Transcoding of MPEG-4 BIFS into MPEG-4 LASeR

摘要

The MPEG-4 BIFS and MPEG-4 LASeR are parts of MPEG-4 standard for describing multimedia scenes in binary format. Scenes are multimedia presentations consisting of text, graphics, animation and real contents such as images, videos, and audios. BIFS and LASeR scenes can be written in XML format and then be encoded into binary format for the consumption of MPEG-4 terminals. While BIFS is a stable standard, LASeR is an emerging standard that is being newly developed for the purpose of lightweight applications in constrained terminals such as mobile phones. This explains why the LASeR specification is much simpler than that of BIFS. In this paper, we present a method of transcoding for converting BIFS XML format into LASeR XML format. We analyze the differences between BIFS and LASeR specifications and propose a set of mapping rules for the conversion purpose. The transcoding is done using an XSLT processor for converting the BIFS XML formats into the corresponding LASeR XML formats. The text to text conversion is incorporated into our transcoding system that also adapts real objects in the scenes such as images and videos. The motivation of this paper is to enable a transcoding from BIFS to LASeR so that MPEG-4 content authors can distribute their existing contents to mobile devices without the need of reauthoring and learning of a new standard.