/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim:set ts=2 sw=2 sts=2 et cindent: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef MOZILLA_AUDIOCHANNELFORMAT_H_

#define MOZILLA_AUDIOCHANNELFORMAT_H_

#include <stdint.h>

#include "nsTArrayForwardDeclare.h"

#include "AudioSampleFormat.h"

#include "nsTArray.h"

namespace mozilla {

/*

 * This file provides utilities for upmixing and downmixing channels.

 *

 * The channel layouts, upmixing and downmixing are consistent with the

 * Web Audio spec.

 *

 * Channel layouts for up to 6 channels:

 *   mono   { M }

 *   stereo { L, R }

 *          { L, R, C }

 *   quad   { L, R, SL, SR }

 *          { L, R, C, SL, SR }

 *   5.1    { L, R, C, LFE, SL, SR }

 *

 * Only 1, 2, 4 and 6 are currently defined in Web Audio.

 */

enum {

  SURROUND_L,

  SURROUND_R,

  SURROUND_C,

  SURROUND_LFE,

  SURROUND_SL,

  SURROUND_SR

};

const uint32_t CUSTOM_CHANNEL_LAYOUTS = 6;

// This is defined by some Windows SDK header.

#undef IGNORE

const int IGNORE = CUSTOM_CHANNEL_LAYOUTS;

const float IGNORE_F = 0.0f;

const int gMixingMatrixIndexByChannels[CUSTOM_CHANNEL_LAYOUTS - 1] =

  { 0, 5, 9, 12, 14 };

/**

 * Return a channel count whose channel layout includes all the channels from

 * aChannels1 and aChannels2.

 */

uint32_t

GetAudioChannelsSuperset(uint32_t aChannels1, uint32_t aChannels2);

/**

 * DownMixMatrix represents a conversion matrix efficiently by exploiting the

 * fact that each input channel contributes to at most one output channel,

 * except possibly for the C input channel in layouts that have one. Also,

 * every input channel is multiplied by the same coefficient for every output

 * channel it contributes to.

 */

const float SQRT_ONE_HALF = 0.7071067811865476f;

struct DownMixMatrix {

  // Every input channel c is copied to output channel mInputDestination[c]

  // after multiplying by mInputCoefficient[c].

  uint8_t mInputDestination[CUSTOM_CHANNEL_LAYOUTS];

  // If not IGNORE, then the C channel is copied to this output channel after

  // multiplying by its coefficient.

  uint8_t mCExtraDestination;

  float mInputCoefficient[CUSTOM_CHANNEL_LAYOUTS];

};

static const DownMixMatrix

gDownMixMatrices[CUSTOM_CHANNEL_LAYOUTS*(CUSTOM_CHANNEL_LAYOUTS - 1)/2] =

{

  // Downmixes to mono

  { { 0, 0 }, IGNORE, { 0.5f, 0.5f } },

  { { 0, IGNORE, IGNORE }, IGNORE, { 1.0f, IGNORE_F, IGNORE_F } },

  { { 0, 0, 0, 0 }, IGNORE, { 0.25f, 0.25f, 0.25f, 0.25f } },

  { { 0, IGNORE, IGNORE, IGNORE, IGNORE }, IGNORE, { 1.0f, IGNORE_F, IGNORE_F, IGNORE_F, IGNORE_F } },

  { { 0, 0, 0, IGNORE, 0, 0 }, IGNORE, { SQRT_ONE_HALF, SQRT_ONE_HALF, 1.0f, IGNORE_F, 0.5f, 0.5f } },

  // Downmixes to stereo

  { { 0, 1, IGNORE }, IGNORE, { 1.0f, 1.0f, IGNORE_F } },

  { { 0, 1, 0, 1 }, IGNORE, { 0.5f, 0.5f, 0.5f, 0.5f } },

  { { 0, 1, IGNORE, IGNORE, IGNORE }, IGNORE, { 1.0f, 1.0f, IGNORE_F, IGNORE_F, IGNORE_F } },

  { { 0, 1, 0, IGNORE, 0, 1 }, 1, { 1.0f, 1.0f, SQRT_ONE_HALF, IGNORE_F, SQRT_ONE_HALF, SQRT_ONE_HALF } },

  // Downmixes to 3-channel

  { { 0, 1, 2, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, IGNORE_F } },

  { { 0, 1, 2, IGNORE, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, IGNORE_F, IGNORE_F } },

  { { 0, 1, 2, IGNORE, IGNORE, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, IGNORE_F, IGNORE_F, IGNORE_F } },

  // Downmixes to quad

  { { 0, 1, 2, 3, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, 1.0f, IGNORE_F } },

  { { 0, 1, 0, IGNORE, 2, 3 }, 1, { 1.0f, 1.0f, SQRT_ONE_HALF, IGNORE_F, 1.0f, 1.0f } },

  // Downmixes to 5-channel

  { { 0, 1, 2, 3, 4, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, IGNORE_F } }

};

/**

 * Given an array of input channels, downmix to aOutputChannelCount, and copy

 * the results to the channel buffers in aOutputChannels.  Don't call this with

 * input count <= output count.

 */

template<typename T>

void AudioChannelsDownMix(const nsTArray<const T*>& aChannelArray,

                          T** aOutputChannels,

                          uint32_t aOutputChannelCount,

                          uint32_t aDuration)

{

  uint32_t inputChannelCount = aChannelArray.Length();

  const T* const* inputChannels = aChannelArray.Elements();

  NS_ASSERTION(inputChannelCount > aOutputChannelCount, "Nothing to do");

  if (inputChannelCount > 6) {

    // Just drop the unknown channels.

    for (uint32_t o = 0; o < aOutputChannelCount; ++o) {

      PodCopy(aOutputChannels[o], inputChannels[o], aDuration);

    }

    return;

  }

  // Ignore unknown channels, they're just dropped.

  inputChannelCount = std::min<uint32_t>(6, inputChannelCount);

  const DownMixMatrix& m = gDownMixMatrices[

    gMixingMatrixIndexByChannels[aOutputChannelCount - 1] +

    inputChannelCount - aOutputChannelCount - 1];

  // This is slow, but general. We can define custom code for special

  // cases later.

  for (uint32_t s = 0; s < aDuration; ++s) {

    // Reserve an extra junk channel at the end for the cases where we

    // want an input channel to contribute to nothing

    T outputChannels[CUSTOM_CHANNEL_LAYOUTS + 1] = {0};

    for (uint32_t c = 0; c < inputChannelCount; ++c) {

      outputChannels[m.mInputDestination[c]] +=

        m.mInputCoefficient[c]*(static_cast<const T*>(inputChannels[c]))[s];

    }

    // Utilize the fact that in every layout, C is the third channel.

    if (m.mCExtraDestination != IGNORE) {

      outputChannels[m.mCExtraDestination] +=

        m.mInputCoefficient[SURROUND_C]*(static_cast<const T*>(inputChannels[SURROUND_C]))[s];

    }

    for (uint32_t c = 0; c < aOutputChannelCount; ++c) {

      aOutputChannels[c][s] = outputChannels[c];

    }

  }

}

Unexecuted instantiation: void mozilla::AudioChannelsDownMix<float>(nsTArray<float const*> const&, float**, unsigned int, unsigned int)

Unexecuted instantiation: void mozilla::AudioChannelsDownMix<short>(nsTArray<short const*> const&, short**, unsigned int, unsigned int)

/**

 * UpMixMatrix represents a conversion matrix by exploiting the fact that

 * each output channel comes from at most one input channel.

 */

struct UpMixMatrix {

  uint8_t mInputDestination[CUSTOM_CHANNEL_LAYOUTS];

};

static const UpMixMatrix

gUpMixMatrices[CUSTOM_CHANNEL_LAYOUTS*(CUSTOM_CHANNEL_LAYOUTS - 1)/2] =

{

  // Upmixes from mono

  { { 0, 0 } },

  { { 0, IGNORE, IGNORE } },

  { { 0, 0, IGNORE, IGNORE } },

  { { 0, IGNORE, IGNORE, IGNORE, IGNORE } },

  { { IGNORE, IGNORE, 0, IGNORE, IGNORE, IGNORE } },

  // Upmixes from stereo

  { { 0, 1, IGNORE } },

  { { 0, 1, IGNORE, IGNORE } },

  { { 0, 1, IGNORE, IGNORE, IGNORE } },

  { { 0, 1, IGNORE, IGNORE, IGNORE, IGNORE } },

  // Upmixes from 3-channel

  { { 0, 1, 2, IGNORE } },

  { { 0, 1, 2, IGNORE, IGNORE } },

  { { 0, 1, 2, IGNORE, IGNORE, IGNORE } },

  // Upmixes from quad

  { { 0, 1, 2, 3, IGNORE } },

  { { 0, 1, IGNORE, IGNORE, 2, 3 } },

  // Upmixes from 5-channel

  { { 0, 1, 2, 3, 4, IGNORE } }

};

/**

 * Given an array of input channel data, and an output channel count,

 * replaces the array with an array of upmixed channels.

 * This shuffles the array and may set some channel buffers to aZeroChannel.

 * Don't call this with input count >= output count.

 * This may return *more* channels than requested. In that case, downmixing

 * is required to to get to aOutputChannelCount. (This is how we handle

 * odd cases like 3 -> 4 upmixing.)

 * If aChannelArray.Length() was the input to one of a series of

 * GetAudioChannelsSuperset calls resulting in aOutputChannelCount,

 * no downmixing will be required.

 */

template<typename T>

void

AudioChannelsUpMix(nsTArray<const T*>* aChannelArray,

                   uint32_t aOutputChannelCount,

                   const T* aZeroChannel)

{

  uint32_t inputChannelCount = aChannelArray->Length();

  uint32_t outputChannelCount =

    GetAudioChannelsSuperset(aOutputChannelCount, inputChannelCount);

  NS_ASSERTION(outputChannelCount > inputChannelCount,

               "No up-mix needed");

  MOZ_ASSERT(inputChannelCount > 0, "Bad number of channels");

  MOZ_ASSERT(outputChannelCount > 0, "Bad number of channels");

  aChannelArray->SetLength(outputChannelCount);

  if (inputChannelCount < CUSTOM_CHANNEL_LAYOUTS &&

      outputChannelCount <= CUSTOM_CHANNEL_LAYOUTS) {

    const UpMixMatrix& m = gUpMixMatrices[

      gMixingMatrixIndexByChannels[inputChannelCount - 1] +

      outputChannelCount - inputChannelCount - 1];

    const T* outputChannels[CUSTOM_CHANNEL_LAYOUTS];

    for (uint32_t i = 0; i < outputChannelCount; ++i) {

      uint8_t channelIndex = m.mInputDestination[i];

      if (channelIndex == IGNORE) {

        outputChannels[i] = aZeroChannel;

      } else {

        outputChannels[i] = aChannelArray->ElementAt(channelIndex);

      }

    }

    for (uint32_t i = 0; i < outputChannelCount; ++i) {

      aChannelArray->ElementAt(i) = outputChannels[i];

    }

    return;

  }

  for (uint32_t i = inputChannelCount; i < outputChannelCount; ++i) {

    aChannelArray->ElementAt(i) = aZeroChannel;

  }

}

Unexecuted instantiation: void mozilla::AudioChannelsUpMix<float>(nsTArray<float const*>*, unsigned int, float const*)

Unexecuted instantiation: void mozilla::AudioChannelsUpMix<short>(nsTArray<short const*>*, unsigned int, short const*)

} // namespace mozilla

#endif /* MOZILLA_AUDIOCHANNELFORMAT_H_ */