Expose the internal MatrixBuilder class as ChannelMixingMatrix.

media/base/channel_mixing_matrix.cc

Index: media/base/channel_mixing_matrix.cc
diff --git a/media/base/channel_mixer.cc b/media/base/channel_mixing_matrix.cc
similarity index 65%
copy from media/base/channel_mixer.cc
copy to media/base/channel_mixing_matrix.cc
index ef1bd5c096e96421f2fc6c02fce1ea3a3f57fa42..eee0efd0c33017196f5c3e6481408ac8918285dc 100644
--- a/media/base/channel_mixer.cc
+++ b/media/base/channel_mixing_matrix.cc
@@ -5,15 +5,12 @@
 // MSVC++ requires this to be set before any other includes to get M_SQRT1_2.
 #define _USE_MATH_DEFINES
 
-#include "media/base/channel_mixer.h"
+#include "media/base/channel_mixing_matrix.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/logging.h"
-#include "media/audio/audio_parameters.h"
-#include "media/base/audio_bus.h"
-#include "media/base/vector_math.h"
 
 namespace media {
 
@@ -52,83 +49,14 @@ static void ValidateLayout(ChannelLayout layout) {
   }
 }
 
-class MatrixBuilder {
- public:
-  MatrixBuilder(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) {
-    // 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;
-    }
-  }
-
-  ~MatrixBuilder() { }
-
-  // Create the transformation matrix of input channels to output channels.
-  // Updates the empty matrix with the transformation, and returns true
-  // if the transformation is just a remapping of channels (no mixing).
-  bool CreateTransformationMatrix(std::vector< std::vector<float> >* matrix);
-
- private:
-  // Result transformation of input channels to output channels
-  std::vector< std::vector<float> >* matrix_;
-
-  // Input and output channel layout provided during construction.
-  ChannelLayout input_layout_;
-  int input_channels_;
-  ChannelLayout output_layout_;
-  int output_channels_;
-
-  // Helper variable for tracking which inputs are currently unaccounted,
-  // should be empty after construction completes.
-  std::vector<Channels> unaccounted_inputs_;
-
-  // Helper methods for managing unaccounted input channels.
-  void AccountFor(Channels ch);
-  bool IsUnaccounted(Channels ch) const;
-
-  // Helper methods for checking if |ch| exists in either |input_layout_| or
-  // |output_layout_| respectively.
-  bool HasInputChannel(Channels ch) const;
-  bool HasOutputChannel(Channels ch) const;
-
-  // Helper methods for updating |matrix_| with the proper value for
-  // mixing |input_ch| into |output_ch|.  MixWithoutAccounting() does not
-  // remove the channel from |unaccounted_inputs_|.
-  void Mix(Channels input_ch, Channels output_ch, float scale);
-  void MixWithoutAccounting(Channels input_ch, Channels output_ch, float scale);
-
-  DISALLOW_COPY_AND_ASSIGN(MatrixBuilder);
-};
-
-ChannelMixer::ChannelMixer(ChannelLayout input_layout,
-                           ChannelLayout output_layout) {
-  Initialize(input_layout,
-             ChannelLayoutToChannelCount(input_layout),
-             output_layout,
-             ChannelLayoutToChannelCount(output_layout));
-}
-
-ChannelMixer::ChannelMixer(
-    const AudioParameters& input, const AudioParameters& output) {
-  Initialize(input.channel_layout(),
-             input.channels(),
-             output.channel_layout(),
-             output.channels());
-}
-
-void ChannelMixer::Initialize(
-    ChannelLayout input_layout, int input_channels,
-    ChannelLayout output_layout, int output_channels) {
+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);
 
@@ -138,14 +66,22 @@ void ChannelMixer::Initialize(
   if (output_layout != CHANNEL_LAYOUT_DISCRETE)
     ValidateLayout(output_layout);
 
-  // Create the transformation matrix
-  MatrixBuilder matrix_builder(input_layout, input_channels,
-                               output_layout, output_channels);
-  remapping_ = matrix_builder.CreateTransformationMatrix(&matrix_);
+  // 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;
+  }
 }
 
-bool MatrixBuilder::CreateTransformationMatrix(
-    std::vector< std::vector<float> >* matrix) {
+ChannelMixingMatrix::~ChannelMixingMatrix() {
+}
+
+bool ChannelMixingMatrix::CreateTransformationMatrix(
+    std::vector<std::vector<float>>* matrix) {
   matrix_ = matrix;
 
   // Size out the initial matrix.
@@ -326,70 +262,34 @@ bool MatrixBuilder::CreateTransformationMatrix(
   return true;
 }
 
-ChannelMixer::~ChannelMixer() {}
-
-void ChannelMixer::Transform(const AudioBus* input, AudioBus* output) {
-  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());
-
-  // Zero initialize |output| so we're accumulating from zero.
-  output->Zero();
-
-  // If we're just remapping we can simply copy the correct input to output.
-  if (remapping_) {
-    for (int output_ch = 0; output_ch < output->channels(); ++output_ch) {
-      for (int input_ch = 0; input_ch < input->channels(); ++input_ch) {
-        float scale = matrix_[output_ch][input_ch];
-        if (scale > 0) {
-          DCHECK_EQ(scale, 1.0f);
-          memcpy(output->channel(output_ch), input->channel(input_ch),
-                 sizeof(*output->channel(output_ch)) * output->frames());
-          break;
-        }
-      }
-    }
-    return;
-  }
-
-  for (int output_ch = 0; output_ch < output->channels(); ++output_ch) {
-    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 > 0) {
-        vector_math::FMAC(input->channel(input_ch), scale, output->frames(),
-                          output->channel(output_ch));
-      }
-    }
-  }
-}
-
-void MatrixBuilder::AccountFor(Channels ch) {
+void ChannelMixingMatrix::AccountFor(Channels ch) {
   unaccounted_inputs_.erase(std::find(
       unaccounted_inputs_.begin(), unaccounted_inputs_.end(), ch));
 }
 
-bool MatrixBuilder::IsUnaccounted(Channels ch) const {
+bool ChannelMixingMatrix::IsUnaccounted(Channels ch) const {
   return std::find(unaccounted_inputs_.begin(), unaccounted_inputs_.end(),
                    ch) != unaccounted_inputs_.end();
 }
 
-bool MatrixBuilder::HasInputChannel(Channels ch) const {
+bool ChannelMixingMatrix::HasInputChannel(Channels ch) const {
   return ChannelOrder(input_layout_, ch) >= 0;
 }
 
-bool MatrixBuilder::HasOutputChannel(Channels ch) const {
+bool ChannelMixingMatrix::HasOutputChannel(Channels ch) const {
   return ChannelOrder(output_layout_, ch) >= 0;
 }
 
-void MatrixBuilder::Mix(Channels input_ch, Channels output_ch, float scale) {
+void ChannelMixingMatrix::Mix(Channels input_ch,
+                              Channels output_ch,
+                              float scale) {
   MixWithoutAccounting(input_ch, output_ch, scale);
   AccountFor(input_ch);
 }
 
-void MatrixBuilder::MixWithoutAccounting(Channels input_ch, Channels output_ch,
-                                         float scale) {
+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);