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To find a term in the glossary, click the letter of the alphabet that is the first letter in the term you want to look up.

You can also read glossary terms within the text of Help by clicking the underlined glossary term links. After you click a glossary link, the glossary term and definition appear in a pop-up window. To close the window, click anywhere on the screen.



access control list (ACL)

A list of security protections that applies to either an entire object, a set of the object's properties, or an individual property of an object.


See  definition for:  access control list (ACL)


A Windows Media metafile that gives a player the information needed to receive content. Announcement files contain Extensible Markup Language (XML) scripts.


A name-value data pair.


The process of verifying the identity of a user, computer, process, or other entity by validating the credentials provided by the entity. Common forms of credentials are digital signatures, smart cards, biometric data, and a combination of user names and passwords.


To grant access to a resource on a computer system or network, usually during the authentication of an entity. An authenticated entity might be authorized for different types of access or activity.

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The data transfer capacity of a transmission medium.

*See  Also: *

bit rate

bit rate

The number of bits transferred per unit of time, typically expressed in bits per second.

*See  Also: *

bandwidth ,

multiple bit rate (MBR)


A method by which a client receives a stream. During a broadcast connection, clients cannot control the stream. This is the opposite of an on-demand presentation.

broadcast publishing point

A type of publishing point that streams content to multiple users at once, similar to a television broadcast. Content streamed from a broadcast publishing point can be delivered as a multicast or unicast stream.


An area of memory reserved for temporarily holding data before that data is used by a receiving device or application. Buffering protects against the interruption of data flow.

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A temporary data storage location, or the process of storing data temporarily. A cache is typically used for quick data access.

cache plug-in

A type of plug-in that enables a Windows Media server to provide cache and proxy support for another Windows Media server.

cache/proxy server

A server running Windows Media Services for which a cache/proxy plug-in has been enabled, allowing the server to provide cache and proxy support to another Windows Media server.


A communication approach between a plug-in and a Windows Media server. When the server requests the plug-in to perform a specific task, the plug-in immediately indicates it will do so by returning S_OK. The real result of the executed task is passed back to the server asynchronously through the callback method.


Text that accompanies images or videos, as either a supplemental description or a transcript of spoken words.


Any computer or program connecting to, or requesting the services of, another computer or program. Client can also refer to the software that enables the computer or program to establish the connection.

command context

Used by the OpCenter to describe a single command issued by the end user. Its lifetime is the same as the command duration. The command context itself contains two contexts, a request context and a response context.


A process for removing redundant data from a digital media file or stream to reduce its size or the bandwidth used.


Audio, video, images, text, or any other information that is contained in a digital media file or stream.

*See  Also: *

Windows Media file

content description context

In Windows Media Services, a context that is used to describe the content requested by a client application.

continuous content

An audio file, video file, or other stream that has a measurable and well-understood duration. For example, a 5-second audio clip is continuous content because it has a well-understood duration of 5 seconds.

*See  Also: *

discrete content

control protocol plug-in

A type of plug-in that enables a Windows Media server to communicate with clients and other servers through different network protocols.

custom plug-in

A type of plug-in created by a third-party vendor that is tightly integrated with the Windows Media Services platform architecture.

*See  Also: *


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data source plug-in

A type of plug-in that enables a Windows Media server to use different storage systems.

data writer plug-in

A type of plug-in that enables a Windows Media server to deliver content as a unicast stream, as a multicast stream, or to an archive file.

discrete content

An image file, text file, or other file that has no obvious duration. For example, if a file contains a still image, the image can be viewed for any desired length of time.

*See  Also: *

continuous content


The process of delivering a stream from one server to another.

distribution server

A server running Windows Media Services that publishes content received from another streaming source, such as an encoder or another Windows Media server.

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A fundamental syntactic unit in markup languages, such as HTML or XML. Elements are delimited by start tags and end tags. Empty elements are defined using an empty-element tag.


To convert audio and video content to a specified digital format, usually involving compression technology or encryption technology.


A technology that converts live or prerecorded audio and video content to a specified digital format. Typically, content is compressed during encoding. Windows Media Encoder is an example of an encoder.


An action or occurrence to which a program might respond. Examples include state changes, data transfers, key presses, and mouse movements.

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One of many sequential images that make up video.

frame rate

The number of video frames displayed per second. Higher frame rates generally produce smoother movement in the picture.

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A part of the file structure that contains information required by an application to decompress and render the content. The header in a protected file also contains information required to get a license.


See  definition for:  Hypertext Transfer Protocol (HTTP)

Hypertext Transfer Protocol (HTTP)

A standard set of rules that computers use to transfer information over the Internet.

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intelligent streaming

A type of streaming that detects network conditions and adjusts the properties of a video or audio stream to maximize quality.

interstitial advertisement

An advertisement that appears between pieces of content. When one piece of content finishes playing, the ad appears before the next piece of content plays.

*See  Also: *

wrapper playlist

intrinsic duration

The duration of a referenced item that has no explicit timing markup. Continuous content has an intrinsic duration defined by the media, and discrete content has no intrinsic duration.

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The delay that occurs while data is processed or delivered.

load balancing

A technique used for scaling the performance of a server-based program by distributing client requests across multiple servers.


Close at hand or restricted to a particular area. In communications, a local device is one that can be accessed directly rather than by means of a communications link. In information processing, a local operation is one performed by the computer at hand rather than by a remote computer. For example, the server computer on which Windows Media Services is installed is the local computer with respect to that server.


To record actions that take place on a computer, or the record of those actions.


To repeat a stream continuously.

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See  definition for:  multiple bit rate (MBR)

*See  Also: *

bit rate

media element

A content item that is streamed from a playlist. This can be a file, a stream from an encoder, a remote stream, another playlist file, or a Windows Media file on a Web server.

media parser plug-in

A type of plug-in that that can read different file formats.

*See  Also: *



Data about data. Title, subject, author, and size are examples of a file's metadata.

Microsoft Media Server (MMS) protocol

A proprietary protocol using UDP or TCP to deliver content as a unicast stream.

*See  Also: *

Transmission Control Protocol (TCP) ,

User Datagram Protocol (UDP)

Microsoft Windows Media Player

A client/control that receives a stream from a Windows Media server or local content for playback. It either can run as a stand-alone client executable program or be embedded in a Web page, C++ program, or a Microsoft Visual Basic program that uses the client ActiveX control.

MMS protocol

See  definition for:  Microsoft Media Server (MMS) protocol


A content delivery method in which a single stream is transmitted from a media server to multiple clients. The clients have no connection with the server. Instead, the server sends a single copy of the stream across the network to multicast-enabled routers, which replicate the data. Clients can then receive the stream by monitoring a specific multicast IP address and port.

multicast-enabled network

A network that has routers that can interpret Class D IP addresses.

multiple bit rate (MBR)

A characteristic of a data stream in which the same content is encoded at several different bit rates in order to optimize content delivery.

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on-demand publishing point

A type of publishing point that streams content to clients by request. Content streamed from an on-demand publishing point is always delivered as a unicast stream.

origin context

A context that describes the context for the origin server.

origin server

A Windows Media server from which content is published.

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A unit of information transmitted from one computer or device to another on a network.


To break input into smaller chunks so that a program can act upon the information.

*See  Also: *

media parser plug-in ,

playlist parser plug-in


A client program or control that receives digital media content streamed from a server or played from local files. Windows Media Player is an example of a player.


A list of digital media content.

playlist parser plug-in

A type of plug-in that parses system or custom playlist formats and transforms them into SMIL-compliant XML DOM objects supported by Windows Media Services.

*See  Also: *



An auxiliary software component that extends or enhances the features of other software.


A hardware- or software-based interface used to transfer information between a computer and other devices. Hardware ports are physical connections that are visible on the outside of the computer. Software ports are the numbered gateways in programs that software programs use to exchange information.

presentation context

Describes the instance of the streamed data file, and is different for every streamed file. Contains information such as the URL for the file, a pointer to the DataPath, the play rate, and start and stop


A standard set of formats and procedures that enable computers to exchange information.

*See  Also: *

Microsoft Media Server (MMS) protocol ,

Real-Time Streaming Protocol (RTSP) ,

Transmission Control Protocol (TCP) ,

User Datagram Protocol (UDP)

protocol rollover

A procedure that enables switching from one protocol to another when a Windows Media server fails to make a connection using a particular protocol.

proxy server

A server located on a network between client software, such as a Web browser, and another server. It intercepts all requests to the server to determine whether it can fulfill them itself. If not, it forwards the request to another server.

publishing point

An organized memory location that translates a client request for content into the physical path on the server hosting the content. A publishing point essentially acts as a redirector.

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See  definition for:  Quality of Service (QoS)

Quality of Service (QoS)

A networking feature that enables system administrators to control the performance properties of a network service, including throughput, transit delay, and priority.

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Real-Time Streaming Protocol (RTSP)

A network protocol, defined in RFC 2326, for controlling one or more digital media streams or a presentation (the aggregate of related media streams).


To point a client to a different location.

Resource Reservation Protocol (RSVP)

An Internet protocol being developed to enable the Internet to support specified Quality of Service (QoS) policies. By using RSVP, a program will be able to reserve resources along a route from source to destination. RSVP-enabled routers will then schedule and prioritize packets to meet the QoS policies.


See  definition for:  Resource Reservation Protocol (RSVP)


See  definition for:  Real-Time Streaming Protocol (RTSP)

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In a multicast transmission, the reach of a stream. The scope of a multicast transmission can be set to reach either an immediate subnetwork only or the entire Internet.

script commands

Named data that is associated with a designated time in Windows Media-based content. The data can be used by players to perform a specific action such as displaying a Web page.

Sipro Labs ACELP codec

A type of codec that provides excellent voice compression at low bit rates. This codec comes with several audio formats depending on the network bandwidth you choose.


See  definition for:  Synchronized Multimedia Integration Language (SMIL)


Digital media that is in the process of being delivered in a continuous flow across a network.

stream data object

Data that represents an individual data type within a stream, such as a compressed video frame.

stream format

Information about the properties of a stream, such as the codecs used, frame rate, and frame size. A player uses stream format information to decode a stream.

stream format file

A file used by a player to decode a multicast stream.

*See  Also: *

stream format

Synchronized Multimedia Integration Language (SMIL)

An XML-based language being developed by the World Wide Web Consortium (W3C) that would enable Web developers to divide content into separate streams (audio, video, text, and images), send them to a client computer, and then have them displayed as a single stream. This separation reduces the time required for transmission over the Internet.

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See  definition for:  Transmission Control Protocol (TCP)

time-to-live (TTL)

The number of routers through which a multicast stream can pass before a router stops forwarding the stream.

Transmission Control Protocol (TCP)

The protocol within TCP/IP that governs the breakup of data messages into packets to be sent via IP, and the reassembly and verification of the complete messages from packets received by IP.


See  definition for:  time-to-live (TTL)

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See  definition for:  User Datagram Protocol (UDP)

UDP resend

An error correction method that allows the client to request that the server retransmit lost data packets.


A method used by media servers for providing content to connected clients in which each client receives a discrete stream. No other client has access to that stream.

unicast rollover

Redirection of a client to a unicast stream in the event the client cannot access the multicast stream.

user context

Contains information about the client.

User Datagram Protocol (UDP)

A connectionless transport protocol in the TCP/IP protocol stack that is used in cases where some packet loss is acceptable, for example, with digital media streams.

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video capture device

An add-on device for digitizing video images for use on a computer.

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Windows Management Instrumentation (WMI)

Needs definition.

Windows Media Encoder

A technology that compresses live or prerecorded audio and video into a Windows Media stream, which can either be distributed immediately or saved as a Windows Media file for later distribution.

Windows Media file

A file that contains audio, video, or script data. The content of the file is encoded with one of the Windows Media codecs.

Windows Media Format

The format of a digital media file or stream that was encoded with Windows Media codecs.

Windows Media metafile

In Windows Media technologies, a file that provides information about Windows Media files and their presentation. File name extensions for Windows Media metafiles include .asx, .wax, .wvx, .wmx, and .nsc.

Windows Media Screen codec

A codec used to compress and decompress sequences of computer screen images.

*See  Also: *

Windows Media Video codec

Windows Media server

A server on which Windows Media Services has been installed.

Windows Media Video codec

A codec used to compress and decompress video streams.

*See  Also: *

Windows Media Screen codec


Do not use. See Comments.

wrapper playlist

A Windows Media metafile that places additional content at the beginning or end of a stream. Examples of this content include welcome messages, goodbye messages, advertisements, and station branding.

*See  Also: *

interstitial advertisement

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