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WMFormat Glossary

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.


The data transfer capacity of a transmission medium.

bit rate

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


A transmission medium designed for high-speed data transfers over long distances. Cable modem services and DSL are examples of broadband networks.


A compressed sample that does not depend upon any other sample for decompression. It is only valid to seek to a cleanpoint.

clear content

A Windows Media file that is not encrypted.


An abbreviation for compressor/decompressor. Software or hardware used to compress and decompress digital media.


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

content header

Part of the file structure of a Windows Media file that contains information necessary for a client computer to decompress and render the content data. In a packaged file, an additional content header exists and contains the key ID, content ID, and license acquisition URL. This content header can also include a required individualization version number and attributes defined by the content provider.

content owner

The person or organization that creates Windows Media files, for example, a record label, a movie studio, or artist.


A small data file that is stored on a user's local computer and which contains information about the user that is pertinent to a Web site, such as user preferences.

custom profile

A group of settings, defined by an end user, for configuring the encoder output.


To convert encrypted content back into its original form.


To combine the interlaced fields in a video frame so that, during playback, the lines of the video frame are painted sequentially.

delta frame

A video frame that contains only the changes from the previous frame. In contrast, a key frame contains all the data necessary to construct that frame.

digital rights management (DRM)

Any technology used to protect the interests of owners of digital content and services (such as copyright owners). Typically, authorized recipients or users must acquire a license in order to use the content.

digital rights management (DRM) component

The component of a player that handles all functions of digital rights management, such as decrypting packaged files or initiating license acquisition.

DirectX Media Object (DMO)

A COM object that processes multimedia data streams from buffers allocated by the client.


See definition for: DirectX Media Object (DMO)


See definition for: digital rights management (DRM)


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


To programmatically disguise content to hide its substance.


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.


A standard for adding metadata to MP3 files.


A marker produced by the Windows Media Format Software Development Kit (SDK) to enable seeking in a video file.


The process of making the digital rights management (DRM) component in the consumer's player unique. This process increases security by making it difficult to corrupt more than one player at a time. This process is also known as obtaining a security upgrade.


To display a video frame in two fields. One field contains the even lines of the frame, the other field contains the odd lines. During playback, the lines in one field are displayed first, then the lines in the second field are displayed.

inverse telecine

The process that removes the frames that were added when 24-fps film was converted to 30-fps video.


A piece of data that is required to unlock a packaged Windows Media file. This key is included in a separate license.

key frame

A video frame containing all the data needed to construct an image without reference to previous frames.

key ID

A value that identifies the key for a protected Windows Media file.


Data attached to protected content that describes how the content can be used.

license acquisition

The process of obtaining a license to play a packaged Windows Media file. The player attempts to obtain a license from a license acquisition URL, which is specified in the Windows Media file.

License Management Service

The Microsoft service that runs the license management process in the Windows Media Rights Manager Software Development Kit (SDK).

license revocation

The process of removing licenses from a user's computer.

license revocation acknowledgement

A signed confirmation from a client computer to a licensing server indicating that licenses were revoked.

license revocation challenge

A request from a client computer to a licensing server for license revocation.

license revocation response

A response to a license revocation challenge indicating which licenses to remove from a user's computer.

licensing server

A computer that runs Windows Media License Service and issues licenses.


A text string that is associated with a designated time in Windows Media-based content. Markers often denote convenient points to begin playback, such as the start of a new scene.


See definition for: multiple bit rate (MBR)


See definition for: Multipurpose Internet Mail Extension (MIME)

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.

Multipurpose Internet Mail Extension (MIME)

A standard that extends the Simple Mail Transport Protocol (SMTP) for encoding non-ASCII data files such as video, sound, and binary files for attachment to Internet e-mail.

output protection level

A setting in a license that indicates which technologies can be used to play or copy protected digital media content.

packaged Windows Media file

A Windows Media file encrypted with a key, which consumers cannot play unless they have a key provided by a license. A packaged Windows Media file is produced by and protected through the implementation of digital rights management using the Windows Media Rights Manager Software Development Kit (SDK) or a program based on the Microsoft Windows Media Format SDK.


The process that protects and signs a Windows Media file, producing a packaged Windows Media file. The packaging process includes generating or specifying a key, generating and signing the content header, and then encrypting the Windows Media file with this information.


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


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


A group of settings that match content type and bit rate with appropriate audio and video codecs.


The process in which a consumer enters information to acquire a license, such as an e-mail address.

revocation list

A list that contains all the application certificates of those player applications known to be damaged or corrupted. This list is included in licenses and then is stored on consumers' computers by the digital rights management (DRM) component of the player application.


A color model that describes color information in terms of the red (R), green (G), and blue (B) intensities that make up the color.


See definition for: Secure Digital Music Initiative (SDMI)

Secure Digital Music Initiative (SDMI)

An organization that sets standards for secure digital music. One of the main goals of SDMI is to create a framework for the secure playing, storing, and distribution of digital music.

security upgrade

The process of making the digital rights management (DRM) component in the consumer's player unique. This process increases security by making it difficult to corrupt more than one player at a time. This process is also known as individualization.


A method of delivering digital media across a network in a continuous flow. The digital media is played by client software as it is received. Typically, streaming makes it unnecessary for users to download a file before playing it.

system profile

The default, predefined templates that contain the necessary technical details for encoding a particular piece of content.

system profiles

No definition available.

target bandwidth

The number of bits that are transferred to users based on their network connection speeds.


The film-to-video conversion system that adds frames to video to compensate for the differences in frame rates between film and video.


See definition for: User Datagram Protocol (UDP)

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.

variable bit rate (VBR)

A characteristic of a data stream in which the bit rate fluctuates, depending upon the complexity of the data.


See definition for: variable bit rate (VBR)

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 License Service

A component of the Windows Media Rights Manager SDK that provides license acquisition services.


A color model that describes color information in terms of its brightness (luminance, or Y), and color (chrominance, or U and V).