Declaring Filter Information

Microsoft DirectShow 9.0

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:

Structure	Description
AMOVIESETUP_FILTER	Describes a filter.
AMOVIESETUP_PIN	Describes a pin.
AMOVIESETUP_MEDIATYPE	Describes a media type.

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.