/*
 * Copyright (C) 2010 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 */

#include "HRTFKernel.h"
namespace WebCore {

// Takes the input audio channel |impulseP| as an input impulse response and
// calculates the average group delay. This represents the initial delay before
// the most energetic part of the impulse response. The sample-frame delay is
// removed from the |impulseP| impulse response, and this value  is returned.
// The |length| of the passed in |impulseP| must be must be a power of 2.
static float extractAverageGroupDelay(float* impulseP, size_t length) {
  // Check for power-of-2.
  MOZ_ASSERT(length && (length & (length - 1)) == 0);

  FFTBlock estimationFrame(length);
  estimationFrame.PerformFFT(impulseP);

  float frameDelay =
      static_cast<float>(estimationFrame.ExtractAverageGroupDelay());
  estimationFrame.GetInverse(impulseP);

  return frameDelay;
}

HRTFKernel::HRTFKernel(float* impulseResponse, size_t length, float sampleRate)
    : m_frameDelay(0), m_sampleRate(sampleRate) {
  AlignedTArray<float> buffer;
  // copy to a 32-byte aligned buffer
  if (((uintptr_t)impulseResponse & 31) != 0) {
    buffer.SetLength(length);
    mozilla::PodCopy(buffer.Elements(), impulseResponse, length);
    impulseResponse = buffer.Elements();
  }

  // Determine the leading delay (average group delay) for the response.
  m_frameDelay = extractAverageGroupDelay(impulseResponse, length);

  // The FFT size (with zero padding) needs to be twice the response length
  // in order to do proper convolution.
  unsigned fftSize = 2 * length;

  // Quick fade-out (apply window) at truncation point
  // because the impulse response has been truncated.
  unsigned numberOfFadeOutFrames = static_cast<unsigned>(
      sampleRate / 4410);  // 10 sample-frames @44.1KHz sample-rate
  MOZ_ASSERT(numberOfFadeOutFrames < length);
  if (numberOfFadeOutFrames < length) {
    for (unsigned i = length - numberOfFadeOutFrames; i < length; ++i) {
      float x =
          1.0f - static_cast<float>(i - (length - numberOfFadeOutFrames)) /
                     numberOfFadeOutFrames;
      impulseResponse[i] *= x;
    }
  }

  m_fftFrame = mozilla::MakeUnique<FFTBlock>(fftSize);
  m_fftFrame->PadAndMakeScaledDFT(impulseResponse, length);
}

// Interpolates two kernels with x: 0 -> 1 and returns the result.
nsReturnRef<HRTFKernel> HRTFKernel::createInterpolatedKernel(
    HRTFKernel* kernel1, HRTFKernel* kernel2, float x) {
  MOZ_ASSERT(kernel1 && kernel2);
  if (!kernel1 || !kernel2) return nsReturnRef<HRTFKernel>();

  MOZ_ASSERT(x >= 0.0 && x < 1.0);
  x = mozilla::clamped(x, 0.0f, 1.0f);

  float sampleRate1 = kernel1->sampleRate();
  float sampleRate2 = kernel2->sampleRate();
  MOZ_ASSERT(sampleRate1 == sampleRate2);
  if (sampleRate1 != sampleRate2) return nsReturnRef<HRTFKernel>();

  float frameDelay =
      (1 - x) * kernel1->frameDelay() + x * kernel2->frameDelay();

  UniquePtr<FFTBlock> interpolatedFrame(FFTBlock::CreateInterpolatedBlock(
      *kernel1->fftFrame(), *kernel2->fftFrame(), x));
  return HRTFKernel::create(std::move(interpolatedFrame), frameDelay,
                            sampleRate1);
}

}  // namespace WebCore