Попробуйте класс WmiMonitorConnectionParams, у него есть свойство VideoOutputTechnology, которое возвращает следующие значения:
> typedef enum _D3DKMDT_VIDEO_OUTPUT_TECHNOLOGY {
D3DKMDT_VOT_UNINITIALIZED = -2,
D3DKMDT_VOT_OTHER = -1,
D3DKMDT_VOT_HD15 = 0,
D3DKMDT_VOT_SVIDEO = 1,
D3DKMDT_VOT_COMPOSITE_VIDEO = 2,
D3DKMDT_VOT_COMPONENT_VIDEO = 3,
D3DKMDT_VOT_DVI = 4,
D3DKMDT_VOT_HDMI = 5,
D3DKMDT_VOT_LVDS = 6,
D3DKMDT_VOT_D_JPN = 8,
D3DKMDT_VOT_SDI = 9,
D3DKMDT_VOT_DISPLAYPORT_EXTERNAL = 10,
D3DKMDT_VOT_DISPLAYPORT_EMBEDDED = 11,
D3DKMDT_VOT_UDI_EXTERNAL = 12,
D3DKMDT_VOT_UDI_EMBEDDED = 13,
D3DKMDT_VOT_SDTVDONGLE = 14,
#if (DXGKDDI_INTERFACE_VERSION >= DXGKDDI_INTERFACE_VERSION_WDDM1_3_M1)
D3DKMDT_VOT_MIRACAST = 15,
#endif
D3DKMDT_VOT_INTERNAL = 0x80000000,
D3DKMDT_VOT_SVIDEO_4PIN = D3DKMDT_VOT_SVIDEO,
D3DKMDT_VOT_SVIDEO_7PIN = D3DKMDT_VOT_SVIDEO,
D3DKMDT_VOT_RF = D3DKMDT_VOT_COMPOSITE_VIDEO,
D3DKMDT_VOT_RCA_3COMPONENT = D3DKMDT_VOT_COMPONENT_VIDEO,
D3DKMDT_VOT_BNC = D3DKMDT_VOT_COMPONENT_VIDEO
} D3DKMDT_VIDEO_OUTPUT_TECHNOLOGY;