如何获取directshow网络摄像头视频流的宽度和高度

Question

我发现了一些代码，可以从我的网络摄像头访问原始像素数据。但是，如果图像的宽度，高度，像素格式以及数据跨度（音调，内存填充或任何您想要调用它的内容）的宽度*每像素的字节数*

#include <windows.h> 
#include <dshow.h> 

#pragma comment(lib,"Strmiids.lib") 

#define DsHook(a,b,c) if (!c##_) { INT_PTR* p=b+*(INT_PTR**)a; VirtualProtect(&c##_,4,PAGE_EXECUTE_READWRITE,&no);\ 
              *(INT_PTR*)&c##_=*p; VirtualProtect(p, 4,PAGE_EXECUTE_READWRITE,&no); *p=(INT_PTR)c; } 


// Here you get image video data in buf/len. Process it before calling Receive_ because renderer dealocates it. 
HRESULT (__stdcall * Receive_) (void* inst, IMediaSample *smp) ; 
HRESULT __stdcall Receive (void* inst, IMediaSample *smp) {  
    BYTE*  buf; smp->GetPointer(&buf); DWORD len = smp->GetActualDataLength(); 
    //AM_MEDIA_TYPE* info; 
    //smp->GetMediaType(&info); 
    HRESULT ret = Receive_ (inst, smp); 
    return ret; 
} 

int WINAPI WinMain(HINSTANCE inst,HINSTANCE prev,LPSTR cmd,int show){ 
    HRESULT hr = CoInitialize(0); MSG msg={0}; DWORD no; 

    IGraphBuilder* graph= 0; hr = CoCreateInstance(CLSID_FilterGraph, 0, CLSCTX_INPROC,IID_IGraphBuilder, (void **)&graph); 
    IMediaControl* ctrl = 0; hr = graph->QueryInterface(IID_IMediaControl, (void **)&ctrl); 

    ICreateDevEnum* devs = 0; hr = CoCreateInstance (CLSID_SystemDeviceEnum, 0, CLSCTX_INPROC, IID_ICreateDevEnum, (void **) &devs); 
    IEnumMoniker* cams = 0; hr = devs?devs->CreateClassEnumerator (CLSID_VideoInputDeviceCategory, &cams, 0):0; 
    IMoniker*  mon = 0; hr = cams->Next (1,&mon,0); // get first found capture device (webcam?)  
    IBaseFilter* cam = 0; hr = mon->BindToObject(0,0,IID_IBaseFilter, (void**)&cam); 
           hr = graph->AddFilter(cam, L"Capture Source"); // add web cam to graph as source 
    IEnumPins*  pins = 0; hr = cam?cam->EnumPins(&pins):0; // we need output pin to autogenerate rest of the graph 
    IPin*   pin = 0; hr = pins?pins->Next(1,&pin, 0):0; // via graph->Render 
           hr = graph->Render(pin); // graph builder now builds whole filter chain including MJPG decompression on some webcams 
    IEnumFilters* fil = 0; hr = graph->EnumFilters(&fil); // from all newly added filters 
    IBaseFilter* rnd = 0; hr = fil->Next(1,&rnd,0); // we find last one (renderer) 
           hr = rnd->EnumPins(&pins); // because data we are intersted in are pumped to renderers input pin 
           hr = pins->Next(1,&pin, 0); // via Receive member of IMemInputPin interface 
    IMemInputPin* mem = 0; hr = pin->QueryInterface(IID_IMemInputPin,(void**)&mem); 

    DsHook(mem,6,Receive); // so we redirect it to our own proc to grab image data 

    hr = ctrl->Run(); 

    while (GetMessage( &msg, 0, 0, 0)) { 
     TranslateMessage(&msg); 
     DispatchMessage( &msg); 
    } 
}; 

奖励积分，如果你能告诉我如何让这件事情不呈现一个窗口，但仍然让我访问图像数据。

Answer 1

这真的很丑。请不要这样做。而不是像样本采集器那样插入传递过滤器（因为我在同一主题上回复了您的其他帖子）。将采样器连接到null渲染器可以在不渲染图像的情况下以干净，安全的方式获取位。

要获得跨步，您需要通过ISampleGrabber或IPin :: ConnectionMediaType获取媒体类型。格式块将是VIDEOINFOHEADER或VIDEOINFOHEADER2（检查格式GUID）。 bitmapinfo头文件biWidth和biHeight定义了位图维度（因此也定义了步幅）。如果RECT不是空的，则定义位图内的相关图像区域。

触碰此帖后我现在不得不洗手。

Answer 2

我很抱歉。当界面被创建时，可能不是最好的程序员。

// Here you get image video data in buf/len. Process it before calling Receive_ because renderer dealocates it. 

BITMAPINFOHEADER bmpInfo; // current bitmap header info 
int stride; 

HRESULT (__stdcall * Receive_) (void* inst, IMediaSample *smp) ; 
HRESULT __stdcall Receive (void* inst, IMediaSample *smp) 
{  
    BYTE*  buf; smp->GetPointer(&buf); DWORD len = smp->GetActualDataLength(); 
    HRESULT ret = Receive_ (inst, smp); 

    AM_MEDIA_TYPE* info; 
    HRESULT hr = smp->GetMediaType(&info); 
    if (hr != S_OK) 
    { //TODO: error } 
    else 
    { 
     if (type->formattype == FORMAT_VideoInfo) 
     { 
      const VIDEOINFOHEADER * vi = reinterpret_cast<VIDEOINFOHEADER*>(type->pbFormat); 
      const BITMAPINFOHEADER & bmiHeader = vi->bmiHeader; 
      //! now the bmiHeader.biWidth contains the data stride 
      stride = bmiHeader.biWidth; 

      bmpInfo = bmiHeader; 
      int width = (vi->rcTarget.right - vi->rcTarget.left); 
      //! replace the data stride be the actual width 
      if (width != 0) 
       bmpInfo.biWidth = width; 

     } 
     else 
     { // unsupported format } 
    } 
    DeleteMediaType(info); 

    return ret; 
} 

Answer 3

这里是如何添加Null渲染抑制呈现窗口。创建IGraphBuilder后直接添加*

//create null renderer and add null renderer to graph 
IBaseFilter *m_pNULLRenderer; hr = CoCreateInstance(CLSID_NullRenderer, NULL, CLSCTX_INPROC_SERVER, IID_IBaseFilter, (void **)&m_pNULLRenderer); 
           hr = graph->AddFilter(m_pNULLRenderer, L"Null Renderer"); 

dshook hack是我知道的唯一一个优雅的directshow代码。

以我的经验，DirectShow API是一个令人费解的噩梦，需要数百行代码才能完成最简单的操作，并调整整个编程范例以访问您的网络摄像头。所以如果这个代码为你做了这个工作，就像它为我做的那样，使用它并享受更少的代码行来维护。