我正在使用Logitech C930e网络摄像头进行视频聊天,该应用程序是使用DirectShow创建的。到目前为止,我已能够使用YUY2或mJPEG格式的原始流。无论如何,我发现该网络摄像头支持通过UVC接口进行硬件H264编码。
目前,我正在使用标准方法获取可能的网络摄像头捕获引脚配置,但没有H264引脚。
void list_cameras {
ICreateDevEnum *pDevEnum = nullptr;
IEnumMoniker *pEnum = nullptr;
// Create the System Device Enumerator.
HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, nullptr,
CLSCTX_INPROC_SERVER, IID_ICreateDevEnum,
reinterpret_cast<void**>(&pDevEnum));
if (SUCCEEDED(hr)) {
// Create an enumerator for the video capture category.
hr = pDevEnum->CreateClassEnumerator(
CLSID_VideoInputDeviceCategory,
&pEnum, 0);
if (hr == S_FALSE) {
return;
}
}
IMoniker *pMoniker = nullptr; // IMoniker is the device
int index = 0;
// for each device
while (pEnum->Next(1, &pMoniker, nullptr) == S_OK) {
// bind camera to filter to be able to use it
if (cam.device->BindToObject(nullptr, nullptr, IID_IBaseFilter, reinterpret_cast<void**>(&_pCapture)) != S_OK) {
continue;
}
// fetch the configuration interface
IAMStreamConfig *pConfig = nullptr;
HRESULT hr = _capture->FindInterface(
&PIN_CATEGORY_CAPTURE, // Preview pin.
nullptr, // Any media type.
_pCapture, // Pointer to the capture filter.
IID_IAMStreamConfig, reinterpret_cast<void**>(&pConfig));
if (FAILED(hr)) {
continue;
}
// fetch possible configurations
int iCount = 0, iSize = 0;
if (pConfig->GetNumberOfCapabilities(&iCount, &iSize) != S_OK) {
continue;
}
// store each configuration
AM_MEDIA_TYPE *pmtConfig;
for (int iFormat = 0; iFormat < iCount; iFormat++) {
// get config
VIDEO_STREAM_CONFIG_CAPS scc;
if (pConfig->GetStreamCaps(iFormat, &pmtConfig, reinterpret_cast<BYTE*>(&scc)) != S_OK) {
continue;
}
// copy config data
VIDEOINFOHEADER *pVih = new VIDEOINFOHEADER(); // deleted afterwards
*pVih = *reinterpret_cast<VIDEOINFOHEADER *>(pmtConfig->pbFormat);
AM_MEDIA_TYPE mt;
mt = *pmtConfig;
mt.pbFormat = reinterpret_cast<BYTE *>(pVih);
auto fcc = FOURCCMap(pVih->bmiHeader.biCompression);
// wrap it
CameraConfig config = { mt, pVih->bmiHeader.biWidth, pVih->bmiHeader.biHeight, 1000 / (static_cast<float>(pVih->AvgTimePerFrame) / 10000), fcc };
// if resolution is bad (or unsupported), skip this configuration
if (config.width == 0 || config.height == 0 ) // bad
continue;
cam.configurations.push_back(config);
}
_cameras.push_back(cam);
pConfig->Release();
_pCapture->Release();
}
pEnum->Release();
pDevEnum->Release();
}
_cameras
是一个 Camera 类的向量,定义如下:
typedef struct {
//! Pointer to DirectShow device.
DSDevice device;
//! Camera name
string name;
//! List of supported configurations.
vector<CameraConfig> configurations; // list of all available configurations
//! Index of selected configuration.
int selected;
} Camera;
_pCapture
是指向创建的捕获过滤器的指针。
CameraConfig
定义如下:
typedef struct {
//! Media type.
AM_MEDIA_TYPE _mediaType;
//! Output width.
int width;
//! Outpus height.
int height;
//! Output framerate.
float fps;
//! Compression algoritm. YUY2 and mJPEG are supported for now.
FOURCCMap compression;
} CameraConfig;
如何实现对UVC设备的支持?哪些硬件编码器参数可以被控制?
谢谢。
IAMStreamConfig
等公认的方式(如YUY2,MJPG)或某些供应商特定的方式(SDK等),以特定于该型号的方式暴露出来。 - Roman R.DirectShowCaptureCapabilities
工具,通过IAMStreamConfig
接口以编程方式显示所有内容。另一种方法是使用插入捕获过滤器的GraphStudioNext
并浏览引脚媒体类型。无论哪种方式,您都应该看到H264
或AVC1
子类型或biCompression
值。 - Roman R.IKsPropertySet::Get
方法显示PIN_CATEGORY_CAPTURE
的引脚感兴趣。 - Roman R.