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/*
* Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "audio/utility/channel_mixing_matrix.h"
#include <stddef.h>
#include <algorithm>
#include "audio/utility/channel_mixer.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "system_wrappers/include/field_trial.h"
namespace webrtc {
namespace {
// Selects the default usage of VoIP channel mapping adjustments.
bool UseChannelMappingAdjustmentsByDefault() {
return !field_trial::IsEnabled(
"WebRTC-VoIPChannelRemixingAdjustmentKillSwitch");
}
ChannelLayout CheckInputLayout(ChannelLayout input_layout,
ChannelLayout output_layout) {
// Special case for 5.0, 5.1 with back channels when upmixed to 7.0, 7.1,
// which should map the back LR to side LR.
if (input_layout == CHANNEL_LAYOUT_5_0_BACK &&
output_layout == CHANNEL_LAYOUT_7_0) {
return CHANNEL_LAYOUT_5_0;
} else if (input_layout == CHANNEL_LAYOUT_5_1_BACK &&
output_layout == CHANNEL_LAYOUT_7_1) {
return CHANNEL_LAYOUT_5_1;
}
return input_layout;
}
} // namespace
static void ValidateLayout(ChannelLayout layout) {
RTC_CHECK_NE(layout, CHANNEL_LAYOUT_NONE);
RTC_CHECK_LE(layout, CHANNEL_LAYOUT_MAX);
RTC_CHECK_NE(layout, CHANNEL_LAYOUT_UNSUPPORTED);
RTC_CHECK_NE(layout, CHANNEL_LAYOUT_DISCRETE);
RTC_CHECK_NE(layout, CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC);
// Verify there's at least one channel. Should always be true here by virtue
// of not being one of the invalid layouts, but lets double check to be sure.
int channel_count = ChannelLayoutToChannelCount(layout);
RTC_DCHECK_GT(channel_count, 0);
// If we have more than one channel, verify a symmetric layout for sanity.
// The unit test will verify all possible layouts, so this can be a DCHECK.
// Symmetry allows simplifying the matrix building code by allowing us to
// assume that if one channel of a pair exists, the other will too.
if (channel_count > 1) {
// Assert that LEFT exists if and only if RIGHT exists, and so on.
RTC_DCHECK_EQ(ChannelOrder(layout, LEFT) >= 0,
ChannelOrder(layout, RIGHT) >= 0);
RTC_DCHECK_EQ(ChannelOrder(layout, SIDE_LEFT) >= 0,
ChannelOrder(layout, SIDE_RIGHT) >= 0);
RTC_DCHECK_EQ(ChannelOrder(layout, BACK_LEFT) >= 0,
ChannelOrder(layout, BACK_RIGHT) >= 0);
RTC_DCHECK_EQ(ChannelOrder(layout, LEFT_OF_CENTER) >= 0,
ChannelOrder(layout, RIGHT_OF_CENTER) >= 0);
} else {
RTC_DCHECK_EQ(layout, CHANNEL_LAYOUT_MONO);
}
}
ChannelMixingMatrix::ChannelMixingMatrix(ChannelLayout input_layout,
int input_channels,
ChannelLayout output_layout,
int output_channels)
: use_voip_channel_mapping_adjustments_(
UseChannelMappingAdjustmentsByDefault()),
input_layout_(CheckInputLayout(input_layout, output_layout)),
input_channels_(input_channels),
output_layout_(output_layout),
output_channels_(output_channels) {
// Stereo down mix should never be the output layout.
RTC_CHECK_NE(output_layout, CHANNEL_LAYOUT_STEREO_DOWNMIX);
// Verify that the layouts are supported
if (input_layout != CHANNEL_LAYOUT_DISCRETE)
ValidateLayout(input_layout);
if (output_layout != CHANNEL_LAYOUT_DISCRETE)
ValidateLayout(output_layout);
}
ChannelMixingMatrix::~ChannelMixingMatrix() = default;
bool ChannelMixingMatrix::CreateTransformationMatrix(
std::vector<std::vector<float>>* matrix) {
matrix_ = matrix;
// Size out the initial matrix.
matrix_->reserve(output_channels_);
for (int output_ch = 0; output_ch < output_channels_; ++output_ch)
matrix_->push_back(std::vector<float>(input_channels_, 0));
// First check for discrete case.
if (input_layout_ == CHANNEL_LAYOUT_DISCRETE ||
output_layout_ == CHANNEL_LAYOUT_DISCRETE) {
// If the number of input channels is more than output channels, then
// copy as many as we can then drop the remaining input channels.
// If the number of input channels is less than output channels, then
// copy them all, then zero out the remaining output channels.
int passthrough_channels = std::min(input_channels_, output_channels_);
for (int i = 0; i < passthrough_channels; ++i)
(*matrix_)[i][i] = 1;
return true;
}
// If specified, use adjusted channel mapping for the VoIP scenario.
if (use_voip_channel_mapping_adjustments_ &&
input_layout_ == CHANNEL_LAYOUT_MONO &&
ChannelLayoutToChannelCount(output_layout_) >= 2) {
// Only place the mono input in the front left and right channels.
(*matrix_)[0][0] = 1.f;
(*matrix_)[1][0] = 1.f;
for (size_t output_ch = 2; output_ch < matrix_->size(); ++output_ch) {
(*matrix_)[output_ch][0] = 0.f;
}
return true;
}
// Route matching channels and figure out which ones aren't accounted for.
for (Channels ch = LEFT; ch < CHANNELS_MAX + 1;
ch = static_cast<Channels>(ch + 1)) {
int input_ch_index = ChannelOrder(input_layout_, ch);
if (input_ch_index < 0)
continue;
int output_ch_index = ChannelOrder(output_layout_, ch);
if (output_ch_index < 0) {
unaccounted_inputs_.push_back(ch);
continue;
}
RTC_DCHECK_LT(static_cast<size_t>(output_ch_index), matrix_->size());
RTC_DCHECK_LT(static_cast<size_t>(input_ch_index),
(*matrix_)[output_ch_index].size());
(*matrix_)[output_ch_index][input_ch_index] = 1;
}
// If all input channels are accounted for, there's nothing left to do.
if (unaccounted_inputs_.empty()) {
// Since all output channels map directly to inputs we can optimize.
return true;
}
// Mix front LR into center.
if (IsUnaccounted(LEFT)) {
// When down mixing to mono from stereo, we need to be careful of full scale
// stereo mixes. Scaling by 1 / sqrt(2) here will likely lead to clipping
// so we use 1 / 2 instead.
float scale =
(output_layout_ == CHANNEL_LAYOUT_MONO && input_channels_ == 2)
? 0.5
: ChannelMixer::kHalfPower;
Mix(LEFT, CENTER, scale);
Mix(RIGHT, CENTER, scale);
}
// Mix center into front LR.
if (IsUnaccounted(CENTER)) {
// When up mixing from mono, just do a copy to front LR.
float scale =
(input_layout_ == CHANNEL_LAYOUT_MONO) ? 1 : ChannelMixer::kHalfPower;
MixWithoutAccounting(CENTER, LEFT, scale);
Mix(CENTER, RIGHT, scale);
}
// Mix back LR into: side LR || back center || front LR || front center.
if (IsUnaccounted(BACK_LEFT)) {
if (HasOutputChannel(SIDE_LEFT)) {
// If the input has side LR, mix back LR into side LR, but instead if the
// input doesn't have side LR (but output does) copy back LR to side LR.
float scale = HasInputChannel(SIDE_LEFT) ? ChannelMixer::kHalfPower : 1;
Mix(BACK_LEFT, SIDE_LEFT, scale);
Mix(BACK_RIGHT, SIDE_RIGHT, scale);
} else if (HasOutputChannel(BACK_CENTER)) {
// Mix back LR into back center.
Mix(BACK_LEFT, BACK_CENTER, ChannelMixer::kHalfPower);
Mix(BACK_RIGHT, BACK_CENTER, ChannelMixer::kHalfPower);
} else if (output_layout_ > CHANNEL_LAYOUT_MONO) {
// Mix back LR into front LR.
Mix(BACK_LEFT, LEFT, ChannelMixer::kHalfPower);
Mix(BACK_RIGHT, RIGHT, ChannelMixer::kHalfPower);
} else {
// Mix back LR into front center.
Mix(BACK_LEFT, CENTER, ChannelMixer::kHalfPower);
Mix(BACK_RIGHT, CENTER, ChannelMixer::kHalfPower);
}
}
// Mix side LR into: back LR || back center || front LR || front center.
if (IsUnaccounted(SIDE_LEFT)) {
if (HasOutputChannel(BACK_LEFT)) {
// If the input has back LR, mix side LR into back LR, but instead if the
// input doesn't have back LR (but output does) copy side LR to back LR.
float scale = HasInputChannel(BACK_LEFT) ? ChannelMixer::kHalfPower : 1;
Mix(SIDE_LEFT, BACK_LEFT, scale);
Mix(SIDE_RIGHT, BACK_RIGHT, scale);
} else if (HasOutputChannel(BACK_CENTER)) {
// Mix side LR into back center.
Mix(SIDE_LEFT, BACK_CENTER, ChannelMixer::kHalfPower);
Mix(SIDE_RIGHT, BACK_CENTER, ChannelMixer::kHalfPower);
} else if (output_layout_ > CHANNEL_LAYOUT_MONO) {
// Mix side LR into front LR.
Mix(SIDE_LEFT, LEFT, ChannelMixer::kHalfPower);
Mix(SIDE_RIGHT, RIGHT, ChannelMixer::kHalfPower);
} else {
// Mix side LR into front center.
Mix(SIDE_LEFT, CENTER, ChannelMixer::kHalfPower);
Mix(SIDE_RIGHT, CENTER, ChannelMixer::kHalfPower);
}
}
// Mix back center into: back LR || side LR || front LR || front center.
if (IsUnaccounted(BACK_CENTER)) {
if (HasOutputChannel(BACK_LEFT)) {
// Mix back center into back LR.
MixWithoutAccounting(BACK_CENTER, BACK_LEFT, ChannelMixer::kHalfPower);
Mix(BACK_CENTER, BACK_RIGHT, ChannelMixer::kHalfPower);
} else if (HasOutputChannel(SIDE_LEFT)) {
// Mix back center into side LR.
MixWithoutAccounting(BACK_CENTER, SIDE_LEFT, ChannelMixer::kHalfPower);
Mix(BACK_CENTER, SIDE_RIGHT, ChannelMixer::kHalfPower);
} else if (output_layout_ > CHANNEL_LAYOUT_MONO) {
// Mix back center into front LR.
// TODO(dalecurtis): Not sure about these values?
MixWithoutAccounting(BACK_CENTER, LEFT, ChannelMixer::kHalfPower);
Mix(BACK_CENTER, RIGHT, ChannelMixer::kHalfPower);
} else {
// Mix back center into front center.
// TODO(dalecurtis): Not sure about these values?
Mix(BACK_CENTER, CENTER, ChannelMixer::kHalfPower);
}
}
// Mix LR of center into: front LR || front center.
if (IsUnaccounted(LEFT_OF_CENTER)) {
if (HasOutputChannel(LEFT)) {
// Mix LR of center into front LR.
Mix(LEFT_OF_CENTER, LEFT, ChannelMixer::kHalfPower);
Mix(RIGHT_OF_CENTER, RIGHT, ChannelMixer::kHalfPower);
} else {
// Mix LR of center into front center.
Mix(LEFT_OF_CENTER, CENTER, ChannelMixer::kHalfPower);
Mix(RIGHT_OF_CENTER, CENTER, ChannelMixer::kHalfPower);
}
}
// Mix LFE into: front center || front LR.
if (IsUnaccounted(LFE)) {
if (!HasOutputChannel(CENTER)) {
// Mix LFE into front LR.
MixWithoutAccounting(LFE, LEFT, ChannelMixer::kHalfPower);
Mix(LFE, RIGHT, ChannelMixer::kHalfPower);
} else {
// Mix LFE into front center.
Mix(LFE, CENTER, ChannelMixer::kHalfPower);
}
}
// All channels should now be accounted for.
RTC_DCHECK(unaccounted_inputs_.empty());
// See if the output `matrix_` is simply a remapping matrix. If each input
// channel maps to a single output channel we can simply remap. Doing this
// programmatically is less fragile than logic checks on channel mappings.
for (int output_ch = 0; output_ch < output_channels_; ++output_ch) {
int input_mappings = 0;
for (int input_ch = 0; input_ch < input_channels_; ++input_ch) {
// We can only remap if each row contains a single scale of 1. I.e., each
// output channel is mapped from a single unscaled input channel.
if ((*matrix_)[output_ch][input_ch] != 1 || ++input_mappings > 1)
return false;
}
}
// If we've gotten here, `matrix_` is simply a remapping.
return true;
}
void ChannelMixingMatrix::AccountFor(Channels ch) {
unaccounted_inputs_.erase(
std::find(unaccounted_inputs_.begin(), unaccounted_inputs_.end(), ch));
}
bool ChannelMixingMatrix::IsUnaccounted(Channels ch) const {
return std::find(unaccounted_inputs_.begin(), unaccounted_inputs_.end(),
ch) != unaccounted_inputs_.end();
}
bool ChannelMixingMatrix::HasInputChannel(Channels ch) const {
return ChannelOrder(input_layout_, ch) >= 0;
}
bool ChannelMixingMatrix::HasOutputChannel(Channels ch) const {
return ChannelOrder(output_layout_, ch) >= 0;
}
void ChannelMixingMatrix::Mix(Channels input_ch,
Channels output_ch,
float scale) {
MixWithoutAccounting(input_ch, output_ch, scale);
AccountFor(input_ch);
}
void ChannelMixingMatrix::MixWithoutAccounting(Channels input_ch,
Channels output_ch,
float scale) {
int input_ch_index = ChannelOrder(input_layout_, input_ch);
int output_ch_index = ChannelOrder(output_layout_, output_ch);
RTC_DCHECK(IsUnaccounted(input_ch));
RTC_DCHECK_GE(input_ch_index, 0);
RTC_DCHECK_GE(output_ch_index, 0);
RTC_DCHECK_EQ((*matrix_)[output_ch_index][input_ch_index], 0);
(*matrix_)[output_ch_index][input_ch_index] = scale;
}
} // namespace webrtc