snooper_node.cc | Explore in Territory

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "services/audio/snooper_node.h"

#include <algorithm>
#include <cmath>

#include "base/functional/bind.h"
#include "base/numerics/checked_math.h"
#include "base/trace_event/trace_event.h"
#include "media/base/audio_bus.h"
#include "media/base/audio_timestamp_helper.h"

Helper;

namespace audio {

namespace {

// The delay buffer size is chosen to be a very conservative maximum, just to
// make sure there is an upper bound in-place so that the buffer won't grow
// indefinitely. In most normal cases, reads will cause the delay buffer to
// automatically prune its recording down to well under this maximum (e.g.,
// around 100 milliseconds of audio).
constexpr base::TimeDelta kDelayBufferSize = …;

// A frequency at which people cannot discern tones that differ by 1 Hz. This is
// based on research that shows people can discern tones only when they are more
// than 1 Hz away from 500 Hz. Thus, assume people definitely can't discern
// tones 1 Hz away from 1000 Hz.
constexpr int kStepBasisHz = …;

// The number of frames the resampler should request at a time.
constexpr int kResamplerRequestSize = …;

// Returns the deviation, around an estimated reference time, beyond which a
// SnooperNode considers a skip in input/output to have occurred.
base::TimeDelta GetReferenceTimeSkipThreshold(base::TimeDelta bus_duration) { … }

}  // namespace

// static
constexpr SnooperNode::FrameTicks SnooperNode::kNullPosition;

// static
constexpr SnooperNode::FrameTicks SnooperNode::kWriteStartPosition;

SnooperNode::SnooperNode(const media::AudioParameters& input_params,
                         const media::AudioParameters& output_params)
    : … { … }

SnooperNode::~SnooperNode() = default;

void SnooperNode::OnData(const media::AudioBus& input_bus,
                         base::TimeTicks reference_time,
                         double volume) { … }

std::optional<base::TimeTicks> SnooperNode::SuggestLatestRenderTime(
    FrameTicks duration) { … }

void SnooperNode::Render(base::TimeTicks reference_time,
                         media::AudioBus* output_bus) { … }

void SnooperNode::UpdateCorrectionRate(int correction_fps) { … }

void SnooperNode::ReadFromDelayBuffer(int ignored,
                                      media::AudioBus* resampler_bus) { … }

}  // namespace audio
chromium/services/audio/snooper_node.cc
