Introduction: Besides still images, an incommensurable amount of audiovisual information is becoming available in digital form, in digital archives, on the WorldWideWeb, in broadcast data streams, and in personal and professional databases. This amount is rapidly growing.

• There are great demands for effective content-based retrieval and data mining methods for audio and video data. Typical examples include searching for and multimedia editing of particular video clips in a TV studio, detecting suspicious persons or scenes in surveillance videos, searching for particular events in a personal multimedia repository such as My Life Bits, discovering patterns and outliers in weather radar recordings, and finding a particular melody or tune in your MP3 audio album.
• To facilitate the recording, search, and analysis of audio and video information from multimedia data, industry and standardization committees have made great strides toward developing a set of standards for multimedia information description and compression. For example, MPEG-k (developed by MPEG: Moving Picture Experts Group) and JPEG are typical video compression schemes. The most recently released MPEG-7, formally named “Multimedia Content Description Interface,” is a standard for describing the multimedia content data. It supports some degree of interpretation of the information meaning, which can be passed onto, or accessed by, a device or a computer.
• MPEG-7 is not aimed at any one application in particular; rather, the elements that MPEG-7 standardizes support as broad a range of applications as possible. The audiovisual data description in MPEG-7 includes still pictures, video, graphics, audio, speech, three-dimensional models, and information about how these data elements are combined in the multimedia presentation.
• The MPEG committee standardizes the following elements in MPEG-7: (1) a set of descriptors, where each descriptor defines the syntax and semantics of a feature, such as color, shape, texture, image topology, motion, or title; (2) a set of descriptor schemes, where each scheme specifies the structure and semantics of the relationships between its components (descriptors or description schemes); (3) a set of coding schemes for the descriptors, and (4) a description definition language (DDL) to specify schemes and descriptors. Such standardization greatly facilitates content-based video retrieval and video data mining.
• It is unrealistic to treat a video clip as a long sequence of individual still pictures and analyze each picture since there are too many pictures, and most adjacent images could be rather similar. In order to capture the story or event structure of a video, it is better to treat each video clip as a collection of actions and events in time and first temporarily segment them into video shots. A shot is a group of frames or pictures where the video content from one frame to the adjacent ones does not change abruptly. Moreover, the most representative frame in a video shot is considered the key frame of the shot. Each key frame can be analyzed using the image feature extraction and analysis methods studied above in the content-based image retrieval. The sequence of key frames will then be used to define the sequence of the events happening in the video clip. Thus the detection of shots and the extraction of key frames from video clips become the essential tasks in video processing and mining.

Video data mining is still in its infancy. There are still a lot of research issues to be solved before it becomes general practice. Similarity-based preprocessing, compression, indexing and retrieval, information extraction, redundancy removal, frequent pattern discovery, classification, clustering, and trend and outlier detection are important data mining tasks in this domain.