gecko/content/media/AudioChannelFormat.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */
#include "AudioChannelFormat.h"
#include <algorithm>
namespace mozilla {
enum {
SURROUND_L,
SURROUND_R,
SURROUND_C,
SURROUND_LFE,
SURROUND_SL,
SURROUND_SR
};
static const uint32_t CUSTOM_CHANNEL_LAYOUTS = 6;
uint32_t
GetAudioChannelsSuperset(uint32_t aChannels1, uint32_t aChannels2)
{
if (aChannels1 == 3 && aChannels2 == 4) {
// quad layout has no center channel, but input has a center channel as well
// as L and R, so we actually need a 5-channel layout here.
return 5;
}
return std::max(aChannels1, aChannels2);
}
void
AudioChannelsUpMix(nsTArray<const void*>* aChannelArray,
uint32_t aOutputChannelCount,
const void* aZeroChannel)
{
uint32_t inputChannelCount = aChannelArray->Length();
uint32_t outputChannelCount =
GetAudioChannelsSuperset(aOutputChannelCount, inputChannelCount);
NS_ASSERTION(outputChannelCount > inputChannelCount,
"No up-mix needed");
NS_ASSERTION(inputChannelCount > 0, "Bad number of channels");
NS_ASSERTION(outputChannelCount > 0, "Bad number of channels");
aChannelArray->SetLength(outputChannelCount);
if (inputChannelCount < CUSTOM_CHANNEL_LAYOUTS) {
const void* surroundChannels[CUSTOM_CHANNEL_LAYOUTS] =
{ aZeroChannel, aZeroChannel, aZeroChannel,
aZeroChannel, aZeroChannel, aZeroChannel
};
// First just map everything up to 5.1
switch (inputChannelCount) {
case 1:
surroundChannels[SURROUND_C] = aChannelArray->ElementAt(0);
break;
case 2:
surroundChannels[SURROUND_L] = aChannelArray->ElementAt(0);
surroundChannels[SURROUND_R] = aChannelArray->ElementAt(1);
break;
case 3:
surroundChannels[SURROUND_L] = aChannelArray->ElementAt(0);
surroundChannels[SURROUND_R] = aChannelArray->ElementAt(1);
surroundChannels[SURROUND_C] = aChannelArray->ElementAt(2);
break;
case 4:
surroundChannels[SURROUND_L] = aChannelArray->ElementAt(0);
surroundChannels[SURROUND_R] = aChannelArray->ElementAt(1);
surroundChannels[SURROUND_SL] = aChannelArray->ElementAt(2);
surroundChannels[SURROUND_SR] = aChannelArray->ElementAt(3);
break;
case 5:
surroundChannels[SURROUND_L] = aChannelArray->ElementAt(0);
surroundChannels[SURROUND_R] = aChannelArray->ElementAt(1);
surroundChannels[SURROUND_C] = aChannelArray->ElementAt(2);
surroundChannels[SURROUND_SL] = aChannelArray->ElementAt(3);
surroundChannels[SURROUND_SR] = aChannelArray->ElementAt(4);
break;
}
if (outputChannelCount < CUSTOM_CHANNEL_LAYOUTS) {
// Map back to aOutputChannelCount
switch (outputChannelCount) {
case 2:
// Upmix from mono, so use the center channel.
aChannelArray->ElementAt(0) = surroundChannels[SURROUND_C];
aChannelArray->ElementAt(1) = surroundChannels[SURROUND_C];
break;
case 3:
aChannelArray->ElementAt(0) = surroundChannels[SURROUND_L];
aChannelArray->ElementAt(1) = surroundChannels[SURROUND_R];
aChannelArray->ElementAt(2) = surroundChannels[SURROUND_C];
break;
case 4:
// We avoided this case up above.
NS_ASSERTION(inputChannelCount != 3,
"3->4 upmix not supported directly");
if (inputChannelCount == 1) {
// Output has no center channel, so map the mono to
// L+R channels per Web Audio
aChannelArray->ElementAt(0) = surroundChannels[SURROUND_C];
aChannelArray->ElementAt(1) = surroundChannels[SURROUND_C];
} else {
aChannelArray->ElementAt(0) = surroundChannels[SURROUND_L];
aChannelArray->ElementAt(1) = surroundChannels[SURROUND_R];
}
aChannelArray->ElementAt(2) = surroundChannels[SURROUND_SL];
aChannelArray->ElementAt(3) = surroundChannels[SURROUND_SR];
break;
case 5:
aChannelArray->ElementAt(0) = surroundChannels[SURROUND_L];
aChannelArray->ElementAt(1) = surroundChannels[SURROUND_R];
aChannelArray->ElementAt(2) = surroundChannels[SURROUND_C];
aChannelArray->ElementAt(3) = surroundChannels[SURROUND_SL];
aChannelArray->ElementAt(4) = surroundChannels[SURROUND_SR];
}
return;
}
memcpy(aChannelArray->Elements(), surroundChannels, sizeof(surroundChannels));
inputChannelCount = CUSTOM_CHANNEL_LAYOUTS;
}
for (uint32_t i = inputChannelCount; i < outputChannelCount; ++i) {
aChannelArray->ElementAt(i) = aZeroChannel;
}
}
/**
* 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.
*/
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 int IGNORE = CUSTOM_CHANNEL_LAYOUTS;
static const float IGNORE_F = 0.0f;
static const DownMixMatrix
gDownMixMatrices[CUSTOM_CHANNEL_LAYOUTS*(CUSTOM_CHANNEL_LAYOUTS - 1)/2] =
{
// Downmixes to mono
{ { 0, 0 }, IGNORE, { 0.5f, 0.5f } },
{ { 0, 0, 0 }, IGNORE, { 0.3333f, 0.3333f, 0.3333f } },
{ { 0, 0, 0, 0 }, IGNORE, { 0.25f, 0.25f, 0.25f, 0.25f } },
{ { 0, 0, 0, 0, 0 }, IGNORE, { 0.7071f, 0.7071f, 1.0f, 0.5f, 0.5f } },
{ { 0, 0, 0, IGNORE, 0, 0 }, IGNORE, { 0.7071f, 0.7071f, 1.0f, IGNORE_F, 0.5f, 0.5f } },
// Downmixes to stereo
{ { 0, 1, 0 }, 1, { 1.0f, 1.0f, 0.7071f } },
{ { 0, 1, 0, 1 }, IGNORE, { 0.5f, 0.5f, 0.5f, 0.5f } },
{ { 0, 1, 0, 0, 1 }, 1, { 1.0f, 1.0f, 0.7071f, 0.7071f, 0.7071f } },
{ { 0, 1, 0, IGNORE, 0, 1 }, 1, { 1.0f, 1.0f, 0.7071f, IGNORE_F, 0.7071f, 0.7071f } },
// Downmixes to 3-channel
{ { 0, 1, 0, 1 }, IGNORE, { 0.25f, 0.25f, 0.25f, 0.25f } },
{ { 0, 1, 2, 0, 1 }, IGNORE, { 0.5f, 0.5f, 1.0f, 0.5f, 0.5f } },
{ { 0, 1, 2, IGNORE, 0, 1 }, IGNORE, { 0.5f, 0.5f, 1.0f, IGNORE_F, 0.5f, 0.5f } },
// Downmixes to quad
{ { 0, 1, 0, 2, 3 }, 1, { 1.0f, 1.0f, 0.7071f, 1.0f, 1.0f } },
{ { 0, 1, 0, IGNORE, 2, 3 }, 1, { 1.0f, 1.0f, 0.7071f, IGNORE_F, 1.0f, 1.0f } },
// Downmixes to 5-channel
{ { 0, 1, 2, IGNORE, 3, 4 }, IGNORE, { 1.0f, 1.0f, 1.0f, IGNORE_F, 1.0f, 1.0f } }
};
static const int gDownMixMatrixIndexByOutputChannels[CUSTOM_CHANNEL_LAYOUTS - 1] =
{ 0, 5, 9, 12, 14 };
void
AudioChannelsDownMix(const nsTArray<const void*>& aChannelArray,
float** aOutputChannels,
uint32_t aOutputChannelCount,
uint32_t aDuration)
{
uint32_t inputChannelCount = aChannelArray.Length();
const void* const* inputChannels = aChannelArray.Elements();
NS_ASSERTION(inputChannelCount > aOutputChannelCount, "Nothing to do");
if (aOutputChannelCount >= 6) {
// Just drop the unknown channels.
for (uint32_t o = 0; o < aOutputChannelCount; ++o) {
memcpy(aOutputChannels[o], inputChannels[o], aDuration*sizeof(float));
}
return;
}
// Ignore unknown channels, they're just dropped.
inputChannelCount = std::min<uint32_t>(6, inputChannelCount);
const DownMixMatrix& m = gDownMixMatrices[
gDownMixMatrixIndexByOutputChannels[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
float outputChannels[CUSTOM_CHANNEL_LAYOUTS];
memset(outputChannels, 0, sizeof(float)*(CUSTOM_CHANNEL_LAYOUTS - 1));
for (uint32_t c = 0; c < inputChannelCount; ++c) {
outputChannels[m.mInputDestination[c]] +=
m.mInputCoefficient[c]*(static_cast<const float*>(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 float*>(inputChannels[SURROUND_C]))[s];
}
for (uint32_t c = 0; c < aOutputChannelCount; ++c) {
aOutputChannels[c][s] = outputChannels[c];
}
}
}
}