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layer [video and systems]: One of the levels in the data hierarchy of the video and system specifications defined in Parts 1
and 2 of this International Standard.
luminance (component) [video]: A matrix, block or single pel representing a monochrome representation of the signal and
related to the primary colours in the manner defined in CCIR Rec 601. The symbol used for luminance is Y.
macroblock [video]: The four 8 by 8 blocks of luminance data and the two corresponding 8 by 8 blocks of chrominance data
coming from a 16 by 16 section of the luminance component of the picture. Macroblock is sometimes used to refer to the pel
data and sometimes to the coded representation of the pel values and other data elements defined in the macroblock layer of
the syntax defined in Part 2 of this International Standard. The usage is clear from the context.
mapping [audio]: Conversion of an audio signal from time to frequency domain by subband filtering and/or by MDCT.
masking threshold [audio]: A function in frequency and time below which an audio signal cannot be perceived by the
human auditory system.
masking [audio]: property of the human auditory system by which an audio signal cannot be perceived in the presence of
another audio signal .
MDCT [audio]: Modified Discrete Cosine Transform.
motion compensation [video]: The use of motion vectors to improve the efficiency of the prediction of pel values. The
prediction uses motion vectors to provide offsets into the past and/or future reference pictures containing previously decoded
pel values that are used to form the prediction error signal.
motion estimation [video]: The process of estimating motion vectors during the encoding process.
motion vector [video]: A two-dimensional vector used for motion compensation that provides an offset from the coordinate
position in the current picture to the coordinates in a reference picture.
MS stereo [audio]: A method of exploiting stereo irrelevance or redundancy in stereophonic audio programmes based on
coding the sum and difference signal instead of the left and right channels.
non-intra coding [video]: Coding of a macroblock or picture that uses information both from itself and from macroblocks
and pictures occurring at other times.
non-tonal component [audio]: A noise-like component of an audio signal.
Nyquist sampling: Sampling at or above twice the maximum bandwidth of a signal.
pack [system]: A pack consists of a pack header followed by one or more packets. It is a layer in the system coding syntax
described in Part 1 of this International Standard.
packet data [system]: Contiguous bytes of data from an elementary stream present in a packet.
packet header [system]: The data structure used to convey information about the elementary stream data contained in the
packet data.
packet [system]: A packet consists of a header followed by a number of contiguous bytes from an elementary data stream. It
is a layer in the system coding syntax described in Part 1 of this International Standard.
padding [audio]: A method to adjust the average length of an audio frame in time to the duration of the corresponding PCM
samples, by conditionally adding a slot to the audio frame.