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alac: simplify 1st order prediction and reading of warm-up samples

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This commit is contained in:
Justin Ruggles 2012-07-09 11:12:25 -04:00
parent d0c0bf0d3e
commit 01880d287b
1 changed files with 5 additions and 13 deletions
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18
libavcodec/alac.c
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@ -186,25 +186,17 @@ static void predictor_decompress_fir_adapt(int32_t *error_buffer,
/* simple 1st-order prediction */
if (output_size <= 1)
return;
for (i = 0; i < output_size - 1; i++) {
int32_t prev_value;
int32_t error_value;
prev_value = buffer_out[i];
error_value = error_buffer[i+1];
buffer_out[i+1] =
sign_extend((prev_value + error_value), readsamplesize);
for (i = 1; i < output_size; i++) {
buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i],
readsamplesize);
}
return;
}
/* read warm-up samples */
for (i = 0; i < predictor_coef_num; i++) {
int32_t val;
val = buffer_out[i] + error_buffer[i+1];
val = sign_extend(val, readsamplesize);
buffer_out[i+1] = val;
buffer_out[i + 1] = sign_extend(buffer_out[i] + error_buffer[i + 1],
readsamplesize);
}
/* NOTE: 4 and 8 are very common cases that could be optimized. */