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simplify snr offset and bit allocation 

Originally committed as revision 9784 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2007-07-24 02:08:27 +00:00
parent e9a3824880
commit 4611b64ec1
1 changed files with 31 additions and 52 deletions
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83
libavcodec/ac3dec.c
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@ -107,13 +107,12 @@ typedef struct {
int cplexpstr;
int lfeexpstr;
int chexpstr[5];
int csnroffst;
int cplfsnroffst;
int cplfgaincod;
int fsnroffst[5];
int fgaincod[5];
int lfefsnroffst;
int lfefgaincod;
int cplsnroffst;
int cplfgain;
int snroffst[5];
int fgain[5];
int lfesnroffst;
int lfefgain;
int cpldeltbae;
int deltbae[5];
int cpldeltnseg;
@ -424,41 +423,6 @@ static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
}
}
/* Performs bit allocation.
* This function performs bit allocation for the requested chanenl.
*/
static void do_bit_allocation(AC3DecodeContext *ctx, int chnl)
{
int fgain, snroffset;
if (chnl == 5) {
fgain = ff_fgaintab[ctx->cplfgaincod];
snroffset = (((ctx->csnroffst - 15) << 4) + ctx->cplfsnroffst) << 2;
ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->cplbap,
ctx->dcplexps, ctx->cplstrtmant,
ctx->cplendmant, snroffset, fgain, 0,
ctx->cpldeltbae, ctx->cpldeltnseg,
ctx->cpldeltoffst, ctx->cpldeltlen,
ctx->cpldeltba);
}
else if (chnl == 6) {
fgain = ff_fgaintab[ctx->lfefgaincod];
snroffset = (((ctx->csnroffst - 15) << 4) + ctx->lfefsnroffst) << 2;
ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->lfebap,
ctx->dlfeexps, 0, 7, snroffset, fgain, 1,
DBA_NONE, 0, NULL, NULL, NULL);
}
else {
fgain = ff_fgaintab[ctx->fgaincod[chnl]];
snroffset = (((ctx->csnroffst - 15) << 4) + ctx->fsnroffst[chnl]) << 2;
ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->bap[chnl],
ctx->dexps[chnl], 0, ctx->endmant[chnl],
snroffset, fgain, 0, ctx->deltbae[chnl],
ctx->deltnseg[chnl], ctx->deltoffst[chnl],
ctx->deltlen[chnl], ctx->deltba[chnl]);
}
}
typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
int16_t l3_quantizers[3];
int16_t l5_quantizers[3];
@ -1463,19 +1427,20 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
}
if (get_bits1(gb)) { /* snroffset */
int csnr;
bit_alloc_flags = 127;
ctx->csnroffst = get_bits(gb, 6);
csnr = (get_bits(gb, 6) - 15) << 4;
if (ctx->cplinu) { /* coupling fine snr offset and fast gain code */
ctx->cplfsnroffst = get_bits(gb, 4);
ctx->cplfgaincod = get_bits(gb, 3);
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->fsnroffst[i] = get_bits(gb, 4);
ctx->fgaincod[i] = get_bits(gb, 3);
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->lfefsnroffst = get_bits(gb, 4);
ctx->lfefgaincod = get_bits(gb, 3);
ctx->lfesnroffst = (csnr + get_bits(gb, 4)) << 2;
ctx->lfefgain = ff_fgaintab[get_bits(gb, 3)];
}
}
@ -1533,12 +1498,26 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
if (bit_alloc_flags) {
if (ctx->cplinu && (bit_alloc_flags & 64))
do_bit_allocation(ctx, 5);
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)
do_bit_allocation(ctx, i);
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))
do_bit_allocation(ctx, 6);
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 */