Glossary

B

bandwidth: The upper limit on the amount of data, typically expressed as kilobits per second (Kbps), that can pass through a network connection.
binary tag: A SMIL tag that comprises opening and closing tags, such as <ref> and </ref>. Many unary tags can become binary tags when necessary to enclose other tags.
bit: The smallest unit of measure of data in a computer. A bit has a binary value, either 0 or 1.
bit rate: A measure of bandwidth, expressed as the number of bits transmitted per second. A 28.8 Kbps modem, for example, can transmit or receive around 29,000 bits per second.
blank time: A period during a presentation in which RealOne Player is not paused, but no activity occurs onscreen. You typically insert blank time with the SMIL begin attribute.
broadcast: To deliver a presentation, whether live or prerecorded, in which all viewers join the presentation in progress. Contrast to on-demand.
buffering: The receiving and storing of data before it is played back. A clip's initial buffering is called preroll. After this preroll, excessive buffering may stall the presentation.
byte: A common measurement of data. One byte consists of 8 bits.

C

cable modems: Devices that allow rapid transmission and reception of data over television cable. They are digital devices, unlike dial-up modems, which transmit analog data.
camel case: A capitalization convention in which words in a phrase are joined, and each word after the first begins with a capital letter. SMIL 2.0 attributes and values generally use camel case, as in whenNotActive.
client: A software application that receives data from a server. A Web browser is a client of a Web server. RealOne Player is a client of Helix Universal Server.
clip: A media file within a presentation. Clips typically have an internal timeline, as with RealAudio and RealVideo.
codec: Coder/decoder. Codecs convert data between uncompressed and compressed formats, reducing the bandwidth a clip consumes.

D

download: To send a file over a network with a nonstreaming protocol such as HTTP. Contrast to stream.
DSL: Digital Subscriber Line. A technology for transmitting digital data over a regular telephone line much faster than through dial-up modems.
duress stream: A low-bandwidth SureStream audio or video stream that Helix Universal Server uses if a connection's available bandwidth drops greatly.

E

encoding: Converting a file into a compressed, streaming format. For example, you can encode WAV files as RealAudio clips.

F

Flash: A software application and an animation format created by Macromedia. RealOne Player can play Flash animations and stream them in parallel with other clips, such as RealAudio clips.
Flash Player file: A compressed Flash file format (file extension .swf) suitable for streaming. To stream Flash, you export the Flash Player file and tune it so that it plays well in RealOne Player.
fps: Frames Per Second. The number of video frames that displays each second in a streaming video clip.

H

Helix: A general term for the technology on which RealNetworks products are based. The RealNetworks suite for Helix includes Helix Universal Server and Helix Producer.
Helix Producer: The primary tool for encoding RealAudio and RealVideo clips.
Helix Universal Server: Server software used to stream multimedia presentations to RealOne Player and other media players.
HTTP: Hypertext Transport Protocol. The protocol used by Web servers to communicate with Web browsers. In contrast, Helix Universal Server streams clips to RealOne Player with RTSP.

I

ISDN: Integrated Services Digital Network. Technology that makes digital data connections at 64 or 112 Kbps possible over telephone lines.
ISP: Internet Service Provider. A company that provides access to the Internet. Some ISPs have Helix Universal Server available to stream media clips.

K

kilobit (Kb): A common unit of data measurement equal to 1024 bits. A kilobit is usually referred to in the context of bit rate per unit of time, such as kilobits per second (Kbps).
kilobyte (KB): A common unit of data measurement equal to 1024 bytes or 8 kilobits.

L

LAN: Local Area Network. A computer network confined to a local area, such as a single building. LANs vary in speed, with bandwidth shared among all networked devices.

M

metafile: Another name for a Ram file.
MPEG: A standards-based audio and video format that you can stream to RealOne Player. You can use MPEG-1 and MPEG-4 video, or the MP3 audio format.

N

namespace: A declaration that identifies the features used in a SMIL presentation. For SMIL 2.0 and higher, the <smil> tag must declare a namespace.

O

on-demand: A type of streaming in which a clip plays from start to finish when a user clicks a link. Most clips are streamed this way. Contrast to broadcast.

P

preroll: Buffering that occurs just before a clip plays back. Preroll should be no more than 15 seconds.
presentation: A clip or group of clips streamed from Helix Universal Server to RealOne Player. The presentation can also include HTML URLs that open in the RealOne Player HTML panes.

R

Ram file: A text file that uses the file extension .ram. It launches RealOne Player and gives it the URL to a streaming clip or presentation.
RealAudio: A clip type for streaming audio over a network. RealAudio clips use the .rm extension.
RealOne Player: The successor to RealPlayer 8, RealOne Player combines streaming and digital download technologies. It supports the SMIL 2.0 and 1.0 standards.
RealPix: A clip type (file extension .rp) for streaming still images over a network. RealPix uses a markup language for creating special effects such as fades and zooms.
RealPlayer G2: The RealNetworks client software that introduced plug-ins and the ability to update itself. It, along with the later RealPlayer 7 and RealPlayer 8, supports the SMIL 1.0 standard.
RealSlideshow: A RealNetworks tool for creating streaming slideshows based on the RealPix markup.
RealText: A clip type (file extension .rt) for streaming text over a network. It uses a markup language for formatting text.
RealVideo: A clip type for streaming video over a network. RealVideo clips use the extension .rm.
rebuffering: An undesirable state in which RealOne Player must pause a presentation to wait for streaming data to arrive. Rebuffering can result from network conditions, or a poorly produced presentation.
RTSP: Real-Time Streaming Protocol. An open, standards-based control protocol that Helix Universal Server uses to stream clips to RealOne Player or any RTP-based client. Contrast to HTTP.

S

server: 1. A software application, such as a Web server or Helix Universal Server, that sends requested data over a network.; 2. A computer that runs server software.
SMIL: Synchronized Multimedia Integration Language. A markup language for specifying how and when each clip plays within a presentation. SMIL files use the extension .smil.
stream: 1. To send a media clip over a network so that it begins playing back as quickly as possible.; 2. A flow of a single type of data, measured in kilobits per second (Kbps). A RealVideo clip's soundtrack is one stream, for example.
SureStream: A RealNetworks technology that enables a RealAudio or RealVideo clip to stream at multiple bit rates.

U

unary tag: A SMIL tag that includes a closing slash, as in <ref/>. Many unary tags can become binary tags when necessary to enclose other tags.
URL: Uniform Resource Locator. A location description that enables a Web browser or RealOne Player to receive a clip stored on a Web server or Helix Universal Server.