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fix signed overflow in fixed-point sample rounding before saturation #231

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Merged
fabiangreffrath merged 1 commit into from
Jul 18, 2026
Merged

fix signed overflow in fixed-point sample rounding before saturation #231

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6 changes: 4 additions & 2 deletions libfaad/lt_predict.c
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Original file line number Diff line number Diff line change
Expand Up @@ -137,11 +137,13 @@ static INLINE int16_t real_to_int16(real_t sig_in)
{
if (sig_in >= 0)
{
sig_in += (1 << (REAL_BITS-1));
if (sig_in <= 0x7FFFFFFF - (1 << (REAL_BITS-1)))
sig_in += (1 << (REAL_BITS-1));
if (sig_in >= REAL_CONST(32768))
return 32767;
} else {
sig_in += -(1 << (REAL_BITS-1));
if (sig_in >= (int32_t)0x80000000 + (1 << (REAL_BITS-1)))
sig_in += -(1 << (REAL_BITS-1));
if (sig_in <= REAL_CONST(-32768))
return -32768;
}
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18 changes: 12 additions & 6 deletions libfaad/output.c
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Original file line number Diff line number Diff line change
Expand Up @@ -488,13 +488,15 @@ void* output_to_PCM(NeAACDecStruct *hDecoder,
hDecoder->internal_channel);
if (tmp >= 0)
{
tmp += (1 << (REAL_BITS-1));
if (tmp <= 0x7FFFFFFF - (1 << (REAL_BITS-1)))
tmp += (1 << (REAL_BITS-1));
if (tmp >= REAL_CONST(32767))
{
tmp = REAL_CONST(32767);
}
} else {
tmp += -(1 << (REAL_BITS-1));
if (tmp >= (int32_t)0x80000000 + (1 << (REAL_BITS-1)))
tmp += -(1 << (REAL_BITS-1));
if (tmp <= REAL_CONST(-32768))
{
tmp = REAL_CONST(-32768);
Expand All @@ -511,14 +513,16 @@ void* output_to_PCM(NeAACDecStruct *hDecoder,
hDecoder->internal_channel);
if (tmp >= 0)
{
tmp += (1 << (REAL_BITS-9));
if (tmp <= 0x7FFFFFFF - (1 << (REAL_BITS-9)))
tmp += (1 << (REAL_BITS-9));
tmp >>= (REAL_BITS-8);
if (tmp >= 8388607)
{
tmp = 8388607;
}
} else {
tmp += -(1 << (REAL_BITS-9));
if (tmp >= (int32_t)0x80000000 + (1 << (REAL_BITS-9)))
tmp += -(1 << (REAL_BITS-9));
tmp >>= (REAL_BITS-8);
if (tmp <= -8388608)
{
Expand All @@ -538,9 +542,11 @@ void* output_to_PCM(NeAACDecStruct *hDecoder,
hDecoder->internal_channel);
if (tmp >= 0)
{
tmp += half;
if (tmp <= 0x7FFFFFFF - half)
tmp += half;
} else {
tmp += -half;
if (tmp >= (int32_t)0x80000000 + half)
tmp += -half;
}
tmp = SAT_SHIFT(tmp, exp, sat_shift_mask);
int_sample_buffer[(i*channels)+ch] = tmp;
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