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 RealPlayer 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. RealPlayer is a client of Helix 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 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. RealPlayer 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 RealPlayer.
fps: Frames Per Second. The number of video frames that displays each second in a streaming video clip.

H

Helix Server: Server software used to stream multimedia presentations to RealPlayer 10 and other media players.
HTTP: Hypertext Transport Protocol. The protocol used by Web servers to communicate with Web browsers. In contrast, Helix Server streams clips to RealPlayer 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 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 RealPlayer. 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 Server to RealPlayer 10. The presentation can also include HTML URLs that open in the RealPlayer 10 HTML panes.

R

Ram file: A text file that uses the file extension .ram. It launches RealPlayer 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 version of RealPlayer that introduced three panes for media presentations. It followed RealPlayer 8 and was succeeded by RealPlayer 10.
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.
RealPlayer 10: The latest version of the RealNetworks media player that combines streaming playback and digital download technologies. It supports the SMIL 2.0 and 1.0 standards.
RealProducer: The primary tool for encoding RealAudio and RealVideo clips.
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 RealPlayer 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 Server uses to stream clips to RealPlayer or any RTP-based client. Contrast to HTTP.

S

server: 1. A software application, such as a Web server or Helix 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 RealPlayer to receive a clip stored on a Web server or Helix Server.