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Windows Media Technologies Glossary

This glossary contains many terms that are helpful in understanding Microsoft Windows Media Technologies.

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access control list (ACL) checking
A part of Microsoft Windows security that Windows Media Services uses to verify that a client has permission to access a particular file or directory. Using ACL checking, a system administrator can set permission restrictions on an .asf file and on directories.
ActiveX
A Microsoft technology that enables different programs to share information. ActiveX extends Microsoft Windows-based architecture to include Internet and corporate intranet features and capabilities. Developers use it to build user interactivity into programs and World Wide Web pages.
ActiveX controls
Controls that use ActiveX technology. These controls can be downloaded automatically from a Web page and executed by a Web browser.
Advanced Streaming Format (ASF)
A data format for streaming audio and video content, images, and script commands in packets over a network. ASF content can be an .asf file or a live stream generated by Windows Media Encoder. ASF content that is in the process of being delivered over a network is called an ASF stream.
Advanced Streaming Format (.asf) file
An audio or video file that is formatted in ASF.
alias
A name that is substituted for a URL. For example, when creating a station, you can use an alias to specify the information that defines the connection between the Windows Media server components and Windows Media Encoder. For example, Stream1 is the alias for the URL, msbd://server:port. When you are creating a station, you can type Stream1 in the Alias dialog box. The server components resolve this alias by checking it against the definition on the encoder. The benefit of using aliases is that you do not have to remember constantly changing URLs. As long as you know the alias name, the URL can be resolved correctly.
announcement
A simple .asx file that contains information about the URL for a stream. Announcement files are created by Windows Media Administrator when a unicast publishing point or multicast station is created. The client quickly loads the announcement file, then opens the ASF stream in the unicast publishing point or extracts the URL to the ASF stream from an .nsc file and plays a program at the multicast station.
ASFCheck
A command-line utility for detecting and fixing some of the problems that are commonly found in ASF version 1.0 files.
ASFChop
A command-line utility for trimming the beginning or end of an ASF stream that has been stored by Windows Media Encoder.
ASFEditor
See Windows Media Author.
ASF root directory
See Home publishing point.
ASF Stream Descriptor (.asd) file
A configuration file created and read by Windows Media Encoder. The file contains Encoder settings that describe the characteristics of a multimedia stream. The file also is read by the Windows Media Station service to define the stream format supported by a given station.
ASF Stream Redirector (.asx) file
An ASX metafile that provides information that Microsoft Windows Media Player uses to receive unicast streams, multicast streams, and other supported media from an intranet or the Internet. These files are loaded quickly by Windows Media Player and contain information for the following purposes:
attribute
In an .asx file, a qualifier that describes a property of an ASX element. For example, an .asx file can include the element Repeat that contains the attribute Count. This particular element and attribute define the number of times the client repeats the playback of the piece of content or the playlist.
Audio Compression Manager (ACM)
A device driver manger that controls which applications are required to play or record sounds. The ACM manages the following types of drivers:

If a source file was created on a non-Windows computer, it may not use an ACM codec and thus can not be used by Windows Media Technologies.

authentication
The process of verifying logon information for a client. A Windows Media server can be set to authenticate clients before they are given access to ASF content or streams.
authorization
The process of granting or denying access permissions to clients. A Windows Media server can be set to authorize client requests for ASF content.
bandwidth
The amount of data that can be transmitted in a fixed amount of time. On computer networks, higher bandwidth indicates faster data transfer. Network bandwidth is expressed in bits per second (bps).

In the Windows Media Services environment, Windows Media Administrator can specify bandwidth constraints for a variety of functions, including maximum aggregate bandwidth unicast from a server, maximum bandwidth for a single unicast stream from a server, and continuous bandwidth used by a multicast file transfer from a server.

bit rate
The speed at which binary content can be streamed across a network. It usually is measured in kilobits per second (Kbps)ùfor example, 28.8 Kbps. Windows Media Encoder and Windows Media Administrator have settings for the bit rate of ASF content.
broadcast
Describes how a client experiences receiving a stream. A broadcast stream can be multicast or unicast. In a broadcast connection, the client is passive and does not control when the stream starts or stops. In contrast, in an on-demand connection, the client is active and controls when the stream is started or stopped.
broadcast multicast
Delivery of one stream by a Windows Media server to many clients, which listen to it by monitoring the IP address over which the stream is multicast. From the client perspective, a broadcast multicast is a connectionless experience because the client never connects to a Windows Media server.
broadcast unicast
A point-to-point connection that a client initiates to a publishing point on a Windows Media server.
buffer
An area of memory reserved for use as an intermediate repository in which data is temporarily held while waiting to be transferred between two locations. A buffer ensures that there is an uninterrupted flow of data between computers.

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Caption
A feature that sends a Synchronized Accessible Media Interchange (SAMI) file (a file in closed-caption format) with an ASF stream. Captioning is an accessibility feature that displays captions along with the video and audio, much like the closed-captioning that accompanies some television programs. It also can be used to display subtitles in a foreign language.
channel
See station.
client
Typically, the software that makes requests in client/server communications. Client software requests connections and communicates with servers.
codec
Short for compressor/decompressor. An algorithm or scheme used when recording digital video or audio. A codec is used, for example, when video is transmitted over the Internet; the video is compressed on the sending end and decompressed on the receiving end. Windows Media Tools provides a choice of codecs for ASF content. Users can select a codec based on the audio or image quality, and image size preferred.
content
Data that servers stream to a client or clients via unicast or multicast. Content can originate from live audio or live video presentation, stored audio or video files, still images, or slide shows. The content needs to be transformed from its original state into ASF in order for a server to stream it. Windows Media servers can stream live ASF streams or stored .asf files as content.
destination address
An IP address and port, from which a listening client can receive a multicast. A client instructs its network card to listen for packets arriving at the destination address and port.
distributed Component Object Model (DCOM)
An extension of the Component Object Model (COM). DCOM enables software components to communicate directly with each other across networks, including the Internet and intranets, in a reliable, secure, and efficient manner.
distribution
Delivering an ASF stream from one server to another. Distribution serves many purposes, such as:
distribution mode
A setting of Windows Media server components that indicates whether Windows Media server components are going to multicast the ASF stream, distribute the ASF stream (via unicast), or do both. If the distribution mode is set to multicast only, then the server broadcasts the ASF stream via multicast and unicast. If the distribution mode is set to distribution only, then the server delivers the ASF stream if requested by another server that is going to broadcast the ASF stream. If the distribution mode is set to both, then the multicast mode and the distribution mode are functional.
element
In an .asx file, an entity that defines a particular setting or action to the client. Elements can be modified by attributes. For example, a ref element has attributes that define the URL that points to particular content.
encoder
See Windows Media Encoder.
error correction
A method for controlling data transfer errors in a unidirectional communication system. Extra information is sent, along with the data, that the receiver uses to check and correct the data.
Error Correction Code (ECC)
The method of error correction used in an earlier version of Windows Media Services. Redundant data is sent with the data stream to detect and control single bit errors in the data stream. In the current version of Windows Media Services, streaming errors are corrected through UDP resend.
File Transfer service (FTS)
A feature of Windows Media Services that multicasts files over a network to an ActiveX control (Nsfile.ocx) on a client computer.
firewall
A system or combination of systems that enforces a boundary between two or more networks, and keeps unauthorized users out of private networks. A firewall system checks all incoming and outgoing messages to make sure they meet predetermined security criteria.
frame
One static image of many sequential images that make up a video title.
frame rate
The speed at which individual frames change. High frame rates generally produce better quality images.
home directory
See Home publishing point.
Home publishing point
The root directory for publishing ASF content. Microsoft Windows Media Player can stream any .asf files placed in this directory or its subdirectories. A home publishing point is also an on-demand publishing point. Unlike other publishing points, a home publishing point does not have an alias. Instead, the computer name is used in a URL for access to the home publishing point. Also called the ASF root directory.

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illustrated audio
A stream that combines audio content with synchronized images to make up an online slide show that runs at low bandwidths.
image color matching (ICM)
An application interface that communicates the color information of each device so that applications can accurately display, print, and pass colors on to other users and applications. Other operating systems may use different color matching schemes. Video content created using non-ICM data does not render correctly on Windows based computers.
Integrated Services Digital Network (ISDN)
A completely digital telephone/telecommunications network for carrying voice, text, images, and video traffic at high speed by sending digitally-encoded signals.
Internet Protocol address (IP address)
A 32-bit number that is the unique IP address of each computer or device on the Internet. This number specifies a physical location, or node, on the network.
Internet Server API (ISAPI)
A framework for creating a dynamic link library (DLL) to provide Internet server-side functionality. Windows Media Services uses ISAPI to provide one of the options for security.
intranet
A network belonging to an organization. Only members of that organization have access to it. An intranet that is connected to the Internet usually is protected by a firewall or other device.
listen
To monitor a specific multicast IP address. Microsoft Windows Media Player monitors a multicast IP address for data that is being streamed from a server.
local
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.
log
To collect and store data about Windows Media Services events. Windows Media Administrator can log information about unicasts, multicasts, and clients.
marker
A pointer to a specific place, measured in time, in an .asf file. Microsoft Windows Media Player uses markers to go directly to a point in an .asf file. Markers in an .asf file allow viewers to skip ahead to a marker or skip back to a previous marker in order to see a particular part of the .asf file again.
Media Stream Broadcast Distribution protocol (MSBD protocol)
A protocol used to reference a Windows Media Encoder, which is the source of a stream, such as msbd://server_name. It also is used when streaming from the Windows Media Station service to a content-storage server. In addition it is used for server to server distribution.
metadata
In a Windows Media Technologies system, information about content, such as the title, author or copyright. The information is contained in an .asx file.
metafile
In a Windows Media Technologies system, a text file that contains information, for media content. Windows Media Services use three kinds of metafiles: .asd file metafiles, .asx file metafiles, and .nsc file metafiles.
Microsoft Internet Explorer
A Windows-based Web browser produced by Microsoft Corporation. Microsoft Internet Explorer version 5 is used by Windows Media Services in several ways. For example, Windows Media Administrator uses Internet Explorer to display its Web pages. Content creators can embed the Microsoft Windows Media Player ActiveX control in an HTML page that is viewed with Internet Explorer.
Microsoft Media Server protocol (MMS protocol)
A protocol used to reference and stream .asf files from a Windows Media server.
Microsoft Windows Backup
A utility that helps you protect data from accidental loss if your system experiences hardware or storage failure.
Microsoft Windows Media Player
A client program or control that receives streaming media from a Windows Media server. This control either can run as a stand-alone client executable program or can be embedded in a Web page, C++ program, or a Microsoft Visual Basic program that uses the client ActiveX control. Microsoft Windows Media Player is the first version that is a universal player.
multicast
A one-to-many connection in which multiple clients can receive the same stream from a server. To receive a multicast, a client must have access to a multicast-enabled network. In contrast, a unicast is a one-to-one connection in which one client receives a distinct stream from a server.
multicast-enabled network
A network that has routers that can interpret Class D IP addresses.
multiple bit rate video
A feature of Windows Media Technologies that supports the creating and streaming of six encoded video streams within one ASF stream. Using multiple bit rate video in Windows Media Encoder creates ASF content that has a variety of video streams at variable bandwidths for either low or high bandwidth target audiences. When creating multiple bit rate content for low bandwidth audiences, the video streams can range from 18 Kbps to 300 Kbps. Alternatively, high bandwidth target audiences include video streams that range from 81 Kbps to 10 Mbps. Both target audiences include a separate encoded audio stream. When encoding multiple bit rate video, an additional insurance video stream is also encoded that is based on a percentage of the lowest selected bandwidth. After receiving this multiple encoded stream, the server determines which bandwidth to stream based on the network bandwidth available. Multiple bit rate video is not supported on generic HTTP servers.
.ocx
Frequently used as a synonym for an ActiveX control, .ocx is the file name extension for a control.
on-demand
Describes stored media content that is available for streaming on a Windows Media Services system. Windows Media Services can stream either stored content from a publishing point, or live content using Windows Media Encoder.
on-demand unicast
A point-to-point connection that a client initiates to a publishing point. In an on-demand unicast, the server streams stored content to the user.

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packet
A unit of data transmitted over a network. A packet is of fixed size, and is routed between a source and a destination. It contains binary information that represents both data and a header containing an ID number, source address, and destination address.
padding
Empty space that is appended to individual packets in a content stream to keep packet size constant. Windows Media Services supports variable packet length. However, Windows Media Encoder limits packets to a fixed length to ensure compatibility with earlier versions of Windows Media Services.
payload
A data unit that contains one or many stream data objects.
player
A client program or control that receives content streamed from a Windows Media server. Throughout the online Help, this refers to Microsoft Windows Media Player.
playlist
A list of streams that Microsoft Windows Media Player plays sequentially. Windows Media Services supports both server-side and client-side playlists.
port
A location on a server from which content streams to a client. A port is represented by a number that is part of a URL. Windows Media server components, when in use, bind to ports. By default, the Windows Media Unicast service binds to port 1755 and the Windows Media Station service binds to port 7007. If HTTP streaming is enabled for a service, then that service switches to use port 80, which is the preferred port for any HTTP streaming. You can change the ports that any of the Windows Media server components use by editing the registry.
program
One or more streams that Windows Media server components manage as a single entity. The program can be thought of as a container holding streams.
property
A characteristic of an object, such as a stream. For example, Windows Media Encoder displays stream properties, such as the bandwidth and the codec used, on a properties page.
protocol
A set of formats and procedures that enable computers to exchange information. Protocols that Windows Media Services use include HTTP, MMS, and MSBD.
protocol rollover
A procedure that allows switching from one protocol to another when a Windows Media server fails to make a connection using a particular protocol. For example, if a client uses MMS protocol to request ASF content, the server attempts to stream the ASF content using UDP. If that protocol fails, then the server attempts to stream the content using TCP, and then if that fails, the server attempts to use HTTP, if it has been enabled. Protocol rollover is not utilized if either MMSU protocol (MMS over UDP) or MMST protocol (MMS over TCP) is used to request ASF content.
proxy server
A server computer that controls Web-based traffic between local area networks and the Internet or other intranets.
publishing point
A virtual directory used for storing content that is available to clients, or for accessing a live stream. Clients reach a publishing point through its URL.
Publishing Point Events Monitor
A tool that monitors and displays server unicast events. Specifically, the Publishing Point Events Monitor displays unicast server (publishing point) event activities.
QuickStart
A group of wizards in Windows Media Technologies that are used for such tasks as configuring Windows Media Encoder and creating stations or publishing points.
remote
Not in the immediate vicinity or not directly accessible. A computer or other device located in another place (room, building, or city) and accessible through some type of communications link. For example, Windows Media Administrator can be run on a computer (a remote computer) other than the Windows Media server, so that a remote administrator can administer the server. Windows Media Encoder also can be run from a remote computer.
router
A device that connects two or more networks, and carries data forward. A router determines where the destination computer is located, and then finds the best way to transmit the data there.
scope
In multicasting, the reach of a stream. Windows Media Administrator enables the user to define the scope of a multicast. The scope of a multicast stream can be set to reach only an immediate subnet, or it can be set to reach the entire Internet. Scope is also equal to time-to-live (TTL).
script commands
Special instructions that are included in ASF data streams and delivered to the client. Microsoft Windows Media Player passes script commands to a device or an application that interprets them. Script commands are used for such tasks as calling specific files or navigating to a specific Web site.
security
The process of controlling access to resources based on user credentials and permissions. In a Windows Media Services environment, security means restricting and controlling access to Windows Media server components, Windows Media Administrator, and Windows Media content, both stored and streamed. Windows Media Services has built-in security mechanisms that integrate with Microsoft NTLM. Windows Media Services supports both server-side and client-side authentication.
station
A defined location from which a player can receive streams. In effect, it is an IP address and a port. Windows Media server components use stations with ASF streams only, and save station information as a file with an .nsc extension.
stream
Data transmitted across a network and any properties associated with the data. Streaming data allows the player to begin rendering the data immediately instead of waiting for the entire file to be downloaded.
stream data object
Data that represents an individual data type within the ASF stream, for example, a compressed video frame.
stream format
Information about the correct settings necessary for a player to render a stream properly. This information contains such settings as the bit rate, the size of the image, and the codec. Stream formats can be template stream formats or custom stream formats. Stream formats are contained in .nsc, .asd, and .asf files.
template stream format (TSF)
In Windows Media Technologies, a predefined group of settings that match content type and bit rate with appropriate audio and video codecs. Windows Media Encoder uses this feature to assist the user in quickly configuring the encoder to create ASF content.
time-to-live (TTL)
In multicasting, a value that defines the number of routers through which a multicast can pass before a router stops forwarding the multicast. TTL is equivalent to scope.

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unicast
A client/server connection in which a client receives an on-demand stream of stored content from a server, or receives a broadcast of live content. No other client has access to this stream. In contrast, a single multicast stream is available to multiple clients.
unicast rollover
A procedure that Microsoft Windows Media Player follows if it cannot receive a multicast from a station on a Windows Media server. Windows Media Player sometimes cannot receive a multicast for several reasons, including the absence of multicast-enabled routers on the network. If Windows Media Player cannot receive the multicast, it uses the unicast rollover URL contained in the .nsc file to connect to a server and request a unicast of the stream.
Universal Naming Convention (UNC)
Also called Uniform Naming Convention. A convention for specifying directories, servers, and other resources on a network, using two slashes // or backslashes \\ to indicate the name of the computer, and one slash to indicate path or directory levels within the computer, in this format: \\computer\directory.
URL flips
A set of instructions to the browser to change the content being displayed on a Web page, regardless of the state of the display. This is what enables the user to link from one page to another without waiting for the content on the first page to be completely rendered.
URL rollover
A rollover method used to specify different Windows Media servers that contain the same content. For example, if the first REF tag in a .asx file specifies an .asf file on a server called hound1 and the second REF tag specifies a copy of the file on hound2, Windows Media Player can reach the file using either server. If hound1 is too busy or fails, Windows Media Player automatically connects to hound2.
User Datagram Protocol (UDP)
A connectionless transport protocol in the TCP/IP protocol stack that, like TCP, runs on top of IP networks.
video capture card
An add-on board for providing digitized images on a computer. With a video capture card, you can provide live camera or VCR input to Windows Media Encoder.
VidToASF
A command-line utility that quickly converts an edited .avi or .mov file to an .asf file so that it can be stored on a Windows Media server and streamed to clients.
WavToASF
A command-line utility that quickly converts an edited .wav audio file to an .asf file so that it can be stored on a Windows Media server and streamed to clients.
Windows Media Administrator
A Web-based administrative application for monitoring real-time usage of Windows Media component services, managing content, and configuring the system.
Windows Media ASF Indexer
A Windows-based utility for deleting portions of an ASF stream that has been stored by Windows Media Encoder. You also can use Windows Media ASF Indexer to edit properties, markers, and script commands.
Windows Media Audio (.wma) file
A special type of advanced streaming format file for use with audio-only content encoded with the Windows Media Audio codec.
Windows Media Audio Redirector (.wax) file
A special type of .asx metafile for use with .wma files. The .wax file includes information about the location of the .wma file on the Windows Media server and the properties of the file.
Windows Media Author
A graphical interface tool for creating and testing illustrated audio. The tool is designed to combine and synchronize audio and image files. Using it, the author can manage objectsùsounds, images, and URLsùso that they appear at the correct time during playback. This tool uses technology from Digital Renaissance, Inc.
Windows Media client
The ActiveX control called Microsoft Windows Media Player that receives and renders ASF content from Windows Media server components. The client can be on the same computer as the server, or it can be on another computer.
Windows Media component services
A set of services running on a Windows Media server. These services multicast and unicast live audio and video presentations and stored files to client computers.
Windows Media Encoder
A feature of Windows Media Technologies used to create live ASF streams. Windows Media Encoder turns live audio and video content into an ASF stream and distributes that stream through a port. Windows Media Encoder also can save an ASF stream as an .asf file. Windows Media Encoder can distribute an ASF stream via MSBD protocol or HTTP.
Windows Media Plug-in for Adobe Premiere
A utility that allows a content creator to use Adobe Premiere to produce ASF content for Windows Media Technologies.
Windows Media Presenter for Microsoft PowerPoint 97
A Windows Media Technologies feature, available from within Microsoft PowerPoint 97. It enables PowerPoint to connect to Windows Media Encoder and to send a PowerPoint presentation to a Windows Media server for distribution to client computers.
Windows Media program (.nsp) file
A file that contains information about a Windows Media Services program, used primarily in backing up and restoring Windows Media Services program definitions.
Windows Media server components
Another term for Windows Media Services, which is used to multicast and unicast live audio and video presentations and stored files to client computers. Includes both Windows Media component services, which run on a Windows Media server and Windows Media Administrator, which is used to manage these services.
Windows Media Services
Another term for Windows Media server components, which is used to multicast and unicast live audio and video presentations and stored files to client computers. Includes both Windows Media component services, which run on a Windows Media server and Windows Media Administrator, which is used to manage these services.
Windows Media Station (.nsc) file
A file that describes a station to the player. The player accesses the station file indirectly by way of an .asx file that directs the client to a specific .nsc file.
Windows Media Monitor service
One of the Windows Media component services.
Windows Media Program service
One of the Windows Media component services.
Windows Media Station service
One of the Windows Media component services that provides multicasting, distribution, and storage functions for ASF streams. It can manage multiple stations, with each station having an ASF stream as input, and direct the stream to a multicast address, one or more distribution servers, a disk, or a combination of all three. A similar feature, Windows Media Unicast service, is available for unicasting ASF streams.
Windows Media Technologies
The family of streaming media applications that includes Windows Media Services, Windows Media Tools, and Windows Media Player. Windows Media Tools create ASF content that can be served to client computers using Windows Media Services and played with Windows Media Player.
Windows Media Tools
A set of tools that can be used to create ASF content for Windows Media Services. These tools include Windows Media Encoder, Windows Media Author, and Windows Media ASF Indexer; the conversion utilities VidToASF and WavToASF; and the file utilities ASFCheck and ASFChop.
Windows Media Unicast service
One of the Windows Media component services that provides unicasting functions for ASF streams. This service manages publishing points to which clients connect in order to receive either broadcast unicast streams or on-demand unicast streams. A similar feature, Windows Media Station service, is available for multicasting ASF streams.


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