Rapid shake detection using a cascade of quad-tree motion detectors

A method of detecting shake of a camera, comprising:

• segmenting a previous image captured by the camera into a foreground region and a background region;
• estimating a background region of a current image using tracking of the foreground region of the previous image;
• determining an amount of motion in the current image from the estimated background region of the current image and the background region of the previous image;
• and
• determining the shake of camera based on the determined amount of motion from the background region of the current image.

A method of detecting changed regions in a video, comprising:

• determining whether a current frame of the video is a shaky frame or a non-shaky frame;
• detecting changed regions using one set of parameters where the current frame is a non-shaky frame;
• and
• detecting changed regions using a different set of parameters where the current frame is a shaky frame.

A method of detecting changed pixels in a video using a background model, comprising:

• obtaining a previously detected foreground mask from a previous frame of the video;
• tracking the foreground mask from the previous frame to a probable foreground region in a current frame of the video;
• selecting a plurality of image blocks in the current frame outside the probable foreground region;
• determining a plurality of motion vectors from the selected plurality of image blocks of the current frame and corresponding image blocks of a reference frame;
• determining a global motion of the current frame with respect to the reference frame using the determined motion vectors;
• warping the current frame using the determined global motion to correct for misalignment between the current frame and the reference frame;
• performing change detection of the current frame using the warped frame and the background model;
• and
• updating the background model using change detection results of the current frame.

Apparatus for detecting shake of a camera, the apparatus comprising:

• an input for an image captured with the camera;
• a processor coupled to the input and configured to:
• determine a magnitude of a motion from at least the image, and where the determined magnitude of motion is not larger than a first threshold, determining the camera to be stable;
• and
• where the determined magnitude of motion is larger than the first threshold, determining if a magnitude of motion for each of a number of blocks of the image is larger than at least one further threshold, and determining the shake of camera based on the number of motions having a magnitude exceeding the at least one further threshold.