How to write an avi file with DirectShow - c++

Question

I'm trying to write an avi video file based on the streaming of my Decklink SDI card, after looking in the internet and here I wrote this code by my problem is that the program doesn't write the file here 's the code:
#include <Windows.h>
#include <DShow.h>
#include <iostream>
int main(void)
{
IGraphBuilder* pGraph = NULL;
ICaptureGraphBuilder2* pBuild = NULL;
IMediaControl* pControl = NULL;
ICreateDevEnum* pDevEnum = NULL;
IEnumMoniker* pEnum = NULL;
IMoniker *pMoniker = NULL;
IMoniker* goodMoniker = NULL;
IBaseFilter* pCap;
HRESULT hr;
//Initialize pGraph
hr = CoInitialize(NULL);
hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void **) &pGraph);
if(FAILED(hr))
{
printf("ERROR - Could not initialize COM library");
return 1;
}
//Initialize pBuild
hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL, CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void**) &pBuild);
if(FAILED(hr))
{
printf("ERROR - Could not create the Filter Graph Manager.");
return 2;
}
pBuild->SetFiltergraph(pGraph);
hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, reinterpret_cast<void**>(&pDevEnum));
if(SUCCEEDED(hr))
{
hr = pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pEnum, 0);
}
HWND hList;
while(pEnum->Next(1, &pMoniker, NULL) == S_OK)
{
IPropertyBag* pPropBag;
hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void**)(&pPropBag));
if(FAILED(hr))
{
pMoniker->Release();
continue;
}
VARIANT varName;
VariantInit(&varName);
hr = pPropBag->Read(L"Description", &varName, 0);
if(FAILED(hr))
{
hr = pPropBag->Read(L"FriendlyName", &varName, 0);
}
if(SUCCEEDED(hr))
{
for(int i=0;i<20;i++)
{
std::cout<<(char)*(varName.bstrVal + i);
}
char yn;
std::cin>>yn;
if(yn=='Y')
{
std::cout<<"SUCCESSFUL"<<std::endl;
goodMoniker = pMoniker;
VariantClear(&varName);
}
}
pPropBag->Release();
if(pMoniker != goodMoniker)
{
pMoniker->Release();
}
}
hr = goodMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)(&pCap));
if(SUCCEEDED(hr))
{
hr = pGraph->AddFilter(pCap, L"Capture Filter");
}
IBaseFilter *pMux = NULL;
// hr = pBuild->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video, pCap, NULL, NULL);
hr = pBuild->SetOutputFileName(
&MEDIASUBTYPE_Avi, // Specifies AVI for the target file.
L"C:\\stuff.avi", // File name.
&pCap, // Receives a pointer to the mux.
NULL); // (Optional) Receives a pointer to the file sink.
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.
hr = pCap->QueryInterface(IID_IMediaControl,(void**) pControl);
printf("START ");
hr = pControl->Run();
Sleep(100000);
hr = pControl->Stop();
CoUninitialize();
pGraph->Release();
pBuild->Release();
pCap->Release();
}
here is the error message that I get when I try to debbug it :
Unhandled exception at 0x776015de in STREAMMMMM.exe: 0xC0000005: Access violation reading location 0x00000000.
the program crashes in this line :
r = pCap->QueryInterface(IID_IMediaControl,(void**) pControl);

Answer 1

There are tens, if not hundreds, of examples on how to write into AVI with DirectShow on Internet.
This particular code snippet does not even start writing. It only prepares the pipeline and you are not even doing IMediaControl::Run, what you are supposed to do. Further on, you should wait until you wrote enough, and then stop recording and only then release the interface pointers.
Have a look at this Q: Using a DirectShow filter without registering it, via a private CoCreateInstance on what you are missing to start actual capture and writing (IMediaControl::Run and Sleep in particular).