directshow编译出现的问题
[Linker Error] Unresolved external 'CMediaType::~CMediaType()' referenced from E:\XIU\复件 VIDEO CAPTURE\UNIT1.OBJ
[Linker Error] Unresolved external 'CMediaType::CMediaType()' referenced from E:\XIU\复件 VIDEO CAPTURE\UNIT1.OBJ
[Linker Error] Unresolved external 'CMediaType::SetType(const _GUID *)' referenced from E:\XIU\复件 VIDEO CAPTURE\UNIT1.OBJ
[Linker Error] Unresolved external 'CMediaType::SetSubtype(const _GUID *)' referenced from E:\XIU\复件 VIDEO CAPTURE\UNIT1.OBJ
[Linker Error] Unresolved external '__stdcall FreeMediaType(_AMMediaType&)' referenced from E:\XIU\复件 VIDEO CAPTURE\UNIT1.OBJ
是什么原因啊?