Multimedia Glossary: M

mailto

email (electronic mail)

The mailto method is used to activate "send email" from a web page. This method starts the email program on the client. Originally email was handled by special programs that were totally separate from web browsers, but later versions of web browsers could handle email to such an integrated degree that users are not even aware that they are busy with a different service.

MDS

MPEG-7

Multimedia Description Scheme

sdfdsf

Media type

Content stored in electronic format can be delivered on many different types of devices. The following media are presently recognized as valid delivery systems on an internet. This list may be expanded in future versions:

• screen
  used for computer screens; documents are delivbered in a non-paged format, i.e. a user needs to scroll through the document
• tty
  used for media that have a fixed-pitch character grid, such as teletypes, terminals, or portable devices with limited display capabilities
• tv
  used for television-type devices (which, compared to computer monitors, have low resolution, color, limited scrollability).
• projection
  used for projectors, such as used in boardrooms
• handheld
  used for handheld devices that have small screens, typically monochrome, with bitmap graphics, and limited bandwidth
• print
  used for material to be printed and for documents viewed on screen in print preview mode
• braille
  used for braille tactile feedback devices
• aural
  used for speech synthesizers
• all
  used for documents that can be delivered on all the above devices.

See MIME and Content type

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Measurements

Transport measurements

There are different units of measurements used in computing technology. Transport size is measured in bits, and speed in bps (bits per second). As there are a many millions of bits involved in processing, larger units have been established to make it easier to talk about these units.

Here is a table with terms used for larger units. One byte = 8 bits.

		Bytes
1 Kilobyte	1Kb	1'000 (= 8'000 bits)
1 Megabyte	1Mb	1'000'000
1 Gigabyte	1Gb	1'000'000'000
1 Terabyte	1Tb	1'000'000'000'000

Dimension measurements

There are various measures available for measuring the dimensions of objects. Some units are based on an absolute reference, while other units have values relative to other objects.

Absolute units
• in (inch): unit of measurement (originally a British system of measurement)
  1 in = 2.54 cm
• cm (centimeter): unit in the decimal measuring system
  1 cm = 0.39 in = 10 mm
• mm (millimeter): unit in the decimal measuring system
  10 mm = 1 cm
• pt (point): there are different possible absolute values for point. In CSS2 the value of a point is fixed at 1/72th of an inch.
  1 pt = 0.013 inch (ie 1/72th) = 1 pt = 0.357 cm
• pc (pica): there are different possible absolute values for pica. The length of a pica depends on the length of a point. In CSS2 the length of a pica is 12 points.
  1 pc = 12 pts = 1 pc = 4.28 cm

Table with points, centimeters and picas

pt	cm	pica
12	4.284	1.000
11	3.927	0.916
10	3.570	0.833
9	3.213	0.750
8	2.856	0.666
7	2.499	0.583
6	2.142	0.500
5	1.785	0.417
4	1.428	0.333
3	1.071	0.250
2	0.714	0.170
1	0.357	0.083

Relative units
Some dimensions may be expressed as a percentage value with reference to another object, typically a containing box.
Fonts have a special set of relative units:

• em (or quad-width): this is the value of the computed font size. A font-size value in em refers to the font size of the parent element.
• ex (x-height) : a font's x-height, equaling the height of the lowercase "x" character.
• px (pixel): a device-dependent measurement. A pixel is the smallest unit on a viewing device. Its actual size varies according to screen resolution.

Angles
Some objects may be at an angle to other objects, given an imaginery baseline shared by them. Some units for expressing angles are:

• degrees
• grads
• radians

Frequency
Frequency is typically measured by

• Hz: Hertz
  200Hz (or 200hz) is a bass sound
• kHz: kilo Hertz
  6kHz (or 6khz) is a treble sound

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Metalanguage

A metalanguage is a formal language used to create a "lower level" language. A metalanguage consists of the rules and conventions to be used when the lower-level language is created. SGML is the metalanguage of both HTML and XML.

MIDI

Musical Instrument Digital Interface

MIDI is a system containing music related commands for a synthesizer or other MIDI-compliant device. A MIDI file thus does not contain any music, but instructions about music events and objects. The device interprets the commands in the MIDI file and reproduces the music-related events. A MIDI file can only be rendered as playable sound on a PC if there is an onboard synthesizer -- or at least a MIDI connected synthesizer to the PC. MIDI files can be embedded in HTML files. MIDI files take the extension *.MID or *.MIDI.

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MIME

Multipurpose Internet Mail Extensions

MIME Type (also known as Content Type) was first proposed in 1992 to specify more complex data than plain text. In essence MIME is used to specify the datatype for HTTP. Its purpose is to include textual and non-textual objects in the same message. The HTTP 'Content-Type' value is thus stating the type of content of the document, and by implication the application program through which it would be rendered. Today MIME types include sound, video, graphics, HTML, PostScript, and others.

The Mime type is specified to inform user agents about the type of content a document contains.

By following RFC2045 and RFC2046 the phrase Content type is used rather than MIME type. So whenever you need to specify a MIME type, remember to use Content type.

See Media and Content type

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Mosaic

Mosaic was the first popular browser that supported images and was developed by Marc Andreessen at NCSA.

Movie

When the film industry began images could "move" and the term moving pictures, shortened to movies, began to be used.

In Macromedia Flash and Director a movie is a multimedia application for the Web that may contain graphics, text, sound and video. A Flash movie also contains some level of user interactivity. The basis of a Flash movie is vector graphics, but it can contain bitmaps and other media such as sound and video.

MPEG

Motion Picture Experts Group

MPEG consists of a group of international experts that write ISO standards for moving images. There are several MPEG standards (see below).

MPEG-1

MPEG-1 is used for digital video at low compression rate. It allows for image compression for up to 1.5 megabits per second.
MPEG-1 is the standard on which Video CD and MP3 are based.
Compressed video to be used on the Web in its present status would rely on MPEG-1.

MPEG-2

MPEG-2 is used for digital video at low compression rate. It allows for image compression for up to 10 megabits per second.
MPEG-3 is the standard on which such products as Digital Television set top boxes and DVD are based.

MPEG-3

MPEG-3 is used for digital video at low compression rate.
It allows for image compression for up to 40 megabits per second. In practice this is hardly implemented as MPEG-2 is sufficient for most cases.

MPEG-4

MPEG-4 is used for integrated multimedia and a compression standard for long audio or video files with limited digital storage media (DSM) or low bandwidth availablity.
MPEG-4 isthe standard for multimedia for the fixed and mobile web

MPEG-7

Multimedia Content Description Interface

MPEG-7 is an XML-based standard for the inclusion of metadata in multimedia products. It makes possible interactive TV and faciltates the managing of multimedia stock. It is the standard for description and search of audio and visual content.

MPEG-21

Multimedia Framework.
The purpose of MPEG-21 is to build an infrastructure for the delivery and consumption of multimedia content.

MP3

MP3 is a sound compression format based on MPEG-1, Layer 3, which is the audio compression format used in the MPEG-1 algorithm.

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Multimedia Description Scheme

MPEG-7

See MDS

Multiplexing Protocol

See MUX

Multipurpose Internet Mail Extensions

See MIME

Musical Instrument Digital Interface

See MIDI

MUX

Multiplexing Protocol

MUX is an asynchronous messaging support at a layer below HTTP

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