media/base/channel_mixer.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/base/channel_mixer.h"
   6
   7 #include "base/logging.h"
   8 #include "media/audio/audio_parameters.h"
   9 #include "media/base/audio_bus.h"
  10 #include "media/base/channel_mixing_matrix.h"
  11 #include "media/base/vector_math.h"
  12
  13 namespace media {
  14
  15 ChannelMixer::ChannelMixer(ChannelLayout input_layout,
  16                            ChannelLayout output_layout) {
  17   Initialize(input_layout,
  18              ChannelLayoutToChannelCount(input_layout),
  19              output_layout,
  20              ChannelLayoutToChannelCount(output_layout));
  21 }
  22
  23 ChannelMixer::ChannelMixer(
  24     const AudioParameters& input, const AudioParameters& output) {
  25   Initialize(input.channel_layout(),
  26              input.channels(),
  27              output.channel_layout(),
  28              output.channels());
  29 }
  30
  31 void ChannelMixer::Initialize(
  32     ChannelLayout input_layout, int input_channels,
  33     ChannelLayout output_layout, int output_channels) {
  34   // Create the transformation matrix
  35   ChannelMixingMatrix matrix_builder(input_layout, input_channels,
  36                                      output_layout, output_channels);
  37   remapping_ = matrix_builder.CreateTransformationMatrix(&matrix_);
  38 }
  39
  40 ChannelMixer::~ChannelMixer() {}
  41
  42 void ChannelMixer::Transform(const AudioBus* input, AudioBus* output) {
  43   CHECK_EQ(matrix_.size(), static_cast<size_t>(output->channels()));
  44   CHECK_EQ(matrix_[0].size(), static_cast<size_t>(input->channels()));
  45   CHECK_EQ(input->frames(), output->frames());
  46
  47   // Zero initialize |output| so we're accumulating from zero.
  48   output->Zero();
  49
  50   // If we're just remapping we can simply copy the correct input to output.
  51   if (remapping_) {
  52     for (int output_ch = 0; output_ch < output->channels(); ++output_ch) {
  53       for (int input_ch = 0; input_ch < input->channels(); ++input_ch) {
  54         float scale = matrix_[output_ch][input_ch];
  55         if (scale > 0) {
  56           DCHECK_EQ(scale, 1.0f);
  57           memcpy(output->channel(output_ch), input->channel(input_ch),
  58                  sizeof(*output->channel(output_ch)) * output->frames());
  59           break;
  60         }
  61       }
  62     }
  63     return;
  64   }
  65
  66   for (int output_ch = 0; output_ch < output->channels(); ++output_ch) {
  67     for (int input_ch = 0; input_ch < input->channels(); ++input_ch) {
  68       float scale = matrix_[output_ch][input_ch];
  69       // Scale should always be positive.  Don't bother scaling by zero.
  70       DCHECK_GE(scale, 0);
  71       if (scale > 0) {
  72         vector_math::FMAC(input->channel(input_ch), scale, output->frames(),
  73                           output->channel(output_ch));
  74       }
  75     }
  76   }
  77 }
  78
  79 }  // namespace media