diff options
Diffstat (limited to 'media/libstagefright/codecs/amrwbenc/src/lp_dec2.c')
| -rw-r--r-- | media/libstagefright/codecs/amrwbenc/src/lp_dec2.c | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/amrwbenc/src/lp_dec2.c b/media/libstagefright/codecs/amrwbenc/src/lp_dec2.c new file mode 100644 index 0000000..1d5d076 --- /dev/null +++ b/media/libstagefright/codecs/amrwbenc/src/lp_dec2.c @@ -0,0 +1,70 @@ +/* + ** Copyright 2003-2010, VisualOn, Inc. + ** + ** Licensed under the Apache License, Version 2.0 (the "License"); + ** you may not use this file except in compliance with the License. + ** You may obtain a copy of the License at + ** + ** http://www.apache.org/licenses/LICENSE-2.0 + ** + ** Unless required by applicable law or agreed to in writing, software + ** distributed under the License is distributed on an "AS IS" BASIS, + ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + ** See the License for the specific language governing permissions and + ** limitations under the License. + */ + +/*********************************************************************** +* File: lp_dec2.c * +* * +* Description:Decimate a vector by 2 with 2nd order fir filter * +* * +************************************************************************/ + +#include "typedef.h" +#include "basic_op.h" +#include "cnst.h" + +#define L_FIR 5 +#define L_MEM (L_FIR-2) + +/* static float h_fir[L_FIR] = {0.13, 0.23, 0.28, 0.23, 0.13}; */ +/* fixed-point: sum of coef = 32767 to avoid overflow on DC */ +static Word16 h_fir[L_FIR] = {4260, 7536, 9175, 7536, 4260}; + +void LP_Decim2( + Word16 x[], /* in/out: signal to process */ + Word16 l, /* input : size of filtering */ + Word16 mem[] /* in/out: memory (size=3) */ + ) +{ + Word16 *p_x, x_buf[L_FRAME + L_MEM]; + Word32 i, j; + Word32 L_tmp; + /* copy initial filter states into buffer */ + p_x = x_buf; + for (i = 0; i < L_MEM; i++) + { + *p_x++ = mem[i]; + mem[i] = x[l - L_MEM + i]; + } + for (i = 0; i < l; i++) + { + *p_x++ = x[i]; + } + for (i = 0, j = 0; i < l; i += 2, j++) + { + p_x = &x_buf[i]; + L_tmp = ((*p_x++) * h_fir[0]); + L_tmp += ((*p_x++) * h_fir[1]); + L_tmp += ((*p_x++) * h_fir[2]); + L_tmp += ((*p_x++) * h_fir[3]); + L_tmp += ((*p_x++) * h_fir[4]); + x[j] = (L_tmp + 0x4000)>>15; + } + return; +} + + + + |