| /* |
| * Copyright 2016 The Chromium Authors. All rights reserved. |
| * Copyright (C) 2020, Apple Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY |
| * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY |
| * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON |
| * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #pragma once |
| |
| #include <wtf/Vector.h> |
| |
| namespace WebCore { |
| |
| class IIRFilter { |
| WTF_MAKE_FAST_ALLOCATED; |
| public: |
| static constexpr size_t maxOrder { 20 }; |
| IIRFilter(const Vector<double>& feedforward, const Vector<double>& feedback); |
| |
| void reset(); |
| |
| void process(const float* source, float* destination, size_t framesToProcess); |
| void getFrequencyResponse(unsigned length, const float* frequency, float* magResponse, float* phaseResponse); |
| double tailTime(double sampleRate, bool isFilterStable); |
| |
| const Vector<double>& feedforward() const { return m_feedforward; } |
| const Vector<double>& feedback() const { return m_feedback; } |
| |
| private: |
| // Filter memory |
| // |
| // For simplicity, we assume |m_xBuffer| and |m_yBuffer| have the same length, |
| // and the length is a power of two. Since the number of coefficients has a |
| // fixed upper length, the size of xBuffer and yBuffer is fixed. |m_xBuffer| |
| // holds the old input values and |m_yBuffer| holds the old output values |
| // needed to compute the new output value. |
| // |
| // m_yBuffer[m_bufferIndex] holds the most recent output value, say, y[n]. |
| // Then m_yBuffer[m_bufferIndex - k] is y[n - k]. Similarly for m_xBuffer. |
| // |
| // To minimize roundoff, these arrays are double's instead of floats. |
| Vector<double> m_xBuffer; |
| Vector<double> m_yBuffer; |
| |
| // Index into the xBuffer and yBuffer arrays where the most current x and y |
| // values should be stored. xBuffer[bufferIndex] corresponds to x[n], the |
| // current x input value and yBuffer[bufferIndex] is where y[n], the current |
| // output value. |
| size_t m_bufferIndex { 0 }; |
| |
| // Those Vectors are owned by the IIRProcess, which owns the IIRFilters via |
| // the IIRDSPKernels. This is a memory optimization to avoid having copies |
| // of these vectors in each IIRDSPKernel / IIRFilter. |
| const Vector<double>& m_feedforward; |
| const Vector<double>& m_feedback; |
| }; |
| |
| } // namespace WebCore |