ISO/IEC 18477-8:2020 情報技術—連続トーン静止画像のスケーラブルな圧縮とコーディング—パート8：ロスレスおよびほぼロスレスコーディング | ページ 6

3.1.1

AC coefficient

any DCT coefficient for which the frequency is not zero in at least one dimension

3.1.2

ASCII encoding

encoding of text characters and text strings

Note 1 to entry: In accordance with ISO/IEC 10646.

3.1.3

base decoding path

process of decoding legacy codestream and refinement data to the base image, jointly with all further steps until residual data is added to the values obtained from the residual codestream

3.1.4

base image

collection of sample values obtained by entropy decoding the DCT coefficients of the legacy codestream and the refinement codestream, and inversely DCT transforming them jointly

3.1.5

box

structured collection of data describing the image or the image decoding process embedded into one or multiple APP₁₁ marker segments

Note 1 to entry: See ISO/IEC 18477‑3:2015, Annex B for the definition of boxes.

3.1.6

coding process

encoding process, a decoding process, or both

3.1.7

DC coefficient

DCT coefficient for which the frequency is zero in both dimensions

3.1.8

DCT coefficient

amplitude of a specific cosine basis function

Note 1 to entry: May refer to an original DCT coefficient, to a quantized DCT coefficient, or to a dequantized DCT coefficient.

3.1.9

decoder

embodiment of a decoding process

3.1.10

decoding process

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

3.1.11

dequantization

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

3.1.12

encoder

embodiment of an encoding process

3.1.13

encoding process

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

3.1.14

extension image

residual image

sample values as reconstructed by inverse quantization and inverse DCT transformation applied to the entropy-decoded coefficients described by the residual scan and residual refinement scans

[SOURCE:ISO/IEC 18477‑6:2016, 3.1.54]

3.1.15

fixed point discrete cosine transformation

implementation of the discrete cosine transformation based on fixed point arithmetic

Note 1 to entry: As specified in Annex E.

3.1.16

forward DCT bypass

transformation that takes an 8×8 sample block and prepares it for entropy coding without applying a discrete cosine transformation

3.1.17

forward fixed point DCT

transformation of an 8×8 sample block from the spatial domain to the frequency domain using the fixed point arithmetic

Note 1 to entry: As specified in Annex E.

3.1.18

forward integer DCT

transformation of an 8×8 sample block from the spatial domain to the frequency domain using the integer approximation of the discrete cosine transformation

Note 1 to entry: As specified in Annex E.

3.1.19

inverse DCT bypass

transformation that takes an 8×8 sample block as generated by entropy decoding and level-shifts it without applying a discrete cosine transformation

3.1.20

inverse fixed point DCT

transformation of an 8×8 sample block from the frequency domain to the spatial domain using the fixed point arithmetic

Note 1 to entry: As specified in Annex E.

3.1.21

inverse integer DCT

the transformation of an 8×8 sample block from the frequency domain to the spatial domain using the integer approximation of the discrete cosine transformation

Note 1 to entry: As specified in Annex E.

3.1.22

frequency

two-dimensional index into the two-dimensional array of DCT coefficients

[SOURCE:ISO/IEC 10918‑1:1994, 3.1.61]

3.1.23

high dynamic range

HDR

image or image data comprised of more than eight bits per sample

3.1.24

Huffman encoding

entropy encoding procedure which assigns a variable length code to each input symbol

3.1.25

intermediate dynamic range

image or image data comprised of more than eight bits per sample

3.1.26

legacy codestream

collection of markers and syntax elements

Note 1 to entry: The legacy codestream, as defined by Rec. ITU-T T.81 | ISO/IEC 10918-1 and any syntax elements defined by the ISO/IEC 18477 series, consists of the collection of all markers except those APP₁₁ markers that describe JPEG XT boxes by the syntax defined in ISO/IEC 18477-3:2015, Annex A.

3.1.27

lossless

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)

3.1.28

lossless coding

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

Note 1 to entry: Coding processes defined in ISO/IEC 18477-8.

3.1.29

lossy

encoding and decoding processes which are not lossless

3.1.30

low-dynamic range

LDR

image or image data comprised of data with no more than eight bits per sample

3.1.31

noise shaping

signal processing technique that removes quantization noise from the low frequency components and injects it into the high frequency domain where it can be removed by filtering

3.1.32

point transformation

application of a location independent global function to reconstructed sample values in the spatial domain

3.1.33

residual decoding path

collection of operations applied to the entropy coded data contained in the residual data box and residual refinement scan boxes up to the point where this data is merged with the legacy data to form the final output image

3.1.34

residual image

sample values as reconstructed by inverse quantization and inverse DCT transformation applied to the entropy-decoded coefficients described by the residual scan and residual refinement scans

3.1.35

residual scan

additional pass over the image data invisible to legacy decoders which provides additive and/or multiplicative correction data of the legacy scans to allow reproduction of high-dynamic range or wide colour gamut data

3.1.36

refinement scan

additional pass over the image data invisible to legacy decoders which provides additional least significant bits to extend the precision of the DCT transformed coefficients

Note 1 to entry: Refinement scans can be either applied in the legacy or residual decoding path.

3.1.37

superbox

box that carries other boxes as payload data

3.1.38

sub box

box that is contained as payload data within a superbox

3.1.39

uniform quantization

procedure by which DCT coefficients are linearly scaled in order to achieve compression

3.1.40

upsampling

procedure by which the spatial resolution of a component is increased