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