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amrwbdec: fix invalid pointer arithmetic

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Subtracting a (positive) value from the address of an array violates
C99 section 6.5.6:

  If both the pointer operand and the result point to elements of the
  same array object, or one past the last element of the array object,
  the evaluation shall not produce an overflow; otherwise, the
  behavior is undefined.

Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard 2012-10-26 22:44:38 +01:00
parent 4521645b1a
commit 50be207759
1 changed files with 10 additions and 11 deletions
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21
libavcodec/amrwbdec.c
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@ -902,10 +902,9 @@ static float auto_correlation(float *diff_isf, float mean, int lag)
static void extrapolate_isf(float isf[LP_ORDER_16k])
{
float diff_isf[LP_ORDER - 2], diff_mean;
float *diff_hi = diff_isf - LP_ORDER + 1; // diff array for extrapolated indexes
float corr_lag[3];
float est, scale;
int i, i_max_corr;
int i, j, i_max_corr;
isf[LP_ORDER_16k - 1] = isf[LP_ORDER - 1];
@ -936,20 +935,20 @@ static void extrapolate_isf(float isf[LP_ORDER_16k])
scale = 0.5 * (FFMIN(est, 7600) - isf[LP_ORDER - 2]) /
(isf[LP_ORDER_16k - 2] - isf[LP_ORDER - 2]);
for (i = LP_ORDER - 1; i < LP_ORDER_16k - 1; i++)
diff_hi[i] = scale * (isf[i] - isf[i - 1]);
for (i = LP_ORDER - 1, j = 0; i < LP_ORDER_16k - 1; i++, j++)
diff_isf[j] = scale * (isf[i] - isf[i - 1]);
/* Stability insurance */
for (i = LP_ORDER; i < LP_ORDER_16k - 1; i++)
if (diff_hi[i] + diff_hi[i - 1] < 5.0) {
if (diff_hi[i] > diff_hi[i - 1]) {
diff_hi[i - 1] = 5.0 - diff_hi[i];
for (i = 1; i < LP_ORDER_16k - LP_ORDER; i++)
if (diff_isf[i] + diff_isf[i - 1] < 5.0) {
if (diff_isf[i] > diff_isf[i - 1]) {
diff_isf[i - 1] = 5.0 - diff_isf[i];
} else
diff_hi[i] = 5.0 - diff_hi[i - 1];
diff_isf[i] = 5.0 - diff_isf[i - 1];
}
for (i = LP_ORDER - 1; i < LP_ORDER_16k - 1; i++)
isf[i] = isf[i - 1] + diff_hi[i] * (1.0f / (1 << 15));
for (i = LP_ORDER - 1, j = 0; i < LP_ORDER_16k - 1; i++, j++)
isf[i] = isf[i - 1] + diff_isf[j] * (1.0f / (1 << 15));
/* Scale the ISF vector for 16000 Hz */
for (i = 0; i < LP_ORDER_16k - 1; i++)