Reland "SelectSettings algorithm for audio constraints."

content/renderer/media/media_stream_constraints_util_audio.cc

Index: content/renderer/media/media_stream_constraints_util_audio.cc
diff --git a/content/renderer/media/media_stream_constraints_util_audio.cc b/content/renderer/media/media_stream_constraints_util_audio.cc
new file mode 100644
index 0000000000000000000000000000000000000000..155d70698f2d68525e728362a9c7dd848b71b8f6
--- /dev/null
+++ b/content/renderer/media/media_stream_constraints_util_audio.cc
@@ -0,0 +1,614 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/renderer/media/media_stream_constraints_util_audio.h"
+
+#include <algorithm>
+#include <cmath>
+#include <utility>
+#include <vector>
+
+#include "content/common/media/media_stream_options.h"
+#include "content/renderer/media/media_stream_constraints_util_sets.h"
+#include "content/renderer/media/media_stream_video_source.h"
+#include "media/base/limits.h"
+#include "third_party/WebKit/public/platform/WebMediaConstraints.h"
+#include "third_party/WebKit/public/platform/WebString.h"
+
+namespace content {
+
+namespace {
+
+// This class has the same data as ::mojom::AudioInputDeviceCapabilities, but
+// adds extra operations to simplify the device-selection code.
+class AudioDeviceInfo {
+ public:
+  // This constructor is intended for device capture.
+  explicit AudioDeviceInfo(
+      const ::mojom::AudioInputDeviceCapabilitiesPtr& device_info)
+      : device_id_(device_info->device_id),
+        parameters_(device_info->parameters) {
+    DCHECK(parameters_.IsValid());
+  }
+
+  // This constructor is intended for content capture, where constraints on
+  // audio parameters are not supported.
+  explicit AudioDeviceInfo(std::string device_id)
+      : device_id_(std::move(device_id)) {}
+
+  bool operator==(const AudioDeviceInfo& other) const {
+    return device_id_ == other.device_id_;
+  }
+
+  // Accessors
+  const std::string& device_id() const { return device_id_; }
+  const media::AudioParameters& parameters() const { return parameters_; }
+
+  // Convenience accessors
+  int SampleRate() const {
+    DCHECK(parameters_.IsValid());
+    return parameters_.sample_rate();
+  }
+  int SampleSize() const {
+    DCHECK(parameters_.IsValid());
+    return parameters_.bits_per_sample();
+  }
+  int ChannelCount() const {
+    DCHECK(parameters_.IsValid());
+    return parameters_.channels();
+  }
+  int Effects() const {
+    DCHECK(parameters_.IsValid());
+    return parameters_.effects();
+  }
+
+ private:
+  std::string device_id_;
+  media::AudioParameters parameters_;
+};
+
+using AudioDeviceSet = DiscreteSet<AudioDeviceInfo>;
+
+AudioDeviceSet AudioDeviceSetForDeviceCapture(
+    const blink::WebMediaTrackConstraintSet& constraint_set,
+    const AudioDeviceCaptureCapabilities& capabilities,
+    const char** failed_constraint_name) {
+  std::vector<AudioDeviceInfo> result;
+  *failed_constraint_name = "";
+  for (auto& device_capabilities : capabilities) {
+    if (!constraint_set.device_id.Matches(
+            blink::WebString::FromASCII(device_capabilities->device_id))) {
+      if (failed_constraint_name)
+        *failed_constraint_name = constraint_set.device_id.GetName();
+      continue;
+    }
+    *failed_constraint_name =
+        IsOutsideConstraintRange(constraint_set.sample_rate,
+                                 device_capabilities->parameters.sample_rate());
+    if (*failed_constraint_name)
+      continue;
+
+    *failed_constraint_name = IsOutsideConstraintRange(
+        constraint_set.sample_size,
+        device_capabilities->parameters.bits_per_sample());
+    if (*failed_constraint_name)
+      continue;
+
+    *failed_constraint_name =
+        IsOutsideConstraintRange(constraint_set.channel_count,
+                                 device_capabilities->parameters.channels());
+    if (*failed_constraint_name)
+      continue;
+
+    result.push_back(AudioDeviceInfo(device_capabilities));
+  }
+
+  if (!result.empty())
+    *failed_constraint_name = nullptr;
+
+  return AudioDeviceSet(result);
+}
+
+AudioDeviceSet AudioDeviceSetForContentCapture(
+    const blink::WebMediaTrackConstraintSet& constraint_set,
+    const char** failed_constraint_name = nullptr) {
+  if (!constraint_set.device_id.HasExact())
+    return AudioDeviceSet::UniversalSet();
+
+  std::vector<AudioDeviceInfo> result;
+  for (auto& device_id : constraint_set.device_id.Exact())
+    result.push_back(AudioDeviceInfo(device_id.Utf8()));
+
+  return AudioDeviceSet(result);
+}
+
+// This class represents a set of possible candidate settings.
+// The SelectSettings algorithm starts with a set containing all possible
+// candidates based on hardware capabilities and/or allowed values for supported
+// properties. The is then reduced progressively as the basic and advanced
+// constraint sets are applied.
+// In the end, if the set of candidates is empty, SelectSettings fails.
+// If not, the ideal values (if any) or tie breaker rules are used to select
+// the final settings based on the candidates that survived the application
+// of the constraint sets.
+// This class is implemented as a collection of more specific sets for the
+// various supported properties. If any of the specific sets is empty, the
+// whole AudioCaptureCandidates set is considered empty as well.
+class AudioCaptureCandidates {
+ public:
+  enum BoolConstraint {
+    // Constraints not related to audio processing.
+    HOTWORD_ENABLED,
+    DISABLE_LOCAL_ECHO,
+    RENDER_TO_ASSOCIATED_SINK,
+
+    // Constraints that enable/disable audio processing.
+    ECHO_CANCELLATION,
+    GOOG_ECHO_CANCELLATION,
+
+    // Constraints that control audio-processing behavior.
+    GOOG_AUDIO_MIRRORING,
+    GOOG_AUTO_GAIN_CONTROL,
+    GOOG_EXPERIMENTAL_ECHO_CANCELLATION,
+    GOOG_TYPING_NOISE_DETECTION,
+    GOOG_NOISE_SUPPRESSION,
+    GOOG_EXPERIMENTAL_NOISE_SUPPRESSION,
+    GOOG_BEAMFORMING,
+    GOOG_HIGHPASS_FILTER,
+    GOOG_EXPERIMENTAL_AUTO_GAIN_CONTROL,
+    NUM_BOOL_CONSTRAINTS
+  };
+
+  AudioCaptureCandidates();
+
+  AudioCaptureCandidates(
+      const blink::WebMediaTrackConstraintSet& constraint_set,
+      const AudioDeviceCaptureCapabilities& capabilities,
+      bool is_device_capture);
+
+  // Set operations.
+  bool IsEmpty() const { return failed_constraint_name_ != nullptr; }
+  AudioCaptureCandidates Intersection(const AudioCaptureCandidates& other);
+
+  // Accessors.
+  const char* failed_constraint_name() const { return failed_constraint_name_; }
+  const AudioDeviceSet& audio_device_set() const { return audio_device_set_; }
+  const DiscreteSet<std::string>& goog_array_geometry_set() const {
+    return goog_array_geometry_set_;
+  }
+
+  // Accessor for boolean sets.
+  const DiscreteSet<bool>& GetBoolSet(BoolConstraint property) const {
+    DCHECK_GE(property, 0);
+    DCHECK_LT(property, NUM_BOOL_CONSTRAINTS);
+    return bool_sets_[property];
+  }
+
+  // Convenience accessors.
+  const DiscreteSet<bool>& hotword_enabled_set() const {
+    return bool_sets_[HOTWORD_ENABLED];
+  }
+  const DiscreteSet<bool>& disable_local_echo_set() const {
+    return bool_sets_[DISABLE_LOCAL_ECHO];
+  }
+  const DiscreteSet<bool>& render_to_associated_sink_set() const {
+    return bool_sets_[RENDER_TO_ASSOCIATED_SINK];
+  }
+  const DiscreteSet<bool>& echo_cancellation_set() const {
+    return bool_sets_[ECHO_CANCELLATION];
+  }
+  const DiscreteSet<bool>& goog_echo_cancellation_set() const {
+    return bool_sets_[GOOG_ECHO_CANCELLATION];
+  }
+  const DiscreteSet<bool>& goog_audio_mirroring_set() const {
+    return bool_sets_[GOOG_AUDIO_MIRRORING];
+  }
+
+ private:
+  void MaybeUpdateFailedNonDeviceConstraintName();
+  void CheckContradictoryEchoCancellation();
+
+  // Maps BoolConstraint values to fields in blink::WebMediaTrackConstraintSet.
+  static const blink::BooleanConstraint blink::WebMediaTrackConstraintSet::*
+      kBlinkBoolConstraintFields[NUM_BOOL_CONSTRAINTS];
+
+  const char* failed_constraint_name_;
+
+  AudioDeviceSet audio_device_set_;  // Device-related constraints.
+  std::array<DiscreteSet<bool>, NUM_BOOL_CONSTRAINTS> bool_sets_;
+  DiscreteSet<std::string> goog_array_geometry_set_;
+};
+
+const blink::BooleanConstraint blink::WebMediaTrackConstraintSet::*
+    AudioCaptureCandidates::kBlinkBoolConstraintFields[NUM_BOOL_CONSTRAINTS] = {
+        &blink::WebMediaTrackConstraintSet::hotword_enabled,
+        &blink::WebMediaTrackConstraintSet::disable_local_echo,
+        &blink::WebMediaTrackConstraintSet::render_to_associated_sink,
+        &blink::WebMediaTrackConstraintSet::echo_cancellation,
+        &blink::WebMediaTrackConstraintSet::goog_echo_cancellation,
+        &blink::WebMediaTrackConstraintSet::goog_audio_mirroring,
+        &blink::WebMediaTrackConstraintSet::goog_auto_gain_control,
+        &blink::WebMediaTrackConstraintSet::goog_experimental_echo_cancellation,
+        &blink::WebMediaTrackConstraintSet::goog_typing_noise_detection,
+        &blink::WebMediaTrackConstraintSet::goog_noise_suppression,
+        &blink::WebMediaTrackConstraintSet::goog_experimental_noise_suppression,
+        &blink::WebMediaTrackConstraintSet::goog_beamforming,
+        &blink::WebMediaTrackConstraintSet::goog_highpass_filter,
+        &blink::WebMediaTrackConstraintSet::
+            goog_experimental_auto_gain_control};
+
+// directly mapped boolean sets to audio properties
+struct BoolSetPropertyEntry {
+  DiscreteSet<bool> AudioCaptureCandidates::*bool_set;
+  bool AudioProcessingProperties::*bool_field;
+  bool default_value;
+};
+
+AudioCaptureCandidates::AudioCaptureCandidates()
+    : failed_constraint_name_(nullptr) {}
+
+AudioCaptureCandidates::AudioCaptureCandidates(
+    const blink::WebMediaTrackConstraintSet& constraint_set,
+    const AudioDeviceCaptureCapabilities& capabilities,
+    bool is_device_capture)
+    : failed_constraint_name_(nullptr),
+      audio_device_set_(
+          is_device_capture
+              ? AudioDeviceSetForDeviceCapture(constraint_set,
+                                               capabilities,
+                                               &failed_constraint_name_)
+              : AudioDeviceSetForContentCapture(constraint_set,
+                                                &failed_constraint_name_)),
+      goog_array_geometry_set_(
+          StringSetFromConstraint(constraint_set.goog_array_geometry)) {
+  for (size_t i = 0; i < NUM_BOOL_CONSTRAINTS; ++i) {
+    bool_sets_[i] =
+        BoolSetFromConstraint(constraint_set.*kBlinkBoolConstraintFields[i]);
+  }
+  MaybeUpdateFailedNonDeviceConstraintName();
+}
+
+AudioCaptureCandidates AudioCaptureCandidates::Intersection(
+    const AudioCaptureCandidates& other) {
+  AudioCaptureCandidates intersection;
+  intersection.audio_device_set_ =
+      audio_device_set_.Intersection(other.audio_device_set_);
+  if (intersection.audio_device_set_.IsEmpty()) {
+    // To mark the intersection as empty, it is necessary to assign a
+    // a non-null value to |failed_constraint_name_|. The specific value
+    // for an intersection does not actually matter, since the intersection
+    // is discarded if empty.
+    intersection.failed_constraint_name_ = "some device constraint";
+    return intersection;
+  }
+  for (size_t i = 0; i < NUM_BOOL_CONSTRAINTS; ++i) {
+    intersection.bool_sets_[i] =
+        bool_sets_[i].Intersection(other.bool_sets_[i]);
+  }
+  intersection.goog_array_geometry_set_ =
+      goog_array_geometry_set_.Intersection(other.goog_array_geometry_set_);
+  intersection.MaybeUpdateFailedNonDeviceConstraintName();
+
+  return intersection;
+}
+
+void AudioCaptureCandidates::MaybeUpdateFailedNonDeviceConstraintName() {
+  blink::WebMediaTrackConstraintSet constraint_set;
+  for (size_t i = 0; i < NUM_BOOL_CONSTRAINTS; ++i) {
+    if (bool_sets_[i].IsEmpty()) {
+      failed_constraint_name_ =
+          (constraint_set.*kBlinkBoolConstraintFields[i]).GetName();
+    }
+  }
+  if (goog_array_geometry_set_.IsEmpty())
+    failed_constraint_name_ = constraint_set.goog_array_geometry.GetName();
+
+  CheckContradictoryEchoCancellation();
+}
+
+void AudioCaptureCandidates::CheckContradictoryEchoCancellation() {
+  DiscreteSet<bool> echo_cancellation_intersection =
+      bool_sets_[ECHO_CANCELLATION].Intersection(
+          bool_sets_[GOOG_ECHO_CANCELLATION]);
+  // echoCancellation and googEchoCancellation constraints should not
+  // contradict each other. Mark the set as empty if they do.
+  if (echo_cancellation_intersection.IsEmpty()) {
+    failed_constraint_name_ =
+        blink::WebMediaTrackConstraintSet().echo_cancellation.GetName();
+  }
+}
+
+// Fitness function for constraints involved in device selection.
+//  Based on https://w3c.github.io/mediacapture-main/#dfn-fitness-distance
+double DeviceInfoFitness(
+    bool is_device_capture,
+    const AudioDeviceInfo& device_info,
+    const blink::WebMediaTrackConstraintSet& basic_constraint_set) {
+  double fitness = 0.0;
+  fitness += StringConstraintFitnessDistance(
+      blink::WebString::FromASCII(device_info.device_id()),
+      basic_constraint_set.device_id);
+
+  if (!is_device_capture)
+    return fitness;
+
+  if (basic_constraint_set.sample_rate.HasIdeal()) {
+    fitness += NumericConstraintFitnessDistance(
+        device_info.SampleRate(), basic_constraint_set.sample_rate.Ideal());
+  }
+
+  if (basic_constraint_set.sample_size.HasIdeal()) {
+    fitness += NumericConstraintFitnessDistance(
+        device_info.SampleSize(), basic_constraint_set.sample_size.Ideal());
+  }
+
+  if (basic_constraint_set.channel_count.HasIdeal()) {
+    fitness += NumericConstraintFitnessDistance(
+        device_info.ChannelCount(), basic_constraint_set.channel_count.Ideal());
+  }
+
+  return fitness;
+}
+
+AudioDeviceInfo SelectDevice(
+    const AudioDeviceSet& audio_device_set,
+    const blink::WebMediaTrackConstraintSet& basic_constraint_set,
+    const std::string& default_device_id,
+    bool is_device_capture) {
+  DCHECK(!audio_device_set.IsEmpty());
+  if (audio_device_set.is_universal()) {
+    DCHECK(!is_device_capture);
+    std::string device_id;
+    if (basic_constraint_set.device_id.HasIdeal()) {
+      device_id = basic_constraint_set.device_id.Ideal().begin()->Utf8();
+    }
+    return AudioDeviceInfo(std::move(device_id));
+  }
+
+  std::vector<double> best_fitness({HUGE_VAL, HUGE_VAL});
+  auto best_candidate = audio_device_set.elements().end();
+  for (auto it = audio_device_set.elements().begin();
+       it != audio_device_set.elements().end(); ++it) {
+    std::vector<double> fitness;
+    // First criterion is spec-based fitness function. Second criterion is
+    // being the default device.
+    fitness.push_back(
+        DeviceInfoFitness(is_device_capture, *it, basic_constraint_set));
+    fitness.push_back(it->device_id() == default_device_id ? 0.0 : HUGE_VAL);
+    if (fitness < best_fitness) {
+      best_fitness = std::move(fitness);
+      best_candidate = it;
+    }
+  }
+  DCHECK(best_candidate != audio_device_set.elements().end());
+  return *best_candidate;
+}
+
+bool SelectBool(const DiscreteSet<bool>& set,
+                const blink::BooleanConstraint& constraint,
+                bool default_value) {
+  DCHECK(!set.IsEmpty());
+  if (constraint.HasIdeal() && set.Contains(constraint.Ideal())) {
+    return constraint.Ideal();
+  }
+
+  // Return default value if unconstrained.
+  if (set.is_universal()) {
+    return default_value;
+  }
+  DCHECK_EQ(set.elements().size(), 1U);
+  return set.FirstElement();
+}
+
+base::Optional<bool> SelectOptionalBool(
+    const DiscreteSet<bool>& set,
+    const blink::BooleanConstraint& constraint) {
+  DCHECK(!set.IsEmpty());
+  if (constraint.HasIdeal() && set.Contains(constraint.Ideal())) {
+    return constraint.Ideal();
+  }
+
+  // Return no value if unconstrained.
+  if (set.is_universal()) {
+    return base::Optional<bool>();
+  }
+  DCHECK_EQ(set.elements().size(), 1U);
+  return set.FirstElement();
+}
+
+base::Optional<std::string> SelectOptionalString(
+    const DiscreteSet<std::string>& set,
+    const blink::StringConstraint& constraint) {
+  DCHECK(!set.IsEmpty());
+  if (constraint.HasIdeal()) {
+    for (const auto& ideal_candidate : constraint.Ideal()) {
+      std::string candidate = ideal_candidate.Utf8();
+      if (set.Contains(candidate)) {
+        return candidate;
+      }
+    }
+  }
+
+  // Return no value if unconstrained.
+  if (set.is_universal()) {
+    return base::Optional<std::string>();
+  }
+  return set.FirstElement();
+}
+
+bool SelectEnableSwEchoCancellation(
+    base::Optional<bool> echo_cancellation,
+    base::Optional<bool> goog_echo_cancellation,
+    const media::AudioParameters& audio_parameters,
+    bool default_audio_processing_value) {
+  // If there is hardware echo cancellation, return false.
+  if (audio_parameters.IsValid() &&
+      (audio_parameters.effects() & media::AudioParameters::ECHO_CANCELLER))
+    return false;
+  DCHECK(echo_cancellation && goog_echo_cancellation
+             ? *echo_cancellation == *goog_echo_cancellation
+             : true);
+  if (echo_cancellation)
+    return *echo_cancellation;
+  if (goog_echo_cancellation)
+    return *goog_echo_cancellation;
+
+  return default_audio_processing_value;
+}
+
+struct AudioPropertyConstraintPair {
+  bool AudioProcessingProperties::*audio_property;
+  AudioCaptureCandidates::BoolConstraint bool_set_index;
+  blink::BooleanConstraint blink::WebMediaTrackConstraintSet::*constraint;
+};
+
+// Boolean audio properties that are mapped directly to a boolean constraint
+// and which are subject to the same processing.
+const AudioPropertyConstraintPair kAudioPropertyConstraintMap[] = {
+    {&AudioProcessingProperties::goog_auto_gain_control,
+     AudioCaptureCandidates::GOOG_AUTO_GAIN_CONTROL,
+     &blink::WebMediaTrackConstraintSet::goog_auto_gain_control},
+    {&AudioProcessingProperties::goog_experimental_echo_cancellation,
+     AudioCaptureCandidates::GOOG_EXPERIMENTAL_ECHO_CANCELLATION,
+     &blink::WebMediaTrackConstraintSet::goog_experimental_echo_cancellation},
+    {&AudioProcessingProperties::goog_typing_noise_detection,
+     AudioCaptureCandidates::GOOG_TYPING_NOISE_DETECTION,
+     &blink::WebMediaTrackConstraintSet::goog_typing_noise_detection},
+    {&AudioProcessingProperties::goog_noise_suppression,
+     AudioCaptureCandidates::GOOG_NOISE_SUPPRESSION,
+     &blink::WebMediaTrackConstraintSet::goog_noise_suppression},
+    {&AudioProcessingProperties::goog_experimental_noise_suppression,
+     AudioCaptureCandidates::GOOG_EXPERIMENTAL_NOISE_SUPPRESSION,
+     &blink::WebMediaTrackConstraintSet::goog_experimental_noise_suppression},
+    {&AudioProcessingProperties::goog_beamforming,
+     AudioCaptureCandidates::GOOG_BEAMFORMING,
+     &blink::WebMediaTrackConstraintSet::goog_beamforming},
+    {&AudioProcessingProperties::goog_highpass_filter,
+     AudioCaptureCandidates::GOOG_HIGHPASS_FILTER,
+     &blink::WebMediaTrackConstraintSet::goog_highpass_filter},
+    {&AudioProcessingProperties::goog_experimental_auto_gain_control,
+     AudioCaptureCandidates::GOOG_EXPERIMENTAL_AUTO_GAIN_CONTROL,
+     &blink::WebMediaTrackConstraintSet::goog_experimental_auto_gain_control}};
+
+AudioProcessingProperties SelectAudioProcessingProperties(
+    const AudioCaptureCandidates& candidates,
+    const blink::WebMediaTrackConstraintSet& basic_constraint_set,
+    const media::AudioParameters& audio_parameters,
+    bool is_device_capture) {
+  DCHECK(!candidates.IsEmpty());
+  base::Optional<bool> echo_cancellation =
+      SelectOptionalBool(candidates.echo_cancellation_set(),
+                         basic_constraint_set.echo_cancellation);
+  // Audio-processing properties are disabled by default for content capture, or
+  // if the |echo_cancellation| constraint is false.
+  bool default_audio_processing_value = true;
+  if (!is_device_capture || (echo_cancellation && !*echo_cancellation))
+    default_audio_processing_value = false;
+
+  base::Optional<bool> goog_echo_cancellation =
+      SelectOptionalBool(candidates.goog_echo_cancellation_set(),
+                         basic_constraint_set.goog_echo_cancellation);
+
+  AudioProcessingProperties properties;
+  properties.enable_sw_echo_cancellation = SelectEnableSwEchoCancellation(
+      echo_cancellation, goog_echo_cancellation, audio_parameters,
+      default_audio_processing_value);
+  properties.disable_hw_echo_cancellation =
+      (echo_cancellation && !*echo_cancellation) ||
+      (goog_echo_cancellation && !*goog_echo_cancellation);
+
+  properties.goog_audio_mirroring =
+      SelectBool(candidates.goog_audio_mirroring_set(),
+                 basic_constraint_set.goog_audio_mirroring,
+                 properties.goog_audio_mirroring);
+
+  for (auto& entry : kAudioPropertyConstraintMap) {
+    properties.*entry.audio_property = SelectBool(
+        candidates.GetBoolSet(entry.bool_set_index),
+        basic_constraint_set.*entry.constraint,
+        default_audio_processing_value && properties.*entry.audio_property);
+  }
+
+  base::Optional<std::string> array_geometry =
+      SelectOptionalString(candidates.goog_array_geometry_set(),
+                           basic_constraint_set.goog_array_geometry);
+  std::vector<media::Point> parsed_positions;
+  if (array_geometry)
+    parsed_positions = media::ParsePointsFromString(*array_geometry);
+  bool are_valid_parsed_positions =
+      !parsed_positions.empty() || (array_geometry && array_geometry->empty());
+  properties.goog_array_geometry = are_valid_parsed_positions
+                                       ? std::move(parsed_positions)
+                                       : audio_parameters.mic_positions();
+
+  return properties;
+}
+
+AudioCaptureSettings SelectResult(
+    const AudioCaptureCandidates& candidates,
+    const blink::WebMediaTrackConstraintSet& basic_constraint_set,
+    const std::string& default_device_id,
+    const std::string& media_stream_source) {
+  bool is_device_capture = media_stream_source.empty();
+  AudioDeviceInfo device_info =
+      SelectDevice(candidates.audio_device_set(), basic_constraint_set,
+                   default_device_id, is_device_capture);
+  bool hotword_enabled =
+      SelectBool(candidates.hotword_enabled_set(),
+                 basic_constraint_set.hotword_enabled, false);
+  bool disable_local_echo_default =
+      media_stream_source != kMediaStreamSourceDesktop;
+  bool disable_local_echo = SelectBool(candidates.disable_local_echo_set(),
+                                       basic_constraint_set.disable_local_echo,
+                                       disable_local_echo_default);
+  bool render_to_associated_sink =
+      SelectBool(candidates.render_to_associated_sink_set(),
+                 basic_constraint_set.render_to_associated_sink, false);
+
+  AudioProcessingProperties audio_processing_properties =
+      SelectAudioProcessingProperties(candidates, basic_constraint_set,
+                                      device_info.parameters(),
+                                      is_device_capture);
+
+  return AudioCaptureSettings(device_info.device_id(), device_info.parameters(),
+                              hotword_enabled, disable_local_echo,
+                              render_to_associated_sink,
+                              audio_processing_properties);
+}
+
+}  // namespace
+
+AudioCaptureSettings SelectSettingsAudioCapture(
+    const AudioDeviceCaptureCapabilities& capabilities,
+    const blink::WebMediaConstraints& constraints) {
+  std::string media_stream_source = GetMediaStreamSource(constraints);
+  bool is_device_capture = media_stream_source.empty();
+  if (is_device_capture && capabilities.empty())
+    return AudioCaptureSettings();
+
+  AudioCaptureCandidates candidates(constraints.Basic(), capabilities,
+                                    is_device_capture);
+  if (candidates.IsEmpty()) {
+    return AudioCaptureSettings(candidates.failed_constraint_name());
+  }
+
+  for (const auto& advanced_set : constraints.Advanced()) {
+    AudioCaptureCandidates advanced_candidates(advanced_set, capabilities,
+                                               is_device_capture);
+    AudioCaptureCandidates intersection =
+        candidates.Intersection(advanced_candidates);
+    if (!intersection.IsEmpty())
+      candidates = std::move(intersection);
+  }
+  DCHECK(!candidates.IsEmpty());
+
+  std::string default_device_id;
+  if (!capabilities.empty())
+    default_device_id = (*capabilities.begin())->device_id;
+
+  return SelectResult(candidates, constraints.Basic(), default_device_id,
+                      media_stream_source);
+}
+
+}  // namespace content