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Glossary

This glossary defines terms and spells out abbreviations you may encounter while working with online help or the QTSS and DSS Administrator’s Guide. References to terms defined elsewhere in the glossary appear in italics.

A access file

A text file called qtaccess that contains information about users and groups who are authorized to view media in the directory in which the access file is stored.

administrator

A user with server or directory domain administration privileges. administrator computer

A computer with server administrator software installed that can be used to configure and manage another computer.

announced broadcast

A method such as Automatic Unicast (Announce) enabling a broadcaster to negotiate with a server to accept a broadcast.

AppleScript

A scripting language with English-like syntax, used to write script files that can control your computer. AppleScript is part of the Mac operating system and is included on every Macintosh.

Automatic Unicast (Announce)

A method of delivering a broadcast to a streaming server in which an SDP file is automatically copied and kept current on the server. A

broadcast user name and password must be created before starting such a broadcast.

AVI (Audio Visual Interleave)

A Windows video file format.

B bandwidth

The capacity of a network connection, measured in bits or bytes per second, for carrying data.

bit

A single piece of information, with a value of either 0 or 1.

bit rate

The speed at which bits are transmitted on a network, usually expressed in bits per second.

broadcast

Transmitting one copy of a stream over the whole network.

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A user who has permission to broadcast to the streaming server. The broadcast user name and password are set in the General Settings pane of Streaming Server

Admin and are used in conjunction with announced broadcasts. It is not necessary to create a broadcast user for UDP broadcasts.

browser plug-in

Software that you attach to a browser to enable it to display specific data formats.

byte

Eight bits.

C client

The user-side software or computer used to display streaming media.

codec

Any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both.

CVS

Concurrent Versions System, a programming code management system.

D, E data rate

Amount of information per second.

DNS (Domain Name Service)

A service that translates host names to IP addresses.

DSL (digital subscriber line)

A broadband data transmission technology that operates over telephone lines.

DV (digital video)

A digital tape-recording format using approximately 5:1 compression to produce Betacam quality on a very small cassette.

F, G firewall

Software that protects the network applications and networking stack of a server.

IP Firewall service, which is part of Mac OS X Server software, scans incoming IP packets and rejects or accepts these packets based on a set of filters you create.

FireWire

A hardware technology for exchanging data with peripheral devices, defined by

IEEE Standard 1394. Also called iLink.

frame

A single image in a movie or sequence of images.

frame rate

In a movie, the number of frames per second.

FTP (File Transfer Protocol)

A protocol that allows computers to transfer files over a network. FTP clients using any operating system that supports FTP can connect to a file server and download files, depending on their access privileges. Most Internet browsers and a number of freeware applications can be used to access an FTP server.

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H hinting

Hinting creates a track for each streamable media track in the file that tells

QuickTime Streaming Server how and when to deliver each frame of media. The hinting process performs in advance the required calculations, allowing QTSS to serve up a larger number of streams. Hinting also allows new codecs to be used without the need to upgrade the server.

HTML (Hypertext Markup Language)

The code inserted in a file to be displayed on a web browser page. The markup tells the web browser how to display a web page’s words and images for the user.

HTTP (Hypertext Transfer Protocol)

An application protocol that defines the set of rules for linking and exchanging files on a network.

I

IEEE

The Institute of Electrical and Electronics Engineers, Inc., an organization dedicated to promoting standards in computing and electrical engineering.

Instant On

An advance in Apple’s patent-pending Skip Protection technology that dramatically reduces buffer, or wait, time for an instantaneous viewing experience with

streaming video on a broadband connection.

IP (Internet Protocol)

A connectionless protocol used to transmit packets of data from one machine to another. TCP and UDP use IP for their host-to-host data communications.

IP address

A unique numeric address that identifies a computer on the Internet.

IP subnet

A portion of an IP network, which may be a physically independent network segment, which shares a network address with other portions of the network and is identified by a subnet number.

ISP (Internet service provider)

A business that sells Internet access and often provides web hosting for ecommerce applications as well as mail services.

J, K, L

JavaScript

A scripting language used to add interactivity to web pages.

key frame

A sample in a sequence of temporally compressed samples that does not rely on other samples in the sequence for any of its information. Key frames are placed into

temporally compressed sequences at a frequency that is determined by the key frame rate. key frame rate

The frequency with which key frames are placed into temporally compressed data sequences.

LAN (local area network)

A network maintained within a facility, as opposed to a WAN

(wide area network) that links geographically separated facilities.

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A mechanism for prioritizing the tracks in a movie or the overlapping of sprites. When it plays a movie, QuickTime displays the movie’s images according to their layer—images with lower layer numbers are displayed on top; images with higher layer numbers may be obscured by images with lower layer numbers.

M

M3U file

An audio metafile that is created using a text editor and saved to a web server. The file directs a user’s web browser to an MP3 playlist residing on the same web server and opens the user’s MP3 player.

Mac OS X

The latest version of the Apple operating system, which combines the reliability of UNIX with the ease of use of Macintosh.

Mac OS X Server

An industrial-strength server platform that supports Mac, Windows,

UNIX, and Linux clients out of the box and provides a suite of scalable workgroup and network services plus advanced remote management tools.

Manual Unicast

A method for transmitting a live stream to a single QuickTime Player client or to a computer running QTSS or DSS. An SDP file is usually created by the broadcaster application and then must be manually sent to the viewer or streaming server.

Mbone

Short for Multicast Backbone, a virtual network for real-time streaming over the

Internet.

MIDI (Musical Instrument Digital Interface)

A standard format for sending instructions to a musical synthesizer.

modifier track

A track in a movie that modifies the data or presentation of other tracks.

For example, a tween track is a modifier track.

mount point

A string used to identify a live stream, which can be a relayed movie stream, a nonrelayed movie stream, or an MP3 stream. Mount points that describe live movie streams always end with an .sdp extension.

MOV

The Apple QuickTime movie file extension used to name both movie redirect files and actual QuickTime media files.

movie

A structure of time-based data that is managed by QuickTime. A QuickTime movie may contain sound, video, animation, or a combination of data types. A QuickTime movie contains one or more tracks; each track represents a single data stream in the movie.

MP3 (MPEG layer 3)

A popular format for compressing music.

MPEG-4

An ISO standard based on the QuickTime file format that defines multimedia file and compression formats.

multicast

An efficient, one-to-many form of streaming. Users can join or leave a multicast but cannot otherwise interact with it.

multihomed

A server with multiple IP addresses.

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N, O

NAT (Network Address Translation)

A technique sometimes used so that multiple computers can share a single IP address. open source

A term for the cooperative development of software by the Internet community. The basic principle is to involve as many people as possible in writing and debugging code by publishing the source code and encouraging the formation of a large community of developers who will submit modifications and enhancements.

P packet

A unit of data information consisting of header, information, error detection, and trailer records. QTSS uses TCP, UDP, and IP packets to communicate with streaming clients.

pixel

A single dot in a graphic image with a given color and brightness value.

playlist

A set of media files in the QTSS or DSS media folder specified to play one after the other or in random sequence.

port

A sort of virtual mail slot. A server uses port numbers to determine which application should receive data packets. Firewalls use port numbers to determine whether or not data packets are allowed to traverse a local network. "Port" usually refers to either a TCP or UDP port.

privileges

Settings that define the kind of access users have to shared items. You can assign four types of privileges to a share point, folder, or file: read and write, read only, write only, and none (no access).

progressive download

Movie data that is pushed via HTTP to the client. The movie can be viewed by the user as it is being transferred. This is not a form of media streaming. protocol

A set of rules that determines how data is sent back and forth between two applications.

proxy server

A server that sits between a client and server and negotiates communication between those two hosts. The client and server only communicate with the proxy server and never interact with each other. There are proxy applications for many network protocols, including HTTP (for web traffic) and RTSP (for streaming traffic).

Q qtaccess

The name of the plain text access file that contains information about users and groups who are authorized to view media in the directory in which the access file is stored.

QTSS (QuickTime Streaming Server)

A technology that lets you deliver media over the

Internet in real time.

QuickTime

A set of Macintosh system extensions or a Windows dynamic-link library that supports the composition and playing of movies.

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QuickTime Player

An application, included with the QuickTime system software, that plays QuickTime movies.

QuickTime Pro

A version of QuickTime Player with advanced features, primarily the addition of editing capabilities.

R

RAID (Redundant Array of Independent Disks)

A hard disk array that either increases the speed of disk input-output or mirrors the data for redundancy, or provides both of these features. Users may access the RAID as if it were one drive, although it may be divided into multiple partitions.

reference movie

A .mov file created using a utility program like MakeRefMovie, available at no cost from Apple for Macintosh and Windows. The file contains the location of a streaming media file and can also contain the locations of multiple streaming files. A reference file linked from a web page, for example, can direct a client player to the ondemand presentation encoded for its particular connection speed.

reflected stream

A live broadcast delivered as a unicast stream. Movie and MP4 playlists also generate reflected streams.

relayed stream

A stream that is passed from one server to one or more other servers.

Relays can also be used to generate a multicast stream. QTSS does not support relaying of

MP3 streams.

RTP (Real-Time Transport Protocol)

A network-transport protocol used for transmitting real-time multimedia content over multicast or unicast network services.

RTSP (Real Time Streaming Protocol)

A protocol for controlling a stream of real-time multimedia content. Sources of data can include both live feeds and stored clips.

S sample rate

The number of samples per second used for audio. Higher sample rates yield higher quality audio than lower sample rates.

SDP (Session Description Protocol)

A text file used with QuickTime Streaming Server that provides information about the format, timing, and authorship of a live streaming broadcast and gives the user’s computer instructions for tuning in.

SMTP (Simple Mail Transport Protocol)

A protocol for sending email.

sprite

An animated image that is managed by QuickTime. A sprite is defined once and is then animated by commands that change its position or appearance.

SSL (Secure Sockets Layer)

An Internet protocol that allows you to send encrypted, authenticated information across the Internet.

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An IP address that is assigned to a computer or device once and is never changed.

streaming

Delivery of video or audio data over a network in real-time, as a stream of

packets instead of a single file download.

T

TCP (Transmission Control Protocol)

A method used along with the Internet Protocol

(IP) to send data in the form of message units between computers over the Internet. IP takes care of handling the actual delivery of the data, and TCP takes care of keeping track of the individual units of data (called packets) into which a message is divided for efficient routing through the Internet.

temporal compression

Image compression that is performed between frames in a sequence. This compression technique takes advantage of redundancy between adjacent frames in a sequence to reduce the amount of data that is required to accurately represent each frame in the sequence. Sequences that have been temporally compressed typically contain key frames at regular intervals.

track

A QuickTime data structure that represents a single data stream in a QuickTime

movie. A movie may contain one or more tracks. Each track is independent of other tracks in the movie and represents its own data stream.

TTL (time-to-live)

A multicast broadcast has a TTL value that is set by the user. It specifies the number of routers the stream will pass through before it stops propagating over the network.

tween track

A track that modifies the display of other tracks.

U

UDP (User Datagram Protocol)

A data transport protocol that does not support retransmission of lost packets, sometimes used instead of TCP/IP. unicast

The one-to-one form of streaming. If RTSP is provided, the user can move freely from point to point in an on-demand movie.

URL (Universal Resource Locator)

A uniform way of specifying locations on the

Internet or a local file system.

V, W, X, Y, Z

VBR (variable bit rate)

A method of compressing data that takes advantage of changes in the media’s data rate.

WAV

A Windows format for sound files.

webcast

A broadcast of live video or audio on the Internet.

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XLR plug

A three-pin audio connector that can be used with three-wire balanced cables, which cause electro-magnetic interference to be canceled out.

XML

An extensible markup language, similar to HTML but more formal and more flexible.

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