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.

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.

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.

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 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 at speeds much faster than dial-up modems.

E

encoding

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

events file

A text file that specifies URLs to display at specific points as a RealAudio or RealVideo clip plays. A utility included with Helix Producer events file is merged into the clip using a utility.

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.

H

Helix Producer

The primary RealNetworks tool for encoding RealAudio and RealVideo clips.

Helix Server

RealNetworks server software used to stream multimedia presentations to RealOne Player.

HTTP

Hypertext Transport Protocol. The protocol used by Web servers to communicate with Web browsers. In contrast, Helix Server streams clips to RealOne Player with RTSP.

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.

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

prefetch

To stream clip data to RealOne Player before the clip plays back. A clip's preroll can be prefetched minutes before the clip plays, for example, masking the preroll from the viewer.

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 RealOne Player. The presentation can also include HTML URLs that open in the RealOne Player HTML windows.

R

RealAudio

A clip type for streaming audio over a network. RealAudio clips use the .rm extension.

RealOne Player

The successor to RealPlayer 8, the RealOne Player combines streaming and digital download technologies. It supports the SMIL 2.0 standard.

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.

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.

RTP

Real-Time Protocol. The open, standards-based data package protocol Helix Server uses (along with RTSP) to communicate with RTP-based clients. Contrast to RealAudio.

RTSP

Real-Time Streaming Protocol. An open, standards-based control protocol that Helix 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 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

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 Server.

V

visualization

An animation built into RealOne Player that the viewer can display when playing audio-only clips.

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