Intel Intercast technology makes it possible for home PCs to receive HTML-formatted web pages and streaming data (such as a stock ticker) along with regular television programming. The Intercast medium involves two key pieces: the broadcaster front-end that sends Intercast content, and the home PC that receives it.

Broadcasters, cable TV companies, networks, and television producers take advantage of the Intercast medium by embedding data associated with their programming within the Vertical Blanking Interval (VBI) portion of a conventional television signal. To receive Intercast programming, the consumer must have a PC equipped with the appropriate enabling software and hardware (Figure 2). In addition, the consumer must be in an area where the Intercast content is passed through by the local cable operator or broadcast affiliate. (Check http://www.intel.com/iaweb/intercast/ to determine availability in your area).

Intercast programming in the form of web pages is created by content providers, then integrated into the broadcasted program using software tools based on Intercast technology. The web pages are then received by the PC and cached, or intelligently stored, on the PC's hard drive. Hundreds or even thousands of pages of information can be stored in this way using just a fraction of the capacity of today's typical 1GB hard drive. For example, assuming a typical 40K web page and 25MB of hard disk space set aside for cached pages, the user could store 625 pages. (More information on how cached pages are handled is included later in this document under the section titled "The Intel Intercast Viewer Software.")

Figure 2. Intercast content is transmitted from the broadcaster site and received at home PCs.

Using Intel Intercast technology, consumers can interactively browse the cached pages, just as if the pages were being retrieved from the Internet.

Today's high-performance PC--based on Intel Pentium® and Pentium Pro processors--serves as the platform for Intel Intercast technology. The digital storage capability of the PC compensates for bandwidth not available today, allowing users to browse broadcast web pages on their PCs rather than requiring them to log on to the Internet.

The key advantage of using broadcast technology is that the web information can be accessed at the speed of the hard drive rather than the speed of a modem, and retrieving the information from the disk costs nothing. This is particularly important when one considers that today's Internet infrastructure makes it impossible for a television-sized audience to dial in to the same website during a program. With Intel Intercast technology, information from that website is broadcast with the television programming, giving all users immediate access.

Because it is written in HTML, the Intercast content broadcast with the television signal appears to a consumer as typical web pages, exactly as if he or she were accessing the Web. These broadcast web pages might also include embedded hyperlinks to related information on the Internet. Using a modem and any direct Internet connection, users of Intercast technology-enabled PCs can click the hyperlinks to move between television programming and Internet sites directly related to that programming.

Intel Intercast technology uses the Vertical Blanking Interval (VBI) portion of a conventional television signal to transmit associated data. In the United States, the VBI refers to the 21 horizontal lines of a National TV Standards Committee (NTSC) video signal that separate the two fields comprising a single television frame. (Similar standards exist in other countries.) In technical terms, the VBI is the point in the analog video signal at which the beam is in retrace and the intensity of the signal is zero--in other words, "dead time" in the signal. In more familiar terms, the VBI commonly appears on the television screen as the "black band" between frames when a TV image loses vertical hold and "rolls."

Figure 3. Intercast content uses the VBI portion of a conventional television signal.

During the VBI portion of the video signal, a limited amount of data can be inserted into the signal. Broadcast stations typically modulate the signal with data during the VBI. In the United States, for example, line 21 in the VBI is reserved for transmitting closed-captioning for the hearing-impaired. Lines 1 through 9 in the VBI are used by television receivers for video signal synchronization, and according to FCC regulations that allocation cannot be modified. Other lines in the VBI are sometimes used at times to transmit station identification, local time and Nielsen ratings information.

Essentially, up to 10 lines of the VBI are available per TV channel for inserting data, which can then be transmitted as an integral part of the television signal (see Figure 3). The throughput of each VBI line, with forward error-correction, is roughly equivalent to the data transfer capability of a 9600bps modem (approximately 4.3 megabytes per hour). The North American Basic Teletext Service (NABTS) is the U.S. standard that defines how data is encoded.

The data inserted into the VBI and broadcast along with the television signal using Intel Intercast technology can be picked up by a set-top or rooftop TV antenna, cable connection, or standard C-band satellite dish.

HTML is ideally suited to creating associated data for VBI insertion because it is applicable to a wide range of content (text, video, images, programs) and supports a broad array of embedded data types. Broadcasters can use a familiar, standard HTML authoring tool set to generate web pages related to TV programs, then take advantage of Intel Intercast technology to integrate the HTML-formatted text and graphics with television video.

HTML provides the additional advantage of allowing content providers to include URLs (Universal Resource Locators) that can point to any website on the Internet with the broadcast HTML pages. Consequently, a user with a modem and Internet connection can be directed to a website to gather additional information or order merchandise.