chromium/src/third_party/blink/renderer/platform/audio/hrtf_database.cc

/*
 * Copyright (C) 2010 Google Inc. All rights reserved.
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 *     from this software without specific prior written permission.
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#include "third_party/blink/renderer/platform/audio/hrtf_database.h"

#include <memory>
#include <utility>

#include "base/memory/ptr_util.h"
#include "third_party/blink/public/resources/grit/blink_resources.h"
#include "third_party/blink/renderer/platform/wtf/math_extras.h"

namespace blink {

const int HRTFDatabase::kMinElevation = -45;
const int HRTFDatabase::kMaxElevation = 90;
const unsigned HRTFDatabase::kRawElevationAngleSpacing = 15;
const unsigned HRTFDatabase::kNumberOfRawElevations =
    10;  // -45 -> +90 (each 15 degrees)
const unsigned HRTFDatabase::kInterpolationFactor = 1;
const unsigned HRTFDatabase::kNumberOfTotalElevations =
    kNumberOfRawElevations * kInterpolationFactor;

HRTFDatabase::HRTFDatabase(float sample_rate)
    : elevations_(kNumberOfTotalElevations), sample_rate_(sample_rate) {
  unsigned elevation_index = 0;
  for (int elevation = kMinElevation; elevation <= kMaxElevation;
       elevation += kRawElevationAngleSpacing) {
    std::unique_ptr<HRTFElevation> hrtf_elevation =
        HRTFElevation::CreateForSubject(IDR_AUDIO_SPATIALIZATION_COMPOSITE,
                                        elevation, sample_rate);
    DCHECK(hrtf_elevation.get());

    elevations_[elevation_index] = std::move(hrtf_elevation);
    elevation_index += kInterpolationFactor;
  }

  // Now, go back and interpolate elevations.
  if (kInterpolationFactor > 1) {
    for (unsigned i = 0; i < kNumberOfTotalElevations;
         i += kInterpolationFactor) {
      unsigned j = (i + kInterpolationFactor);
      if (j >= kNumberOfTotalElevations)
        j = i;  // for last elevation interpolate with itself

      // Create the interpolated convolution kernels and delays.
      for (unsigned jj = 1; jj < kInterpolationFactor; ++jj) {
        float x =
            static_cast<float>(jj) / static_cast<float>(kInterpolationFactor);
        elevations_[i + jj] = HRTFElevation::CreateByInterpolatingSlices(
            elevations_[i].get(), elevations_[j].get(), x, sample_rate);
        DCHECK(elevations_[i + jj].get());
      }
    }
  }
}

void HRTFDatabase::GetKernelsFromAzimuthElevation(double azimuth_blend,
                                                  unsigned azimuth_index,
                                                  double elevation_angle,
                                                  HRTFKernel*& kernel_l,
                                                  HRTFKernel*& kernel_r,
                                                  double& frame_delay_l,
                                                  double& frame_delay_r) {
  unsigned elevation_index = IndexFromElevationAngle(elevation_angle);
  SECURITY_DCHECK(elevation_index < elevations_.size());
  SECURITY_DCHECK(elevations_.size() > 0);

  if (elevation_index > elevations_.size() - 1)
    elevation_index = elevations_.size() - 1;

  HRTFElevation* hrtf_elevation = elevations_[elevation_index].get();
  DCHECK(hrtf_elevation);

  hrtf_elevation->GetKernelsFromAzimuth(azimuth_blend, azimuth_index, kernel_l,
                                        kernel_r, frame_delay_l, frame_delay_r);
}

unsigned HRTFDatabase::IndexFromElevationAngle(double elevation_angle) {
  // Clamp to allowed range.
  elevation_angle =
      clampTo<double, double>(elevation_angle, kMinElevation, kMaxElevation);

  unsigned elevation_index = static_cast<int>(
      kInterpolationFactor * (elevation_angle - kMinElevation) /
      kRawElevationAngleSpacing);
  return elevation_index;
}

}  // namespace blink