A S t r e a m i n g M e d i a P r i m e r :
G L O S S A R Y
HTTP command is sent to a Web server directing it to
lossless: A process that does not affect signal fi delity;
fetch and transmit the requested Web page.
e.g. the transfer of DV via an IEEE 1394 connection.
HTTP streaming: See
hypertext: A database system wherein objects (text,
M Bone: The MBONE (Multicast Backbone) is a
images, video, audio, and applications) can be linked to
virtual network layered on top of the physical Internet
each other. For example, while reading an article about
to support the routing of multicast packets. For more
jazz music, you might click on the name of a musician
information, see www.mbone.com.
to see a photograph, biography, or discography; you
Mbps: Megabits per second
might click on the name of a song to hear it played or
MBR: Short for multiple (or multi) bit rate, and also
to view score. A Web page is simply a graphical user
known as adaptive streaming, MBR is a technique by
interface (GUI) used to convey a hypertext document.
which several streams, compressed at different bitrates,
IEEE 1394: The interface standard that enables the
are encoded together into a single fi le. When the client
direct transfer of DV between devices such as a DV
calls for the media fi le, a negotiation between client
camcorder and a computer; also used to describe the
and server determines the available bandwidth, and the
cables and connectors utilizing this standard.
appropriate stream is transmitted.
i.LINK: The Sony trade name for IEEE 1394.
media: A term with many different meanings, in the
inter frame compression: Also known as temporal
context of streaming media, it refers to video, anima
compression, inter frame compression reduces the
tion, and audio. The term media may also refer to
amount of video information by storing only the dif
something used for storage or transmission, such as
ferences between frames.
tapes, diskettes, CD ROMs, DVDs, or networks such
as the Internet.
interlacing: System developed for early television
and still in use in standard television displays. To
media server: Specialized server software that takes
compensate for limited persistence, the electron gun
advantage of appropriate Web transfer protocols such as
used to illuminate the phosphors coating the inside of
RTSP (real time streaming protocol), as well as special
the screen alternately draws even, then odd horizontal
communication techniques between clients and servers,
lines. By the time the even lines are dimming, the odd
to facilitate the continuous playback of synchronized
lines are illuminated. We perceive these interlaced
audio and video in real time, adjusting the streams
fi elds of lines as complete pictures.
transmitted to the actual bandwidth available. Media
server software may be running on discrete hardware,
intra frame compression: Also known as spatial com
or can be deployed in combination with Web server
pression, intra frame compression reduces the amount
software running on the same device.
of video information within each frame individually.
metafi le: A fi le containing information that describes
IP: Internet Protocol, the basis of most Internet proto
or specifi es another fi le. Some streaming media formats
cols, breaks up large chunks of information into digest
use metafi les to invoke the client media player and/or
ible packets. In addition to the data being conveyed,
to specify the location of a streaming fi le on a media
each packet (also known as a datagram) carries a header
containing the source and destination IP addresses, as
well as a sequence number that allows the destination
mic: Pronounced like mike; short for microphone.
computer to reconstruct the packets in the correct
MPEG: Motion Pictures Expert Group of the Inter
sequence, when they arrive.
national Organization for Standardization (ISO) has
IP address: A numeric identifi er for a computer
defi ned multiple standards for compressing audio and
or device on the Internet. An IP address consists
video sequences. Setting it apart from JPEG which
of four numbers separated by periods, or dots (e.g.,
compresses individual frames, MPEG compression uses
192.168.0.1), representing a unique 32 bit address. An
a technique where the differences in what has changed
IP address consists of a network portion and a host
between one frame and its predecessor are calculated
portion; how many bits designate the network and how
and encoded. MPEG is both a type of compression
many designate the host varies.
and a video format. MPEG 1 was initially designed
to deliver near broadcast quality video through a
standard speed CD ROM. Playback of MPEG 1
Kbps: Kilobits per second
video requires either a software decoder coupled
keyframe: A frame selected at the beginning or end of
with a high end machine, or a hardware decoder.
a sequence of frames, that is used as a reference for any
MPEG 2 is the broadcast quality video found
of a variety of functions. In inter frame video compres
on DVD's. It requires a hardware decoder (e.g.; a
sion, keyframes typically store complete information
DVD ROM player) for playback. MPEG 4 is a rela
about the image, while the frames in between may store
tively new standard, now being used in some architec
only the differences between two keyframes.
tures for streaming media.
live feed: Data which is fed to a server in real time (i.e.,
multiple (or multi) bit rate: See MBR.
as it is recorded), rather than being pre recorded.
multicast: Multicast is an effi cient way to transmit the
live live: Sometimes used to refer to the streaming
same media stream to many recipients simultaneously,
of a live feed.
by replicating the stream at router hops where the
path to different multicast group members diverges.
lossy: Generally refers to a compression scheme or
Multicast end users experience the same portion of the
other process, such as duplication, that causes degrada
media, at the same time (in contrast to unicast, which
tion of signal fi delity.
can allow each end user to control their own experience