Section: Scientific Foundations
Multimedia Document Formats and Description
Work on specific formats for audio has started recently in WAM. More specifically, we are participating in an international initiative for creating a new format for digital interactive audio for mobiles. Seven years after the completion of the I3DL2 guidelines (3D Audio Rendering), IAsig (Interactive Audio special interest group) should announce in 2007 the completion of a new interactive audio file format (C data structures) to complement I3DL2. This new format, based on the open standard XMF file format, will be called Interactive XMF (iXMF). At some point, iXMF will play the same role for audio as SMIL-based declarative animation is playing for SVG graphics objects and special effects. Main objects in iXMF are cues like “get the ball rolling”, a cue being defined as a symbolic name associated to a graph of audio elements producing a continuous soundtrack from discrete media chunks. However, iXMF with its 4-level hierarchical model for mixing and muting (t! rack, chunk, cue, and mixgroups) is a complex file format, which has not been designed with mobiles in mind. No reference implementation (C++ or Java) has been scheduled in the near future.
Regarding discrete media in multimedia documents, popular document languages such as XHTML can represent a very broad range of documents, because they contain very general components that can be used in many different situations. This advantage comes at the price of a very low level of representation. The concepts of microformats and semantic XHTML were developed to tackle this weakness. They add semantics to Web pages while taking advantage of the existing (X)HTML infrastructure. This approach enables new applications that can be deployed smoothly on the Web. But there is currently no way to describe rigorously this type of markup and authors of Web pages have very little help for creating and encoding semantic markup. A language that addresses these issues is developed in the team. Called XTiger, its role is to specify semantically rich XML languages in terms of other XML languages, such as XHTML.
Whereas document formats represent a multimedia document with all its internal structures, description languages describe a document from outside and provide metadata. In the area of description languages for multimedia documents, significant standardization efforts have been spent recently, such as MPEG-7 for instance, but the problem is not solved yet. Many application domains cannot cope with the description languages available today. We are working on this issue in cooperation with INA, the French archive of broadcast radio and television. We are defining a structure description language for audio-visual documents, focusing on formal consistency to make descriptions usable in very large bases, such as archives of audio-visual documents. Typical applications of this work are producing a thematic audio-visual offer from archives, or producing the same interactive application on various media (CD-ROM, DVD, Web).