Add GetMatchingOutputDeviceID to CoreAudioUtil.

media/audio/win/core_audio_util_win.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 "media/audio/win/core_audio_util_win.h"
 
 #include <audioclient.h>
 #include <devicetopology.h>
 #include <functiondiscoverykeys_devpkey.h>
 
@@ skipping 347 matching lines @@
   }
 
   std::string controller_id;
   WideToUTF8(instance_id.get().pwszVal,
              wcslen(instance_id.get().pwszVal),
              &controller_id);
 
   return controller_id;
 }
 
+std::string CoreAudioUtil::GetMatchingOutputDeviceID(
+    const std::string& input_device_id) {
+  ScopedComPtr<IMMDevice> input_device(CreateDevice(input_device_id));
+  if (!input_device)
+    return std::string();
+
+  // See if we can get id of the associated controller.
+  ScopedComPtr<IMMDeviceEnumerator> enumerator(CreateDeviceEnumerator());
+  std::string controller_id(GetAudioControllerID(input_device, enumerator));
+  if (controller_id.empty())
+    return std::string();
+
+  // Now enumerate the available (and active) output devices and see if any of
+  // them is associated with the same controller.
+  ScopedComPtr<IMMDeviceCollection> collection;
+  enumerator->EnumAudioEndpoints(eRender, DEVICE_STATE_ACTIVE,
+      collection.Receive());
+  if (!collection)
+    return std::string();
+
+  UINT count = 0;
+  collection->GetCount(&count);
+  ScopedComPtr<IMMDevice> output_device;
+  for (UINT i = 0; i < count; ++i) {
+    collection->Item(i, output_device.Receive());
+    std::string output_controller_id(CoreAudioUtil::GetAudioControllerID(
+        output_device, enumerator));
+    if (output_controller_id == controller_id)
+      break;
+    output_device = NULL;

[henrika (OOO until Aug 14), 2013/08/30 09:45:40]

Is this needed?

[tommi (sloooow) - chröme, 2013/08/30 10:45:34]

Yes, otherwise output_device will be assigned to the last element in the
collection when the loop ends and it will belong to the wrong controller.

+  }
+
+  std::string id;
+

[henrika (OOO until Aug 14), 2013/08/30 09:45:40]

Remove this empty line?

[tommi (sloooow) - chröme, 2013/08/30 10:45:34]

Done.

+  if (output_device) {
+    ScopedCoMem<WCHAR> wide_id;
+    output_device->GetId(&wide_id);
+    WideToUTF8(wide_id, wcslen(wide_id), &id);
+  }
+
+  return id;
+}
+
 std::string CoreAudioUtil::GetFriendlyName(const std::string& device_id) {
   DCHECK(IsSupported());
   ScopedComPtr<IMMDevice> audio_device = CreateDevice(device_id);
   if (!audio_device)
     return std::string();
 
   AudioDeviceName device_name;
   HRESULT hr = GetDeviceName(audio_device, &device_name);
   if (FAILED(hr))
     return std::string();
@@ skipping 379 matching lines @@
     return false;
 
   // Using the AUDCLNT_BUFFERFLAGS_SILENT flag eliminates the need to
   // explicitly write silence data to the rendering buffer.
   DVLOG(2) << "filling up " << num_frames_to_fill << " frames with silence";
   return SUCCEEDED(render_client->ReleaseBuffer(num_frames_to_fill,
                                                 AUDCLNT_BUFFERFLAGS_SILENT));
 }
 
 }  // namespace media