| /* |
| ** 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; |
| } |
| |
| |