Multicast — A network technology for the delivery of information to a group of destinations
simultaneously. A single stream is sent from the source to a group of devices at the same
time in one transmission. Delivery is managed by network switches using the most efficient
strategy to deliver the messages over each link of the network only once, and creating
copies only when the links to the group of destinations split.
Network Address Translation (NAT) — A network protocol that allows multiple devices to
have their own, individual, private addresses, but they share one public IP address (IPv4) for
connection to the internet or other networks.
Network Time Protocol (NTP) — A protocol used for synchronizing the clocks of
computer systems over networks.
Opencast Server — An opencast server is an open-source platform to support the
management of audio and video content in the education market. Institutions can use an
opencast server to produce, manage, and distribute lecture recordings.
Overscan — An applied "zoom" on SMPTE inputs (NTSC, PAL, 480p, 576p,
720p,1080i,1080p) to hide closed caption/ancillary data, edge effects, or other video
artifacts.
Parity (or Parity checking) — An error detection technique that tests the integrity of the
digital data being sent. Parity can be set to None, Even, or Odd.
Predictive frame (P-frame) — In video compression schemes, predictive frames follow
I-frames and contain data that has changed from the preceding I-frame see page 210).
Pull streaming — Streaming method that allows users to search for content. Users specify
a content source and initiate a download or view the stream. The content streaming is
initiated by the end user (at the decoder rather than at the encoder).
Push streaming — A streaming method where the encoder sends content out to one
(unicast) or more (multicast) decoders using one of the transport protocols. Content
streaming is initiated at the encoder.
Quality of Service (QoS) — The grade of performance, such as transmission rates and
error rates, of a communications channel or system. QoS provides a level of predictability
and control beyond the best-effort delivery that the router provides by default (best-
effort service provides packet transmission with no assurance of reliability, delay, jitter, or
throughput).
Real-time Streaming Protocol (RTSP) — A network control protocol designed for use in
audio visual and communications systems to control streaming media.
Real-time Transport Protocol (RTP) — An Internet Engineering Task Force (IETF)
standard for streaming real-time multimedia over IP in packets.
Router — A network device that forwards packets from one network to another.
Secure File Transfer Protocol (SFTP) — Similar to FTP, this protocol adds encryption and
requires credentials for file transfers.
Session Announcement Protocol (SAP) — Used by source devices (encoders or servers)
in conjunction with SDP to publicize the availability of a stream to decoders and players.
The SAP periodically broadcasts session description information on an industry standard
multicast address and port. When received by remote clients, these announcements can be
used to facilitate the viewing of streams, eliminating the need for user configuration.
Session Description Protocol (SDP) — This protocol is used to describe streaming
media initialization parameters. It covers session announcement, session invitation, media
type and format, and other forms of multimedia session initiation (as defined in RFC 2327).
SDP does not deliver media itself. It simply details the stream parameters and how the
stream will be started.
SMP351 • Reference Information 211
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