Add support for channel transforms.

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/stringprintf.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++) {
+    for (ChannelLayout output_layout = CHANNEL_LAYOUT_MONO;
+         output_layout < CHANNEL_LAYOUT_STEREO_DOWNMIX; output_layout++) {
+      SCOPED_TRACE(base::StringPrintf(
+          "Input Layout: %d, Output Layout: %d", input_layout, output_layout));
+      ChannelMixer mixer(input_layout, output_layout);
+      scoped_ptr<AudioBus> input_bus = AudioBus::Create(
+          ChannelLayoutToChannelCount(input_layout), kFrames);
+      scoped_ptr<AudioBus> output_bus = AudioBus::Create(
+          ChannelLayoutToChannelCount(output_layout), kFrames);
+      for (int ch = 0; ch < input_bus->channels(); ++ch)
+        std::fill(input_bus->channel(ch), input_bus->channel(ch) + kFrames, 1);
+
+      mixer.Rematrix(input_bus.get(), output_bus.get());
+    }
+  }
+}
+
+// Tuple containing the input layout, output layout, fill value for each input
+// channel, the number of channel values, and the expected channel scale.
+typedef std::tr1::tuple<ChannelLayout, ChannelLayout, float*, int, float>

[scherkus (not reviewing), 2012/10/18 05:39:23]

hrmmm... is it possible to use a struct instead of a tuple?

[DaleCurtis, 2012/10/18 06:30:38]

Yeah, it's about 30 lines of boiler plate though. Done.

[DaleCurtis, 2012/10/18 06:46:05]

Argh, windows doesn't like this:
http://build.chromium.org/p/tryserver.chromium/builders/win_rel/builds/71716/...

Will experiment tomorrow, or just roll back to using a tuple.

+ChannelMixerTestData;
+class ChannelMixerTest
+    : public testing::TestWithParam<ChannelMixerTestData> {
+};
+
+// Verify channels are mixed and scaled correctly.  The test only works if all
+// output channels have the same value.
+TEST_P(ChannelMixerTest, Mixing) {
+  ChannelLayout input_layout = std::tr1::get<0>(GetParam());
+  ChannelLayout output_layout = std::tr1::get<1>(GetParam());
+
+  SCOPED_TRACE(base::StringPrintf(
+      "Input Layout: %d, Output Layout: %d", input_layout, output_layout));
+
+  ChannelMixer mixer(input_layout, output_layout);
+  scoped_ptr<AudioBus> input_bus = AudioBus::Create(
+      ChannelLayoutToChannelCount(input_layout), kFrames);
+  scoped_ptr<AudioBus> output_bus = AudioBus::Create(
+      ChannelLayoutToChannelCount(output_layout), kFrames);
+
+  float* channel_values = std::tr1::get<2>(GetParam());
+  int num_channel_values = std::tr1::get<3>(GetParam());
+  ASSERT_EQ(input_bus->channels(), num_channel_values);
+
+  float expected_value = 0;
+  float scale = std::tr1::get<4>(GetParam());
+  for (int ch = 0; ch < input_bus->channels(); ++ch) {
+    std::fill(input_bus->channel(ch), input_bus->channel(ch) + kFrames,
+              channel_values[ch]);
+    expected_value += channel_values[ch] * scale;
+  }
+
+  mixer.Rematrix(input_bus.get(), output_bus.get());
+
+  for (int ch = 0; ch < output_bus->channels(); ++ch) {
+    for (int frame = 0; frame < output_bus->frames(); ++frame) {
+      ASSERT_FLOAT_EQ(output_bus->channel(ch)[frame], expected_value);
+    }
+  }
+}
+
+static float kStereoToMonoValues[] = { 0.5, 0.75 };
+static float kMonoToStereoValues[] = { 0.5 };
+// Zero the center channel since it will be mixed at scale 1 vs M_SQRT1_2.
+static float kFiveOneToMonoValues[] = { 0.1, 0.2, 0, 0.4, 0.5, 0.6 };
+
+// Run through basic sanity tests for some common conversions.
+INSTANTIATE_TEST_CASE_P(ChannelMixerTest, ChannelMixerTest, testing::Values(
+    std::tr1::make_tuple(CHANNEL_LAYOUT_STEREO, CHANNEL_LAYOUT_MONO,
+                         kStereoToMonoValues, arraysize(kStereoToMonoValues),
+                         0.5f),
+    std::tr1::make_tuple(CHANNEL_LAYOUT_MONO, CHANNEL_LAYOUT_STEREO,
+                         kMonoToStereoValues, arraysize(kMonoToStereoValues),
+                         1.0f),
+    std::tr1::make_tuple(CHANNEL_LAYOUT_5_1, CHANNEL_LAYOUT_MONO,
+                         kFiveOneToMonoValues, arraysize(kFiveOneToMonoValues),
+                         static_cast<float>(M_SQRT1_2))
+));
+
+}  // namespace media