1 /* 2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 12 /* 13 * This file contains the function WebRtcSpl_FilterAR(). 14 * The description header can be found in signal_processing_library.h 15 * 16 */ 17 18 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h" 19 20 int WebRtcSpl_FilterAR(const int16_t* a, 21 int a_length, 22 const int16_t* x, 23 int x_length, 24 int16_t* state, 25 int state_length, 26 int16_t* state_low, 27 int state_low_length, 28 int16_t* filtered, 29 int16_t* filtered_low, 30 int filtered_low_length) 31 { 32 int32_t o; 33 int32_t oLOW; 34 int i, j, stop; 35 const int16_t* x_ptr = &x[0]; 36 int16_t* filteredFINAL_ptr = filtered; 37 int16_t* filteredFINAL_LOW_ptr = filtered_low; 38 39 for (i = 0; i < x_length; i++) 40 { 41 // Calculate filtered[i] and filtered_low[i] 42 const int16_t* a_ptr = &a[1]; 43 int16_t* filtered_ptr = &filtered[i - 1]; 44 int16_t* filtered_low_ptr = &filtered_low[i - 1]; 45 int16_t* state_ptr = &state[state_length - 1]; 46 int16_t* state_low_ptr = &state_low[state_length - 1]; 47 48 o = (int32_t)(*x_ptr++) << 12; 49 oLOW = (int32_t)0; 50 51 stop = (i < a_length) ? i + 1 : a_length; 52 for (j = 1; j < stop; j++) 53 { 54 o -= WEBRTC_SPL_MUL_16_16(*a_ptr, *filtered_ptr--); 55 oLOW -= WEBRTC_SPL_MUL_16_16(*a_ptr++, *filtered_low_ptr--); 56 } 57 for (j = i + 1; j < a_length; j++) 58 { 59 o -= WEBRTC_SPL_MUL_16_16(*a_ptr, *state_ptr--); 60 oLOW -= WEBRTC_SPL_MUL_16_16(*a_ptr++, *state_low_ptr--); 61 } 62 63 o += (oLOW >> 12); 64 *filteredFINAL_ptr = (int16_t)((o + (int32_t)2048) >> 12); 65 *filteredFINAL_LOW_ptr++ = (int16_t)(o - ((int32_t)(*filteredFINAL_ptr++) 66 << 12)); 67 } 68 69 // Save the filter state 70 if (x_length >= state_length) 71 { 72 WebRtcSpl_CopyFromEndW16(filtered, x_length, a_length - 1, state); 73 WebRtcSpl_CopyFromEndW16(filtered_low, x_length, a_length - 1, state_low); 74 } else 75 { 76 for (i = 0; i < state_length - x_length; i++) 77 { 78 state[i] = state[i + x_length]; 79 state_low[i] = state_low[i + x_length]; 80 } 81 for (i = 0; i < x_length; i++) 82 { 83 state[state_length - x_length + i] = filtered[i]; 84 state[state_length - x_length + i] = filtered_low[i]; 85 } 86 } 87 88 return x_length; 89 } 90