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simplify AC-3 bit allocation

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Originally committed as revision 8302 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2007-03-09 03:17:43 +00:00
parent 3a8bf52983
commit abfe5a4a75
1 changed files with 24 additions and 77 deletions
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101
libavcodec/ac3enc.c
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@ -83,13 +83,12 @@ static inline int16_t fix15(float a)
return v;
}
static inline int calc_lowcomp1(int a, int b0, int b1)
static inline int calc_lowcomp1(int a, int b0, int b1, int c)
{
if ((b0 + 256) == b1) {
a = 384;
a = c;
} else if (b0 > b1) {
a = a - 64;
if (a < 0) a=0;
a = FFMAX(a - 64, 0);
}
return a;
}
@ -97,24 +96,12 @@ static inline int calc_lowcomp1(int a, int b0, int b1)
static inline int calc_lowcomp(int a, int b0, int b1, int bin)
{
if (bin < 7) {
if ((b0 + 256) == b1) {
a = 384;
} else if (b0 > b1) {
a = a - 64;
if (a < 0) a=0;
}
return calc_lowcomp1(a, b0, b1, 384);
} else if (bin < 20) {
if ((b0 + 256) == b1) {
a = 320;
} else if (b0 > b1) {
a= a - 64;
if (a < 0) a=0;
}
return calc_lowcomp1(a, b0, b1, 320);
} else {
a = a - 128;
if (a < 0) a=0;
return FFMAX(a - 128, 0);
}
return a;
}
/* AC3 bit allocation. The algorithm is the one described in the AC3
@ -125,7 +112,7 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
int deltbae,int deltnseg,
uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
{
int bin,i,j,k,end1,v,v1,bndstrt,bndend,lowcomp,begin;
int bin,i,j,k,end1,v,bndstrt,bndend,lowcomp,begin;
int fastleak,slowleak,address,tmp;
int16_t psd[256]; /* scaled exponents */
int16_t bndpsd[50]; /* interpolated exponents */
@ -143,22 +130,11 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
do {
v=psd[j];
j++;
end1=bndtab[k+1];
if (end1 > end) end1=end;
end1 = FFMIN(bndtab[k+1], end);
for(i=j;i<end1;i++) {
int c,adr;
/* logadd */
v1=psd[j];
c=v-v1;
if (c >= 0) {
adr=c >> 1;
if (adr > 255) adr=255;
v=v + latab[adr];
} else {
adr=(-c) >> 1;
if (adr > 255) adr=255;
v=v1 + latab[adr];
}
int adr = FFMIN(FFABS(v - psd[j]) >> 1, 255);
v = FFMAX(v, psd[j]) + latab[adr];
j++;
}
bndpsd[k]=v;
@ -171,14 +147,14 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
if (bndstrt == 0) {
lowcomp = 0;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1]);
lowcomp = calc_lowcomp1(lowcomp, bndpsd[0], bndpsd[1], 384);
excite[0] = bndpsd[0] - fgain - lowcomp;
lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2]);
lowcomp = calc_lowcomp1(lowcomp, bndpsd[1], bndpsd[2], 384);
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]);
lowcomp = calc_lowcomp1(lowcomp, bndpsd[bin], bndpsd[bin+1], 384);
fastleak = bndpsd[bin] - fgain;
slowleak = bndpsd[bin] - s->sgain;
excite[bin] = fastleak - lowcomp;
@ -197,18 +173,9 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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;
slowleak -= s->sdecay;
v = bndpsd[bin] - s->sgain;
if (slowleak < v) slowleak = v;
v=fastleak - lowcomp;
if (slowleak > v) v=slowleak;
excite[bin] = v;
fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
excite[bin] = FFMAX(fastleak - lowcomp, slowleak);
}
begin = 22;
} else {
@ -220,29 +187,19 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
}
for (bin = begin; bin < bndend; bin++) {
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;
v=fastleak;
if (slowleak > v) v = slowleak;
excite[bin] = v;
fastleak = FFMAX(fastleak - s->fdecay, bndpsd[bin] - fgain);
slowleak = FFMAX(slowleak - s->sdecay, bndpsd[bin] - s->sgain);
excite[bin] = FFMAX(fastleak, slowleak);
}
/* compute masking curve */
for (bin = bndstrt; bin < bndend; bin++) {
v1 = excite[bin];
tmp = s->dbknee - bndpsd[bin];
if (tmp > 0) {
v1 += tmp >> 2;
excite[bin] += tmp >> 2;
}
v=hth[bin >> s->halfratecod][s->fscod];
if (v1 > v) v=v1;
mask[bin] = v;
mask[bin] = FFMAX(hth[bin >> s->halfratecod][s->fscod], excite[bin]);
}
/* delta bit allocation */
@ -269,20 +226,10 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
i = start;
j = masktab[start];
do {
v=mask[j];
v -= snroffset;
v -= s->floor;
if (v < 0) v = 0;
v &= 0x1fe0;
v += s->floor;
end1=bndtab[j] + bndsz[j];
if (end1 > end) end1=end;
v = (FFMAX(mask[j] - snroffset - s->floor, 0) & 0x1FE0) + s->floor;
end1 = FFMIN(bndtab[j] + bndsz[j], end);
for (k = i; k < end1; k++) {
address = (psd[i] - v) >> 5;
if (address < 0) address=0;
else if (address > 63) address=63;
address = av_clip((psd[i] - v) >> 5, 0, 63);
bap[i] = baptab[address];
i++;
}