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preparing integration of new AC3 decoder 

Originally committed as revision 1089 to svn://svn.ffmpeg.org/ffmpeg/trunk
tags/v0.5
Fabrice Bellard 22 years ago
parent
bb6f569072
commit
6107fa87b4
4 changed files with 206 additions and 121 deletions
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  1. +56
    -0
      libavcodec/ac3.h
  2. +139
    -79
      libavcodec/ac3enc.c
  3. +0
    -34
      libavcodec/ac3enc.h
  4. +11
    -8
      libavcodec/ac3tab.h

+ 56
- 0
libavcodec/ac3.h View File

@@ -0,0 +1,56 @@
/*
* Common code between AC3 encoder and decoder
* Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/

#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
#define AC3_MAX_CHANNELS 6 /* including LFE channel */

#define NB_BLOCKS 6 /* number of PCM blocks inside an AC3 frame */
#define AC3_FRAME_SIZE (NB_BLOCKS * 256)

/* exponent encoding strategy */
#define EXP_REUSE 0
#define EXP_NEW 1

#define EXP_D15 1
#define EXP_D25 2
#define EXP_D45 3

typedef struct AC3BitAllocParameters {
int fscod; /* frequency */
int halfratecod;
int sgain, sdecay, fdecay, dbknee, floor;
int cplfleak, cplsleak;
} AC3BitAllocParameters;

extern const UINT16 ac3_freqs[3];
extern const UINT16 ac3_bitratetab[19];
extern const INT16 ac3_window[256];
extern const UINT8 sdecaytab[4];
extern const UINT8 fdecaytab[4];
extern const UINT16 sgaintab[4];
extern const UINT16 dbkneetab[4];
extern const UINT16 floortab[8];
extern const UINT16 fgaintab[8];

void ac3_common_init(void);
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, UINT8 *bap,
INT8 *exp, int start, int end,
int snroffset, int fgain, int is_lfe,
int deltbae,int deltnseg,
UINT8 *deltoffst, UINT8 *deltlen, UINT8 *deltba);

+ 139
- 79
libavcodec/ac3enc.c View File

@@ -20,25 +20,46 @@
//#define DEBUG_BITALLOC
#include "avcodec.h"

#include "ac3enc.h"
#include "ac3tab.h"
#include "ac3.h"

typedef struct AC3EncodeContext {
PutBitContext pb;
int nb_channels;
int nb_all_channels;
int lfe_channel;
int bit_rate;
int sample_rate;
int bsid;
int frame_size_min; /* minimum frame size in case rounding is necessary */
int frame_size; /* current frame size in words */
int halfratecod;
int frmsizecod;
int fscod; /* frequency */
int acmod;
int lfe;
int bsmod;
short last_samples[AC3_MAX_CHANNELS][256];
int chbwcod[AC3_MAX_CHANNELS];
int nb_coefs[AC3_MAX_CHANNELS];
/* bitrate allocation control */
int sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;
AC3BitAllocParameters bit_alloc;
int csnroffst;
int fgaincod[AC3_MAX_CHANNELS];
int fsnroffst[AC3_MAX_CHANNELS];
/* mantissa encoding */
int mant1_cnt, mant2_cnt, mant4_cnt;
} AC3EncodeContext;

#include "ac3tab.h"

#define MDCT_NBITS 9
#define N (1 << MDCT_NBITS)
#define NB_BLOCKS 6 /* number of PCM blocks inside an AC3 frame */

/* new exponents are sent if their Norm 1 exceed this number */
#define EXP_DIFF_THRESHOLD 1000

/* exponent encoding strategy */
#define EXP_REUSE 0
#define EXP_NEW 1

#define EXP_D15 1
#define EXP_D25 2
#define EXP_D45 3

static void fft_init(int ln);
static void ac3_crc_init(void);

@@ -88,11 +109,12 @@ static inline int calc_lowcomp(int a, int b0, int b1, int bin)
}

/* AC3 bit allocation. The algorithm is the one described in the AC3
spec with some optimizations because of our simplified encoding
assumptions. */
void parametric_bit_allocation(AC3EncodeContext *s, UINT8 *bap,
INT8 *exp, int start, int end,
int snroffset, int fgain, int is_lfe)
spec. */
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, UINT8 *bap,
INT8 *exp, int start, int end,
int snroffset, int fgain, int is_lfe,
int deltbae,int deltnseg,
UINT8 *deltoffst, UINT8 *deltlen, UINT8 *deltba)
{
int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
int fastleak,slowleak,address,tmp;
@@ -138,48 +160,57 @@ void parametric_bit_allocation(AC3EncodeContext *s, UINT8 *bap,
bndstrt = masktab[start];
bndend = masktab[end-1] + 1;
lowcomp = 0;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;
excite[0] = bndpsd[0] - fgain - lowcomp ;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;
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]) ;
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 ;
}
}
}
if (bndstrt == 0) {
lowcomp = 0;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]) ;
excite[0] = bndpsd[0] - fgain - lowcomp ;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]) ;
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]) ;
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;
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) ;
for (bin = begin; bin < end1; bin++) {
if (!(is_lfe && bin == 6))
lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
fastleak -= s->fdecay ;
v = bndpsd[bin] - fgain;
if (fastleak < v) fastleak = v;
fastleak -= s->fdecay ;
v = bndpsd[bin] - fgain;
if (fastleak < v) fastleak = v;
slowleak -= s->sdecay ;
v = bndpsd[bin] - s->sgain;
if (slowleak < v) slowleak = v;
slowleak -= s->sdecay ;
v = bndpsd[bin] - s->sgain;
if (slowleak < v) slowleak = v;
v=fastleak - lowcomp;
if (slowleak > v) v=slowleak;
v=fastleak - lowcomp;
if (slowleak > v) v=slowleak;
excite[bin] = v;
excite[bin] = v;
}
begin = 22;
} else {
/* coupling channel */
begin = bndstrt;
fastleak = (s->cplfleak << 8) + 768;
slowleak = (s->cplsleak << 8) + 768;
}

for (bin = 22; bin < bndend; bin++) {
for (bin = begin; bin < bndend; bin++) {
fastleak -= s->fdecay ;
v = bndpsd[bin] - fgain;
if (fastleak < v) fastleak = v;
@@ -205,6 +236,25 @@ void parametric_bit_allocation(AC3EncodeContext *s, UINT8 *bap,
mask[bin] = v;
}

/* 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 ;
@@ -600,12 +650,14 @@ static int bit_alloc(AC3EncodeContext *s,
s->mant2_cnt = 0;
s->mant4_cnt = 0;
for(ch=0;ch<s->nb_all_channels;ch++) {
parametric_bit_allocation(s, bap[i][ch], (INT8 *)encoded_exp[i][ch],
0, s->nb_coefs[ch],
(((csnroffst-15) << 4) +
fsnroffst) << 2,
fgaintab[s->fgaincod[ch]],
ch == s->lfe_channel);
ac3_parametric_bit_allocation(&s->bit_alloc,
bap[i][ch], (INT8 *)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]);
}
@@ -641,12 +693,14 @@ static int compute_bit_allocation(AC3EncodeContext *s,
s->fgaincod[ch] = 4;
/* compute real values */
s->sdecay = sdecaytab[s->sdecaycod] >> s->halfratecod;
s->fdecay = fdecaytab[s->fdecaycod] >> s->halfratecod;
s->sgain = sgaintab[s->sgaincod];
s->dbknee = dbkneetab[s->dbkneecod];
s->floor = floortab[s->floorcod];

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)
@@ -738,16 +792,31 @@ static int compute_bit_allocation(AC3EncodeContext *s,
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, k, l, ch, v;
int i, j, ch;
float alpha;
static unsigned short freqs[3] = { 48000, 44100, 32000 };
static int acmod_defs[6] = {
static const UINT8 acmod_defs[6] = {
0x01, /* C */
0x02, /* L R */
0x03, /* L C R */
@@ -771,7 +840,7 @@ static int AC3_encode_init(AVCodecContext *avctx)
/* frequency */
for(i=0;i<3;i++) {
for(j=0;j<3;j++)
if ((freqs[j] >> i) == freq)
if ((ac3_freqs[j] >> i) == freq)
goto found;
}
return -1;
@@ -785,7 +854,7 @@ static int AC3_encode_init(AVCodecContext *avctx)
/* bitrate & frame size */
bitrate /= 1000;
for(i=0;i<19;i++) {
if ((bitratetab[i] >> s->halfratecod) == bitrate)
if ((ac3_bitratetab[i] >> s->halfratecod) == bitrate)
break;
}
if (i == 19)
@@ -810,16 +879,7 @@ static int AC3_encode_init(AVCodecContext *avctx)
/* initial snr offset */
s->csnroffst = 40;

/* 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;
ac3_common_init();

/* mdct init */
fft_init(MDCT_NBITS - 2);
@@ -1282,8 +1342,8 @@ static int output_frame_end(AC3EncodeContext *s)
return frame_size * 2;
}

int AC3_encode_frame(AVCodecContext *avctx,
unsigned char *frame, int buf_size, void *data)
static int AC3_encode_frame(AVCodecContext *avctx,
unsigned char *frame, int buf_size, void *data)
{
AC3EncodeContext *s = avctx->priv_data;
short *samples = data;


+ 0
- 34
libavcodec/ac3enc.h View File

@@ -1,34 +0,0 @@

#define AC3_FRAME_SIZE (6*256)
#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
#define AC3_MAX_CHANNELS 6

typedef struct AC3EncodeContext {
PutBitContext pb;
int nb_channels;
int nb_all_channels;
int lfe_channel;
int bit_rate;
int sample_rate;
int bsid;
int frame_size_min; /* minimum frame size in case rounding is necessary */
int frame_size; /* current frame size in words */
int halfratecod;
int frmsizecod;
int fscod; /* frequency */
int acmod;
int lfe;
int bsmod;
short last_samples[AC3_MAX_CHANNELS][256];
int chbwcod[AC3_MAX_CHANNELS];
int nb_coefs[AC3_MAX_CHANNELS];
/* bitrate allocation control */
int sgaincod, sdecaycod, fdecaycod, dbkneecod, floorcod;
int sgain, sdecay, fdecay, dbknee, floor;
int csnroffst;
int fgaincod[AC3_MAX_CHANNELS];
int fsnroffst[AC3_MAX_CHANNELS];
/* mantissa encoding */
int mant1_cnt, mant2_cnt, mant4_cnt;
} AC3EncodeContext;

+ 11
- 8
libavcodec/ac3tab.h View File

@@ -1,7 +1,10 @@
/* tables taken directly from AC3 spec */

/* possible frequencies */
const UINT16 ac3_freqs[3] = { 48000, 44100, 32000 };

/* possible bitrates */
static const UINT16 bitratetab[19] = {
const UINT16 ac3_bitratetab[19] = {
32, 40, 48, 56, 64, 80, 96, 112, 128,
160, 192, 224, 256, 320, 384, 448, 512, 576, 640
};
@@ -9,7 +12,7 @@ static const UINT16 bitratetab[19] = {
/* AC3 MDCT window */

/* MDCT window */
static const INT16 ac3_window[256]= {
const INT16 ac3_window[256] = {
4, 7, 12, 16, 21, 28, 34, 42,
51, 61, 72, 84, 97, 111, 127, 145,
164, 184, 207, 231, 257, 285, 315, 347,
@@ -138,27 +141,27 @@ static const UINT8 baptab[64]= {
15, 15, 15, 15,
};

static const UINT8 sdecaytab[4]={
const UINT8 sdecaytab[4]={
0x0f, 0x11, 0x13, 0x15,
};

static const UINT8 fdecaytab[4]={
const UINT8 fdecaytab[4]={
0x3f, 0x53, 0x67, 0x7b,
};

static const UINT16 sgaintab[4]= {
const UINT16 sgaintab[4]= {
0x540, 0x4d8, 0x478, 0x410,
};

static const UINT16 dbkneetab[4]= {
const UINT16 dbkneetab[4]= {
0x000, 0x700, 0x900, 0xb00,
};

static const UINT16 floortab[8]= {
const UINT16 floortab[8]= {
0x2f0, 0x2b0, 0x270, 0x230, 0x1f0, 0x170, 0x0f0, 0xf800,
};

static const UINT16 fgaintab[8]= {
const UINT16 fgaintab[8]= {
0x080, 0x100, 0x180, 0x200, 0x280, 0x300, 0x380, 0x400,
};



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