Add support for multichannel playback to OpenSLES output.

media/audio/android/opensles_util.cc

+// Copyright 2016 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.
+
+#include "media/audio/android/opensles_util.h"
+
+namespace media {
+
+#define SL_ANDROID_SPEAKER_QUAD                                            \
+  (SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT | SL_SPEAKER_BACK_LEFT | \
+   SL_SPEAKER_BACK_RIGHT)
+#define SL_ANDROID_SPEAKER_5DOT1                                              \
+  (SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT | SL_SPEAKER_FRONT_CENTER | \
+   SL_SPEAKER_LOW_FREQUENCY | SL_SPEAKER_BACK_LEFT | SL_SPEAKER_BACK_RIGHT)
+#define SL_ANDROID_SPEAKER_7DOT1 \
+  (SL_ANDROID_SPEAKER_5DOT1 | SL_SPEAKER_SIDE_LEFT | SL_SPEAKER_SIDE_RIGHT)
+
+// Ported from:
+// https://android.googlesource.com/platform/frameworks/wilhelm/+/refs/heads/master/src/android/channels.h
+// https://android.googlesource.com/platform/frameworks/wilhelm/+/refs/heads/master/src/android/channels.c
+SLuint32 ChannelCountToSLESChannelMask(int channel_count) {

[henrika (OOO until Aug 14), 2016/04/28 07:52:54]

I understand that you want to avoid the existing DCHECK here but do you have any
hopes of actually notice any real effect of this mapping? 

[DaleCurtis, 2016/04/28 17:27:26]

AndroidTV devices and those hooked up via HDMI should be able to output > stereo
audio; these devices frequently use WebView or similar content/ based shells
that will need to output multichannel. At lease on M+ devices the audio is
automatically downmixed by the OS if necessary. I need to test K, L variants.

[henrika (OOO until Aug 14), 2016/04/29 07:46:31]

Thanks. Just hope it works then ;-)

+  if (channel_count > 2) {
+    LOG(WARNING) << "Guessing channel layout for " << channel_count
+                 << " channels; speaker order may be incorrect.";
+  }
+
+  switch (channel_count) {
+    case 1:
+      return SL_SPEAKER_FRONT_LEFT;
+    case 2:
+      return SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT;
+    case 3:
+      return SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT |
+             SL_SPEAKER_FRONT_CENTER;
+    case 4:
+      return SL_ANDROID_SPEAKER_QUAD;
+    case 5:
+      return SL_ANDROID_SPEAKER_QUAD | SL_SPEAKER_FRONT_CENTER;
+    case 6:
+      return SL_ANDROID_SPEAKER_5DOT1;
+    case 7:
+      return SL_ANDROID_SPEAKER_5DOT1 | SL_SPEAKER_BACK_CENTER;
+    case 8:
+      return SL_ANDROID_SPEAKER_7DOT1;
+  }
+
+  return 0;
+}
+
+}  // namespace media