| /* |
| * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| |
| /* |
| * This file contains the function WebRtcSpl_FilterAR(). |
| * The description header can be found in signal_processing_library.h |
| * |
| */ |
| |
| #include "common_audio/signal_processing/include/signal_processing_library.h" |
| |
| #include "rtc_base/checks.h" |
| |
| size_t WebRtcSpl_FilterAR(const int16_t* a, |
| size_t a_length, |
| const int16_t* x, |
| size_t x_length, |
| int16_t* state, |
| size_t state_length, |
| int16_t* state_low, |
| size_t state_low_length, |
| int16_t* filtered, |
| int16_t* filtered_low, |
| size_t filtered_low_length) |
| { |
| int64_t o; |
| int32_t oLOW; |
| size_t i, j, stop; |
| const int16_t* x_ptr = &x[0]; |
| int16_t* filteredFINAL_ptr = filtered; |
| int16_t* filteredFINAL_LOW_ptr = filtered_low; |
| |
| for (i = 0; i < x_length; i++) |
| { |
| // Calculate filtered[i] and filtered_low[i] |
| const int16_t* a_ptr = &a[1]; |
| // The index can become negative, but the arrays will never be indexed |
| // with it when negative. Nevertheless, the index cannot be a size_t |
| // because of this. |
| int filtered_ix = (int)i - 1; |
| int16_t* state_ptr = &state[state_length - 1]; |
| int16_t* state_low_ptr = &state_low[state_length - 1]; |
| |
| o = (int32_t)(*x_ptr++) * (1 << 12); |
| oLOW = (int32_t)0; |
| |
| stop = (i < a_length) ? i + 1 : a_length; |
| for (j = 1; j < stop; j++) |
| { |
| RTC_DCHECK_GE(filtered_ix, 0); |
| o -= *a_ptr * filtered[filtered_ix]; |
| oLOW -= *a_ptr++ * filtered_low[filtered_ix]; |
| --filtered_ix; |
| } |
| for (j = i + 1; j < a_length; j++) |
| { |
| o -= *a_ptr * *state_ptr--; |
| oLOW -= *a_ptr++ * *state_low_ptr--; |
| } |
| |
| o += (oLOW >> 12); |
| *filteredFINAL_ptr = (int16_t)((o + (int32_t)2048) >> 12); |
| *filteredFINAL_LOW_ptr++ = |
| (int16_t)(o - ((int32_t)(*filteredFINAL_ptr++) * (1 << 12))); |
| } |
| |
| // Save the filter state |
| if (x_length >= state_length) |
| { |
| WebRtcSpl_CopyFromEndW16(filtered, x_length, a_length - 1, state); |
| WebRtcSpl_CopyFromEndW16(filtered_low, x_length, a_length - 1, state_low); |
| } else |
| { |
| for (i = 0; i < state_length - x_length; i++) |
| { |
| state[i] = state[i + x_length]; |
| state_low[i] = state_low[i + x_length]; |
| } |
| for (i = 0; i < x_length; i++) |
| { |
| state[state_length - x_length + i] = filtered[i]; |
| state[state_length - x_length + i] = filtered_low[i]; |
| } |
| } |
| |
| return x_length; |
| } |