Expose the internal MatrixBuilder class as ChannelMixingMatrix.

media/base/channel_mixer_unittest.cc

 // 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
 
 #include <cmath>
 
 #include "base/strings/stringprintf.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/audio_bus.h"
 #include "media/base/channel_mixer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace media {
 
 // Number of frames to test with.
 enum { kFrames = 16 };
 
 // Test all possible layout conversions can be constructed and mixed.
 TEST(ChannelMixerTest, ConstructAllPossibleLayouts) {
   for (ChannelLayout input_layout = CHANNEL_LAYOUT_MONO;
        input_layout <= CHANNEL_LAYOUT_MAX;
        input_layout = static_cast<ChannelLayout>(input_layout + 1)) {
     for (ChannelLayout output_layout = CHANNEL_LAYOUT_MONO;
+         // TODO(wtc): why do we only test up to CHANNEL_LAYOUT_STEREO_DOWNMIX?

[DaleCurtis, 2014/10/23 16:49:05]

Hmm, I don't remember, may be a bug. What happens if you change it to MAX? Is
there any git blame info on that line?

[wtc, 2014/10/23 18:39:45]

If I change it to MAX, this CHECK will fail:

  // Stereo down mix should never be the output layout.
  CHECK_NE(output_layout, CHANNEL_LAYOUT_STEREO_DOWNMIX);

I can fix the CHECK failure by skipping the test if output_layout ==
CHANNEL_LAYOUT_STEREO_DOWNMIX on line 35.
Yes. You added it in the initial revision of this file:

https://chromiumcodereview.appspot.com/11150034

[DaleCurtis, 2014/10/23 19:23:50]

Haha, whoops. Thanks for fixing :)

          output_layout < CHANNEL_LAYOUT_STEREO_DOWNMIX;
          output_layout = static_cast<ChannelLayout>(output_layout + 1)) {
       // DISCRETE can't be tested here based on the current approach.
       // CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC is not mixable.
       if (input_layout == CHANNEL_LAYOUT_DISCRETE ||
           input_layout == CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC ||
           output_layout == CHANNEL_LAYOUT_DISCRETE ||
           output_layout == CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC) {
         continue;
       }
@@ skipping 142 matching lines @@
                          kStereoToMonoValues, arraysize(kStereoToMonoValues)),
     ChannelMixerTestData(CHANNEL_LAYOUT_DISCRETE, 2,
                          CHANNEL_LAYOUT_DISCRETE, 5,
                          kStereoToMonoValues, arraysize(kStereoToMonoValues)),
     ChannelMixerTestData(CHANNEL_LAYOUT_DISCRETE, 5,
                          CHANNEL_LAYOUT_DISCRETE, 2,
                          kFiveDiscreteValues, arraysize(kFiveDiscreteValues))
 ));
 
 }  // namespace media