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
when accessing pre recorded, or on demand, fi les). The
progressive download: Also known as pseudo
infrastructure to handle multicasting, known as the
streaming, progressive download allows end users to
M Bone (multicast backbone) is still emerging; the
experience media accessed via a network such as the
Internet is not yet ready for the popular proliferation of
Internet, while the media fi le is still in the process
multicasting. The terms multicast and narrowcast are
of downloading; as opposed to downloadable media,
sometimes used interchangeably, although multicast
which cannot be played back until the entire fi le is
more specifi cally refers to the actual technology inher
received. Unlike true streaming, progressive download
ent in the process.
leaves a copy of the media fi le on the client. Progressive
narrowband: Low bandwidth (typically dial up) net
download is also called HTTP streaming because Web
work connections usually 56 Kbps or lower.
server software using standard protocols (HTTP serv
ers) can deliver progressive download fi les, unlike
narrowcast: Transmission of media to multiple end
true streaming, which takes advantage of the special
users but, as differentiated from broadcast, not to
protocols used by media server software to adjust
everyone on a network
transmission to match the actual available bandwidth.
NTSC: National Television Standards Committee stan
protocol: A formal description of, i.e., rules for, how
dard for color television transmission used in the
specifi c types of computer systems interact.
United States, Japan and elsewhere. NTSC incorporates
an interlaced display with 60 fi elds per second, 29.97
pseudo streaming: See progressive download.
frames per second.
QuickTime: Apple's multi platform, multimedia soft
on demand: Media which is not transmitted live, as
ware architecture; used by software developers, hard
it is recorded, but is made available as an archive
ware manufacturers, and content creators to author
on a server, for end users to access when they wish.
and publish synchronized graphics, sound, video, text,
A television broadcast is live; renting a video and
music, VR, and 3D media. QuickTime 4 includes
watching it at home is on demand.
strong support for real (RTSP) streaming.
optimize: Another term for pre process.
RealMedia: Architecture developed by RealNetworks
to deliver audio and video content on the Web. Along
packet: Although computers and modems can send
with QuickTime and Windows Media, one of three
data one character at a time, it's more effi cient to send
dominant streaming architectures.
information in larger blocks called data packets, or
datagrams. When using the standard Internet protocol,
real time: In computing, refers to an operating mode
TCP/IP, packets are typically around 1,500 characters.
under which data is received, processed and the results
Packets consist of the data being transmitted plus the IP
returned so quickly as to seem instantaneous. In terms
address information of the sender and the recipient
of streaming media, refers to content streamed live, or
as it happens.
PAL: Phase alternating line television standard popu
lar in most European and South American countries.
reference movie: A metafi le in the QuickTime archi
PAL uses an interlaced display with 50 fi elds per second,
tecture, used to invoke the QuickTime player and/or to
25 frames per second.
refer the browser to an adaptive bit rate (MBR) fi le.
pixel: An abbreviation for picture element. The mini
resolution: The amount of information in each frame
mum computer display element, represented as a point
of video, normally represented by the number of hori
with a specifi ed color and intensity level. One way to
zontal pixels times the number of vertical pixels (e.g.
measure image resolution is by the number of pixels
640x480). All other things being equal, a higher resolu
used to create the image.
tion will result in a better quality image.
player: In a multimedia architecture, the client soft
rich media: Another term for multimedia.
ware application, typically a plug in, that enables play
RTP: Realtime Transfer Protocol is used as the transfer
back of the media.
protocol for RTSP streaming (true streaming), and can
plug in: A plug in extends the capabilities of a Web
deliver a streaming media fi le to one or more end users
browser, enabling the client to display or playback a fi le
simultaneously (i.e., can unicast or multicast).
type which the browser itself cannot handle.
RTSP: Realtime Streaming Protocol provides the func
Pre processing: Sometimes called optimizing, pre
tionality allowing end users to randomly access and
processing removes non essential information from
control the delivery of streaming media content.
your video and audio information that is diffi cult
server cluster or server farm: A group of networked
to encode and/or does not substantively add to the
servers that streamline internal processes by distribut
quality of the streamed media. So pre processing prior
ing the workload and expedite computing processes
to encoding reduces the burden on the compressor,
by harnessing the power of multiple servers. Load
potentially saving time and CPU capacity.
balancing software tracks demand for processing power
post production: The phase of a fi lm or video project
from different machines, prioritizing the tasks, and
that involves editing and assembling footage and adding
scheduling and rescheduling them depending on prior
effects, graphics, titles, and sound.
ity and demand users put on the network. Redundancy
ensures that if one server in the farm fails, another can
pre production: The planning phase of a fi lm or
step in as backup.
video project usually completed prior to commencing
SECAM: Similar to PAL at 25 FPS, the SECAM format
is employed primarily in France, the Middle East, and
production: The phase of a fi lm or video project
Africa. It is only used for broadcasting. In countries
comprised of shooting or recording raw footage.
employing the SECAM standard, PAL format cameras
and decks are used.