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/*
Copyright 2018 Google Inc. All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS-IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#include "graph/occlusion_node.h"
#include <cmath>
#include "base/logging.h"
#include "base/spherical_angle.h"
#include "dsp/occlusion_calculator.h"
namespace vraudio {
namespace {
// Low pass filter coefficient for smoothing the applied occlusion. This avoids
// sudden unrealistic changes in the volume of a sound object. Range [0, 1].
// The value below has been calculated empirically.
const float kOcclusionSmoothingCoefficient = 0.75f;
// This function provides first order low-pass filtering. It is used to smooth
// the occlusion parameter.
float Interpolate(float coefficient, float previous_value, float target_value) {
return target_value + coefficient * (previous_value - target_value);
}
} // namespace
OcclusionNode::OcclusionNode(SourceId source_id,
const SystemSettings& system_settings)
: system_settings_(system_settings),
low_pass_filter_(0.0f),
current_occlusion_(0.0f),
output_buffer_(kNumMonoChannels, system_settings.GetFramesPerBuffer()) {
output_buffer_.Clear();
output_buffer_.set_source_id(source_id);
}
const AudioBuffer* OcclusionNode::AudioProcess(const NodeInput& input) {
const AudioBuffer* input_buffer = input.GetSingleInput();
DCHECK(input_buffer);
DCHECK_EQ(input_buffer->source_id(), output_buffer_.source_id());
const auto source_parameters =
system_settings_.GetSourceParameters(input_buffer->source_id());
if (source_parameters == nullptr) {
LOG(WARNING) << "Could not find source parameters";
return nullptr;
}
const WorldPosition& listener_position = system_settings_.GetHeadPosition();
const WorldRotation& listener_rotation = system_settings_.GetHeadRotation();
const ObjectTransform& source_transform = source_parameters->object_transform;
// Compute the relative listener/source direction in spherical angles.
WorldPosition relative_direction;
GetRelativeDirection(listener_position, listener_rotation,
source_transform.position, &relative_direction);
const SphericalAngle listener_direction =
SphericalAngle::FromWorldPosition(relative_direction);
GetRelativeDirection(source_transform.position, source_transform.rotation,
listener_position, &relative_direction);
const SphericalAngle source_direction =
SphericalAngle::FromWorldPosition(relative_direction);
// Calculate low-pass filter coefficient based on listener/source directivity
// and occlusion values.
const float listener_directivity = CalculateDirectivity(
source_parameters->listener_directivity_alpha,
source_parameters->listener_directivity_order, listener_direction);
const float source_directivity = CalculateDirectivity(
source_parameters->directivity_alpha,
source_parameters->directivity_order, source_direction);
current_occlusion_ =
Interpolate(kOcclusionSmoothingCoefficient, current_occlusion_,
source_parameters->occlusion_intensity);
const float filter_coefficient = CalculateOcclusionFilterCoefficient(
listener_directivity * source_directivity, current_occlusion_);
low_pass_filter_.SetCoefficient(filter_coefficient);
if (!low_pass_filter_.Filter((*input_buffer)[0], &output_buffer_[0])) {
return input_buffer;
}
// Copy buffer parameters.
return &output_buffer_;
}
} // namespace vraudio
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