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- // Copyright (c) 2012 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "media/base/channel_mixing_matrix.h"
- #include <stddef.h>
- #include <algorithm>
- #include "base/check_op.h"
- #include "media/base/channel_mixer.h"
- namespace media {
- static void ValidateLayout(ChannelLayout layout) {
- CHECK_NE(layout, CHANNEL_LAYOUT_NONE);
- CHECK_LE(layout, CHANNEL_LAYOUT_MAX);
- CHECK_NE(layout, CHANNEL_LAYOUT_UNSUPPORTED);
- CHECK_NE(layout, CHANNEL_LAYOUT_DISCRETE);
- 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);
- 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.
- DCHECK_EQ(ChannelOrder(layout, LEFT) >= 0,
- ChannelOrder(layout, RIGHT) >= 0);
- DCHECK_EQ(ChannelOrder(layout, SIDE_LEFT) >= 0,
- ChannelOrder(layout, SIDE_RIGHT) >= 0);
- DCHECK_EQ(ChannelOrder(layout, BACK_LEFT) >= 0,
- ChannelOrder(layout, BACK_RIGHT) >= 0);
- DCHECK_EQ(ChannelOrder(layout, LEFT_OF_CENTER) >= 0,
- ChannelOrder(layout, RIGHT_OF_CENTER) >= 0);
- } else {
- DCHECK_EQ(layout, CHANNEL_LAYOUT_MONO);
- }
- }
- ChannelMixingMatrix::ChannelMixingMatrix(ChannelLayout input_layout,
- int input_channels,
- ChannelLayout output_layout,
- int output_channels)
- : input_layout_(input_layout),
- input_channels_(input_channels),
- output_layout_(output_layout),
- output_channels_(output_channels) {
- // Stereo down mix should never be the output layout.
- 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);
- // 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) {
- input_layout_ = CHANNEL_LAYOUT_5_0;
- } else if (input_layout_ == CHANNEL_LAYOUT_5_1_BACK &&
- output_layout_ == CHANNEL_LAYOUT_7_1) {
- input_layout_ = CHANNEL_LAYOUT_5_1;
- }
- }
- 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;
- }
- // 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 ||
- (ch == CENTER && input_layout_ == CHANNEL_LAYOUT_MONO &&
- input_layout_ != output_layout_)) {
- unaccounted_inputs_.push_back(ch);
- continue;
- }
- DCHECK_LT(static_cast<size_t>(output_ch_index), matrix_->size());
- 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.
- 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);
- DCHECK(IsUnaccounted(input_ch));
- DCHECK_GE(input_ch_index, 0);
- DCHECK_GE(output_ch_index, 0);
- DCHECK_EQ((*matrix_)[output_ch_index][input_ch_index], 0);
- (*matrix_)[output_ch_index][input_ch_index] = scale;
- }
- } // namespace media
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