Digital video fingerprinting
From Wikipedia, the free encyclopedia
Video fingerprinting is a technique in which sophisticated software identifies, extracts and then compresses characteristic components of a video, enabling that video to be immediately and uniquely identified by its resultant “fingerprint”. Video fingerprinting is a new and emerging technology that has proven itself to be significantly more effective at identifying and comparing digital video data than either of its predecessors, hash value comparisons and digital watermarking.
Video Fingerprinting analysis may be based on any number of visual video features including, but not limited to, color and motion changes during a video sequence.
Limitations of Hash Value Comparisons
Normally, digital data are compared based on hash values that are directly derived from the digital components of a file. However, such methods are incomplete as they can only determine absolute equality or non-equality of video data files or parts. More often than not, differences in a video codec and digital processing artifacts may cause small differences in the digital components without changing the video perceptually. Thus, when employing hash methods, a comparison for absolute equality may fail even when two video segments are perceptually identical. Moreover, hash value comparisons are also of little value when one wishes to identify video segments that are similar (but not identical) to a given reference clip. The limitations of the equality / inequality dichotomy inherent to hash value techniques render “similar searching” impossible.
Principles Behind Video Fingerprinting Technology
Video fingerprinting methods extract several unique features of a digital video that can be stored in form of a perceptual hash of the video content. The evaluation and identification of video content is then performed by comparing the extracted video fingerprints. For digital video data, both audio and video fingerprints can be extracted, each having individual significance for different application areas.
The creation of a video fingerprint involves the use of specialized software that decodes the video data and then applies several feature extraction algorithms. Video fingerprints are highly compressed when compared to the original source file and can therefore be easily stored in databases for later comparison. They may be seen as an extreme form of lossy compression and cannot be used to reconstruct the original video content.
Video fingerprinting should not be confused with digital watermarking which relies on inserting identifying features into the content itself, and therefore changing the nature of the content. Watermarks must be inserted at the source in order to identify content and may be changed or removed at a later time by anyone. Video fingerprinting, however, can identify any content regardless of whether it has been previously manipulated and remains a static value.
Video Fingerprinting Applications
Video Fingerprinting is of interest in the Digital Rights Management (DRM) arena, particularly regarding the distribution of unauthorized content on the Internet. Video Fingerprinting systems enable content providers (e.g. film studios) or distributors (e.g. UGC sites) to determine the presence of unauthorized content within a database and to subsequently remove it. Moreover, video fingerprinting may be used for broadcast monitoring (e.g. advertisement monitoring, News monitoring) and general Media monitoring. For broadcast monitoring solutions in particular, there is high demand because content providers and content owners wish to detect when and where their video content appears on TV.
Fingerprinting visual content is similar to audio fingerprinting but uses a different technology. From a content provider's point of view, audio fingerprinting is not as reliable as visual fingerprinting. In most cases, audio tracks can be changed or manipulated with relative ease. For an example, consider online "mash-ups". Most “mash-ups” consist of unauthorized content that is compiled together and is set to a unique audio track. Since the audio track is different from the original version, the copyrighted material in the mash-ups would go undetected using only audio fingerprinting techniques.
This discrepancy has real applications in the global online community in terms of film distribution. Films shown in countries other than their country of origin are often dubbed into other languages. This change in audio renders the films virtually unrecognizable by audio fingerprinting technologies unless a copy of all known versions has been previously fingerprinted. Employing video fingerprinting, however, enables the content owner to fingerprint just once and have each subsequent version remain recognizable.
