The Moving Picture Experts Group



A central concept in the MPEG-4 design is transmission and interaction with audio-visual objects, of synthetic or natural nature. The Audio, Visual part of the standard provide the encoding algorithms for individual audio-visual objects. In order to combine these media together into complete presentations, a scene description capability is needed. 
BIFS provides the input data to the presentation layer of the MPEG-4 terminal. No other scene format covers all the requirements of the MPEG-4 presentation engine. The main concepts driving the design of the BIFS specification are the following:

  • Integration of 2D and 3D synthetic media together in a single format. By avoiding the burden of mixing multiple media formats together, the content creator has a way to design a complete multimedia content without the hassle of dealing with many different formats, and the end users to benefit from a lighter terminal with state of the art media capabilities;
  • Streaming environment: all existing scene description formats are designed in a way that a complete scene has to be downloaded before anything can be viewed on the terminal. In MPEG-4, the terminal is linked to one or several MPEG-4 servers. The scene description, as any other media, has to be streamed to the client. Allowing the scene to be "cut into pieces" and streamed to the client, as well as its animation parameters provide a more efficient model of transmission, that matches the MPEG-4 usual requirements. When dealing with communication applications these streaming features are also necessary in order to send new data to the user during the communication.
  • Compression: most existing scene representations are in text format, making them editable but very inefficiently represented in terms of data size. The size of scenes are often much smaller than other media. However, complex scenes can be large data sets. Sometimes several mega bytes. Even for smaller scenes, being able to reduce the data size can bring significant improvements in transmission time, especially for low bit rates, or broadcast environments in which the scene has to be repeatedly transmitted. Moreover, animation data can also be streamed in MPEG-4. The efficient compression of such data can significantly reduce the bit rates. A typical example : for a BIFS-Anim streams that consumes 10 kbit/s, non compressed data would consume more than 120 kbit/s.