diff options
Diffstat (limited to 'media/libstagefright/codecs/amrwbenc/src/hp50.c')
| -rw-r--r-- | media/libstagefright/codecs/amrwbenc/src/hp50.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/amrwbenc/src/hp50.c b/media/libstagefright/codecs/amrwbenc/src/hp50.c new file mode 100644 index 0000000..c1c7b83 --- /dev/null +++ b/media/libstagefright/codecs/amrwbenc/src/hp50.c @@ -0,0 +1,106 @@ +/* + ** 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: hp50.c * +* * +* Description: * +* 2nd order high pass filter with cut off frequency at 31 Hz. * +* Designed with cheby2 function in MATLAB. * +* Optimized for fixed-point to get the following frequency response: * +* * +* frequency: 0Hz 14Hz 24Hz 31Hz 37Hz 41Hz 47Hz * +* dB loss: -infdB -15dB -6dB -3dB -1.5dB -1dB -0.5dB * +* * +* Algorithm: * +* * +* y[i] = b[0]*x[i] + b[1]*x[i-1] + b[2]*x[i-2] * +* + a[1]*y[i-1] + a[2]*y[i-2]; * +* * +* Word16 b[3] = {4053, -8106, 4053}; in Q12 * +* Word16 a[3] = {8192, 16211, -8021}; in Q12 * +* * +* float --> b[3] = {0.989501953, -1.979003906, 0.989501953}; * +* a[3] = {1.000000000, 1.978881836, -0.979125977}; * +************************************************************************/ + +#include "typedef.h" +#include "basic_op.h" +#include "oper_32b.h" +#include "cnst.h" +#include "acelp.h" + +/* filter coefficients */ +static Word16 b[3] = {4053, -8106, 4053}; /* Q12 */ +static Word16 a[3] = {8192, 16211, -8021}; /* Q12 (x2) */ + +/* Initialization of static values */ + +void Init_HP50_12k8(Word16 mem[]) +{ + Set_zero(mem, 6); +} + + +void HP50_12k8( + Word16 signal[], /* input/output signal */ + Word16 lg, /* lenght of signal */ + Word16 mem[] /* filter memory [6] */ + ) +{ + Word16 x2; + Word16 y2_hi, y2_lo, y1_hi, y1_lo, x0, x1; + Word32 L_tmp; + Word32 num; + + y2_hi = *mem++; + y2_lo = *mem++; + y1_hi = *mem++; + y1_lo = *mem++; + x0 = *mem++; + x1 = *mem; + num = (Word32)lg; + do + { + x2 = x1; + x1 = x0; + x0 = *signal; + /* y[i] = b[0]*x[i] + b[1]*x[i-1] + b140[2]*x[i-2] */ + /* + a[1]*y[i-1] + a[2] * y[i-2]; */ + L_tmp = 8192 ; /* rounding to maximise precision */ + L_tmp += y1_lo * a[1]; + L_tmp += y2_lo * a[2]; + L_tmp = L_tmp >> 14; + L_tmp += (y1_hi * a[1] + y2_hi * a[2] + (x0 + x2) * b[0] + x1 * b[1]) << 1; + L_tmp <<= 2; /* coeff Q12 --> Q13 */ + y2_hi = y1_hi; + y2_lo = y1_lo; + y1_hi = (Word16)(L_tmp>>16); + y1_lo = (Word16)((L_tmp & 0xffff)>>1); + *signal++ = extract_h((L_add((L_tmp<<1), 0x8000))); + }while(--num !=0); + + *mem-- = x1; + *mem-- = x0; + *mem-- = y1_lo; + *mem-- = y1_hi; + *mem-- = y2_lo; + *mem-- = y2_hi; + + return; +} + + |