1e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard/* 2e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** Copyright 2003-2010, VisualOn, Inc. 3e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** 4e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** Licensed under the Apache License, Version 2.0 (the "License"); 5e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** you may not use this file except in compliance with the License. 6e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** You may obtain a copy of the License at 7e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** 8e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** http://www.apache.org/licenses/LICENSE-2.0 9e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** 10e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** Unless required by applicable law or agreed to in writing, software 11e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** distributed under the License is distributed on an "AS IS" BASIS, 12e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** See the License for the specific language governing permissions and 14e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ** limitations under the License. 15e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard */ 16e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 17e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard/*********************************************************************** 18e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard* File: lp_dec2.c * 19e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard* * 20e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard* Description:Decimate a vector by 2 with 2nd order fir filter * 21e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard* * 22e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard************************************************************************/ 23e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 24e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard#include "typedef.h" 25e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard#include "basic_op.h" 26e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard#include "cnst.h" 27e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 28e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard#define L_FIR 5 29e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard#define L_MEM (L_FIR-2) 30e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 31e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard/* static float h_fir[L_FIR] = {0.13, 0.23, 0.28, 0.23, 0.13}; */ 32e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard/* fixed-point: sum of coef = 32767 to avoid overflow on DC */ 33e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgardstatic Word16 h_fir[L_FIR] = {4260, 7536, 9175, 7536, 4260}; 34e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 35e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgardvoid LP_Decim2( 36e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard Word16 x[], /* in/out: signal to process */ 37e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard Word16 l, /* input : size of filtering */ 38e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard Word16 mem[] /* in/out: memory (size=3) */ 39e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard ) 40e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard{ 41e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard Word16 *p_x, x_buf[L_FRAME + L_MEM]; 42e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard Word32 i, j; 43e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard Word32 L_tmp; 44e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard /* copy initial filter states into buffer */ 45b676a05348e4c516fa8b57e33b10548e6142c3f8Mans Rullgard p_x = x_buf; 46e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard for (i = 0; i < L_MEM; i++) 47e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard { 48b676a05348e4c516fa8b57e33b10548e6142c3f8Mans Rullgard *p_x++ = mem[i]; 49b676a05348e4c516fa8b57e33b10548e6142c3f8Mans Rullgard mem[i] = x[l - L_MEM + i]; 50e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard } 51e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard for (i = 0; i < l; i++) 52e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard { 53b676a05348e4c516fa8b57e33b10548e6142c3f8Mans Rullgard *p_x++ = x[i]; 54e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard } 55e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard for (i = 0, j = 0; i < l; i += 2, j++) 56e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard { 57b676a05348e4c516fa8b57e33b10548e6142c3f8Mans Rullgard p_x = &x_buf[i]; 58e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard L_tmp = ((*p_x++) * h_fir[0]); 59e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard L_tmp += ((*p_x++) * h_fir[1]); 60e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard L_tmp += ((*p_x++) * h_fir[2]); 61e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard L_tmp += ((*p_x++) * h_fir[3]); 62e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard L_tmp += ((*p_x++) * h_fir[4]); 63b676a05348e4c516fa8b57e33b10548e6142c3f8Mans Rullgard x[j] = (L_tmp + 0x4000)>>15; 64e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard } 65e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard return; 66e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard} 67e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 68e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 69e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 70e2e838afcf03e603a41a0455846eaf9614537c16Mans Rullgard 71