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fix bug where overflow of total_error caused it to go negative

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This commit is contained in:
Josh Coalson
2001-02-28 23:44:27 +00:00
parent f6237c8c3b
commit fe9ba6f44f
1 changed files with 13 additions and 7 deletions
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20
src/libFLAC/fixed.c
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@@ -34,7 +34,7 @@
#ifdef local_abs
#undef local_abs
#endif
#define local_abs(x) ((x)<0? -(x) : (x))
#define local_abs(x) ((unsigned)((x)<0? -(x) : (x)))
unsigned FLAC__fixed_compute_best_predictor(const int32 data[], unsigned data_len, real residual_bits_per_sample[FLAC__MAX_FIXED_ORDER+1])
{
@@ -43,7 +43,7 @@ unsigned FLAC__fixed_compute_best_predictor(const int32 data[], unsigned data_le
int32 last_error_2 = last_error_1 - (data[-2] - data[-3]);
int32 last_error_3 = last_error_2 - (data[-2] - 2*data[-3] + data[-4]);
int32 error_0, error_1, error_2, error_3, error_4;
int32 total_error_0 = 0, total_error_1 = 0, total_error_2 = 0, total_error_3 = 0, total_error_4 = 0;
uint32 total_error_0 = 0, total_error_1 = 0, total_error_2 = 0, total_error_3 = 0, total_error_4 = 0;
unsigned i, order;
for(i = 0; i < data_len; i++) {
@@ -53,6 +53,12 @@ unsigned FLAC__fixed_compute_best_predictor(const int32 data[], unsigned data_le
error_3 = error_2 - last_error_2; total_error_3 += local_abs(error_3);
error_4 = error_3 - last_error_3; total_error_4 += local_abs(error_4);
/* WATCHOUT - total_error_* has been know to overflow when encoding
* erratic signals when the bits-per-sample is large. We avoid the
* speed penalty of watching for overflow, and instead rely on the
* encoder's evaluation of the subframe to catch these cases.
*/
last_error_0 = error_0;
last_error_1 = error_1;
last_error_2 = error_2;
@@ -73,11 +79,11 @@ unsigned FLAC__fixed_compute_best_predictor(const int32 data[], unsigned data_le
/* Estimate the expected number of bits per residual signal sample. */
/* 'total_error*' is linearly related to the variance of the residual */
/* signal, so we use it directly to compute E(|x|) */
residual_bits_per_sample[0] = (real)((total_error_0 > 0 && data_len > 0) ? log(M_LN2 * total_error_0 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[1] = (real)((total_error_1 > 0 && data_len > 0) ? log(M_LN2 * total_error_1 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[2] = (real)((total_error_2 > 0 && data_len > 0) ? log(M_LN2 * total_error_2 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[3] = (real)((total_error_3 > 0 && data_len > 0) ? log(M_LN2 * total_error_3 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[4] = (real)((total_error_4 > 0 && data_len > 0) ? log(M_LN2 * total_error_4 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[0] = (real)((data_len > 0) ? log(M_LN2 * (real)total_error_0 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[1] = (real)((data_len > 0) ? log(M_LN2 * (real)total_error_1 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[2] = (real)((data_len > 0) ? log(M_LN2 * (real)total_error_2 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[3] = (real)((data_len > 0) ? log(M_LN2 * (real)total_error_3 / (real) data_len) / M_LN2 : 0.0);
residual_bits_per_sample[4] = (real)((data_len > 0) ? log(M_LN2 * (real)total_error_4 / (real) data_len) / M_LN2 : 0.0);
return order;
}