// Make a graph builder object we can use for capture graph building//BOOL MakeBuilder(){ // We have one already if (gcap.pBuilder)return TRUE;

• AMCap的 MakeBuilder函数建立了一个capture graph builer对象，通过调用CoCreateInstance获得了ICaptureGraphBuilder 接口指针。AMCap把他存储到gcap结构的pBuilder中。