Directshow 两次无法启动捕获

Question

我正在尝试按照 windows 开发中心上的 DirectShow 示例来制作我自己的应用程序，该应用程序可以将屏幕和音频捕获到视频：Capturing Video to an AVI File

第一次开始抓图一切正常，但第二次没有任何反应，没有出现带视频的文件。有没有可能我忘记取消初始化 sometfing？

更新问题似乎不在于缺少发布。第二次流写入文件 1.avi 正在创建但它是空的，当 pMediaControl->Stop(); 完成后它会自动删除

更新2 第二次我发现：

                hr = pBuild->RenderStream(
                &PIN_CATEGORY_CAPTURE, // Pin category.
                &MEDIATYPE_Video,      // Media type.
                pCap,                  // Capture filter.
                NULL,                  // Intermediate filter (optional).
                pMux);                 // Mux or file sink filter.

returnsE_INVALIDARG。所以我添加了 (using this):

                if (a == 1) {
                    CComPtr<IPin> sourcePin;
                    CComPtr<IPin> dumpPin;
                    sourcePin = GetPin(pMux, PINDIR_OUTPUT);
                    dumpPin   = GetPin(pCap, PINDIR_INPUT);
                    hr = ppGraph->Connect(sourcePin, dumpPin);
                }

而且我第二次发现 dumpPin 值为 NULL。hr = ppGraph->AddFilter(pCap, L"Capture Filter"); 运行正常。接下来我可以在哪里挖掘以查找错误？

（代码已更新）

我的代码：

#include "stdafx.h"
#include <iostream>

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

#include <atlbase.h>
#include <dshow.h>


#include <vector>
#include <string> 

#pragma comment(lib, "strmiids")


IPin *GetPin(IBaseFilter *pFilter, PIN_DIRECTION PinDir)
{
    BOOL       bFound = FALSE;
    IEnumPins  *pEnum;
    IPin       *pPin;

    pFilter->EnumPins(&pEnum);
    while (pEnum->Next(1, &pPin, 0) == S_OK)
    {
        PIN_DIRECTION PinDirThis;
        pPin->QueryDirection(&PinDirThis);
        if (bFound = (PinDir == PinDirThis))
            break;
        pPin->Release();
    }
    pEnum->Release();
    return (bFound ? pPin : 0);
}

HRESULT EnumerateDevices(REFGUID category, IEnumMoniker **ppEnum)
{
    // Create the System Device Enumerator.
    ICreateDevEnum *pDevEnum;
    HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL,
        CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pDevEnum));

    if (SUCCEEDED(hr))
    {
        // Create an enumerator for the category.
        hr = pDevEnum->CreateClassEnumerator(category, ppEnum, 0);
        if (hr == S_FALSE)
        {
            hr = VFW_E_NOT_FOUND;  // The category is empty. Treat as an error.
        }
        pDevEnum->Release();
    }
    return hr;
}

HRESULT InitCaptureGraphBuilder(
    IGraphBuilder **ppGraph,  // Receives the pointer.
    ICaptureGraphBuilder2 **ppBuild  // Receives the pointer.
)
{
    if (!ppGraph || !ppBuild)
    {
        return E_POINTER;
    }
    IGraphBuilder *pGraph = NULL;
    ICaptureGraphBuilder2 *pBuild = NULL;

    // Create the Capture Graph Builder.
    HRESULT hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL,
        CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void**)&pBuild);
    if (SUCCEEDED(hr))
    {
        // Create the Filter Graph Manager.
        hr = CoCreateInstance(CLSID_FilterGraph, 0, CLSCTX_INPROC_SERVER,
            IID_IGraphBuilder, (void**)&pGraph);
        if (SUCCEEDED(hr))
        {
            // Initialize the Capture Graph Builder.
            pBuild->SetFiltergraph(pGraph);

            // Return both interface pointers to the caller.
            *ppBuild = pBuild;
            *ppGraph = pGraph; // The caller must release both interfaces.
            return S_OK;
        }
        else
        {
            pBuild->Release();
        }
    }
    return hr; // Failed
}

struct Capture {
    IPropertyBag *pPropBag;
    IGraphBuilder *ppGraph;
    IBaseFilter *pCap;
    ICaptureGraphBuilder2 *pBuild;
};

void DisplayDeviceInformation(IEnumMoniker *pEnum,int a)
{
    IMoniker *pMoniker = NULL;
    std::vector<Capture> captures;

    while (pEnum->Next(1, &pMoniker, NULL) == S_OK)
    {
        IPropertyBag *pPropBag;
        HRESULT hr = pMoniker->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
        if (FAILED(hr))
        {
            pMoniker->Release();
            continue;
        }

        VARIANT var;
        VariantInit(&var);

        hr = pPropBag->Read(L"DevicePath", &var, 0);
        if (SUCCEEDED(hr))
        {
            // The device path is not intended for display.
            printf("Device path: %S\n", var.bstrVal);
            VariantClear(&var);
        }

        IGraphBuilder *ppGraph;
        ICaptureGraphBuilder2 *pBuild; // Capture Graph Builder
        hr = InitCaptureGraphBuilder(&ppGraph, &pBuild);


        IBaseFilter *pCap; // Video capture filter.
        hr = pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pCap);
        if (SUCCEEDED(hr))
        {
            std::wstring name = std::wstring(L"C:\a\") + std::to_wstring(a) + std::wstring(L".avi");
            const wchar_t *cname = name.c_str();
            hr = ppGraph->AddFilter(pCap, L"Capture Filter");
            if (SUCCEEDED(hr)) {
                IBaseFilter *pMux;
                hr = pBuild->SetOutputFileName(
                    &MEDIASUBTYPE_Avi,  // Specifies AVI for the target file.
                    cname, // File name.
                    &pMux,              // Receives a pointer to the mux.
                    NULL);              // (Optional) Receives a pointer to the file sink.

                if (a == 1) {
                    CComPtr<IPin> sourcePin;
                    CComPtr<IPin> dumpPin;

                    sourcePin = GetPin(pMux, PINDIR_OUTPUT);
                    dumpPin   = GetPin(pCap, PINDIR_INPUT);

                    hr = ppGraph->Connect(sourcePin, dumpPin);

                }

                hr = pBuild->RenderStream(
                    &PIN_CATEGORY_CAPTURE, // Pin category.
                    &MEDIATYPE_Video,      // Media type.
                    pCap,                  // Capture filter.
                    NULL,                  // Intermediate filter (optional).
                    pMux);                 // Mux or file sink filter.

                                           // Release the mux filter.
                pMux->Release();

                IConfigAviMux *pConfigMux = NULL;
                hr = pMux->QueryInterface(IID_IConfigAviMux, (void**)&pConfigMux);
                if (SUCCEEDED(hr))
                {
                    pConfigMux->SetMasterStream(0);
                    pConfigMux->Release();
                }

                IConfigInterleaving *pInterleave = NULL;
                hr = pMux->QueryInterface(IID_IConfigInterleaving, (void**)&pInterleave);
                if (SUCCEEDED(hr))
                {
                    pInterleave->put_Mode(INTERLEAVE_CAPTURE);
                    pInterleave->Release();
                }
                pMux->Release();
            }
        }

        Capture capt;
        capt.ppGraph  = ppGraph;
        capt.pPropBag = pPropBag;
        capt.pCap = pCap;
        capt.pBuild = pBuild;
        captures.push_back(capt);

    }

    for (auto cap : captures)
    {
        IMediaControl* pMediaControl;
        cap.ppGraph->QueryInterface(&pMediaControl);
        pMediaControl->Run();
    }

    Sleep(5000);

    for (auto cap : captures)
    {
        IMediaControl* pMediaControl;
        cap.ppGraph->QueryInterface(&pMediaControl);
        pMediaControl->Stop();
        pMediaControl->Release();

        cap.pCap->Release();

        cap.ppGraph->Release();
        cap.pBuild->Release();

        cap.pPropBag->Release();
    }

    pMoniker->Release();
}

int _tmain(int argc, _TCHAR* argv[])
{
    HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
    for (int a = 0; a <= 1; a++) {

        if (SUCCEEDED(hr))
        {
            IEnumMoniker *pEnum;

            hr = EnumerateDevices(CLSID_VideoInputDeviceCategory, &pEnum);
            if (SUCCEEDED(hr))
            {
                DisplayDeviceInformation(pEnum,a);
                pEnum->Release();
            }

        }
    }
    if (SUCCEEDED(hr))
    {
        CoUninitialize();
    }


    int i;
    std::cin >> i;
    return 0;
}

Answer 1

您可能需要在 DisplayDeviceInformation 函数结束时释放 ppGraph、pBuild、pMediaControl 和 pCap，并在循环结束时释放 pMux。最好改用某种智能指针。

Answer 2

我没有弄清楚如何解决这个问题，所以我只是使用了外部进程的生成。

Directshow 两次无法启动捕获

Directshow cant start capture twice

c++

webcam

directshow