Declaring Filter Information

Declaring Filter Information

The first step is to declare the filter information, if needed. DirectShow defines the following structures for describing filters, pins, and media types:

These structures are nested. The AMOVEIESETUP_FILTER structure has a pointer to an array of AMOVIESETUP_PIN structures, and each of these has a pointer to an array of AMOVEIESETUP_MEDIATYPE structures. Taken together, these structures provide enough information for the IFilterMapper2 interface to locate a filter. They are not a complete description of a filter. For example, if the filter creates multiple instances of the same pin, you should declare only one AMOVIESETUP_PIN structure for that pin. Also, a filter is not required to support every combination of media types that it registers; nor is required to register every media type that it supports.

Declare the set-up structures as global variables within your DLL. The following example shows a filter with one output pin:

static const WCHAR g_wszName[] = L"Some Filter";

AMOVIESETUP_MEDIATYPE sudMediaTypes[] = {
    { &MEDIATYPE_Video, &MEDIASUBTYPE_RGB24 },
    { &MEDIATYPE_Video, &MEDIASUBTYPE_RGB32 },
};

AMOVIESETUP_PIN sudOutputPin = {
    L"",            // Obsolete, not used.
    FALSE,          // Is this pin rendered?
    TRUE,           // Is it an output pin?
    FALSE,          // Can the filter create zero instances?
    FALSE,          // Does the filter create multiple instances?
    &GUID_NULL,     // Obsolete.
    NULL,           // Obsolete.
    2,              // Number of media types.
    sudMediaTypes   // Pointer to media types.
};

AMOVIESETUP_FILTER sudFilterReg = {
    &CLSID_SomeFilter,      // Filter CLSID.
    g_wszName,              // Filter name.
    MERIT_NORMAL,           // Merit.
    1,                      // Number of pin types.
    &sudOutputPin           // Pointer to pin information.
};

The filter name is declared as a static global variable, because it will be used again elsewhere.