text: /*
  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 "dsp/stereo_panner.h"
  
  #include <cmath>
  #include <vector>
  
  #include "third_party/googletest/googletest/include/gtest/gtest.h"
  #include "base/constants_and_types.h"
  
  namespace vraudio {
  
  namespace {
  
  const float kMinusThreeDecibels = kInverseSqrtTwo;
  
  // Tests that the |CalculateStereoPanGains| method will generate correct stereo
  // pan gains.
  TEST(StereoPannerTest, StereoTest) {
    std::vector<float> speaker_gains;
  
    SphericalAngle source_direction = SphericalAngle::FromDegrees(-90.0f, 0.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(0.0f, speaker_gains[0], kEpsilonFloat);
    EXPECT_NEAR(1.0f, speaker_gains[1], kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(-45.0f, 0.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(kMinusThreeDecibels, speaker_gains[1] - speaker_gains[0],
                kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(0.0f, 0.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(speaker_gains[0], speaker_gains[1], kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(45.0f, 0.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(kMinusThreeDecibels, speaker_gains[0] - speaker_gains[1],
                kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(90.0f, 0.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(1.0f, speaker_gains[0], kEpsilonFloat);
    EXPECT_NEAR(0.0f, speaker_gains[1], kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(0.0f, 45.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(0.5f, speaker_gains[0], kEpsilonFloat);
    EXPECT_NEAR(0.5f, speaker_gains[1], kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(0.0f, -60.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(0.5f, speaker_gains[0], kEpsilonFloat);
    EXPECT_NEAR(0.5f, speaker_gains[1], kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(0.0f, 90.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(0.5f, speaker_gains[0], kEpsilonFloat);
    EXPECT_NEAR(0.5f, speaker_gains[1], kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(0.0f, -90.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(0.5f, speaker_gains[0], kEpsilonFloat);
    EXPECT_NEAR(0.5f, speaker_gains[1], kEpsilonFloat);
  
    source_direction = SphericalAngle::FromDegrees(45.0f, 45.0f);
    CalculateStereoPanGains(source_direction, &speaker_gains);
    EXPECT_NEAR(0.75f, speaker_gains[0], kEpsilonFloat);
    EXPECT_NEAR(0.25f, speaker_gains[1], kEpsilonFloat);
  }
  
  }  // namespace
  
  }  // namespace vraudio
  