Question

我发现了一些代码，可以让我访问网络摄像头的原始像素数据。但是我需要知道图像的宽度，高度，像素格式，最好是数据步幅（音高，内存填充或任何你想要调用它），如果它不是宽度*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 ); 
    }
};

如果你可以告诉我如何让这个东西不渲染窗口但仍让我访问图像数据，那么

奖励积分。

Answer 1

那真的很难看。请不要这样做。插入一个像样本采集器一样的传递过滤器（因为我在同一主题上回复了你的另一篇文章）。将样本抓取器连接到空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。

要获得进步，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标头biWidth和biHeight定义位图尺寸（因此是步幅）。如果RECT不为空，则定义位图内的相关图像区域。

触摸这篇文章后，我现在要洗手了。

Answer 2

我很抱歉。创建界面时，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

以下是添加禁止渲染窗口的Null Renderer的方法。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");

那个dshook hack是我所知道的唯一优雅的directshow代码。

根据我的经验，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，并且需要调整整个编程范例才能访问您的网络摄像头。因此，如果此代码为您完成工作，就像它为我所做的那样，使用它并享受更少的代码行来维护。

如何获得directshow网络摄像头视频流的宽度和高度

3 个答案: