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alac: simplify lpc coefficient adaptation

This commit is contained in:
Justin Ruggles 2012-07-09 11:33:31 -04:00
parent abc4376b31
commit f2515cd629
1 changed files with 10 additions and 31 deletions
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41
libavcodec/alac.c
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@ -206,6 +206,7 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
int j;
int val = 0;
int error_val = error_buffer[i];
int error_sign;
for (j = 0; j < predictor_coef_num; j++) {
val += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
@ -218,39 +219,17 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
buffer_out[predictor_coef_num + 1] = sign_extend(val, readsamplesize);
if (error_val > 0) {
int predictor_num = predictor_coef_num - 1;
while (predictor_num >= 0 && error_val > 0) {
/* adapt LPC coefficients */
error_sign = sign_only(error_val);
if (error_sign) {
for (j = predictor_coef_num - 1; j >= 0 && error_val * error_sign > 0; j--) {
int sign;
val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
sign = sign_only(val);
predictor_coef_table[predictor_num] -= sign;
val *= sign; /* absolute value */
val = buffer_out[0] - buffer_out[predictor_coef_num - j];
sign = sign_only(val) * error_sign;
predictor_coef_table[j] -= sign;
val *= sign;
error_val -= ((val >> predictor_quantitization) *
(predictor_coef_num - predictor_num));
predictor_num--;
}
} else if (error_val < 0) {
int predictor_num = predictor_coef_num - 1;
while (predictor_num >= 0 && error_val < 0) {
int sign;
val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
sign = -sign_only(val);
predictor_coef_table[predictor_num] -= sign;
val *= sign; /* neg value */
error_val -= ((val >> predictor_quantitization) *
(predictor_coef_num - predictor_num));
predictor_num--;
(predictor_coef_num - j));
}
}