frame_common is a package containing the definition for the frame_common::Frame class, used in vslam_system for storing feature information for visual odometry.
The two classes of interest are frame_common::Frame and frame_common::FrameProc.
frame_common::Frame contains the image and image features.
frame_common::FrameProc is the class that contains a feature detector (FrameProc::detector) and extractor (FrameProc::extractor). This class is used for filling in the Frame class from a monocular image or from a stereo pair of images.