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| author | Justin Ruggles <justin.ruggles@gmail.com> | 2012-07-09 11:33:31 -0400 |
|---|---|---|
| committer | Justin Ruggles <justin.ruggles@gmail.com> | 2012-07-19 13:26:47 -0400 |
| commit | f2515cd629d64484be5747639b485ddad9b6bf85 (patch) | |
| tree | 8fdb8c396abf2bcdace0752f1608e91c975c68af /libavcodec | |
| parent | abc4376b31b672f8f38c30851cbe1acd016b6e18 (diff) | |
| download | ffmpeg-f2515cd629d64484be5747639b485ddad9b6bf85.tar.gz | |
alac: simplify lpc coefficient adaptation
Diffstat (limited to 'libavcodec')
| -rw-r--r-- | libavcodec/alac.c | 41 |
1 files changed, 10 insertions, 31 deletions
diff --git a/libavcodec/alac.c b/libavcodec/alac.c index 7306e57405..110d2cbcb1 100644 --- a/libavcodec/alac.c +++ b/libavcodec/alac.c @@ -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)); } } |