V4L2_CTRL_CLASS_USER   40 extra_lib/include/avcap/linux/uvc_compat.h #define V4L2_CID_BASE			(V4L2_CTRL_CLASS_USER | 0x900)
V4L2_CTRL_CLASS_USER   42 extra_lib/include/avcap/linux/uvc_compat.h #define V4L2_CID_USER_CLASS		(V4L2_CTRL_CLASS_USER | 1)