1 This section defines the abbreviations and terms used in the Dirac specification.
3 \subsection{Abbreviations
}
6 \item[4CIF:
] Four times CIF
7 \item[4SIF:
] Four times SIF
8 \item[CIE:
] Commission internationale de l'\'
{e
}clairage (International Commission on Illumination)
9 \item[CIF:
] Common Image Format
10 \item[DC:
] Direct Current
11 \item[DCI:
] Digital Cinema Initiatives
12 \item[DWT:
] Discrete Wavelet Transform
13 \item[HD(TV):
] High Definition (Television)
14 \item[HH:
] High-High (subband)
15 \item[HL:
] High-Low (subband)
16 \item[IDWT:
] Inverse Discrete Wavelet Transform
17 \item[ITU:
] International Telecommunications Union
18 \item[LH:
] Low-High (subband)
19 \item[LL:
] Low-Low (subband)
20 \item[NTSC:
] National Television Systems Committee
21 \item[QCIF:
] Quarter CIF
22 \item[QSIF:
] Quarter SIF
23 \item[SD(TV):
] Standard Definition (Television)
24 \item[SIF:
] Source Input Format
25 \item[VC:
] Video Codec
26 \item[VLC:
] Variable Length Code
31 \item[AC (sub)Band:
] any signal band that is not the DC sub-band.
32 \item[Arithmetic coding:
] a form of entropy coding used by Dirac, which is used
33 in addition to exp-Golomb coding.
34 \item[Chroma:
] a pair of colour difference components. The term chroma is the
35 direct equivalent to luma (see luma definition below). In this specification,
36 the term chroma is not the same as that used in composite colour television. It
37 is used to cover both gamma-corrected and non-gamma-corrected signals.
38 \item[Codeblock:
] a rectangular array of wavelet coefficients within a component
40 \item[Codec:
] a truncation of the terms "coder" and "decoder".
41 \item[DC subband:
] the signal band that represents data composed from the lowest
42 frequency band of a wavelet transform (
0-LL).
43 \item[Discrete Wavelet Transform (DWT):
] a means of transforming an array of
44 values into space-frequency components through the use of a filter bank.
45 \item[Entropy Coding:
] a term for describing any mathematical process used to
46 encode data in a lossless manner, intended to reduce the required bit rate.
47 \item[Exp-Golomb:
] a form of variable-length code. This specification uses an
49 \item[Intra DC Prediction:
] the prediction of coefficients within the dc subband
50 of intra pictures from neighbouring coefficients..
51 \item[Inverse Discrete Wavelet Transform (IDWT):
] the inverse of the DWT that
52 converts an array of space- frequency components back into an array of values.
53 \item[Inverse Quantisation:
] a process whereby each sample of a sub-band has
54 its signal range expanded by a defined value.
55 \item[Lifting:
] the name given to reducing a DWT filtering operations into a
57 filters, each operating on half the samples.
58 (Note: see Bibliography item "Ripples in Mathematics", chapter
3, for
60 \item[Low Delay:
] a term used to define a Dirac mode which can be
61 used to compress video with a delay of less than one frame duration.
62 \item[Luma:
] the weighted sum of RGB components of colour video, which may or
63 may not be gamma-corrected. (This term is used to prevent confusion with the
64 term luminance that is created only from linear light levels as used in colour
66 \item[Parse Info header:
] identifies the beginning of major Dirac syntax
67 elements (sequence start, picture, sequence end, padding and auxiliary data)
68 with defined parse code values.
69 \item[Parsing:
] a process by which numerical and text strings within binary data
70 are recognised and used to provide syntactic meaning.
71 \item[Picture:
] a single frame or field of video.
72 \item[Quantisation:
] a process whereby each sample of a sub-band has its signal
73 range compressed by a defined value.
74 \item[Quantiser:
] The defined value used for the purposes of quantisation or
76 \item[Raster scan:
] any
2-dimensional array of samples, whether as video samples
77 or as wavelet transformed values, that is scanned in accordance with television
78 systems; namely left to right, then top to bottom.
79 \item[Sequence:
] the data contained in a Dirac sequence corresponds to a single
80 video sequence with constant video parameters as defined in Section
81 \ref{sequenceheader
}. A
82 Dirac sequence is preceded by a `Parse Info' header that indicates the beginning
83 of the sequence with a unique parse code. A Dirac sequence can be extracted
84 from a Dirac bit-stream and decoded entirely independently.
85 \item[Slice:
] a component part of the low-delay syntax that provides for
86 compression of small parts (slices) of a picture in order to reduce delay.
87 \item[State:
] the set of current decoder variable values.
88 \item[Stream:
] a concatenation of Dirac sequences.
89 \item[Subband:
] the signal band that represents data composed from a single
90 space-frequency band of a wavelet transform.
