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simplify stereo rematrixing

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Originally committed as revision 9824 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2007-07-29 00:58:32 +00:00
parent b6acc57f88
commit 8b60bbbf5b
1 changed files with 29 additions and 41 deletions
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70
libavcodec/ac3dec.c
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@ -38,6 +38,12 @@
#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)
*/
@ -92,6 +98,7 @@ typedef struct {
int cplcoe;
uint32_t cplbndstrc;
int rematstr;
int nrematbnd;
int rematflg[AC3_MAX_CHANNELS];
int cplexpstr;
int lfeexpstr;
@ -648,43 +655,28 @@ static int get_transform_coeffs(AC3DecodeContext * ctx)
return 0;
}
/* Rematrixing routines. */
static void do_rematrixing1(AC3DecodeContext *ctx, int start, int end)
{
float tmp0, tmp1;
while (start < end) {
tmp0 = ctx->transform_coeffs[1][start];
tmp1 = ctx->transform_coeffs[2][start];
ctx->transform_coeffs[1][start] = tmp0 + tmp1;
ctx->transform_coeffs[2][start] = tmp0 - tmp1;
start++;
}
}
/**
* Performs stereo rematrixing.
* reference: Section 7.5.4 Rematrixing : Decoding Technique
*/
static void do_rematrixing(AC3DecodeContext *ctx)
{
int bnd1 = 13, bnd2 = 25, bnd3 = 37, bnd4 = 61;
int bnd, i;
int end, bndend;
float tmp0, tmp1;
end = FFMIN(ctx->endmant[0], ctx->endmant[1]);
if (ctx->rematflg[0])
do_rematrixing1(ctx, bnd1, bnd2);
if (ctx->rematflg[1])
do_rematrixing1(ctx, bnd2, bnd3);
bndend = bnd4;
if (bndend > end) {
bndend = end;
if (ctx->rematflg[2])
do_rematrixing1(ctx, bnd3, bndend);
} else {
if (ctx->rematflg[2])
do_rematrixing1(ctx, bnd3, bnd4);
if (ctx->rematflg[3])
do_rematrixing1(ctx, bnd4, end);
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;
}
}
}
}
@ -766,7 +758,7 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
{
int nfchans = ctx->nfchans;
int acmod = ctx->acmod;
int i, bnd, rbnd, seg, grpsize, ch;
int i, bnd, seg, grpsize, ch;
GetBitContext *gb = &ctx->gb;
int bit_alloc_flags = 0;
int8_t *dexps;
@ -857,15 +849,11 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
ctx->rematstr = get_bits1(gb);
if (ctx->rematstr) {
if (!(ctx->cplinu) || ctx->cplstrtmant > 61)
for (rbnd = 0; rbnd < 4; rbnd++)
ctx->rematflg[rbnd] = get_bits1(gb);
if (ctx->cplstrtmant > 37 && ctx->cplstrtmant <= 61 && ctx->cplinu)
for (rbnd = 0; rbnd < 3; rbnd++)
ctx->rematflg[rbnd] = get_bits1(gb);
if (ctx->cplstrtmant == 37 && ctx->cplinu)
for (rbnd = 0; rbnd < 2; rbnd++)
ctx->rematflg[rbnd] = get_bits1(gb);
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);
}
}