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Unified Diff: media/base/channel_mixer.cc

Issue 11150034: Add support for channel transforms. (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Rebase. Created 8 years, 2 months ago
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Index: media/base/channel_mixer.cc
diff --git a/media/base/channel_mixer.cc b/media/base/channel_mixer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b6af6a61c0a3a3947fe4eb8773a0b1692c60a039
--- /dev/null
+++ b/media/base/channel_mixer.cc
@@ -0,0 +1,263 @@
+// 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.
+
+// MSVC++ requires this to be set before any other includes to get M_SQRT1_2.
+#define _USE_MATH_DEFINES
scherkus (not reviewing) 2012/10/18 01:30:39 nit: move closer to where we need it (i.e., after
DaleCurtis 2012/10/18 01:56:44 Can't do that, since channel_mixer.h and headers i
scherkus (not reviewing) 2012/10/18 02:24:03 Gah.
+
+#include "media/base/channel_mixer.h"
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+
+#include "base/logging.h"
+#include "media/base/audio_bus.h"
+#include "media/base/vector_math.h"
+
+namespace media {
+
+// Scale factor for mixing two channels together; could use 1 / 2 as well.
+// TODO(dalecurtis): Figure out which value we should use here. Per crogers it
+// may depend on whether we're down mixing from multichannel or upmixing.
+// FFmpeg uses 1 / sqrt(2) so I've left it the same for now.
+static const float kDefaultScale = static_cast<float>(M_SQRT1_2);
+
+static int ValidateLayout(ChannelLayout layout) {
+ CHECK_NE(layout, CHANNEL_LAYOUT_NONE);
+ CHECK_NE(layout, CHANNEL_LAYOUT_UNSUPPORTED);
+ CHECK_NE(layout, CHANNEL_LAYOUT_MAX);
+
+ // 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) {
scherkus (not reviewing) 2012/10/18 01:30:39 is it worth asserting that channel_count == 1 iff
DaleCurtis 2012/10/18 05:22:04 Can't hurt, done.
+ DCHECK((ChannelOrder(layout, LEFT) >= 0 &&
Chris Rogers 2012/10/17 19:46:50 Where's the ChannelOrder() function defined?
DaleCurtis 2012/10/17 20:06:47 http://codereview.chromium.org/11198018/ Will lan
+ ChannelOrder(layout, RIGHT) >= 0) ||
+ (ChannelOrder(layout, SIDE_LEFT) >= 0 &&
+ ChannelOrder(layout, SIDE_RIGHT) >= 0) ||
+ (ChannelOrder(layout, BACK_LEFT) >= 0 &&
+ ChannelOrder(layout, BACK_RIGHT) >= 0) ||
+ (ChannelOrder(layout, LEFT_OF_CENTER) >= 0 &&
+ ChannelOrder(layout, RIGHT_OF_CENTER) >= 0) ||
+ (ChannelOrder(layout, STEREO_LEFT) >= 0 &&
+ ChannelOrder(layout, STEREO_RIGHT) >= 0))
+ << "Non-symmetric channel layout encountered.";
+ }
+
+ return channel_count;
+}
+
+ChannelMixer::ChannelMixer(ChannelLayout input, ChannelLayout output)
+ : input_layout_(input),
+ output_layout_(output) {
+ // Stereo downmix should never be the output layout.
+ CHECK_NE(output_layout_, CHANNEL_LAYOUT_STEREO_DOWNMIX);
+
+ int input_channels = ValidateLayout(input_layout_);
+ int output_channels = ValidateLayout(output_layout_);
+
+ // 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));
+
+ // Route matching channels and figure out which ones aren't accounted for.
+ for (Channels ch = LEFT; ch < CHANNELS_MAX;
+ ch = static_cast<Channels>(ch + 1)) {
+
Chris Rogers 2012/10/17 19:46:50 extra blank line
DaleCurtis 2012/10/18 05:22:04 Done.
+ int input_ch_index = ChannelOrder(input_layout_, ch);
+ int output_ch_index = ChannelOrder(output_layout_, ch);
+
+ if (input_ch_index < 0)
+ continue;
+
+ if (output_ch_index < 0) {
+ 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_[0].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())
+ return;
+
+ // Mix front LR into center.
+ if (IsUnaccounted(LEFT)) {
+ Mix(LEFT, CENTER, kDefaultScale);
+ Mix(RIGHT, CENTER, kDefaultScale);
+ }
Chris Rogers 2012/10/17 19:46:50 I think this is the wrong approach for stereo -> m
DaleCurtis 2012/10/17 20:06:47 Okay, sounds like we just need two special case bl
DaleCurtis 2012/10/18 01:56:44 Done.
+
+ // Mix center into front LR.
+ if (IsUnaccounted(CENTER)) {
+ MixWithoutAccounting(CENTER, LEFT, kDefaultScale);
+ Mix(CENTER, RIGHT, kDefaultScale);
+ }
Chris Rogers 2012/10/17 19:46:50 This is odd and very much different from what audi
DaleCurtis 2012/10/17 20:06:47 Ditto.
DaleCurtis 2012/10/18 01:56:44 Done.
+
+ // Mix back LR into: side LR || back center || front LR || front center.
+ if (IsUnaccounted(BACK_LEFT)) {
+ if (HasOutputChannel(SIDE_LEFT)) {
+ // If we have 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) ? kDefaultScale : 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, kDefaultScale);
+ Mix(BACK_RIGHT, BACK_CENTER, kDefaultScale);
+ } else if (output > CHANNEL_LAYOUT_MONO) {
+ // Mix back LR into front LR.
+ Mix(BACK_LEFT, LEFT, kDefaultScale);
+ Mix(BACK_RIGHT, RIGHT, kDefaultScale);
+ } else {
+ // Mix back LR into front center.
+ Mix(BACK_LEFT, CENTER, kDefaultScale);
+ Mix(BACK_RIGHT, CENTER, kDefaultScale);
+ }
+ }
+
+ // Mix side LR into: back LR || back center || front LR || front center.
+ if (IsUnaccounted(SIDE_LEFT)) {
+ if (HasOutputChannel(BACK_LEFT)) {
+ // If we have 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) ? kDefaultScale : 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, kDefaultScale);
+ Mix(SIDE_RIGHT, BACK_CENTER, kDefaultScale);
+ } else if (output > CHANNEL_LAYOUT_MONO) {
+ // Mix side LR into front LR.
+ Mix(SIDE_LEFT, LEFT, kDefaultScale);
+ Mix(SIDE_RIGHT, RIGHT, kDefaultScale);
+ } else {
+ // Mix side LR into front center.
+ Mix(SIDE_LEFT, CENTER, kDefaultScale);
+ Mix(SIDE_RIGHT, CENTER, kDefaultScale);
+ }
+ }
+
+ // 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, kDefaultScale);
+ Mix(BACK_CENTER, BACK_RIGHT, kDefaultScale);
+ } else if (HasOutputChannel(SIDE_LEFT)) {
+ // Mix back center into side LR.
+ MixWithoutAccounting(BACK_CENTER, SIDE_LEFT, kDefaultScale);
+ Mix(BACK_CENTER, SIDE_RIGHT, kDefaultScale);
+ } else if (output > CHANNEL_LAYOUT_MONO) {
+ // Mix back center into front LR.
+ // TODO(dalecurtis): Not sure about these values?
+ MixWithoutAccounting(BACK_CENTER, LEFT, kDefaultScale * kDefaultScale);
+ Mix(BACK_CENTER, RIGHT, kDefaultScale * kDefaultScale);
+ } else {
+ // Mix back center into front center.
+ // TODO(dalecurtis): Not sure about these values?
+ Mix(BACK_CENTER, CENTER, kDefaultScale * kDefaultScale);
+ }
+ }
+
+ // Mix LR of center into: front center || front LR.
+ if (IsUnaccounted(LEFT_OF_CENTER)) {
+ if (HasOutputChannel(CENTER)) {
+ // Mix LR of center into front center.
+ Mix(LEFT_OF_CENTER, CENTER, kDefaultScale);
+ Mix(RIGHT_OF_CENTER, CENTER, kDefaultScale);
+ } else {
+ // Mix LR of center into front LR.
+ Mix(LEFT_OF_CENTER, LEFT, kDefaultScale);
+ Mix(RIGHT_OF_CENTER, RIGHT, kDefaultScale);
+ }
+ }
+
+ // Mix LFE into: front LR || front center.
+ if (IsUnaccounted(LFE)) {
+ if (!HasOutputChannel(CENTER)) {
+ // Mix LFE into front LR.
+ MixWithoutAccounting(LFE, LEFT, kDefaultScale);
+ Mix(LFE, RIGHT, kDefaultScale);
+ } else {
+ // Mix LFE into front center.
+ Mix(LFE, CENTER, kDefaultScale);
+ }
+ }
+
+ // All channels should now be accounted for.
+ DCHECK(unaccounted_inputs_.empty());
+}
+
+ChannelMixer::~ChannelMixer() {}
+
+void ChannelMixer::Rematrix(const AudioBus* input, AudioBus* output) {
Chris Rogers 2012/10/17 19:46:50 What is our plan for simple channel swizzling to a
DaleCurtis 2012/10/17 20:06:47 Yes I plan to add an AudioBus::Remap(int ch, int c
+ CHECK_EQ(matrix_.size(), static_cast<size_t>(output->channels()));
+ CHECK_EQ(matrix_[0].size(), static_cast<size_t>(input->channels()));
+ CHECK_EQ(input->frames(), output->frames());
+
+ for (int output_ch = 0; output_ch < output->channels(); ++output_ch) {
+ // Zero initialize |output| so we're accumulating from zero.
scherkus (not reviewing) 2012/10/18 01:30:39 silly optimization question... (I think chris aske
DaleCurtis 2012/10/18 01:56:44 Hmm, we don't need to accumulate when the output l
scherkus (not reviewing) 2012/10/18 02:24:03 Not sure. I was thinking of a situation (for what
DaleCurtis 2012/10/18 05:22:04 Added memcpy support for remaps, pretty trivial an
+ memset(output->channel(output_ch), 0,
+ output->frames() * sizeof(*output->channel(output_ch)));
Chris Rogers 2012/10/17 19:46:50 This cries out for a AudioBus::ZeroChannel() metho
DaleCurtis 2012/10/17 20:06:47 Good idea. Will add.
DaleCurtis 2012/10/18 05:22:04 Actually, output->Zero() outside of the loop is be
+
+ for (int input_ch = 0; input_ch < input->channels(); ++input_ch) {
+ float scale = matrix_[output_ch][input_ch];
+ // Scale should always be positive. Don't bother scaling by zero.
+ DCHECK_GE(scale, 0);
+ if (scale > std::numeric_limits<float>::epsilon()) {
+ vector_math::FMAC(input->channel(input_ch), scale, output->frames(),
+ output->channel(output_ch));
Chris Rogers 2012/10/17 19:46:50 What if the scale is 1, or does FMAC optimize for
DaleCurtis 2012/10/17 20:06:47 FMAC doesn't optimize for this case. I could add a
+ }
+ }
+ }
+}
+
+void ChannelMixer::AccountFor(Channels ch) {
+ unaccounted_inputs_.erase(std::find(
+ unaccounted_inputs_.begin(), unaccounted_inputs_.end(), ch));
+}
+
+bool ChannelMixer::IsUnaccounted(Channels ch) {
+ return std::find(unaccounted_inputs_.begin(), unaccounted_inputs_.end(),
+ ch) != unaccounted_inputs_.end();
+}
+
+bool ChannelMixer::HasInputChannel(Channels ch) {
+ return ChannelOrder(input_layout_, ch) >= 0;
+}
+
+bool ChannelMixer::HasOutputChannel(Channels ch) {
+ return ChannelOrder(output_layout_, ch) >= 0;
+}
+
+void ChannelMixer::Mix(Channels input_ch, Channels output_ch, float scale) {
+ MixWithoutAccounting(input_ch, output_ch, scale);
+ AccountFor(input_ch);
+}
+
+void ChannelMixer::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);
+
+ matrix_[output_ch_index][input_ch_index] += scale;
+}
+
+} // namespace media

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