Introduction:
There are a number of technologies evolving that will enhance the ability to efficiently stream geographic visualizations across the Web. The large size of spatial data can easily produce the World Wide Wait for clients receiving information from Internet Map Servers and other online geographic and cartographic activities. In this short discussion, we highlight the concept of streaming, provide a general overview of SMIL, MPEG-4, and RichMedia 3D standards, and present an example of the use of streaming in online planning research.
The Concept of Streaming Media:
The concept of streaming media is based on the notion that it is not necessary to completely download content from the Internet before it is played. Streaming audio is likely one of the most widely known applications of streaming media across the Web. In 1995, RealNetworks Inc. released their RealPlayer plug-in to facilitate real-time or streaming audio via Web browsers. The company expanded to address real video with their streaming media plug-ins. As of 2000, there were three leading streaming media players: RealPlayer, from RealNetworks, had over 130 million users. Windows Media, from Microsoft, had over 100 million users. QuickTime, from Apple Computer, had 50 million users. For strictly streaming audio purposes, MP3 had 50 million users. Nokia, the mobile handset supplier, will offer RealNetworks’ RealPlayer tool on its EPOC-based communicators and smart phones. This and other similar announcements provide opportunities for rich streaming media content delivery to mobile phone and wireless computing devices. The mobile Internet computing market has the potential to grow to 1 billion users by 2005.
Tools for authoring, editing and encoding streaming media are also available from RealNetworks, Apple - QuickTime, Microsoft - Windows Media and other companies. RealSystem Server software supports serving and delivering streaming content across the Web. QuickTime Streaming Server and Windows Media Server are other alternatives for serving streaming video and audio across the Internet. The details of encoding and hosting streaming media are too robust to be covered in this article. An excellent resource on these topics is a book, from Addison-Wesley, entitled: "e-Video: How to Produce Internet Video as Broadband Technologies Converge" by H.P. Alesso. Alesso's Video Software Laboratory Web site is also an effective resource, (http://www.video-software.com/).
SMIL: Synchronized Multimedia Integration Language
The Synchronized Multimedia Integration Language (SMIL) is a markup language for describing the temporal behavior, screen layout and associated hyperlinks of a streaming media presentation. SMIL is a specification based on the Extensible Markup Language (XML). XML is a technology for supporting richly structured documents over the World Wide Web (Web). The XML specification was fostered by the World Wide Web Consortium and is evolving as a technology for next-generation Web development, (see: (http://www.w3.org/TR/REC-xml)). For more information on the SMIL specification, see: (http://www.w3.org/TR/REC-smil/).
There are a number of software tools that support the creation and editing of SMIL files. These tools are similar in functionality to HTML editors and include the GriNS authoring tools from Oratrix Development and Fluition from Confluent Technologies.
The example shown in Figure #1 was created with Fluition. Using a layout template and wizard user interfaces, the GIS-VIS JPEG, terrain JPEG, and the geographic visualization RealMedia files were imported into Fluition. Next, Web links were added. The complete composition was previewed and eventually saved as a SMIL file for posting on or linking to a streaming media server. Since .rm is the file format of the streaming animation file, this example would require linkages to a RealMedia Server.
Figure #1: Still image taken from a streaming mulimedia compostion created with SMIL. Streaming video files, GIF images and Web links are combined together in this geographic visualization example. Image and SMIL files created by Theresa-Marie Rhyne.
MPEG-4: Multimedia Standard
The Moving Pictures Expert Group (MPEG) of the International Organization for Standardization (ISO) is charged with developing standards for code representation, processing, compression and decompression of moving pictures, sound and their combination (multimedia). MPEG-1, introduced in 1992, plays out video and audio in linear streams and operates like a digital video player. MPEG-2, introduced in 1995, supports compression and transmission of digital television signals. MPEG-4 is a multimedia standard that allows users to interact with objects within a scene. MPEG-4 (version 1) was introduced in late 1998 while MPEG-4 (version 2) was approved in December 1999. MPEG-7 is a content representation standard for information searching that is still under development with an expected release in 2001. MPEG-21 is a new effort to define a Multimedia Framework to support the delivery of electronic content that began in December 1999. The MPEG Web site is located at: (http://www.cselt.it/mpeg/).
The MPEG-4 standard defines audio and visual components as objects. When multiple objects are grouped together a composition is defined that results in an MPEG-4 scene. Visual objects for a scene are described mathematically and given a position in 2D or 3D space. Audio objects are placed in a sound space. For 3D space, content only needs to be defined once. When a user changes their viewpoint, the calculations to update the screen and sound are performed locally at the user's computer. This allows for interaction with a MPEG-4 scene.
The Binary Format for Scenes (BIFS) is MPEG-4's language for defining and changing scenes. BIFS commands add and delete objects as well as changing visual and acoustic properties of objects. BIFS commands can also be used to animate objects and build interactive applications.BIFS commands borrow from many concepts associated with the Virtual Reality Modeling Language (VRML). MPEG-4 uses BIFS to support real time streaming of content. A scene does not need to be downloaded completely from the Internet before it is played. VRML uses a client-server model that relies on a complete download of 3D objects. The latest information on MPEG-4 can be found at: (http://www.cselt.it/mpeg/standards/mpeg-4/mpeg-4.htm).
Rich Media 3D:
Announced early in 2001, the Rich Media 3D (RM3D) initiative of the Web3D Consortium is designed to facilitate an emerging category of media-capable Internet and broadcast appliances to receive and present advanced 3D content. With the intent of addressing the interactive TV market, Sony developed much of the technology behind RM3D in its Blendo efforts. Shout Interactive has also developed pioneering 3D on the Web applications for episodic animation and wireless content. Uma, an Austrian-based technology company also contributing to RM3D, has demonstrated visually compelling solutions for visual data management and edutainment. The wide range of companies contributing to RM3D include: 3Dlabs, ATI, Eyematic, iVAST, OpenWorlds, Shout Interactive, Sony, SRI and uma. RM3D is expected to be complete with example implementations by December 2001. For more information on Rich Media 3D, see: (http://www.web3d.org/WorkingGroups/rm3d/rm3dcontacts.html).
Viewpoint and Metastreaming Prototypes: Online Planning Research
Viewpoint Media player is a proprietary plug-in that supports streaming 3D objects over the Internet. Originally named Metastream, it was developed in a joint project with MetaCreations and Intel. Viewpoint (or Metastream) objects stream across the Internet without a server and scale automatically to support the end-user's processing power. With the aid of smart compression technology, users with networking connection speeds ranging from a 56K modem to a T1 (or higher) line are able to examine 3D content in real time. Viewpoint provides a free Web browser plug-in to view content. A modeling tool is required to create the 3D objects. Researchers at the Centre for Advanced Spatial Analysis of the University College London used the early Metastream technology in their Online Planning and Internet based visualization research. Andy Smith, leader of the Shared Architecture project, created a series of architecture prototypes that could be viewed in 3D on the Internet. More information on these projects is available at: (http://www.casa.ucl.ac.uk/public/meta.htm). To learn how the architecture models evolved from photographs, see: (http://www.casa.ucl.ac.uk/public/guidelines.htm). Their research in Online Planning is currently being used for a public access information system in the regeneration of the Woodberry Down Estate, Hackney, London.
Figure # 2: Snapshot from a Metastreaming example of "Shared Architecture". Researchers at the Centre for Advanced Spatial Analysis of the University College London are using Metastream technology in their Online Planning and Internet based visualization research. Image shown courtesy of Andy Smith.
Future Directions and Conclusions:
Streaming technologies have the potential to reduce the World Wide Wait that can occur when downloading large spatial data file and interacting with 3D geographic models on the Internet. As mobile computing technology continues to evolve, with Global Positioning System (GPS) information, there will be increased interest in visualizing online cartographic information. We see streaming technologies as aids in the visualization of geographic information on personal digital assistants as well. This discussion has provided an overview of emerging multimedia standards that will assist with streaming technologies. We have also highlighted an online planning example that serves as a prototype for the use of future streaming technologies.