VideoCaptureDevice Win: Enumerate devices' supported formats when they don't have a DevicePath prop…

media/video/capture/win/video_capture_device_factory_win.cc

Index: media/video/capture/win/video_capture_device_factory_win.cc
diff --git a/media/video/capture/win/video_capture_device_factory_win.cc b/media/video/capture/win/video_capture_device_factory_win.cc
index 920126df09e2558b16048b0081d1669b68205f2e..f94f0cc3ae56c01dfef1eca48e13ba16475831ba 100644
--- a/media/video/capture/win/video_capture_device_factory_win.cc
+++ b/media/video/capture/win/video_capture_device_factory_win.cc
@@ -219,13 +219,22 @@ static void GetDeviceSupportedFormatsDirectShow(
       continue;
     }
 
+    std::string id;
     device_id.Reset();
     hr = prop_bag->Read(L"DevicePath", device_id.Receive(), 0);
-    if (FAILED(hr)) {
-      DVLOG(1) << "Couldn't read a device's DevicePath.";
-      return;
+    if (FAILED(hr) || device_id.type() != VT_BSTR) {
+      // If there is no clear DevicePath, try with Description and FriendlyName.

[tommi (sloooow) - chröme, 2014/06/10 07:36:29]

Is fetching the Description before FriendlyName the right thing to do?  I would
have guessed the opposite order but I don't have any data to back that up.  Can
you document in what cases this can happen? (no devicepath, description is more
correct than FriendlyName, etc.

[mcasas, 2014/06/10 15:01:14]

The idea/sinppet comes from l.128-l.130 of this file, GetDeviceNames().

Added some documentation.

+      ScopedVariant name;
+      if (SUCCEEDED(prop_bag->Read(L"Description", name.Receive(), 0)) ||
+          SUCCEEDED(prop_bag->Read(L"FriendlyName", name.Receive(), 0))) {
+        id = base::SysWideToUTF8(V_BSTR(&name));
+      }
+    } else {
+      DCHECK_EQ(device_id.type(), VT_BSTR);
+      id = base::SysWideToUTF8(V_BSTR(&device_id));
     }
-    if (device.id() == base::SysWideToUTF8(V_BSTR(&device_id)))
+
+    if (device.id() == id)
       break;
     moniker.Release();
   }
@@ -288,8 +297,9 @@ static void GetDeviceSupportedFormatsDirectShow(
                                   h->bmiHeader.biHeight);
         // Trust the frame rate from the VIDEOINFOHEADER.
         format.frame_rate = (h->AvgTimePerFrame > 0) ?
-            static_cast<int>(kSecondsToReferenceTime / h->AvgTimePerFrame) :
-            0;
+            (kSecondsToReferenceTime / static_cast<float>(h->AvgTimePerFrame)) :

[tommi (sloooow) - chröme, 2014/06/10 07:36:29]

nit: extra parenthesis aren't needed

[mcasas, 2014/06/10 15:01:14]

Done.

+            0.0;
+
         formats->push_back(format);
         DVLOG(1) << device.name() << " resolution: "
              << format.frame_size.ToString() << ", fps: " << format.frame_rate
@@ -336,7 +346,8 @@ static void GetDeviceSupportedFormatsMediaFoundation(
       DLOG(ERROR) << "MFGetAttributeSize: " << std::hex << hr;
       return;
     }
-    capture_format.frame_rate = denominator ? numerator / denominator : 0;
+    capture_format.frame_rate = denominator ?
+        numerator / static_cast<float>(denominator) : 0.0f;
 
     GUID type_guid;
     hr = type->GetGUID(MF_MT_SUBTYPE, &type_guid);