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* encoding of AC3 with more than 2 channels

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by Takashi Iwai <tiwai@suse.de>

Originally committed as revision 383 to svn://svn.ffmpeg.org/ffmpeg/trunk
pull/126/head
Zdenek Kabelac 23 years ago
parent 10bb7023a2
commit 30b68f33aa
4 changed files with 107 additions and 69 deletions
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  1. 3
      libav/raw.c
  2. 45
      libavcodec/ac3dec.c
  3. 122
      libavcodec/ac3enc.c
  4. 6
      libavcodec/ac3enc.h

3
libav/raw.c
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@ -201,6 +201,9 @@ AVFormat ac3_format = {
raw_write_header,
raw_write_packet,
raw_write_trailer,
raw_read_header,
raw_read_packet,
raw_read_close,
};
AVFormat h263_format = {

45
libavcodec/ac3dec.c
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@ -26,6 +26,7 @@ typedef struct AC3DecodeState {
UINT8 *inbuf_ptr;
int frame_size;
int flags;
int channels;
ac3_state_t state;
} AC3DecodeState;
@ -52,24 +53,16 @@ static inline int blah (int32_t i)
return i - 0x43c00000;
}
static inline void float_to_int (float * _f, INT16 * s16)
static inline void float_to_int (float * _f, INT16 * s16, int nchannels)
{
int i;
int i, j, c;
int32_t * f = (int32_t *) _f; // XXX assumes IEEE float format
j = 0;
nchannels *= 256;
for (i = 0; i < 256; i++) {
s16[2*i] = blah (f[i]);
s16[2*i+1] = blah (f[i+256]);
}
}
static inline void float_to_int_mono (float * _f, INT16 * s16)
{
int i;
int32_t * f = (int32_t *) _f; // XXX assumes IEEE float format
for (i = 0; i < 256; i++) {
s16[i] = blah (f[i]);
for (c = 0; c < nchannels; c += 256)
s16[j++] = blah (f[i + c]);
}
}
@ -87,6 +80,9 @@ static int ac3_decode_frame(AVCodecContext *avctx,
int sample_rate, bit_rate;
short *out_samples = data;
float level;
static int ac3_channels[8] = {
2, 1, 2, 3, 3, 4, 4, 5
};
*data_size = 0;
buf_ptr = buf;
@ -111,10 +107,13 @@ static int ac3_decode_frame(AVCodecContext *avctx,
s->frame_size = len;
/* update codec info */
avctx->sample_rate = sample_rate;
if ((s->flags & AC3_CHANNEL_MASK) == AC3_MONO)
avctx->channels = 1;
else
avctx->channels = 2;
s->channels = ac3_channels[s->flags & 7];
if (s->flags & AC3_LFE)
s->channels++;
if (s->channels < avctx->channels) {
fprintf(stderr, "Source channels are less than specified: output to %d channels..\n", s->channels);
avctx->channels = s->channels;
}
avctx->bit_rate = bit_rate;
}
}
@ -128,11 +127,14 @@ static int ac3_decode_frame(AVCodecContext *avctx,
s->inbuf_ptr += len;
buf_size -= len;
} else {
#if 0
if (avctx->channels == 1)
flags = AC3_MONO;
else
flags = AC3_STEREO;
#else
flags = s->flags;
#endif
flags |= AC3_ADJUST_LEVEL;
level = 1;
if (ac3_frame (&s->state, s->inbuf, &flags, &level, 384)) {
@ -144,10 +146,7 @@ static int ac3_decode_frame(AVCodecContext *avctx,
for (i = 0; i < 6; i++) {
if (ac3_block (&s->state))
goto fail;
if (avctx->channels == 1)
float_to_int_mono (*samples, out_samples + i * 256);
else
float_to_int (*samples, out_samples + i * 512);
float_to_int (*samples, out_samples + i * 256 * avctx->channels, avctx->channels);
}
s->inbuf_ptr = s->inbuf;
s->frame_size = 0;

122
libavcodec/ac3enc.c
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@ -93,7 +93,7 @@ static inline int calc_lowcomp(int a, int b0, int b1, int bin)
assumptions. */
void parametric_bit_allocation(AC3EncodeContext *s, UINT8 *bap,
INT8 *exp, int start, int end,
int snroffset, int fgain)
int snroffset, int fgain, int is_lfe)
{
int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
int fastleak,slowleak,address,tmp;
@ -146,21 +146,25 @@ void parametric_bit_allocation(AC3EncodeContext *s, UINT8 *bap,
excite[1] = bndpsd[1] - fgain - lowcomp ;
begin = 7 ;
for (bin = 2; bin < 7; bin++) {
lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1]) ;
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 (bndpsd[bin] <= bndpsd[bin+1]) {
begin = bin + 1 ;
break ;
}
if (!(is_lfe && bin == 6)) {
if (bndpsd[bin] <= bndpsd[bin+1]) {
begin = bin + 1 ;
break ;
}
}
}
end1=bndend;
if (end1 > 22) end1=22;
for (bin = begin; bin < end1; bin++) {
lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
if (!(is_lfe && bin == 6))
lowcomp = calc_lowcomp(lowcomp, bndpsd[bin], bndpsd[bin+1], bin) ;
fastleak -= s->fdecay ;
v = bndpsd[bin] - fgain;
@ -395,7 +399,7 @@ static int calc_exp_diff(UINT8 *exp1, UINT8 *exp2, int n)
static void compute_exp_strategy(UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
UINT8 exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
int ch)
int ch, int is_lfe)
{
int i, j;
int exp_diff;
@ -413,6 +417,9 @@ static void compute_exp_strategy(UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS]
else
exp_strategy[i][ch] = EXP_REUSE;
}
if (is_lfe)
return;
/* now select the encoding strategy type : if exponents are often
recoded, we use a coarse encoding */
i = 0;
@ -432,7 +439,7 @@ static void compute_exp_strategy(UINT8 exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS]
exp_strategy[i][ch] = EXP_D15;
break;
}
i = j;
i = j;
}
}
@ -593,12 +600,13 @@ static int bit_alloc(AC3EncodeContext *s,
s->mant1_cnt = 0;
s->mant2_cnt = 0;
s->mant4_cnt = 0;
for(ch=0;ch<s->nb_channels;ch++) {
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]]);
fgaintab[s->fgaincod[ch]],
ch == s->lfe_channel);
frame_bits += compute_mantissa_size(s, bap[i][ch],
s->nb_coefs[ch]);
}
@ -622,6 +630,7 @@ static int compute_bit_allocation(AC3EncodeContext *s,
int i, ch;
int csnroffst, fsnroffst;
UINT8 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;
@ -629,7 +638,7 @@ static int compute_bit_allocation(AC3EncodeContext *s,
s->sgaincod = 1;
s->dbkneecod = 2;
s->floorcod = 4;
for(ch=0;ch<s->nb_channels;ch++)
for(ch=0;ch<s->nb_all_channels;ch++)
s->fgaincod[ch] = 4;
/* compute real values */
@ -641,18 +650,21 @@ static int compute_bit_allocation(AC3EncodeContext *s,
/* header size */
frame_bits += 65;
if (s->acmod == 2)
frame_bits += 2;
// 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;
frame_bits += s->nb_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
if (s->acmod == 2)
frame_bits++;
frame_bits += 2 * s->nb_channels;
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;
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
}
frame_bits++; /* baie */
frame_bits++; /* snr */
@ -660,7 +672,10 @@ static int compute_bit_allocation(AC3EncodeContext *s,
}
frame_bits++; /* cplinu for block 0 */
/* bit alloc info */
frame_bits += 2*4 + 3 + 6 + s->nb_channels * (4 + 3);
/* 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;
@ -670,11 +685,11 @@ static int compute_bit_allocation(AC3EncodeContext *s,
csnroffst = s->csnroffst;
while (csnroffst >= 0 &&
bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)
csnroffst -= SNR_INC1;
bit_alloc(s, bap, encoded_exp, exp_strategy, frame_bits, csnroffst, 0) < 0)
csnroffst -= SNR_INC1;
if (csnroffst < 0) {
fprintf(stderr, "Error !!!\n");
return -1;
fprintf(stderr, "Yack, Error !!!\n");
return -1;
}
while ((csnroffst + SNR_INC1) <= 63 &&
bit_alloc(s, bap1, encoded_exp, exp_strategy, frame_bits,
@ -703,14 +718,14 @@ static int compute_bit_allocation(AC3EncodeContext *s,
}
s->csnroffst = csnroffst;
for(ch=0;ch<s->nb_channels;ch++)
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_channels;ch++) {
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++) {
@ -733,18 +748,26 @@ static int AC3_encode_init(AVCodecContext *avctx)
int i, j, k, l, ch, v;
float alpha;
static unsigned short freqs[3] = { 48000, 44100, 32000 };
static int 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;
avctx->key_frame = 1; /* always key frame */
/* number of channels */
if (channels == 1)
s->acmod = 1;
else if (channels == 2)
s->acmod = 2;
else
return -1;
s->nb_channels = 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++) {
@ -782,6 +805,9 @@ static int AC3_encode_init(AVCodecContext *avctx)
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;
@ -821,10 +847,13 @@ static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
put_bits(&s->pb, 5, s->bsid);
put_bits(&s->pb, 3, s->bsmod);
put_bits(&s->pb, 3, s->acmod);
if (s->acmod == 2) {
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, 0); /* no LFE */
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 */
@ -920,13 +949,17 @@ static void output_audio_block(AC3EncodeContext *s,
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_channels; ch++) {
for (ch = 0; ch < s->nb_all_channels; ch++) {
switch(exp_strategy[ch]) {
case EXP_REUSE:
continue;
@ -941,7 +974,7 @@ static void output_audio_block(AC3EncodeContext *s,
group_size = 4;
break;
}
nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
p = encoded_exp[ch];
/* first exponent */
@ -969,7 +1002,8 @@ static void output_audio_block(AC3EncodeContext *s,
put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
}
put_bits(&s->pb, 2, 0); /* no gain range info */
if (ch != s->lfe_channel)
put_bits(&s->pb, 2, 0); /* no gain range info */
}
/* bit allocation info */
@ -987,7 +1021,7 @@ static void output_audio_block(AC3EncodeContext *s,
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_channels;ch++) {
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]);
}
@ -1004,7 +1038,7 @@ static void output_audio_block(AC3EncodeContext *s,
mant1_cnt = mant2_cnt = mant4_cnt = 0;
qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
for (ch = 0; ch < s->nb_channels; ch++) {
for (ch = 0; ch < s->nb_all_channels; ch++) {
int b, c, e, v;
for(i=0;i<s->nb_coefs[ch];i++) {
@ -1091,7 +1125,7 @@ static void output_audio_block(AC3EncodeContext *s,
}
/* second pass : output the values */
for (ch = 0; ch < s->nb_channels; ch++) {
for (ch = 0; ch < s->nb_all_channels; ch++) {
int b, q;
for(i=0;i<s->nb_coefs[ch];i++) {
@ -1265,7 +1299,7 @@ int AC3_encode_frame(AVCodecContext *avctx,
int frame_bits;
frame_bits = 0;
for(ch=0;ch<s->nb_channels;ch++) {
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 *sptr;
@ -1273,7 +1307,7 @@ int AC3_encode_frame(AVCodecContext *avctx,
/* compute input samples */
memcpy(input_samples, s->last_samples[ch], N/2 * sizeof(INT16));
sinc = s->nb_channels;
sinc = s->nb_all_channels;
sptr = samples + (sinc * (N/2) * i) + ch;
for(j=0;j<N/2;j++) {
v = *sptr;
@ -1319,7 +1353,7 @@ int AC3_encode_frame(AVCodecContext *avctx,
}
}
compute_exp_strategy(exp_strategy, exp, ch);
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

6
libavcodec/ac3enc.h
Unescape View File

@ -1,12 +1,13 @@
#define AC3_FRAME_SIZE (6*256)
#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
#define AC3_MAX_CHANNELS 2 /* we handle at most two channels, although
AC3 allows 6 channels */
#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;
@ -16,6 +17,7 @@ typedef struct AC3EncodeContext {
int frmsizecod;
int fscod; /* frequency */
int acmod;
int lfe;
int bsmod;
short last_samples[AC3_MAX_CHANNELS][256];
int chbwcod[AC3_MAX_CHANNELS];

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