Glossary

A

Advertising Application: A RealSystem option that inserts ads into SMIL-based presentations. The SMIL files use <RealAdInsert/> tags to indicate ad placement.

B

bandwidth: The upper limit on the amount of data, typically expressed as Kilobits per second (Kbps), that can pass through a network connection.
banner ad: An ad that appears alongside a requested clip or presentation. A banner ad can also rotate, making new ad images appear at regular intervals.
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.
buffering: Receiving and storing data before playing it back. The initial buffering time is called preroll. After preroll, excessive buffering may stall the presentation.
byte: A common measurement of data. One byte comprises eight (8) bits.

C

CHTTP: A version of HTTP supported by RealPlayer. Resources designated with chttp:// are downloaded through HTTP and stored in RealPlayer's cache.
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 RealServer.
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.

E

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

F

Flash: 1. A Macromedia tool for creating animations.; 2. A RealSystem clip type comprising Shockwave Flash and RealAudio. See also Shockwave Flash.

H

HTTP: The protocol used by Web servers to communicate with Web browsers. RealServer can use HTTP, but it streams clips to RealPlayer with RTSP. See also CHTTP.

I

interstitial ad: An ad that interrupts playback of a requested clip. It is like a commercial break on television.
ISP: Internet Service Provider. A company that provides access to the Internet. Many ISPs have RealServer available to stream media clips.

K

Kilobit: 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: A common unit of data measurement equal to 1024 bytes. Also equal to 8 Kilobits.

P

PNA: A proprietary protocol RealServer supports for backwards compatibility with RealSystem 3.0 through 5.0. URLs using PNA start with pnm://.
port: A connection to a server designated by a number such as 8080. RealServer uses different ports for the RTSP, HTTP, and PNA protocols.
preroll: Buffering that occurs at the start of a presentation. Preroll should be 15 seconds or less.
presentation: A group of clips coordinated through SMIL and streamed from RealServer to RealPlayer.

R

RDP: The proprietary data package protocol RealServer uses (along with RTSP) when communicating with RealPlayer. Contrast to RTP.
RealAudio: A RealSystem clip type for streaming audio over a network. RealAudio clips use the .rm or .ra extension.
RealPix: A RealSystem clip type (file extension .rp) for streaming still images over a network. It uses a mark-up language for creating special effects such as fades and zooms.
RealPlayer: RealNetworks client designed to play multimedia presentations streamed by RealServer or a Web server.
RealServer: RealNetworks server software used to stream multimedia presentations to RealPlayer.
RealSystem: The system for streaming clips such as RealAudio and RealVideo over a network. It consists of RealServer, RealPlayer, and production tools.
RealText: A RealSystem clip type (file extension .rt) for streaming text over a network. It uses a mark-up language for formatting text.
real-time: Delivered as it occurs. For example, a live broadcast is streamed across a network in real-time.
RealVideo: A RealSystem clip type for streaming video over a network. RealVideo clips use the .rm extension.
rotating banner ads: Banner advertisements that change at a specified interval, such as a new ad banner every 30 seconds.
RTP: The open, standards-based data package protocol RealServer uses (along with RTSP) to communicate with RTP-based clients. Contrast to RDP.
RTSP: The open, standards-based control protocol RealServer 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 RealServer, that sends clips over a network.; 2. A computer that runs server software.
Shockwave Flash: A compressed Flash file format (file extension .swf) used as the animation component in Flash.
SMIL: Synchronized Multimedia Integration Language. A mark-up language for specifying how and when each clip plays. SMIL files use the extension .smil or .smi.
stream: v. To send a media clip over a network so that it begins playing back as quickly as possible.; n. 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 technology that allows switching to a lower-bandwidth encoding in a RealAudio or RealVideo clip to compensate for network congestion. Available only in RealSystem.

U

URL: Uniform Resource Locator. A location description that lets a Web browser or RealPlayer receive a clip stored on a Web server or RealServer.