Apple QuickTime Technical Information download pdf (Page 77)

Glossary 77

RTSP Real Time Streaming Protocol. An application-level protocol for controlling the

delivery of data with real-time properties. RTSP provides an extensible framework to

enable controlled, on-demand delivery of real-time data, such as audio and video.

Sources of data can include both live data feeds and stored clips.

sample rate The number of samples per second used for audio. Higher sample rates

yield higher quality audio than lower sample rates.

SDP Session Description Protocol. A text file used with QuickTime Streaming Server

that provides information about the format, timing, and authorship of a live streaming

broadcast and gives the user’s computer instructions for tuning in.

SMTP Simple Mail Transfer Protocol. A protocol used to send and transfer mail. Its

ability to queue incoming messages is limited, so SMTP usually is used only to send

mail, and POP or IMAP is used to receive mail.

sprite An animated image that’s managed by QuickTime. A sprite is defined once and

is then animated by commands that change its position or appearance.

SSL Secure Sockets Layer. An Internet protocol that allows you to send encrypted,

authenticated information across the Internet. More recent versions of SSL are known

as TLS (Transport Level Security).

streaming Delivery of video or audio data over a network in real time, as a stream of

packets instead of a single file download.

TCP Transmission Control Protocol. A method used along with the Internet Protocol

(IP) to send data in the form of message units between computers over the Internet. IP

takes care of handling the actual delivery of the data, and TCP takes care of keeping

track of the individual units of data (called packets) into which a message is divided for

efficient routing through the Internet.

temporal compression Image compression that’s performed between frames in a

sequence. This compression technique takes advantage of redundancy between

adjacent frames in a sequence to reduce the amount of data that’s required to

accurately represent each frame in the sequence. Sequences that have been temporally

compressed typically contain key frames at regular intervals.

track A QuickTime data structure that represents a single data stream in a QuickTime

movie. A movie may contain one or more tracks. Each track is independent of other

tracks in the movie and represents its own data stream.

TTL Time-to-live. The specified length of time that DNS information is stored in a

cache. When a domain name-IP address pair has been cached longer than the TTL

value, the entry is deleted from the name server’s cache (but not from the primary DNS

server).

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Apple QuickTime Technical Information Page 77