1.1 Glossary

This document uses the following terms:

bit rate: A measure of the average bandwidth that is required to deliver a track, in bits per second (bps).

composition time: The time that a sample needs to be presented to the client, as defined in [ISO/IEC-14496-12].

decoding: The reversal of the encoding process, used by a client or server to correctly interpret a received object.

document type definition (DTD): A language that can be used to define the rules of an XML document, as specified in [XML] section 2.8.

DVR window: The length of time that content is available as DVR content.

encoding: A process that specifies a Content-Transfer-Encoding for transforming character data from one form to another.

fragment: An independently downloadable unit of media that comprises one or more samples.

HTTP cache proxy: A proxy that can deliver a stored copy of a response to clients.

live: Content that is streamed while it is still being encoded by an encoder.

manifest: Metadata about the presentation that allows a client to make requests for media.

media: Compressed audio, video, and text data that is used by the client to play a presentation.

media format: A well-defined format for representing audio or video as a compressed sample.

on-demand: A presentation that is available in its entirety when playback begins.

packet: A unit of audio media that defines natural boundaries for optimizing audio decoding.

parent track: A track with which one or more sparse tracks is associated, and that is used to transmit timing information for the sparse track. Parent stream fragments always contain the time stamp for the last sparse fragment.

presentation: A set of audio and video data streams and related metadata that are synchronized for playback on a client.

request: An HTTP message sent from the client to the server, as defined in [RFC2616].

response: An HTTP message sent from the server to the client, as defined in [RFC2616].

sample: The smallest fundamental unit (such as a frame) in which media is stored and processed.

sparse stream: A stream that contains one or more sparse tracks.

sparse track: A track that is characterized by fragments that occur at irregular time intervals. It can be used to send metadata to clients to support scenarios such as ad signaling. This contrasts with non-sparse streams (for example, audio, video) in which fragments are sent at regular time intervals. A sparse track is always associated with a non-sparse parent track that is used to transmit timing information for the sparse track. Each sparse fragment includes a reference to any sparse track fragments that are created immediately before it.

stream: A set of tracks interchangeable at the client when playing media.

track: A time-ordered collection of samples of a particular type (such as audio or video).

MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.