| Streaming video is a sequence of "moving images" | | | | compression. It operates under the auspices of the |
| that are sent in compressed form over the Internet | | | | International Organization for Standardization (ISO). The |
| and displayed by the viewer as they arrive. Streaming | | | | MPEG standards are an evolving series, each |
| media is streaming video with sound. With streaming | | | | designed for a different purpose. To use MPEG video |
| video or streaming media, a Web user does not have | | | | files, you need a personal computer with sufficient |
| to wait to download a large file before seeing the | | | | processor speed, internal memory, and hard disk |
| video or hearing the sound. Instead, the media is sent in | | | | space to handle and play the typically large MPEG file |
| a continuous stream and is played as it arrives. The | | | | (which has a file name suffix of .mpg). You also need |
| user needs a player, which is a special program that | | | | an MPEG viewer or client software that plays MPEG |
| uncompresses and sends video data to the display | | | | files. (Note that .mp3 file suffixes indicate MP3 (MPEG-1 |
| and audio data to speakers. A player can be either an | | | | audio layer-3) files, not MPEG-3 standard files.) You |
| integral part of a browser or downloaded from the | | | | can download shareware or commercial MPEG |
| software maker's Web site. | | | | players from a number of sites on the Web. |
| Major streaming video and streaming media | | | | The term codec is an acronym that stands for |
| technologies include RealSystem G2 from | | | | "compression/decompression." A codec is an algorithm, |
| RealNetwork, Microsoft Windows Media Technologies | | | | or specialized computer program, that reduces the |
| (including its NetShow Services and Theater Server), | | | | number of bytes consumed by large files and |
| and VDO. Microsoft's approach uses the standard | | | | programs. In order to minimize the amount of storage |
| MPEG compression algorithm for video. The other | | | | space required for a complicated file, such as a video, |
| approaches use proprietary algorithms. (The program | | | | compression is used. Compression works by |
| that does the compression and decompression is | | | | eliminating redundancies in data. Compression can be |
| sometimes called the codec.) Microsoft's technology | | | | done for any kind of file, including text, programs, |
| offers streaming audio at up to 96 Kbps and | | | | images, audio, video, and virtual reality (VR). |
| streaming video at up to 8 Mbps (for the NetShow | | | | Compression can reduce the size of a file by a factor |
| Theater Server). However, for most Web users, the | | | | of 100 or more in some cases. For example, a |
| streaming video will be limited to the data rates of the | | | | 15-megabyte video might be reduced to 150 kilobytes. |
| connection (for example, up to 128 Kbps with an ISDN | | | | The uncompressed file would be far too large to |
| connection). Microsoft's streaming media files are in its | | | | download from the Web in a reasonable length of |
| Advanced Streaming Format (ASF). | | | | time, but the compressed file could usually be |
| Streaming video is usually sent from prerecorded | | | | downloaded in a few seconds. For viewing, a |
| video files, but can be distributed as part of a live | | | | decompression algorithm, which "undoes" the |
| broadcast "feed." In a live broadcast, the video signal is | | | | compression, would have to be used. |
| converted into a compressed digital signal and | | | | There are numerous standard codec schemes. Some |
| transmitted from a special Web server that is able to | | | | are used mainly to minimize file transfer time, and are |
| do multicast, sending the same file to multiple users at | | | | employed on the Internet. Others are intended to |
| the same time. | | | | maximize the data that can be stored in a given |
| Streaming media is audio and video that are | | | | amount of disk space, or on a CD-ROM. Codec's are |
| transmitted on the Internet in a streaming or continuous | | | | used in many popular Internet products, including |
| fashion, using data packets. The most effective | | | | QuickTime, Netmeeting, Cu-Seeme, and VDOphone. |
| reception of streaming media requires some form of | | | | Flash, is a popular authoring software developed by |
| broadband technology such as cable modem or DSL. | | | | Macromedia, and is used to create vector |
| A packet is the unit of data that is routed between an | | | | graphics-based animation programs with full-screen |
| origin and a destination on the Internet or any other | | | | navigation interfaces, graphic illustrations, and simple |
| packet-switched network. When any file (e-mail | | | | interactivity in an antialiased, resizable file format that is |
| message, HTML file, Graphics Interchange Format file, | | | | small enough to stream across a normal modem |
| URL - Uniform Recourse Locater request, and so | | | | connection. The software is ubiquitous on the Web, |
| forth) is sent from one place to another on the Internet, | | | | both because of its speed (vector-based animations, |
| the Transmission Control Protocol (TCP) layer of TCP | | | | which can adapt to different display sizes and |
| IP divides the file into "chunks" of an efficient size for | | | | resolutions, play as they download) and for the smooth |
| routing. Each of these packets is separately numbered | | | | way it renders graphics. Flash files, unlike animated but |
| and includes the Internet address of the destination. | | | | rasterized GIF and JPEG, are compact, efficient, and |
| The individual packets for a given file may travel | | | | designed for optimized delivery. |
| different routes through the Internet. When they have | | | | Known as a do-it-yourself animation package, Flash 4 |
| all arrived, they are reassembled into the original file (by | | | | gives Web designers the ability to import artwork using |
| the TCP layer at the receiving end). | | | | whatever bitmap or illustration tool they prefer, and to |
| A packet-switching scheme is an efficient way to | | | | create animation and special effects, and add sound |
| handle transmissions on a connectionless network | | | | and interactivity. The content is then saved as file with |
| such as the Internet. An alternative scheme, | | | | a .SWF file name extension. |
| circuit-switched, is used for networks allocated for | | | | Web users with Intel Pentium or Power Macintosh |
| voice connections. In circuit-switching, lines in the | | | | processors can download Flash Player to view Flash |
| network are shared among many users as with | | | | content, which performs across multiple browsers and |
| packet-switching, but each connection requires the | | | | platforms. Flash is lauded for being one of the Web's |
| dedication of a particular path for the duration of the | | | | most accessible plug-in. According to an independent |
| connection. "Packet" and "datagram" are similar in | | | | study cited by Macromedia, over 90 percent of Web |
| meaning. A protocol similar to TCP, the User Datagram | | | | users already have Flash Player installed. Macromedia |
| Protocol (UDP) uses the term datagram. | | | | was recently acquired by Adobe in a 3.4 billion dollar |
| MPEG, the Moving Picture Experts Group, develops | | | | deal. |
| standards for digital video and digital audio | | | | |