Support more than 8 channels for AudioContext.destination node on OSX

content/renderer/renderer_blink_platform_impl.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.
 
 #include "content/renderer/renderer_blink_platform_impl.h"
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
@@ skipping 683 matching lines @@
     const blink::WebString& input_device_id) {
   // Use a mock for testing.
   blink::WebAudioDevice* mock_device =
       GetContentClient()->renderer()->OverrideCreateAudioDevice(sample_rate);
   if (mock_device)
     return mock_device;
 
   // The |channels| does not exactly identify the channel layout of the
   // device. The switch statement below assigns a best guess to the channel
   // layout based on number of channels.
-  // TODO(crogers): WebKit should give the channel layout instead of the hard

[Raymond Toy, 2015/01/08 21:55:54]

This TODO is still true isn't it?  WebKit does still give the channel count and
not the layout, right?

[hongchan, 2015/01/08 21:58:33]

Still true for WebKit, but here at Blink we have the implementation of
CHANNEL_LAYOUT_*. I thought it only applies to WebKit and the comment is
outdated - but I don't mind reverting the comment back.

[Raymond Toy, 2015/01/08 22:02:57]

But creatAudioDevice still takes unsigned channels, and not some kind of channel
layout enum or object. I think that's what the comment is referring to. 
(Substitute Blink for WebKit).

-  // channel count.
   media::ChannelLayout layout = media::CHANNEL_LAYOUT_UNSUPPORTED;
   switch (channels) {
     case 1:
       layout = media::CHANNEL_LAYOUT_MONO;
       break;
     case 2:
       layout = media::CHANNEL_LAYOUT_STEREO;
       break;
     case 3:
       layout = media::CHANNEL_LAYOUT_2_1;
       break;
     case 4:
       layout = media::CHANNEL_LAYOUT_4_0;
       break;
     case 5:
       layout = media::CHANNEL_LAYOUT_5_0;
       break;
     case 6:
       layout = media::CHANNEL_LAYOUT_5_1;
       break;
     case 7:
       layout = media::CHANNEL_LAYOUT_7_0;
       break;
     case 8:
       layout = media::CHANNEL_LAYOUT_7_1;
       break;
     default:
-      layout = media::CHANNEL_LAYOUT_STEREO;
+      // If the layout is not supported (more than 9 channels), falls back to
+      // discrete mode.
+      layout = media::CHANNEL_LAYOUT_DISCRETE;
   }
 
   int session_id = 0;
   if (input_device_id.isNull() ||
       !base::StringToInt(base::UTF16ToUTF8(input_device_id), &session_id)) {
     if (input_channels > 0)
       DLOG(WARNING) << "createAudioDevice(): request for audio input ignored";
 
     input_channels = 0;
   }
 
+  // For CHANNEL_LAYOUT_DISCRETE, pass the explicit channel count along with
+  // the channel layout when creating an |AudioParameters| object.
   media::AudioParameters params(
       media::AudioParameters::AUDIO_PCM_LOW_LATENCY,
-      layout, static_cast<int>(sample_rate), 16, buffer_size,
+      layout, channels, static_cast<int>(sample_rate), 16, buffer_size,
       media::AudioParameters::NO_EFFECTS);
 
   return new RendererWebAudioDeviceImpl(params, callback, session_id);
 }
 
 #if defined(OS_ANDROID)
 bool RendererBlinkPlatformImpl::loadAudioResource(
     blink::WebAudioBus* destination_bus,
     const char* audio_file_data,
     size_t data_size) {
@@ skipping 466 matching lines @@
 //------------------------------------------------------------------------------
 
 void RendererBlinkPlatformImpl::MockBatteryStatusChangedForTesting(
     const blink::WebBatteryStatus& status) {
   if (!g_test_battery_status_listener)
     return;
   g_test_battery_status_listener->updateBatteryStatus(status);
 }
 
 }  // namespace content