devs/foxbox
1
0
Fork 0
forked from len0rd/rockbox
Code Pull requests Activity

Correct autocorrelation function in libfaad. It used the wrong fract part for the multiplication macros. Introduce appropriate solution to avoid overflow.

Browse source 
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28079 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andree Buschmann 2010-09-14 19:05:09 +00:00
parent f4e886158c
commit b543a2a5d2
1 changed files with 32 additions and 41 deletions
Download patch file Download diff file Expand all files Collapse all files

73
apps/codecs/libfaad/sbr_hfgen.c
View file

@ -196,24 +196,17 @@ static void auto_correlation(sbr_info *sbr, acorr_coef *ac,
uint8_t offset = sbr->tHFAdj;
#ifdef FIXED_POINT
const real_t rel = FRAC_CONST(0.999999); // 1 / (1 + 1e-6f);
uint32_t maxi = 0;
uint32_t pow2, exp;
uint32_t exp = 2;
#else
const real_t rel = 1 / (1 + 1e-6f);
#endif
#ifdef FIXED_POINT
mask = 0;
for (j = (offset-2); j < (len + offset); j++)
{
real_t x;
x = QMF_RE(buffer[j][bd])>>REAL_BITS;
mask |= x ^ (x >> 31);
}
exp = wl_min_lzc(mask);
/* A pre-shift of >>2 is needed to avoid overflow when multiply-adding
* the FRACT-variables buffer -- FRACT part is 31 bits. After the
* calculation has been finished the result 'ac.det' needs to be
* post-shifted by <<(2*exp). */
for (j = offset; j < len + offset; j++)
{
@ -253,6 +246,9 @@ static void auto_correlation(sbr_info *sbr, acorr_coef *ac,
RE(ac->r11) = r11;
ac->det = MUL_R(RE(ac->r11), RE(ac->r22)) - MUL_F(MUL_R(RE(ac->r12), RE(ac->r12)), rel);
#ifdef FIXED_POINT
ac->det <<= (4*exp);
#endif
}
#else
static void auto_correlation(sbr_info *sbr, acorr_coef *ac, qmf_t buffer[MAX_NTSRHFG][64],
@ -262,7 +258,7 @@ static void auto_correlation(sbr_info *sbr, acorr_coef *ac, qmf_t buffer[MAX_NTS
real_t temp1_r, temp1_i, temp2_r, temp2_i, temp3_r, temp3_i, temp4_r, temp4_i, temp5_r, temp5_i;
#ifdef FIXED_POINT
const real_t rel = FRAC_CONST(0.999999); // 1 / (1 + 1e-6f);
uint32_t mask, exp;
uint32_t exp = 2;
#else
const real_t rel = 1 / (1 + 1e-6f);
#endif
@ -270,18 +266,10 @@ static void auto_correlation(sbr_info *sbr, acorr_coef *ac, qmf_t buffer[MAX_NTS
uint8_t offset = sbr->tHFAdj;
#ifdef FIXED_POINT
mask = 0;
for (j = (offset-2); j < (len + offset); j++)
{
real_t x;
x = QMF_RE(buffer[j][bd])>>REAL_BITS;
mask |= x ^ (x >> 31);
x = QMF_IM(buffer[j][bd])>>REAL_BITS;
mask |= x ^ (x >> 31);
}
exp = wl_min_lzc(mask);
/* A pre-shift of >>2 is needed to avoid overflow when multiply-adding
* the FRACT-variables buffer -- FRACT part is 31 bits. After the
* calculation has been finished the result 'ac.det' needs to be
* post-shifted by <<(2*exp). */
temp2_r = (QMF_RE(buffer[offset-2][bd])) >> exp;
temp2_i = (QMF_IM(buffer[offset-2][bd])) >> exp;
@ -295,25 +283,25 @@ static void auto_correlation(sbr_info *sbr, acorr_coef *ac, qmf_t buffer[MAX_NTS
for (j = offset; j < len + offset; j++)
{
temp1_r = temp2_r; // temp1_r = (QMF_RE(buffer[offset-2][bd] + (1<<(exp-1))) >> exp;
temp1_i = temp2_i; // temp1_i = (QMF_IM(buffer[offset-2][bd] + (1<<(exp-1))) >> exp;
temp2_r = temp3_r; // temp2_r = (QMF_RE(buffer[offset-1][bd] + (1<<(exp-1))) >> exp;
temp2_i = temp3_i; // temp2_i = (QMF_IM(buffer[offset-1][bd] + (1<<(exp-1))) >> exp;
temp1_r = temp2_r;
temp1_i = temp2_i;
temp2_r = temp3_r;
temp2_i = temp3_i;
temp3_r = (QMF_RE(buffer[j][bd])) >> exp;
temp3_i = (QMF_IM(buffer[j][bd])) >> exp;
r01r += MUL_R(temp3_r, temp2_r) + MUL_R(temp3_i, temp2_i);
r01i += MUL_R(temp3_i, temp2_r) - MUL_R(temp3_r, temp2_i);
r02r += MUL_R(temp3_r, temp1_r) + MUL_R(temp3_i, temp1_i);
r02i += MUL_R(temp3_i, temp1_r) - MUL_R(temp3_r, temp1_i);
r11r += MUL_R(temp2_r, temp2_r) + MUL_R(temp2_i, temp2_i);
r01r += MUL_F(temp3_r, temp2_r) + MUL_F(temp3_i, temp2_i);
r01i += MUL_F(temp3_i, temp2_r) - MUL_F(temp3_r, temp2_i);
r02r += MUL_F(temp3_r, temp1_r) + MUL_F(temp3_i, temp1_i);
r02i += MUL_F(temp3_i, temp1_r) - MUL_F(temp3_r, temp1_i);
r11r += MUL_F(temp2_r, temp2_r) + MUL_F(temp2_i, temp2_i);
}
RE(ac->r12) = r01r - (MUL_R(temp3_r, temp2_r) + MUL_R(temp3_i, temp2_i)) +
(MUL_R(temp5_r, temp4_r) + MUL_R(temp5_i, temp4_i));
IM(ac->r12) = r01i - (MUL_R(temp3_i, temp2_r) - MUL_R(temp3_r, temp2_i)) +
(MUL_R(temp5_i, temp4_r) - MUL_R(temp5_r, temp4_i));
RE(ac->r22) = r11r - (MUL_R(temp2_r, temp2_r) + MUL_R(temp2_i, temp2_i)) +
(MUL_R(temp4_r, temp4_r) + MUL_R(temp4_i, temp4_i));
RE(ac->r12) = r01r - (MUL_F(temp3_r, temp2_r) + MUL_F(temp3_i, temp2_i)) +
(MUL_F(temp5_r, temp4_r) + MUL_F(temp5_i, temp4_i));
IM(ac->r12) = r01i - (MUL_F(temp3_i, temp2_r) - MUL_F(temp3_r, temp2_i)) +
(MUL_F(temp5_i, temp4_r) - MUL_F(temp5_r, temp4_i));
RE(ac->r22) = r11r - (MUL_F(temp2_r, temp2_r) + MUL_F(temp2_i, temp2_i)) +
(MUL_F(temp4_r, temp4_r) + MUL_F(temp4_i, temp4_i));
#else
temp2_r = QMF_RE(buffer[offset-2][bd]);
temp2_i = QMF_IM(buffer[offset-2][bd]);
@ -353,7 +341,10 @@ static void auto_correlation(sbr_info *sbr, acorr_coef *ac, qmf_t buffer[MAX_NTS
IM(ac->r02) = r02i;
RE(ac->r11) = r11r;
ac->det = MUL_R(RE(ac->r11), RE(ac->r22)) - MUL_F(rel, (MUL_R(RE(ac->r12), RE(ac->r12)) + MUL_R(IM(ac->r12), IM(ac->r12))));
ac->det = MUL_F(RE(ac->r11), RE(ac->r22)) - MUL_F(rel, (MUL_F(RE(ac->r12), RE(ac->r12)) + MUL_F(IM(ac->r12), IM(ac->r12))));
#ifdef FIXED_POINT
ac->det <<= (4*exp);
#endif
}
#endif