An object mask tracking method for object-based access in MPEG-2 system

Abstract

This paper proposes an effective inter-frame object tracking method from inter-frame object masks in MPEG-2 decoder. This method can facilitate object-based interactive service in MPEG-2 system. To define objects exactly in moving picture, object masks for all frames must exist. However, all successive inter-frame object masks can be tracked from intra-frame object masks in MPEG-2 decoder using motion vector associated with inter-frame object masks. Therefore, it is possible to define objects in video sequence with a little increment of transmission data. As a result, frame-based MEPG-2 system can have object-based access capability if intra-frame object masks can be segmented before the MPEG-2 encoder. In this paper, object mask tracking procedure consists of four steps. The reference object mask can have more than one object. Firstly, each object in reference mask is separated using watershed labeling. Then only one object exists in each object mask. Secondly, object mask tracking in MPEG-2 decoder is performed by reconstructing inter-frame object mask using motion vector for each object mask. Thirdly, watershed algorithm is applied in order to eliminate errors that might occur during reconstruction procedure. In the watershed algorithm, each object and error in the image is labeled and only erroneous blocks or pixels in the background area can be removed by area comparison scheme. Finally, all object masks are combined into a single inter-frame object mask. With this object-based access in MPEG-2 decoder, various object-based applications can be possible, such as education and e-commerce.