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split out coupling coefficient reconstruction into a separate function 

Originally committed as revision 9882 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2007-08-03 23:53:53 +00:00
parent 7cacf1e86a
commit d7dc7ad05c
1 changed files with 38 additions and 36 deletions
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74
libavcodec/ac3dec.c
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@ -148,6 +148,7 @@ typedef struct {
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. */
@ -421,6 +422,31 @@ static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
}
}
/**
* 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];
@ -438,40 +464,18 @@ typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantizati
static int get_transform_coeffs_cpling(AC3DecodeContext *ctx, mant_groups *m)
{
GetBitContext *gb = &ctx->gb;
int ch, start, end, cplbndstrc, bnd, gcode, tbap;
float cplcos[5], cplcoeff;
int start, gcode, tbap;
float cplcoeff;
uint8_t *exps = ctx->dcplexps;
uint8_t *bap = ctx->cplbap;
cplbndstrc = ctx->cplbndstrc;
start = ctx->cplstrtmant;
bnd = 0;
while (start < ctx->cplendmant) {
end = start + 12;
while (cplbndstrc & 1) {
end += 12;
cplbndstrc >>= 1;
}
cplbndstrc >>= 1;
for (ch = 0; ch < ctx->nfchans; ch++)
cplcos[ch] = ctx->cplco[ch][bnd];
bnd++;
while (start < end) {
tbap = bap[start];
switch(tbap) {
case 0:
for (ch = 0; ch < ctx->nfchans; ch++)
if (ctx->chincpl[ch]) {
if (ctx->dithflag[ch]) {
cplcoeff = (av_random(&ctx->dith_state) & 0xFFFF) * scale_factors[exps[start]];
ctx->transform_coeffs[ch + 1][start] = cplcoeff * cplcos[ch] * LEVEL_MINUS_3DB;
} else
ctx->transform_coeffs[ch + 1][start] = 0;
}
start++;
continue;
cplcoeff = (av_random(&ctx->dith_state) & 0xFFFF);
break;
case 1:
if (m->l3ptr > 2) {
gcode = get_bits(gb, 5);
@ -480,7 +484,7 @@ static int get_transform_coeffs_cpling(AC3DecodeContext *ctx, mant_groups *m)
m->l3_quantizers[2] = l3_quantizers_3[gcode];
m->l3ptr = 0;
}
cplcoeff = m->l3_quantizers[m->l3ptr++] * scale_factors[exps[start]];
cplcoeff = m->l3_quantizers[m->l3ptr++];
break;
case 2:
@ -491,11 +495,11 @@ static int get_transform_coeffs_cpling(AC3DecodeContext *ctx, mant_groups *m)
m->l5_quantizers[2] = l5_quantizers_3[gcode];
m->l5ptr = 0;
}
cplcoeff = m->l5_quantizers[m->l5ptr++] * scale_factors[exps[start]];
cplcoeff = m->l5_quantizers[m->l5ptr++];
break;
case 3:
cplcoeff = l7_quantizers[get_bits(gb, 3)] * scale_factors[exps[start]];
cplcoeff = l7_quantizers[get_bits(gb, 3)];
break;
case 4:
@ -505,21 +509,18 @@ static int get_transform_coeffs_cpling(AC3DecodeContext *ctx, mant_groups *m)
m->l11_quantizers[1] = l11_quantizers_2[gcode];
m->l11ptr = 0;
}
cplcoeff = m->l11_quantizers[m->l11ptr++] * scale_factors[exps[start]];
cplcoeff = m->l11_quantizers[m->l11ptr++];
break;
case 5:
cplcoeff = l15_quantizers[get_bits(gb, 4)] * scale_factors[exps[start]];
cplcoeff = l15_quantizers[get_bits(gb, 4)];
break;
default:
cplcoeff = (get_sbits(gb, qntztab[tbap]) << (16 - qntztab[tbap])) * scale_factors[exps[start]];
cplcoeff = get_sbits(gb, qntztab[tbap]) << (16 - qntztab[tbap]);
}
for (ch = 0; ch < ctx->nfchans; ch++)
if (ctx->chincpl[ch])
ctx->transform_coeffs[ch + 1][start] = cplcoeff * cplcos[ch];
ctx->transform_coeffs_cpl[start] = cplcoeff * scale_factors[exps[start]];
start++;
}
}
return 0;
@ -635,6 +636,7 @@ static int get_transform_coeffs(AC3DecodeContext * ctx)
av_log(NULL, AV_LOG_ERROR, "error in decoupling channels\n");
return -1;
}
uncouple_channels(ctx);
got_cplchan = 1;
}
end = ctx->cplendmant;