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

media/video/capture/win/video_capture_device_factory_win.cc

 // Copyright 2014 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/video/capture/win/video_capture_device_factory_win.h"
 
 #include <mfapi.h>
 #include <mferror.h>
 
 #include "base/command_line.h"
@@ skipping 201 matching lines @@
   int index = 0;
   ScopedVariant device_id;
   while (enum_moniker->Next(1, moniker.Receive(), NULL) == S_OK) {
     ScopedComPtr<IPropertyBag> prop_bag;
     hr = moniker->BindToStorage(0, 0, IID_IPropertyBag, prop_bag.ReceiveVoid());
     if (FAILED(hr)) {
       moniker.Release();
       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();
   }
 
   if (moniker.get()) {
     base::win::ScopedComPtr<IBaseFilter> capture_filter;
     hr = VideoCaptureDeviceWin::GetDeviceFilter(device,
                                                 capture_filter.Receive());
     if (!capture_filter) {
       DVLOG(2) << "Failed to create capture filter.";
@@ skipping 42 matching lines @@
             VideoCaptureDeviceWin::TranslateMediaSubtypeToPixelFormat(
                 media_type->subtype);
         if (format.pixel_format == PIXEL_FORMAT_UNKNOWN)
           continue;
         VIDEOINFOHEADER* h =
             reinterpret_cast<VIDEOINFOHEADER*>(media_type->pbFormat);
         format.frame_size.SetSize(h->bmiHeader.biWidth,
                                   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
              << ", pixel format: " << format.pixel_format;
       }
     }
   }
 }
 
 static void GetDeviceSupportedFormatsMediaFoundation(
@@ skipping 26 matching lines @@
     }
     VideoCaptureFormat capture_format;
     capture_format.frame_size.SetSize(width, height);
 
     UINT32 numerator, denominator;
     hr = MFGetAttributeRatio(type, MF_MT_FRAME_RATE, &numerator, &denominator);
     if (FAILED(hr)) {
       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);
     if (FAILED(hr)) {
       DLOG(ERROR) << "GetGUID: " << std::hex << hr;
       return;
     }
     VideoCaptureDeviceMFWin::FormatFromGuid(type_guid,
                                             &capture_format.pixel_format);
     type.Release();
@@ skipping 77 matching lines @@
     const VideoCaptureDevice::Name& device,
     VideoCaptureFormats* formats) {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (use_media_foundation_)
     GetDeviceSupportedFormatsMediaFoundation(device, formats);
   else
     GetDeviceSupportedFormatsDirectShow(device, formats);
 }
 
 }  // namespace media