ISO/IEC 21122-1:2024 情報技術 ― JPEG XS 低遅延・軽量画像符号化方式 ― 第1部:コア符号化方式 | ページ 5

3.1.1

band

input data to a specific wavelet filter type (3.1.54) that contributes to the generation of one of the components (3.1.14) of the image

3.1.2

band type

single number collapsing the information on the component, and horizontal and vertical wavelet filter types that are applied in the filter cascade reconstructing spatial image samples from inversely quantized wavelet coefficients

3.1.3

bit

binary choice encoded as either 0 or 1

3.1.4

bitplane

array of bits having all the same significance

3.1.5

bitplane count

number of significant bitplanes of a code group, counting from the LSB up to the most significant, non-empty bitplane

3.1.6

bitplane count subpacket

subset of a packet which decodes to the bitplane counts of all code groups within a packet, followed by padding and optional filler bytes

Note 1 to entry: See subclause C.5.3.

3.1.7

byte

group of 8 bits

3.1.8

colour filter array

CFA

rectangular array of sensor elements yielding a 1-component image where the colour to which a sensor element is sensitive to depends on the position of the sensor element

3.1.9

codestream

compressed image data representation that includes all necessary data to allow a (full or approximate) reconstruction of the sample values of a digital image

3.1.10

code group

group of quantization indices in sign-magnitude representation before inverse quantization

3.1.11

coefficient

input value to the inverse wavelet transformation resulting from inverse quantization

3.1.12

coefficient group

number of horizontally adjacent wavelet coefficients from the same band

3.1.13

column

set of vertically aligned precincts

3.1.14

component

two-dimensional array of samples having the same designation such as red, green or blue in the output or display device

3.1.15

compression

process of reducing the number of bits used to represent source image data

3.1.16

continuous-tone image

image whose components have more than one bit per sample

3.1.17

data subpacket

subset of a packet which consists of the quantization index magnitudes, followed by padding and optional filler bytes

Note 1 to entry: See subclause C.5.4.

3.1.18

deadzone quantizer

quantizer whose zero bucket has a size different from all other buckets

3.1.19

decoder

embodiment of a decoding process

3.1.20

decoding process

process which takes as its input a codestream and outputs a continuous-tone image

3.1.21

decomposition level

number of times a wavelet filter is applied to reconstruct image data from wavelet coefficients

3.1.22

encoder

embodiment of an encoding process

3.1.23

encoding process

process which outputs compressed image data in the form of a codestream

3.1.24

filler bytes

integer number of bytes a decoder will skip over on decoding without interpreting the values of the bytes itself

3.1.25

intra coding

coding process which decodes data independent from data decoded in a previous frame

Note 1 to entry: ISO/IEC 21122-1:2022 only defined intra coding tools.

3.1.26

inverse quantization

inverse procedure to quantization by which the decoder recovers a representation of the coefficients

3.1.27

inverse reversible multiple component transformation

inverse RCT

inverse transform across multiple component sample values located at the same sample grid point that is invertible without loss

Note 1 to entry: See subclauses F.3 and F.4.

3.1.28

LL band

input to a series of wavelet filters where only inverse low-pass filters are applied in horizontal and vertical direction

3.1.29

lossless

descriptive term for encoding and decoding processes and procedures in which the output of the decoding procedure(s) is identical to the input to the encoding procedure(s)

3.1.30

lossless coding

mode of operation which refers to any one of the coding processes defined in this document in which all of the procedures are lossless

3.1.31

lossy

descriptive term for encoding and decoding processes which are not lossless

3.1.32

packet

segment of the codestream containing entropy coded information on a single precinct, line and a subset of the bands within this precinct and line

3.1.33

padding

bits within the codestream whose only purpose is to align syntax elements to byte boundaries and that carry no information

3.1.34

precinct

collection of quantization indices of all bands contributing to a given spatial region of the image

3.1.35

precision

number of bits allocated to a particular sample, coefficient, or other binary numerical representation

3.1.36

procedure

set of steps which accomplishes one of the tasks which comprise an encoding or decoding process

3.1.37

quantization

method of reducing the precision of the individual coefficients

3.1.38

quantization index

input to the inverse quantization process which reconstructs the quantization index to a wavelet coefficient

3.1.39

quantization index magnitude

absolute value of a quantization index

3.1.40

sample

one element in the two-dimensional image array which comprises a component

3.1.41

sample grid

common coordinate system for all samples of an image, the samples at the top left edge of the image have the coordinates (0,0), the first coordinate increases towards the right, the second towards the bottom

3.1.42

sign subpacket

subset of a packet that consists of the sign information of all non-zero quantization indices within a packet, followed by padding and optional filler bytes

Note 1 to entry: See subclause C.5.5.

3.1.43

significance

attribute of code groups that applies if, depending on the Run Mode flag in the picture header, either at least one of coefficients in the code group is non-zero, or the bitplane count prediction residual of the code group is non-zero

3.1.44

significance group

group of a horizontally adjacent code groups sharing the same significance information in the significance subpacket

3.1.45

significance subpacket

subset of a packet that identifies which significance groups within a packet are insignificant, followed by padding and optional filler bytes

Note 1 to entry: see subclause C.5.2

3.1.46

slice

integral number of precincts whose wavelet coefficients can be entropy-decoded independently

3.1.47

star-tetrix

decorrelation transformation that combines a spatial with an inter-component decorrelation transformation particularly tuned for CFA pattern compression

Note 1 to entry: see subclause F.5

3.1.48

subpacket

substructure of a packet containing information of one or multiple bands of one line of a single precinct

3.1.49

super pixel

2×2 arrangement of sensor elements in a CFA pattern array containing at least one sensor element for each colour filter type

3.1.50

temporal differential coding

TDC

coding process which decodes a differential signal relative to a sample decoded in a previous frame

3.1.51

truncation position

number of least significant bitplanes not included in the quantization index of a wavelet coefficient

3.1.52

uniform quantizer

quantizer whose buckets are all of equal size

3.1.53

upsampling

procedure by which the spatial resolution of a component is increased

3.1.54

wavelet filter type

single number that uniquely identifies each element of the wavelet filter with regard to the number and type of horizontal and vertical decompositions

Note 1 to entry: Unlike the band type, the wavelet filter type does not include component information.