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疑问/问题的DirectShow：视频预览和图像（有工作代码）
- 如果有人可以推荐我一个很好的免费托管的网站，我可以提供整个项目文件。
- 正如下面的文字所述，TakePicture（）方法在HTC HD 2设备上无法正常工作。如果有人能看下面的代码并告诉我这是对还是错，我会这么做。
介绍
最近，我问一个关于question显示视频预览，同时相机的图像和旋转与DirectShow的视频流。关于这个主题的棘手问题是，很难找到好的例子，而且对于那些对Windows编程和C++不熟悉的人来说，文档和框架本身很难理解。
不过，我设法创建了一个实现大多数这些功能的类，并且可能适用于大多数移动设备。可能是因为DirectShow的实现在很大程度上依赖于设备本身。我只能用HTC HD和HTC HD2来测试它，它们被称为非常不兼容。
HTC HD
- 工作：视频预览，写图片文件
- 不工作：设置视频分辨率（崩溃），设置照片分辨率（低质量）
HTC HD 2
- 工作：设置视频分辨率，设置照片分辨率
- 问题的：视频预览旋转
- 不工作：写照片文件
通过提供工作的例子更容易为别人，我决定分享一切我有这么远低于。为了简单起见，我删除了所有的错误处理。就文档而言，我可以推荐您阅读MSDN documentation，之后的代码非常简单。
void Camera::Init()
{
CreateComObjects();
_captureGraphBuilder->SetFiltergraph(_filterGraph);
InitializeVideoFilter();
InitializeStillImageFilter();
}
Dipslay视频预览（使用任何手持式测试工作）：
void Camera::DisplayVideoPreview(HWND windowHandle)
{
IVideoWindow *_vidWin;
_filterGraph->QueryInterface(IID_IMediaControl,(void **) &_mediaControl);
_filterGraph->QueryInterface(IID_IVideoWindow, (void **) &_vidWin);
_videoCaptureFilter->QueryInterface(IID_IAMVideoControl,
(void**) &_videoControl);
_captureGraphBuilder->RenderStream(&PIN_CATEGORY_PREVIEW,
&MEDIATYPE_Video, _videoCaptureFilter, NULL, NULL);
CRect rect;
long width, height;
GetClientRect(windowHandle, &rect);
_vidWin->put_Owner((OAHWND)windowHandle);
_vidWin->put_WindowStyle(WS_CHILD | WS_CLIPSIBLINGS);
_vidWin->get_Width(&width);
_vidWin->get_Height(&height);
height = rect.Height();
_vidWin->put_Height(height);
_vidWin->put_Width(rect.Width());
_vidWin->SetWindowPosition(0,0, rect.Width(), height);
_mediaControl->Run();
}
HTC HD2：如果设置SetPhotoResolution（）被调用FindPin将返回E_FAIL。如果不是，它将创建一个充满空字节的文件。 HTC HD：作品
void Camera::TakePicture(WCHAR *fileName)
{
CComPtr<IFileSinkFilter> fileSink;
CComPtr<IPin> stillPin;
CComPtr<IUnknown> unknownCaptureFilter;
CComPtr<IAMVideoControl> videoControl;
_imageSinkFilter.QueryInterface(&fileSink);
fileSink->SetFileName(fileName, NULL);
_videoCaptureFilter.QueryInterface(&unknownCaptureFilter);
_captureGraphBuilder->FindPin(unknownCaptureFilter, PINDIR_OUTPUT,
&PIN_CATEGORY_STILL, &MEDIATYPE_Video, FALSE, 0, &stillPin);
_videoCaptureFilter.QueryInterface(&videoControl);
videoControl->SetMode(stillPin, VideoControlFlag_Trigger);
}
设置分辨率：适用于HTC HD2。HTC HD不允许SetVideoResolution（），仅提供一个低分辨率照片分辨率：
void Camera::CreateComObjects()
{
CoInitialize(NULL);
CoCreateInstance(CLSID_CaptureGraphBuilder, NULL, CLSCTX_INPROC_SERVER,
IID_ICaptureGraphBuilder2, (void **) &_captureGraphBuilder);
CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,
IID_IGraphBuilder, (void **) &_filterGraph);
CoCreateInstance(CLSID_VideoCapture, NULL, CLSCTX_INPROC,
IID_IBaseFilter, (void**) &_videoCaptureFilter);
CoCreateInstance(CLSID_IMGSinkFilter, NULL, CLSCTX_INPROC,
IID_IBaseFilter, (void**) &_imageSinkFilter);
}
void Camera::InitializeVideoFilter()
{
_videoCaptureFilter->QueryInterface(&_propertyBag);
wchar_t deviceName[MAX_PATH] = L"\0";
GetDeviceName(deviceName);
CComVariant comName = deviceName;
CPropertyBag propertyBag;
propertyBag.Write(L"VCapName", &comName);
_propertyBag->Load(&propertyBag, NULL);
_filterGraph->AddFilter(_videoCaptureFilter,
L"Video Capture Filter Source");
}
void Camera::InitializeStillImageFilter()
{
_filterGraph->AddFilter(_imageSinkFilter, L"Still image filter");
_captureGraphBuilder->RenderStream(&PIN_CATEGORY_STILL,
&MEDIATYPE_Video, _videoCaptureFilter, NULL, _imageSinkFilter);
}
void Camera::GetDeviceName(WCHAR *deviceName)
{
HRESULT hr = S_OK;
HANDLE handle = NULL;
DEVMGR_DEVICE_INFORMATION di;
GUID guidCamera = { 0xCB998A05, 0x122C, 0x4166, 0x84, 0x6A, 0x93, 0x3E,
0x4D, 0x7E, 0x3C, 0x86 };
di.dwSize = sizeof(di);
handle = FindFirstDevice(DeviceSearchByGuid, &guidCamera, &di);
StringCchCopy(deviceName, MAX_PATH, di.szLegacyName);
}
全头文件：
void Camera::SetVideoResolution(int width, int height)
{
SetResolution(true, width, height);
}
void Camera::SetPhotoResolution(int width, int height)
{
SetResolution(false, width, height);
}
void Camera::SetResolution(bool video, int width, int height)
{
IAMStreamConfig *config;
config = NULL;
if (video)
{
_captureGraphBuilder->FindInterface(&PIN_CATEGORY_PREVIEW,
&MEDIATYPE_Video, _videoCaptureFilter, IID_IAMStreamConfig,
(void**) &config);
}
else
{
_captureGraphBuilder->FindInterface(&PIN_CATEGORY_STILL,
&MEDIATYPE_Video, _videoCaptureFilter, IID_IAMStreamConfig,
(void**) &config);
}
int resolutions, size;
VIDEO_STREAM_CONFIG_CAPS caps;
config->GetNumberOfCapabilities(&resolutions, &size);
for (int i = 0; i < resolutions; i++)
{
AM_MEDIA_TYPE *mediaType;
if (config->GetStreamCaps(i, &mediaType,
reinterpret_cast<BYTE*>(&caps)) == S_OK)
{
int maxWidth = caps.MaxOutputSize.cx;
int maxHeigth = caps.MaxOutputSize.cy;
if(maxWidth == width && maxHeigth == height)
{
VIDEOINFOHEADER *info =
reinterpret_cast<VIDEOINFOHEADER*>(mediaType->pbFormat);
info->bmiHeader.biWidth = maxWidth;
info->bmiHeader.biHeight = maxHeigth;
info->bmiHeader.biSizeImage = DIBSIZE(info->bmiHeader);
config->SetFormat(mediaType);
DeleteMediaType(mediaType);
break;
}
DeleteMediaType(mediaType);
}
}
}
用于构建过滤器图表并创建COM对象的其他方法：
#ifndef __CAMERA_H__
#define __CAMERA_H__
class Camera
{
public:
void Init();
void DisplayVideoPreview(HWND windowHandle);
void TakePicture(WCHAR *fileName);
void SetVideoResolution(int width, int height);
void SetPhotoResolution(int width, int height);
private:
CComPtr<ICaptureGraphBuilder2> _captureGraphBuilder;
CComPtr<IGraphBuilder> _filterGraph;
CComPtr<IBaseFilter> _videoCaptureFilter;
CComPtr<IPersistPropertyBag> _propertyBag;
CComPtr<IMediaControl> _mediaControl;
CComPtr<IAMVideoControl> _videoControl;
CComPtr<IBaseFilter> _imageSinkFilter;
void GetDeviceName(WCHAR *deviceName);
void InitializeVideoFilter();
void InitializeStillImageFilter();
void CreateComObjects();
void SetResolution(bool video, int width, int height);
};
#endif