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 = static_cast<ChannelLayout>(input_layout + 1)) {
+    for (ChannelLayout output_layout = CHANNEL_LAYOUT_MONO;
+         output_layout < CHANNEL_LAYOUT_STEREO_DOWNMIX;
+         output_layout = static_cast<ChannelLayout>(output_layout + 1)) {
+      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());
+    }
+  }
+}
+
+struct ChannelMixerTestData {
+  ChannelMixerTestData(ChannelLayout input_layout, ChannelLayout output_layout,

[scherkus (not reviewing), 2012/10/18 16:50:20]

perhaps you have to use regular struct initializers instead of a ctor?

[DaleCurtis, 2012/10/18 20:42:20]

Didn't like the const setting on variables below, I guess it's doing some sort
of copy internally? 

+                       float* channel_values, int num_channel_values,
+                       float scale)
+      : input_layout(input_layout),
+        output_layout(output_layout),
+        channel_values(channel_values),
+        num_channel_values(num_channel_values),
+        scale(scale) {
+  }
+
+  std::string DebugString() const {
+    return base::StringPrintf(
+        "Input Layout: %d, Output Layout %d, Scale: %f", input_layout,
+        output_layout, scale);
+  }
+
+  const ChannelLayout input_layout;
+  const ChannelLayout output_layout;
+  const float* channel_values;
+  const int num_channel_values;
+  const float scale;
+};
+
+std::ostream& operator<<(std::ostream& os, const ChannelMixerTestData& data) {
+  return os << data.DebugString();
+}
+
+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 = GetParam().input_layout;
+  ChannelLayout output_layout = GetParam().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);
+
+  const float* channel_values = GetParam().channel_values;
+  ASSERT_EQ(input_bus->channels(), GetParam().num_channel_values);
+
+  float expected_value = 0;
+  float scale = GetParam().scale;
+  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[] = { 0.5f, 0.75f };
+static float kMonoToStereoValues[] = { 0.5f };
+// Zero the center channel since it will be mixed at scale 1 vs M_SQRT1_2.
+static float kFiveOneToMonoValues[] = { 0.1f, 0.2f, 0.0f, 0.4f, 0.5f, 0.6f };
+
+// Run through basic sanity tests for some common conversions.
+INSTANTIATE_TEST_CASE_P(ChannelMixerTest, ChannelMixerTest, testing::Values(
+    ChannelMixerTestData(CHANNEL_LAYOUT_STEREO, CHANNEL_LAYOUT_MONO,
+                         kStereoToMonoValues, arraysize(kStereoToMonoValues),
+                         0.5f),
+    ChannelMixerTestData(CHANNEL_LAYOUT_MONO, CHANNEL_LAYOUT_STEREO,
+                         kMonoToStereoValues, arraysize(kMonoToStereoValues),
+                         1.0f),
+    ChannelMixerTestData(CHANNEL_LAYOUT_5_1, CHANNEL_LAYOUT_MONO,
+                         kFiveOneToMonoValues, arraysize(kFiveOneToMonoValues),
+                         static_cast<float>(M_SQRT1_2))
+));
+
+}  // namespace media