chromium/third_party/blink/renderer/modules/webaudio/iir_filter_node.cc

// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "third_party/blink/renderer/modules/webaudio/iir_filter_node.h"

#include "base/metrics/histogram_functions.h"
#include "third_party/blink/renderer/bindings/modules/v8/v8_iir_filter_options.h"
#include "third_party/blink/renderer/core/execution_context/execution_context.h"
#include "third_party/blink/renderer/core/inspector/console_message.h"
#include "third_party/blink/renderer/modules/webaudio/audio_graph_tracer.h"
#include "third_party/blink/renderer/modules/webaudio/base_audio_context.h"
#include "third_party/blink/renderer/modules/webaudio/iir_filter_handler.h"
#include "third_party/blink/renderer/modules/webaudio/iir_processor.h"
#include "third_party/blink/renderer/platform/audio/iir_filter.h"
#include "third_party/blink/renderer/platform/bindings/exception_messages.h"
#include "third_party/blink/renderer/platform/wtf/text/string_builder.h"

namespace blink {

namespace {

// Determine if filter is stable based on the feedback coefficients.
// We compute the reflection coefficients for the filter.  If, at any
// point, the magnitude of the reflection coefficient is greater than
// or equal to 1, the filter is declared unstable.
//
// Let A(z) be the feedback polynomial given by
//   A[n](z) = 1 + a[1]/z + a[2]/z^2 + ... + a[n]/z^n
//
// The first reflection coefficient k[n] = a[n].  Then, recursively compute
//
//   A[n-1](z) = (A[n](z) - k[n]*A[n](1/z)/z^n)/(1-k[n]^2);
//
// stopping at A[1](z).  If at any point |k[n]| >= 1, the filter is
// unstable.
bool IsFilterStable(const Vector<double>& feedback_coef) { … }

}  // namespace

IIRFilterNode::IIRFilterNode(BaseAudioContext& context,
                             const Vector<double>& feedforward_coef,
                             const Vector<double>& feedback_coef,
                             bool is_filter_stable)
    : … { … }

IIRFilterNode* IIRFilterNode::Create(BaseAudioContext& context,
                                     const Vector<double>& feedforward_coef,
                                     const Vector<double>& feedback_coef,
                                     ExceptionState& exception_state) { … }

IIRFilterNode* IIRFilterNode::Create(BaseAudioContext* context,
                                     const IIRFilterOptions* options,
                                     ExceptionState& exception_state) { … }

void IIRFilterNode::Trace(Visitor* visitor) const { … }

IIRProcessor* IIRFilterNode::GetIIRFilterProcessor() const { … }

void IIRFilterNode::getFrequencyResponse(
    NotShared<const DOMFloat32Array> frequency_hz,
    NotShared<DOMFloat32Array> mag_response,
    NotShared<DOMFloat32Array> phase_response,
    ExceptionState& exception_state) { … }

void IIRFilterNode::ReportDidCreate() { … }

void IIRFilterNode::ReportWillBeDestroyed() { … }

}  // namespace blink