This is the VideoCaptureDevice implementation for windows.

media/video/capture/win/video_capture_device_win.cc

+// Copyright (c) 2011 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_win.h"
+
+#include <algorithm>
+#include <list>
+
+#include "base/string_util.h"
+#include "base/sys_string_conversions.h"
+#include "base/win/scoped_variant.h"
+
+using base::win::ScopedComPtr;
+using base::win::ScopedVariant;
+
+namespace {
+
+// Finds and creates a DirectShow Video Capture filter matching the device_name.
+HRESULT GetDeviceFilter(const media::VideoCaptureDevice::Name& device_name,
+                        IBaseFilter** filter) {
+  DCHECK(filter);
+
+  ScopedComPtr<ICreateDevEnum> dev_enum;
+  HRESULT hr = dev_enum.CreateInstance(CLSID_SystemDeviceEnum, NULL,
+                                       CLSCTX_INPROC);
+  if (FAILED(hr))
+    return hr;
+
+  ScopedComPtr<IEnumMoniker> enum_moniker;
+  hr = dev_enum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,
+                                       enum_moniker.Receive(), 0);
+  if (FAILED(hr))
+    return NULL;
+
+  ScopedComPtr<IMoniker> moniker;
+  ScopedComPtr<IBaseFilter> capture_filter;
+  DWORD fetched = 0;
+  while (enum_moniker->Next(1, moniker.Receive(), &fetched) == S_OK) {
+    ScopedComPtr<IPropertyBag> prop_bag;
+    hr = moniker->BindToStorage(0, 0, IID_IPropertyBag, prop_bag.ReceiveVoid());
+    if (FAILED(hr)) {
+      moniker.Release();
+      continue;
+    }
+
+    // Find the description or friendly name.
+    static const wchar_t* kPropertyNames[] = {
+      L"DevicePath", L"Description", L"FriendlyName"
+    };
+    ScopedVariant name;
+    for (size_t i = 0;
+         i < arraysize(kPropertyNames) && name.type() != VT_BSTR; ++i) {
+      prop_bag->Read(kPropertyNames[i], name.Receive(), 0);
+    }
+    if (name.type() == VT_BSTR) {
+      std::string device_path(base::SysWideToUTF8(V_BSTR(&name)));
+      if (device_path.compare(device_name.unique_id) == 0) {
+        // We have found the requested device
+        hr = moniker->BindToObject(0, 0, IID_IBaseFilter,
+                                   capture_filter.ReceiveVoid());
+        DVPLOG_IF(2, FAILED(hr)) << "Failed to bind camera filter.";
+        break;
+      }
+    }
+    moniker.Release();
+  }
+
+  *filter = capture_filter.Detach();
+  if (!*filter && SUCCEEDED(hr))
+    hr = HRESULT_FROM_WIN32(ERROR_NOT_FOUND);
+
+  return hr;
+}
+
+// Check if a Pin matches a category.
+bool PinMatchesCategory(IPin* pin, REFGUID category) {
+  DCHECK(pin);
+  bool found = false;
+  ScopedComPtr<IKsPropertySet> ks_property;
+  HRESULT hr = ks_property.QueryFrom(pin);
+  if (SUCCEEDED(hr)) {
+    GUID pin_category;
+    DWORD return_value;
+    hr = ks_property->Get(AMPROPSETID_Pin, AMPROPERTY_PIN_CATEGORY, NULL, 0,
+                          &pin_category, sizeof(pin_category), &return_value);
+    if (SUCCEEDED(hr) && (return_value == sizeof(pin_category))) {
+      found = (pin_category == category) ? true : false;
+    }
+  }
+  return found;
+}
+
+// Finds a IPin on a IBaseFilter given the direction an category.
+HRESULT GetPin(IBaseFilter* filter, PIN_DIRECTION pin_dir, REFGUID category,
+               IPin** pin) {
+  DCHECK(pin);
+  ScopedComPtr<IEnumPins> pin_emum;
+  HRESULT hr = filter->EnumPins(pin_emum.Receive());
+  if (pin_emum == NULL)
+    return hr;
+
+  // Get first unconnected pin.
+  hr = pin_emum->Reset();  // set to first pin
+  while ((hr = pin_emum->Next(1, pin, NULL)) == S_OK) {
+    PIN_DIRECTION this_pin_dir = static_cast<PIN_DIRECTION>(-1);
+    hr = (*pin)->QueryDirection(&this_pin_dir);
+    if (pin_dir == this_pin_dir) {
+      if (category == GUID_NULL || PinMatchesCategory(*pin, category))
+        return S_OK;
+    }
+    (*pin)->Release();
+  }
+
+  return E_FAIL;
+}
+
+// Release the format block for a media type.
+// http://msdn.microsoft.com/en-us/library/dd375432(VS.85).aspx
+void FreeMediaType(AM_MEDIA_TYPE* mt) {
+  if (mt->cbFormat != 0) {
+    CoTaskMemFree(mt->pbFormat);
+    mt->cbFormat = 0;
+    mt->pbFormat = NULL;
+  }
+  if (mt->pUnk != NULL) {
+    NOTREACHED();
+    // pUnk should not be used.
+    mt->pUnk->Release();
+    mt->pUnk = NULL;
+  }
+}
+
+// Delete a media type structure that was allocated on the heap.
+// http://msdn.microsoft.com/en-us/library/dd375432(VS.85).aspx
+void DeleteMediaType(AM_MEDIA_TYPE* mt) {
+  if (mt != NULL) {
+    FreeMediaType(mt);
+    CoTaskMemFree(mt);
+  }
+}
+
+// Help structure used for comparing video capture capabilities.
+struct ResolutionDiff {
+  int capability_index;
+  int diff_height;
+  int diff_width;
+  int diff_frame_rate;
+  media::VideoCaptureDevice::Format color;
+};
+
+bool CompareHeight(ResolutionDiff item1, ResolutionDiff item2) {
+  return abs(item1.diff_height) < abs(item2.diff_height);
+}
+
+bool CompareWidth(ResolutionDiff item1, ResolutionDiff item2) {
+  return abs(item1.diff_width) < abs(item2.diff_width);
+}
+
+bool CompareFrameRate(ResolutionDiff item1, ResolutionDiff item2) {
+  return abs(item1.diff_frame_rate) < abs(item2.diff_frame_rate);
+}
+
+bool CompareColor(ResolutionDiff item1, ResolutionDiff item2) {
+  return (item1.color < item2.color);
+}
+
+}  // namespace
+
+namespace media {
+
+// Name of a fake DirectShow filter that exist on computers with
+// GTalk installed.
+static const char kGoogleCameraAdapter[] = "google camera adapter";

[cpu_(ooo_6.6-7.5), 2011/06/27 18:10:27]

just fyi, this filtering is also done in libjingle, one day we should unify. Not
today though :)

[Per K, 2011/06/28 10:14:07]

Done.

+
+// Gets the names of all video capture devices connected to this computer.
+void VideoCaptureDevice::GetDeviceNames(Names* device_names) {
+  DCHECK(device_names);
+
+  app::win::ScopedCOMInitializer coinit;
+  ScopedComPtr<ICreateDevEnum> dev_enum;
+  HRESULT hr = dev_enum.CreateInstance(CLSID_SystemDeviceEnum, NULL,
+                                       CLSCTX_INPROC);
+  if (FAILED(hr))
+    return;
+
+  ScopedComPtr<IEnumMoniker> enum_moniker;
+  hr = dev_enum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,
+                                       enum_moniker.Receive(), 0);
+  if (FAILED(hr))
+    return;
+
+  device_names->clear();
+
+  // Enumerate all video capture devices.
+  ScopedComPtr<IMoniker> moniker;
+  int index = 0;
+  while (enum_moniker->Next(1, moniker.Receive(), NULL) == S_OK) {
+    Name device;
+    ScopedComPtr<IPropertyBag> prop_bag;
+    hr = moniker->BindToStorage(0, 0, IID_IPropertyBag, prop_bag.ReceiveVoid());
+    if (FAILED(hr)) {
+      moniker.Release();
+      continue;
+    }
+
+    // Find the description or friendly name.
+    ScopedVariant name;
+    hr = prop_bag->Read(L"Description", name.Receive(), 0);
+    if (FAILED(hr))
+      hr = prop_bag->Read(L"FriendlyName", name.Receive(), 0);
+
+    if (SUCCEEDED(hr) && name.type() == VT_BSTR) {
+      // Ignore all VFW drivers and the special Google Camera Adapter.
+      // Google Camera Adapter is not a real DirectShow camera device.
+      // VFW is very old Video for Windows drivers that can not be used.
+      const wchar_t* str_ptr = V_BSTR(&name);

[cpu_(ooo_6.6-7.5), 2011/06/27 18:10:27]

do we need to do this inside the loop?

[Per K, 2011/06/28 10:14:07]

? Yes- device_names is a list of all available video capture devices.

On 2011/06/27 18:10:27, cpu wrote:

+      const int name_length = arraysize(kGoogleCameraAdapter) - 1;
+
+      if ((wcsstr(str_ptr, L"(VFW)") == NULL) &&
+          wcslen(str_ptr) < name_length ||
+          (!(LowerCaseEqualsASCII(str_ptr, str_ptr + name_length,
+                                  kGoogleCameraAdapter)))) {
+        device.device_name = base::SysWideToUTF8(str_ptr);
+        name.Reset();
+        hr = prop_bag->Read(L"DevicePath", name.Receive(), 0);
+        if (FAILED(hr)) {
+          device.unique_id = device.device_name;
+        } else if (name.type() == VT_BSTR) {
+          device.unique_id = base::SysWideToUTF8(V_BSTR(&name));
+        }
+
+        device_names->push_back(device);
+      }
+    }
+    moniker.Release();
+  }
+}
+
+VideoCaptureDevice* VideoCaptureDevice::Create(const Name& device_name) {
+  VideoCaptureDeviceWin* self = new VideoCaptureDeviceWin(device_name);
+  if (!self || !self->Init()) {

[cpu_(ooo_6.6-7.5), 2011/06/27 18:10:27]

if (self && self->Init())
 return self;

[Per K, 2011/06/28 10:14:07]

Done.

+    delete self;
+    return NULL;
+  }
+  return self;
+}
+
+VideoCaptureDeviceWin::VideoCaptureDeviceWin(const Name& device_name)
+    : device_name_(device_name),
+      state_(kIdle) {
+}
+
+VideoCaptureDeviceWin::~VideoCaptureDeviceWin() {
+  if (media_control_)
+    media_control_->Stop();
+
+  if (graph_builder_) {
+    if (sink_filter_) {
+      graph_builder_->RemoveFilter(sink_filter_);
+      sink_filter_ = NULL;
+    }
+
+    if (capture_filter_)
+      graph_builder_->RemoveFilter(capture_filter_);
+
+    if (mjpg_filter_)
+      graph_builder_->RemoveFilter(mjpg_filter_);
+  }
+}
+
+bool VideoCaptureDeviceWin::Init() {
+  HRESULT hr = GetDeviceFilter(device_name_, capture_filter_.Receive());
+  if (!capture_filter_) {
+    DVLOG(2) << "Failed to create capture filter.";
+    return false;
+  }
+
+  hr = GetPin(capture_filter_, PINDIR_OUTPUT, PIN_CATEGORY_CAPTURE,
+              output_capture_pin_.Receive());
+  if (!output_capture_pin_) {
+    DVLOG(2) << "Failed to get capture output pin";
+    return false;
+  }
+
+  // Create the sink filter used for receiving Captured frames.
+  sink_filter_ = new SinkFilter(this);
+  if (sink_filter_ == NULL) {
+    DVLOG(2) << "Failed to create send filter";
+    return false;
+  }
+
+  input_sink_pin_ = sink_filter_->GetPin(0);
+
+  hr = graph_builder_.CreateInstance(CLSID_FilterGraph, NULL,
+                                     CLSCTX_INPROC_SERVER);
+  if (FAILED(hr)) {
+    DVLOG(2) << "Failed to create graph builder.";
+    return false;
+  }
+
+  hr = graph_builder_.QueryInterface(media_control_.Receive());
+  if (FAILED(hr)) {
+    DVLOG(2) << "Failed to create media control builder.";
+    return false;
+  }
+
+  hr = graph_builder_->AddFilter(capture_filter_, NULL);
+  if (FAILED(hr)) {
+    DVLOG(2) << "Failed to add the capture device to the graph.";
+    return false;
+  }
+
+  hr = graph_builder_->AddFilter(sink_filter_, NULL);
+  if (FAILED(hr)) {
+    DVLOG(2)<< "Failed to add the send filter to the graph.";
+    return false;
+  }
+
+  return CreateCapabilityMap();
+}
+
+void VideoCaptureDeviceWin::Allocate(
+    int width,
+    int height,
+    int frame_rate,
+    VideoCaptureDevice::EventHandler* observer) {
+  if (state_ != kIdle)
+    return;
+
+  observer_ = observer;
+  // Get the camera capability that best match the requested resolution.
+  const int capability_index = GetBestMatchedCapability(width, height,
+                                                        frame_rate);
+  Capability capability = capabilities_[capability_index];
+
+  // Reduce the frame rate if the requested frame rate is lower
+  // than the capability.
+  if (capability.frame_rate > frame_rate)
+    capability.frame_rate = frame_rate;
+
+  AM_MEDIA_TYPE* pmt = NULL;
+  VIDEO_STREAM_CONFIG_CAPS caps;
+
+  ScopedComPtr<IAMStreamConfig> stream_config;
+  HRESULT hr = output_capture_pin_.QueryInterface(stream_config.Receive());
+  if (FAILED(hr)) {
+    SetErrorState("Can't get the Capture format settings");
+    return;
+  }
+
+  // Get the windows capability from the capture device.
+  hr = stream_config->GetStreamCaps(capability_index, &pmt,
+                                    reinterpret_cast<BYTE*>(&caps));
+  if (SUCCEEDED(hr)) {
+    if (pmt->formattype == FORMAT_VideoInfo) {
+      VIDEOINFOHEADER* h = reinterpret_cast<VIDEOINFOHEADER*>(pmt->pbFormat);
+      if (capability.frame_rate > 0)
+        h->AvgTimePerFrame = kSecondsToReferenceTime / capability.frame_rate;
+    }
+    // Set the sink filter to request this capability.
+    sink_filter_->SetRequestedMediaCapability(capability);
+    // Order the capture device to use this capability.
+    hr = stream_config->SetFormat(pmt);
+  }
+
+  if (FAILED(hr))
+    SetErrorState("Failed to set capture device output format");
+
+  if (capability.color == VideoCaptureDevice::kMJPEG && !mjpg_filter_.get()) {
+    // Create MJPG filter if we need it.
+    hr = mjpg_filter_.CreateInstance(CLSID_MjpegDec, NULL, CLSCTX_INPROC);
+
+    if (SUCCEEDED(hr)) {
+      GetPin(mjpg_filter_, PINDIR_INPUT, GUID_NULL, input_mjpg_pin_.Receive());
+      GetPin(mjpg_filter_, PINDIR_OUTPUT, GUID_NULL,
+             output_mjpg_pin_.Receive());
+      hr = graph_builder_->AddFilter(mjpg_filter_, NULL);
+    }
+
+    if (FAILED(hr)) {
+      mjpg_filter_.Release();
+      input_mjpg_pin_.Release();
+      output_mjpg_pin_.Release();
+    }
+  }
+
+  if (capability.color == VideoCaptureDevice::kMJPEG && mjpg_filter_.get()) {
+    // Connect the camera to the MJPEG decoder.
+    hr = graph_builder_->ConnectDirect(output_capture_pin_, input_mjpg_pin_,
+                                       NULL);
+    // Connect the MJPEG filter to the Capture filter.
+    hr += graph_builder_->ConnectDirect(output_mjpg_pin_, input_sink_pin_,
+                                        NULL);
+  } else {
+    hr = graph_builder_->ConnectDirect(output_capture_pin_, input_sink_pin_,
+                                       NULL);
+  }
+
+  if (FAILED(hr)) {
+    SetErrorState("Failed to connect the Capture graph.");
+    return;
+  }
+
+  hr = media_control_->Pause();
+  if (FAILED(hr)) {
+    SetErrorState("Failed to Pause the Capture device. "
+                  "Is it already occupied?");
+    return;
+  }
+
+  // Get the capability back from the sink filter after the filter have been
+  // connected.
+  const Capability& used_capability = sink_filter_->ResultingCapability();
+  observer_->OnFrameInfo(used_capability);
+
+  state_ = kAllocated;
+}
+
+void VideoCaptureDeviceWin::Start() {
+  if (state_ != kAllocated)
+    return;
+
+  HRESULT hr = media_control_->Run();
+  if (FAILED(hr)) {
+    SetErrorState("Failed to start the Capture device.");
+    return;
+  }
+
+  state_ = kCapturing;
+}
+
+void VideoCaptureDeviceWin::Stop() {
+  if (state_ != kCapturing)
+    return;
+
+  HRESULT hr = media_control_->Stop();
+  if (FAILED(hr)) {
+    SetErrorState("Failed to stop the capture graph.");
+    return;
+  }
+
+  state_ = kAllocated;
+}
+
+void VideoCaptureDeviceWin::DeAllocate() {
+  if (state_ == kIdle)
+    return;
+
+  HRESULT hr = media_control_->Stop();
+  graph_builder_->Disconnect(output_capture_pin_);
+  graph_builder_->Disconnect(input_sink_pin_);
+
+  // If the _mjpg filter exist disconnect it even if it has not been used.
+  if (mjpg_filter_) {
+    graph_builder_->Disconnect(input_mjpg_pin_);
+    graph_builder_->Disconnect(output_mjpg_pin_);
+  }
+
+  if (FAILED(hr)) {
+    SetErrorState("Failed to Stop the Capture device");
+    return;
+  }
+
+  state_ = kIdle;
+}
+
+const VideoCaptureDevice::Name& VideoCaptureDeviceWin::device_name() {
+  return device_name_;
+}
+
+// Implements SinkFilterObserver::SinkFilterObserver.
+void VideoCaptureDeviceWin::FrameReceived(const uint8* buffer,
+                                          int length) {
+  observer_->OnIncomingCapturedFrame(buffer, length, base::Time::Now());
+}
+
+bool VideoCaptureDeviceWin::CreateCapabilityMap() {
+  ScopedComPtr<IAMStreamConfig> stream_config;
+  HRESULT hr = output_capture_pin_.QueryInterface(stream_config.Receive());
+  if (FAILED(hr)) {
+    DVLOG(2) << "Failed to get IAMStreamConfig interface from "
+                "capture device";
+    return false;
+  }
+
+  // Get interface used for getting the frame rate.
+  ScopedComPtr<IAMVideoControl> video_control;
+  hr = capture_filter_.QueryInterface(video_control.Receive());
+  DVLOG_IF(2, FAILED(hr)) << "IAMVideoControl Interface NOT SUPPORTED";
+
+  AM_MEDIA_TYPE* media_type = NULL;
+  VIDEO_STREAM_CONFIG_CAPS caps;
+  int count, size;
+
+  hr = stream_config->GetNumberOfCapabilities(&count, &size);
+  if (FAILED(hr)) {
+    DVLOG(2) << "Failed to GetNumberOfCapabilities";
+    return false;
+  }
+
+  for (int i = 0; i < count; ++i) {
+    hr = stream_config->GetStreamCaps(i, &media_type,
+                                      reinterpret_cast<BYTE*>(&caps));
+    if (FAILED(hr)) {
+      DVLOG(2) << "Failed to GetStreamCaps";
+      return false;
+    }
+
+    if (media_type->majortype == MEDIATYPE_Video &&
+        media_type->formattype == FORMAT_VideoInfo) {
+      Capability capability;
+      REFERENCE_TIME time_per_frame = 0;
+
+      VIDEOINFOHEADER* h =
+          reinterpret_cast<VIDEOINFOHEADER*>(media_type->pbFormat);
+      capability.width = h->bmiHeader.biWidth;
+      capability.height = h->bmiHeader.biHeight;
+      time_per_frame = h->AvgTimePerFrame;
+
+      // Try to get the max frame rate from IAMVideoControl.
+      if (video_control.get()) {
+        LONGLONG* max_fps_ptr;
+        LONG list_size;
+        SIZE size;
+        size.cx = capability.width;
+        size.cy = capability.height;
+
+        // GetFrameRateList doesn't return max frame rate always
+        // eg: Logitech Notebook. This may be due to a bug in that API
+        // because GetFrameRateList array is reversed in the above camera. So
+        // a util method written. Can't assume the first value will return
+        // the max fps.
+        hr = video_control->GetFrameRateList(output_capture_pin_, i, size,
+                                             &list_size, &max_fps_ptr);
+
+        if (SUCCEEDED(hr) && list_size > 0) {
+          int min_time =  *std::min_element(max_fps_ptr,
+                                            max_fps_ptr + list_size);
+          capability.frame_rate = (min_time > 0) ?
+              kSecondsToReferenceTime / min_time : 0;
+        } else {
+          // Get frame rate from VIDEOINFOHEADER.
+          capability.frame_rate = (time_per_frame > 0) ?
+              static_cast<int>(kSecondsToReferenceTime / time_per_frame) : 0;
+        }
+      } else {
+        // Get frame rate from VIDEOINFOHEADER since IAMVideoControl is
+        // not supported.
+        capability.frame_rate = (time_per_frame > 0) ?
+            static_cast<int>(kSecondsToReferenceTime / time_per_frame) : 0;
+      }
+
+      // We can't switch MEDIATYPE :~(.
+      if (media_type->subtype == kMediaSubTypeI420) {
+        capability.color = VideoCaptureDevice::kI420;
+      } else if (media_type->subtype == MEDIASUBTYPE_IYUV) {
+        // This is identical to kI420.
+        capability.color = VideoCaptureDevice::kI420;
+      } else if (media_type->subtype == MEDIASUBTYPE_RGB24) {
+        capability.color = VideoCaptureDevice::kRGB24;
+      } else if (media_type->subtype == MEDIASUBTYPE_YUY2) {
+        capability.color = VideoCaptureDevice::kYUY2;
+      } else if (media_type->subtype == MEDIASUBTYPE_MJPG) {
+        capability.color = VideoCaptureDevice::kMJPEG;
+      } else {
+        WCHAR guid_str[128];
+        StringFromGUID2(media_type->subtype, guid_str, arraysize(guid_str));
+        DVLOG(2) << "Device support unknown media type " << guid_str;
+        continue;
+      }
+      capabilities_[i] = capability;
+    }
+    DeleteMediaType(media_type);
+    media_type = NULL;
+  }
+
+  return capabilities_.size() > 0;
+}
+
+// Loops through the list of capabilities and returns an index of the best
+// matching capability.
+// The algorithm prioritize height, width, frame rate and color format in that
+// order.
+int VideoCaptureDeviceWin::GetBestMatchedCapability(int requested_width,
+                                                    int requested_height,
+                                                    int requested_frame_rate) {
+  std::list<ResolutionDiff> diff_list;
+
+  // Loop through the candidates to create a list of differentials between the
+  // requested resolution and the camera capability.
+  for (CapabilityMap::iterator iterator = capabilities_.begin();
+       iterator != capabilities_.end();
+       ++iterator) {
+    Capability capability = iterator->second;
+
+    ResolutionDiff diff;
+    diff.capability_index = iterator->first;
+    diff.diff_width = capability.width - requested_width;
+    diff.diff_height = capability.height - requested_height;
+    diff.diff_frame_rate = capability.frame_rate - requested_frame_rate;
+    diff.color = capability.color;
+    diff_list.push_back(diff);
+  }
+
+  // Sort the best height candidates.
+  diff_list.sort(&CompareHeight);
+  int best_diff = diff_list.front().diff_height;
+  for (std::list<ResolutionDiff>::iterator it = diff_list.begin();
+       it != diff_list.end(); ++it) {
+    if (it->diff_height != best_diff) {
+      // Remove all candidates but the best.
+      diff_list.erase(it, diff_list.end());
+      break;
+    }
+  }
+
+  // Sort the best width candidates.
+  diff_list.sort(&CompareWidth);
+  best_diff = diff_list.front().diff_width;
+  for (std::list<ResolutionDiff>::iterator it = diff_list.begin();
+       it != diff_list.end(); ++it) {
+    if (it->diff_width != best_diff) {
+      // Remove all candidates but the best.
+      diff_list.erase(it, diff_list.end());
+      break;
+    }
+  }
+
+  // Sort the best frame rate candidates.
+  diff_list.sort(&CompareFrameRate);
+  best_diff = diff_list.front().diff_frame_rate;
+  for (std::list<ResolutionDiff>::iterator it = diff_list.begin();
+       it != diff_list.end(); ++it) {
+    if (it->diff_frame_rate != best_diff) {
+      diff_list.erase(it, diff_list.end());
+      break;
+    }
+  }
+
+  // Decide the best color format.
+  diff_list.sort(&CompareColor);
+  return diff_list.front().capability_index;
+}
+
+void VideoCaptureDeviceWin::SetErrorState(const char* reason) {
+  DLOG(ERROR) << reason;
+  state_ = kError;
+  observer_->OnError();
+}
+
+}  // namespace media