) / level;
for (j = 0; j < length2; j++)
quantizers[i * length2 + j] = v;
}
for (i = length1 * length2; i < size; i++)
quantizers[i] = 0;
}
static void generate_quantizers_table_2(int16_t quantizers[], int level, int length1, int length2, int size)
{
int i, j;
int16_t v;
for (i = 0; i < length1; i++) {
v = ((2 * (i % level) - level + 1) << 15) / level;
for (j = 0; j < length2; j++)
quantizers[i * length2 + j] = v;
}
for (i = length1 * length2; i < size; i++)
quantizers[i] = 0;
}
static void generate_quantizers_table_3(int16_t quantizers[], int level, int length1, int length2, int size)
{
int i, j;
for (i = 0; i < length1; i++)
for (j = 0; j < length2; j++)
quantizers[i * length2 + j] = ((2 * (j % level) - level + 1) << 15) / level;
for (i = length1 * length2; i < size; i++)
quantizers[i] = 0;
}
/*
* Initialize tables at runtime.
*/
static void ac3_tables_init(void)
{
int i;
/* Quantizer ungrouping tables. */
// for level-3 quantizers
generate_quantizers_table_1(l3_quantizers_1, 3, 3, 9, 32);
generate_quantizers_table_2(l3_quantizers_2, 3, 9, 3, 32);
generate_quantizers_table_3(l3_quantizers_3, 3, 9, 3, 32);
//for level-5 quantizers
generate_quantizers_table_1(l5_quantizers_1, 5, 5, 25, 128);
generate_quantizers_table_2(l5_quantizers_2, 5, 25, 5, 128);
generate_quantizers_table_3(l5_quantizers_3, 5, 25, 5, 128);
//for level-7 quantizers
generate_quantizers_table(l7_quantizers, 7, 7);
//for level-4 quantizers
generate_quantizers_table_2(l11_quantizers_1, 11, 11, 11, 128);
generate_quantizers_table_3(l11_quantizers_2, 11, 11, 11, 128);
//for level-15 quantizers
generate_quantizers_table(l15_quantizers, 15, 15);
/* End Quantizer ungrouping tables. */
//generate scale factors
for (i = 0; i < 25; i++)
scale_factors[i] = pow(2.0, -(i + 15));
/* generate exponent tables
reference: Section 7.1.3 Exponent Decoding */
for(i=0; i<128; i++) {
exp_ungroup_tbl[i][0] = i / 25;
exp_ungroup_tbl[i][1] = (i % 25) / 5;
exp_ungroup_tbl[i][2] = (i % 25) % 5;
}
}
static int ac3_decode_init(AVCodecContext *avctx)
{
AC3DecodeContext *ctx = avctx->priv_data;
ac3_common_init();
ac3_tables_init();
ff_mdct_init(&ctx->imdct_256, 8, 1);
ff_mdct_init(&ctx->imdct_512, 9, 1);
ac3_window_init(ctx->window);
dsputil_init(&ctx->dsp, avctx);
av_init_random(0, &ctx->dith_state);
return 0;
}
/*********** END INIT FUNCTIONS ***********/
/**
* Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
* GetBitContext within AC3DecodeContext must point to
* start of the synchronized ac3 bitstream.
*/
static int ac3_parse_header(AC3DecodeContext *ctx)
{
AC3HeaderInfo hdr;
GetBitContext *gb = &ctx->gb;
int err, i;
err = ff_ac3_parse_header(gb->buffer, &hdr);
if(err)
return err;
/* get decoding parameters from header info */
ctx->bit_alloc_params.fscod = hdr.fscod;
ctx->acmod = hdr.acmod;
ctx->cmixlev = hdr.cmixlev;
ctx->surmixlev = hdr.surmixlev;
ctx->dsurmod = hdr.dsurmod;
ctx->lfeon = hdr.lfeon;
ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
ctx->sampling_rate = hdr.sample_rate;
ctx->bit_rate = hdr.bit_rate;
ctx->nchans = hdr.channels;
ctx->nfchans = ctx->nchans - ctx->lfeon;
ctx->frame_size = hdr.frame_size;
/* set default output to all source channels */
ctx->out_channels = ctx->nchans;
ctx->output_mode = ctx->acmod;
if(ctx->lfeon)
ctx->output_mode |= AC3_OUTPUT_LFEON;
/* skip over portion of header which has already been read */
skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
skip_bits(gb, 16); // skip crc1
skip_bits(gb, 8); // skip fscod and frmsizecod
skip_bits(gb, 11); // skip bsid, bsmod, and acmod
if(ctx->acmod == AC3_ACMOD_STEREO) {
skip_bits(gb, 2); // skip dsurmod
} else {
if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
skip_bits(gb, 2); // skip cmixlev
if(ctx->acmod & 4)
skip_bits(gb, 2); // skip surmixlev
}
skip_bits1(gb); // skip lfeon
/* read the rest of the bsi. read twice for dual mono mode. */
i = !(ctx->acmod);
do {
skip_bits(gb, 5); //skip dialog normalization
if (get_bits1(gb))
skip_bits(gb, 8); //skip compression
if (get_bits1(gb))
skip_bits(gb, 8); //skip language code
if (get_bits1(gb))
skip_bits(gb, 7); //skip audio production information
} while (i--);
skip_bits(gb, 2); //skip copyright bit and original bitstream bit
/* FIXME: read & use the xbsi1 downmix levels */
if (get_bits1(gb))
skip_bits(gb, 14); //skip timecode1
if (get_bits1(gb))
skip_bits(gb, 14); //skip timecode2
if (get_bits1(gb)) {
i = get_bits(gb, 6); //additional bsi length
do {
skip_bits(gb, 8);
} while(i--);
}
return 0;
}
/**
* Decodes the grouped exponents.
* This function decodes the coded exponents according to exponent strategy
* and stores them in the decoded exponents buffer.
*
* @param[in] gb GetBitContext which points to start of coded exponents
* @param[in] expstr Exponent coding strategy
* @param[in] ngrps Number of grouped exponents
* @param[in] absexp Absolute exponent or DC exponent
* @param[out] dexps Decoded exponents are stored in dexps
*/
static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
uint8_t absexp, int8_t *dexps)
{
int i, j, grp, grpsize;
int dexp[256];
int expacc, prevexp;
/* unpack groups */
grpsize = expstr + (expstr == EXP_D45);
for(grp=0,i=0; grp<ngrps; grp++) {
expacc = get_bits(gb, 7);
dexp[i++] = exp_ungroup_tbl[expacc][0];
dexp[i++] = exp_ungroup_tbl[expacc][1];
dexp[i++] = exp_ungroup_tbl[expacc][2];
}
/* convert to absolute exps and expand groups */
prevexp = absexp;
for(i=0; i<ngrps*3; i++) {
prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
for(j=0; j<grpsize; j++) {
dexps[(i*grpsize)+j] = prevexp;
}
}
}
/**
* Generates transform coefficients for each coupled channel in the coupling
* range using the coupling coefficients and coupling coordinates.
* reference: Section 7.4.3 Coupling Coordinate Format
*/
static void uncouple_channels(AC3DecodeContext *ctx)
{
int i, j, ch, bnd, subbnd;
subbnd = -1;
i = ctx->cplstrtmant;
for(bnd=0; bnd<ctx->ncplbnd; bnd++) {
do {
subbnd++;
for(j=0; j<12; j++) {
for(ch=1; ch<=ctx->nfchans; ch++) {
if(ctx->chincpl[ch-1])
ctx->transform_coeffs[ch][i] = ctx->transform_coeffs_cpl[i] * ctx->cplco[ch-1][bnd];
}
i++;
}
} while((ctx->cplbndstrc >> subbnd) & 1);
}
}
typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
int16_t l3_quantizers[3];
int16_t l5_quantizers[3];
int16_t l11_quantizers[2];
int l3ptr;
int l5ptr;
int l11ptr;
} mant_groups;
/* Get the transform coefficients for particular channel */
static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
{
GetBitContext *gb = &ctx->gb;
int i, gcode, tbap, start, end;
uint8_t *exps;
uint8_t *bap;
float *coeffs;
if (ch_index >= 0) { /* fbw channels */
exps = ctx->dexps[ch_index];
bap = ctx->bap[ch_index];
coeffs = ctx->transform_coeffs[ch_index + 1];
start = 0;
end = ctx->endmant[ch_index];
} else if (ch_index == -1) {
exps = ctx->dlfeexps;
bap = ctx->lfebap;
coeffs = ctx->transform_coeffs[0];
start = 0;
end = 7;
} else {
exps = ctx->dcplexps;
bap = ctx->cplbap;
coeffs = ctx->transform_coeffs_cpl;
start = ctx->cplstrtmant;
end = ctx->cplendmant;
}
for (i = start; i < end; i++) {
tbap = bap[i];
switch (tbap) {
case 0:
coeffs[i] = (av_random(&ctx->dith_state) & 0xFFFF) * LEVEL_MINUS_3DB;
break;
case 1:
if (m->l3ptr > 2) {
gcode = get_bits(gb, 5);
m->l3_quantizers[0] = l3_quantizers_1[gcode];
m->l3_quantizers[1] = l3_quantizers_2[gcode];
m->l3_quantizers[2] = l3_quantizers_3[gcode];
m->l3ptr = 0;
}
coeffs[i] = m->l3_quantizers[m->l3ptr++];
break;
case 2:
if (m->l5ptr > 2) {
gcode = get_bits(gb, 7);
m->l5_quantizers[0] = l5_quantizers_1[gcode];
m->l5_quantizers[1] = l5_quantizers_2[gcode];
m->l5_quantizers[2] = l5_quantizers_3[gcode];
m->l5ptr = 0;
}
coeffs[i] = m->l5_quantizers[m->l5ptr++];
break;
case 3:
coeffs[i] = l7_quantizers[get_bits(gb, 3)];
break;
case 4:
if (m->l11ptr > 1) {
gcode = get_bits(gb, 7);
m->l11_quantizers[0] = l11_quantizers_1[gcode];
m->l11_quantizers[1] = l11_quantizers_2[gcode];
m->l11ptr = 0;
}
coeffs[i] = m->l11_quantizers[m->l11ptr++];
break;
case 5:
coeffs[i] = l15_quantizers[get_bits(gb, 4)];
break;
default:
coeffs[i] = get_sbits(gb, qntztab[tbap]) << (16 - qntztab[tbap]);
break;
}
coeffs[i] *= scale_factors[exps[i]];
}
return 0;
}
/**
* Removes random dithering from coefficients with zero-bit mantissas
* reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
*/
static void remove_dithering(AC3DecodeContext *ctx) {
int ch, i;
int end=0;
float *coeffs;
uint8_t *bap;
for(ch=1; ch<=ctx->nfchans; ch++) {
if(!ctx->dithflag[ch-1]) {
coeffs = ctx->transform_coeffs[ch];
bap = ctx->bap[ch-1];
if(ctx->chincpl[ch-1])
end = ctx->cplstrtmant;
else
end = ctx->endmant[ch-1];
for(i=0; i<end; i++) {
if(bap[i] == 0)
coeffs[i] = 0.0f;
}
if(ctx->chincpl[ch-1]) {
bap = ctx->cplbap;
for(; i<ctx->cplendmant; i++) {
if(bap[i] == 0)
coeffs[i] = 0.0f;
}
}
}
}
}
/* Get the transform coefficients.
* This function extracts the tranform coefficients form the ac3 bitstream.
* This function is called after bit allocation is performed.
*/
static int get_transform_coeffs(AC3DecodeContext * ctx)
{
int i, end;
int got_cplchan = 0;
mant_groups m;
m.l3ptr = m.l5ptr = m.l11ptr = 3;
for (i = 0; i < ctx->nfchans; i++) {
/* transform coefficients for individual channel */
if (get_transform_coeffs_ch(ctx, i, &m))
return -1;
/* tranform coefficients for coupling channels */
if (ctx->chincpl[i]) {
if (!got_cplchan) {
if (get_transform_coeffs_ch(ctx, -2, &m)) {
av_log(NULL, AV_LOG_ERROR, "error in decoupling channels\n");
return -1;
}
uncouple_channels(ctx);
got_cplchan = 1;
}
end = ctx->cplendmant;
} else
end = ctx->endmant[i];
do
ctx->transform_coeffs[i + 1][end] = 0;
while(++end < 256);
}
if (ctx->lfeon) {
if (get_transform_coeffs_ch(ctx, -1, &m))
return -1;
for (i = 7; i < 256; i++) {
ctx->transform_coeffs[0][i] = 0;
}
}
/* if any channel doesn't use dithering, zero appropriate coefficients */
if(!ctx->dither_all)
remove_dithering(ctx);
return 0;
}
/**
* Performs stereo rematrixing.
* reference: Section 7.5.4 Rematrixing : Decoding Technique
*/
static void do_rematrixing(AC3DecodeContext *ctx)
{
int bnd, i;
int end, bndend;
float tmp0, tmp1;
end = FFMIN(ctx->endmant[0], ctx->endmant[1]);
for(bnd=0; bnd<ctx->nrematbnd; bnd++) {
if(ctx->rematflg[bnd]) {
bndend = FFMIN(end, rematrix_band_tbl[bnd+1]);
for(i=rematrix_band_tbl[bnd]; i<bndend; i++) {
tmp0 = ctx->transform_coeffs[1][i];
tmp1 = ctx->transform_coeffs[2][i];
ctx->transform_coeffs[1][i] = tmp0 + tmp1;
ctx->transform_coeffs[2][i] = tmp0 - tmp1;
}
}
}
}
/* This function performs the imdct on 256 sample transform
* coefficients.
*/
static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
{
int i, k;
DECLARE_ALIGNED_16(float, x[128]);
FFTComplex z[2][64];
float *o_ptr = ctx->tmp_output;
for(i=0; i<2; i++) {
/* de-interleave coefficients */
for(k=0; k<128; k++) {
x[k] = ctx->transform_coeffs[chindex][2*k+i];
}
/* run standard IMDCT */
ctx->imdct_256.fft.imdct_calc(&ctx->imdct_256, o_ptr, x, ctx->tmp_imdct);
/* reverse the post-rotation & reordering from standard IMDCT */
for(k=0; k<32; k++) {
z[i][32+k].re = -o_ptr[128+2*k];
z[i][32+k].im = -o_ptr[2*k];
z[i][31-k].re = o_ptr[2*k+1];
z[i][31-k].im = o_ptr[128+2*k+1];
}
}
/* apply AC-3 post-rotation & reordering */
for(k=0; k<64; k++) {
o_ptr[ 2*k ] = -z[0][ k].im;
o_ptr[ 2*k+1] = z[0][63-k].re;
o_ptr[128+2*k ] = -z[0][ k].re;
o_ptr[128+2*k+1] = z[0][63-k].im;
o_ptr[256+2*k ] = -z[1][ k].re;
o_ptr[256+2*k+1] = z[1][63-k].im;
o_ptr[384+2*k ] = z[1][ k].im;
o_ptr[384+2*k+1] = -z[1][63-k].re;
}
}
/* IMDCT Transform. */
static inline void do_imdct(AC3DecodeContext *ctx)
{
int ch;
if (ctx->output_mode & AC3_OUTPUT_LFEON) {
ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
ctx->transform_coeffs[0], ctx->tmp_imdct);
ctx->dsp.vector_fmul_add_add(ctx->output[0], ctx->tmp_output,
ctx->window, ctx->delay[0], 384, 256, 1);
ctx->dsp.vector_fmul_reverse(ctx->delay[0], ctx->tmp_output+256,
ctx->window, 256);
}
for (ch=1; ch<=ctx->nfchans; ch++) {
if (ctx->blksw[ch-1])
do_imdct_256(ctx, ch);
else
ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
ctx->transform_coeffs[ch],
ctx->tmp_imdct);
ctx->dsp.vector_fmul_add_add(ctx->output[ch], ctx->tmp_output,
ctx->window, ctx->delay[ch], 384, 256, 1);
ctx->dsp.vector_fmul_reverse(ctx->delay[ch], ctx->tmp_output+256,
ctx->window, 256);
}
}
/* Parse the audio block from ac3 bitstream.
* This function extract the audio block from the ac3 bitstream
* and produces the output for the block. This function must
* be called for each of the six audio block in the ac3 bitstream.
*/
static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
{
int nfchans = ctx->nfchans;
int acmod = ctx->acmod;
int i, bnd, seg, grpsize, ch;
GetBitContext *gb = &ctx->gb;
int bit_alloc_flags = 0;
int8_t *dexps;
int mstrcplco, cplcoexp, cplcomant;
int dynrng, chbwcod, ngrps, cplabsexp, skipl;
for (i = 0; i < nfchans; i++) /*block switch flag */
ctx->blksw[i] = get_bits1(gb);
ctx->dither_all = 1;
for (i = 0; i < nfchans; i++) { /* dithering flag */
ctx->dithflag[i] = get_bits1(gb);
if(!ctx->dithflag[i])
ctx->dither_all = 0;
}
if (get_bits1(gb)) { /* dynamic range */
dynrng = get_sbits(gb, 8);
ctx->dynrng = ((((dynrng & 0x1f) | 0x20) << 13) * scale_factors[3 - (dynrng >> 5)]);
} else if(blk == 0) {
ctx->dynrng = 1.0;
}
if(acmod == AC3_ACMOD_DUALMONO) { /* dynamic range 1+1 mode */
if(get_bits1(gb)) {
dynrng = get_sbits(gb, 8);
ctx->dynrng2 = ((((dynrng & 0x1f) | 0x20) << 13) * scale_factors[3 - (dynrng >> 5)]);
} else if(blk == 0) {
ctx->dynrng2 = 1.0;
}
}
if (get_bits1(gb)) { /* coupling strategy */
ctx->cplinu = get_bits1(gb);
ctx->cplbndstrc = 0;
if (ctx->cplinu) { /* coupling in use */
int cplbegf, cplendf;
for (i = 0; i < nfchans; i++)
ctx->chincpl[i] = get_bits1(gb);
if (acmod == AC3_ACMOD_STEREO)
ctx->phsflginu = get_bits1(gb); //phase flag in use
cplbegf = get_bits(gb, 4);
cplendf = get_bits(gb, 4);
if (3 + cplendf - cplbegf < 0) {
av_log(NULL, AV_LOG_ERROR, "cplendf = %d < cplbegf = %d\n", cplendf, cplbegf);
return -1;
}
ctx->ncplbnd = ctx->ncplsubnd = 3 + cplendf - cplbegf;
ctx->cplstrtmant = cplbegf * 12 + 37;
ctx->cplendmant = cplendf * 12 + 73;
for (i = 0; i < ctx->ncplsubnd - 1; i++) /* coupling band structure */
if (get_bits1(gb)) {
ctx->cplbndstrc |= 1 << i;
ctx->ncplbnd--;
}
} else {
for (i = 0; i < nfchans; i++)
ctx->chincpl[i] = 0;
}
}
if (ctx->cplinu) {
ctx->cplcoe = 0;
for (i = 0; i < nfchans; i++)
if (ctx->chincpl[i])
if (get_bits1(gb)) { /* coupling co-ordinates */
ctx->cplcoe |= 1 << i;
mstrcplco = 3 * get_bits(gb, 2);
for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
cplcoexp = get_bits(gb, 4);
cplcomant = get_bits(gb, 4);
if (cplcoexp == 15)
cplcomant <<= 14;
else
cplcomant = (cplcomant | 0x10) << 13;
ctx->cplco[i][bnd] = cplcomant * scale_factors[cplcoexp + mstrcplco];
}
}
if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && (ctx->cplcoe & 1 || ctx->cplcoe & 2))
for (bnd = 0; bnd < ctx->ncplbnd; bnd++)
if (get_bits1(gb))
ctx->cplco[1][bnd] = -ctx->cplco[1][bnd];
}
if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
ctx->rematstr = get_bits1(gb);
if (ctx->rematstr) {
ctx->nrematbnd = 4;
if(ctx->cplinu && ctx->cplstrtmant <= 61)
ctx->nrematbnd -= 1 + (ctx->cplstrtmant == 37);
for(bnd=0; bnd<ctx->nrematbnd; bnd++)
ctx->rematflg[bnd] = get_bits1(gb);
}
}
ctx->cplexpstr = EXP_REUSE;
ctx->lfeexpstr = EXP_REUSE;
if (ctx->cplinu) /* coupling exponent strategy */
ctx->cplexpstr = get_bits(gb, 2);
for (i = 0; i < nfchans; i++) /* channel exponent strategy */
ctx->chexpstr[i] = get_bits(gb, 2);
if (ctx->lfeon) /* lfe exponent strategy */
ctx->lfeexpstr = get_bits1(gb);
for (i = 0; i < nfchans; i++) /* channel bandwidth code */
if (ctx->chexpstr[i] != EXP_REUSE) {
if (ctx->chincpl[i])
ctx->endmant[i] = ctx->cplstrtmant;
else {
chbwcod = get_bits(gb, 6);
if (chbwcod > 60) {
av_log(NULL, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
return -1;
}
ctx->endmant[i] = chbwcod * 3 + 73;
}
}
if (ctx->cplexpstr != EXP_REUSE) {/* coupling exponents */
bit_alloc_flags = 64;
cplabsexp = get_bits(gb, 4) << 1;
ngrps = (ctx->cplendmant - ctx->cplstrtmant) / (3 << (ctx->cplexpstr - 1));
decode_exponents(gb, ctx->cplexpstr, ngrps, cplabsexp, ctx->dcplexps + ctx->cplstrtmant);
}
for (i = 0; i < nfchans; i++) /* fbw channel exponents */
if (ctx->chexpstr[i] != EXP_REUSE) {
bit_alloc_flags |= 1 << i;
grpsize = 3 << (ctx->chexpstr[i] - 1);
ngrps = (ctx->endmant[i] + grpsize - 4) / grpsize;
dexps = ctx->dexps[i];
dexps[0] = get_bits(gb, 4);
decode_exponents(gb, ctx->chexpstr[i], ngrps, dexps[0], dexps + 1);
skip_bits(gb, 2); /* skip gainrng */
}
if (ctx->lfeexpstr != EXP_REUSE) { /* lfe exponents */
bit_alloc_flags |= 32;
ctx->dlfeexps[0] = get_bits(gb, 4);
decode_exponents(gb, ctx->lfeexpstr, 2, ctx->dlfeexps[0], ctx->dlfeexps + 1);
}
if (get_bits1(gb)) { /* bit allocation information */
bit_alloc_flags = 127;
ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
ctx->bit_alloc_params.sgain = ff_sgaintab[get_bits(gb, 2)];
ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
ctx->bit_alloc_params.floor = ff_floortab[get_bits(gb, 3)];
}
if (get_bits1(gb)) { /* snroffset */
int csnr;
bit_alloc_flags = 127;
csnr = (get_bits(gb, 6) - 15) << 4;
if (ctx->cplinu) { /* coupling fine snr offset and fast gain code */
ctx->cplsnroffst = (csnr + get_bits(gb, 4)) << 2;
ctx->cplfgain = ff_fgaintab[get_bits(gb, 3)];
}
for (i = 0; i < nfchans; i++) { /* channel fine snr offset and fast gain code */
ctx->snroffst[i] = (csnr + get_bits(gb, 4)) << 2;
ctx->fgain[i] = ff_fgaintab[get_bits(gb, 3)];
}
if (ctx->lfeon) { /* lfe fine snr offset and fast gain code */
ctx->lfesnroffst = (csnr + get_bits(gb, 4)) << 2;
ctx->lfefgain = ff_fgaintab[get_bits(gb, 3)];
}
}
if (ctx->cplinu && get_bits1(gb)) { /* coupling leak information */
bit_alloc_flags |= 64;
ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
}
if (get_bits1(gb)) { /* delta bit allocation information */
bit_alloc_flags = 127;
if (ctx->cplinu) {
ctx->cpldeltbae = get_bits(gb, 2);
if (ctx->cpldeltbae == DBA_RESERVED) {
av_log(NULL, AV_LOG_ERROR, "coupling delta bit allocation strategy reserved\n");
return -1;
}
}
for (i = 0; i < nfchans; i++) {
ctx->deltbae[i] = get_bits(gb, 2);
if (ctx->deltbae[i] == DBA_RESERVED) {
av_log(NULL, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
return -1;
}
}
if (ctx->cplinu)
if (ctx->cpldeltbae == DBA_NEW) { /*coupling delta offset, len and bit allocation */
ctx->cpldeltnseg = get_bits(gb, 3);
for (seg = 0; seg <= ctx->cpldeltnseg; seg++) {
ctx->cpldeltoffst[seg] = get_bits(gb, 5);
ctx->cpldeltlen[seg] = get_bits(gb, 4);
ctx->cpldeltba[seg] = get_bits(gb, 3);
}
}
for (i = 0; i < nfchans; i++)
if (ctx->deltbae[i] == DBA_NEW) {/*channel delta offset, len and bit allocation */
ctx->deltnseg[i] = get_bits(gb, 3);
for (seg = 0; seg <= ctx->deltnseg[i]; seg++) {
ctx->deltoffst[i][seg] = get_bits(gb, 5);
ctx->deltlen[i][seg] = get_bits(gb, 4);
ctx->deltba[i][seg] = get_bits(gb, 3);
}
}
} else if(blk == 0) {
if(ctx->cplinu)
ctx->cpldeltbae = DBA_NONE;
for(i=0; i<nfchans; i++) {
ctx->deltbae[i] = DBA_NONE;
}
}
if (bit_alloc_flags) {
if (ctx->cplinu && (bit_alloc_flags & 64))
ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->cplbap,
ctx->dcplexps, ctx->cplstrtmant,
ctx->cplendmant, ctx->cplsnroffst,
ctx->cplfgain, 0,
ctx->cpldeltbae, ctx->cpldeltnseg,
ctx->cpldeltoffst, ctx->cpldeltlen,
ctx->cpldeltba);
for (i = 0; i < nfchans; i++)
if ((bit_alloc_flags >> i) & 1)
ac3_parametric_bit_allocation(&ctx->bit_alloc_params,
ctx->bap[i], ctx->dexps[i], 0,
ctx->endmant[i], ctx->snroffst[i],
ctx->fgain[i], 0, ctx->deltbae[i],
ctx->deltnseg[i], ctx->deltoffst[i],
ctx->deltlen[i], ctx->deltba[i]);
if (ctx->lfeon && (bit_alloc_flags & 32))
ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->lfebap,
ctx->dlfeexps, 0, 7, ctx->lfesnroffst,
ctx->lfefgain, 1,
DBA_NONE, 0, NULL, NULL, NULL);
}
if (get_bits1(gb)) { /* unused dummy data */
skipl = get_bits(gb, 9);
while(skipl--)
skip_bits(gb, 8);
}
/* unpack the transform coefficients
* * this also uncouples channels if coupling is in use.
*/
if (get_transform_coeffs(ctx)) {
av_log(NULL, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
return -1;
}
/* recover coefficients if rematrixing is in use */
if(ctx->acmod == AC3_ACMOD_STEREO)
do_rematrixing(ctx);
/* apply scaling to coefficients (headroom, dynrng) */
if(ctx->lfeon) {
for(i=0; i<7; i++) {
ctx->transform_coeffs[0][i] *= 2.0f * ctx->dynrng;
}
}
for(ch=1; ch<=ctx->nfchans; ch++) {
float gain = 2.0f;
if(ctx->acmod == AC3_ACMOD_DUALMONO && ch == 2) {
gain *= ctx->dynrng2;
} else {
gain *= ctx->dynrng;
}
for(i=0; i<ctx->endmant[ch-1]; i++) {
ctx->transform_coeffs[ch][i] *= gain;
}
}
do_imdct(ctx);
return 0;
}
static inline int16_t convert(int32_t i)
{
if (i > 0x43c07fff)
return 32767;
else if (i <= 0x43bf8000)
return -32768;
else
return (i - 0x43c00000);
}
/* Decode ac3 frame.
*
* @param avctx Pointer to AVCodecContext
* @param data Pointer to pcm smaples
* @param data_size Set to number of pcm samples produced by decoding
* @param buf Data to be decoded
* @param buf_size Size of the buffer
*/
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
{
AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
int16_t *out_samples = (int16_t *)data;
int i, j, k, start;
int32_t *int_ptr[6];
for (i = 0; i < 6; i++)
int_ptr[i] = (int32_t *)(&ctx->output[i]);
//Initialize the GetBitContext with the start of valid AC3 Frame.
init_get_bits(&ctx->gb, buf, buf_size * 8);
//Parse the syncinfo.
if (ac3_parse_header(ctx)) {
av_log(avctx, AV_LOG_ERROR, "\n");
*data_size = 0;
return buf_size;
}
avctx->sample_rate = ctx->sampling_rate;
avctx->bit_rate = ctx->bit_rate;
/* channel config */
if (avctx->channels == 0) {
avctx->channels = ctx->out_channels;
}
if(avctx->channels != ctx->out_channels) {
av_log(avctx, AV_LOG_ERROR, "Cannot mix AC3 to %d channels.\n",
avctx->channels);
return -1;
}
//av_log(avctx, AV_LOG_INFO, "channels = %d \t bit rate = %d \t sampling rate = %d \n", avctx->channels, avctx->bit_rate * 1000, avctx->sample_rate);
//Parse the Audio Blocks.
for (i = 0; i < NB_BLOCKS; i++) {
if (ac3_parse_audio_block(ctx, i)) {
av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
*data_size = 0;
return ctx->frame_size;
}
start = (ctx->output_mode & AC3_OUTPUT_LFEON) ? 0 : 1;
for (k = 0; k < 256; k++)
for (j = start; j <= ctx->nfchans; j++)
*(out_samples++) = convert(int_ptr[j][k]);
}
*data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
return ctx->frame_size;
}
/* Uninitialize ac3 decoder.
*/
static int ac3_decode_end(AVCodecContext *avctx)
{
AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
ff_mdct_end(&ctx->imdct_512);
ff_mdct_end(&ctx->imdct_256);
return 0;
}
AVCodec ac3_decoder = {
.name = "ac3",
.type = CODEC_TYPE_AUDIO,
.id = CODEC_ID_AC3,
.priv_data_size = sizeof (AC3DecodeContext),
.init = ac3_decode_init,
.close = ac3_decode_end,
.decode = ac3_decode_frame,
};
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