Question

Basiclly I just want to capture audio and save it to a file on disk. I came to the conlusion using the AVI format would be best and least annoying. After wading through the DirectShow API, this is what I came up with.

//I find the mic in previous code
hr = pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pSrc);

hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void**)&pGraph);
//Initialize the Capture Graph Builder
hr = pBuild->SetFiltergraph(pGraph);

IBaseFilter *pMux;
//IFileSinkFilter *pSink;
hr = pBuild->SetOutputFileName(
    &MEDIASUBTYPE_Avi,  // Specifies AVI for the target file.
    L"C:\\Example.avi", // File name.
    &pMux,              // Receives a pointer to the mux.
    NULL);              // (Optional) Receives a pointer to the file sink.


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

Now, I figured this would be enough to do what I wanted but no file is created on disk and RenderStream gives me E_INVALDARGS. If I change the function call to:

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

I get the VFW_E_NOT_IN_GRAPH error instead.

What am I doing wrong here? I’d be outmost grateful for any help, thanks in advance!

Answer 1

VFW_E_NOT_IN_GRAPH means that you need to add your pSrc filter you created to the filter graph using IGraphBuilder::AddFilter call.

To save audio-only stream into file, you might want to prefer .WAV format instead, Windows SDK comes with WavDest project/sample which can accept audio from audio filter and output a .WAV file stream compatible with File Writer Filter to save into file.