ISO/IEC 18477-6:2016 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6：IDR整数コーディング | 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 according to ISO/IEC 10646-1

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

binary decision

choice between two alternatives

3.1.6

bitstream

partially encoded or decoded sequence of bits comprising an entropy-coded segment

3.1.7

block

8 × 8 array of samples or an 8 × 8 array of DCT coefficient values of one component

3.1.8

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.

3.1.9

byte

group of 8 bits

3.1.10

coder

embodiment of a coding process

3.1.11

coding

encoding or decoding

3.1.12

coding model

procedure used to convert input data into symbols to be coded

3.1.13

(coding) process

general term for referring to an encoding process, a decoding process, or both

3.1.14

compression

reduction in the number of bits used to represent source image data

3.1.15

component

two-dimensional array of samples having the same designation in the output or display device

Note 1 to entry: An image typically consists of several components, e.g. red, green, and blue.

3.1.16

continuous-tone image

image whose components have more than one bit per sample

3.1.17

DC coefficient

DCT coefficient for which the frequency is zero in both dimensions

3.1.18

decoder

embodiment of a decoding process

3.1.19

decoding process

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

3.1.20

dequantization

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

3.1.21

discrete cosine transform

DCT

either the forward discrete cosine transform or the inverse discrete cosine transform

3.1.22

downsampling

procedure by which the spatial resolution of a component is reduced

3.1.23

encoder

embodiment of an encoding process

3.1.24

encoding process

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

3.1.25

entropy-coded (data) segment

independently decodable sequence of entropy encoded bytes of compressed image data

3.1.26

entropy decoder

embodiment of an entropy decoding procedure

3.1.27

entropy decoding

lossless procedure which recovers the sequence of symbols from the sequence of bits produced by the entropy encoder

3.1.28

entropy encoder

embodiment of an entropy encoding procedure

3.1.29

entropy encoding

lossless procedure which converts a sequence of input symbols into a sequence of bits such that the average number of bits per symbol approaches the entropy of the input symbols

3.1.30

grayscale image

continuous-tone image that has only one component

3.1.31

high dynamic range

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

3.1.32

Huffman decoder

embodiment of a Huffman decoding procedure

3.1.33

Huffman decoding

entropy decoding procedure which recovers the symbol from each variable length code produced by the Huffman encoder

3.1.34

Huffman encoder

embodiment of a Huffman encoding procedure

3.1.35

Huffman encoding

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

3.1.36

intermediate dynamic range

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

3.1.37

joint photographic experts group

JPEG

informal name of the committee which created this part of ISO/IEC 18477

Note 1 to entry: The “joint” comes from the ITU-T and ISO/IEC collaboration.

3.1.38

legacy codestream

collection of markers and syntax elements defined by Rec. ITU-T T.81 | ISO/IEC 10918-1 bare any additional syntax elements defined by the family ISO/IEC 18477 standards, i.e. the legacy codestream 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

3.1.39

legacy decoding path

collection of operations to be performed on the entropy coded data as described by Rec. ITU-T T.81 | ISO/IEC 10918-1 jointly with the Legacy Refinement scans before this data is merged with the residual data to form the final output image

3.1.40

legacy decoder

embodiment of a decoding process conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1, confined to the lossy DCT process and the baseline, sequential, or progressive modes, decoding at most four components to eight bits per component

3.1.41

legacy image

arrangement of sample values as described by applying the decoding process described by Rec. ITU-T T.81 | ISO/IEC 10918-1 on the entropy coded data as defined by said standard

3.1.42

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)

3.1.43

lossless coding

mode of operation which refers to any one of the coding processes defined in this part of ISO/IEC 18477 in which all of the procedures are lossless

Note 1 to entry: See ISO/IEC 18477-8.

3.1.44

lossy

descriptive term for encoding and decoding processes which are not lossless

3.1.45

low dynamic range

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

3.1.46

marker

two-byte code in which the first byte is hexadecimal FF and the second byte is a value between 1 and hexadecimal FE

3.1.47

marker segment

marker together with its associated set of parameters

3.1.48

pixel

collection of sample values in the spatial image domain having all the same sample coordinates, e.g. a pixel may consist of three samples describing its red, green, and blue value

3.1.49

precision

number of bits allocated to a particular sample or DCT coefficient

3.1.50

procedure

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

3.1.51

quantization value

integer value used in the quantization procedure

3.1.52

quantize

act of performing the quantization procedure for a DCT coefficient

3.1.53

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 base image to form the final output image

3.1.54

residual image

extension 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

3.1.55

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

3.1.56

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

3.1.57

sample

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

3.1.58

sample grid

common coordinate system for all samples of an image

Note 1 to entry: 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.

3.1.59

scan

single pass through the data for one or more of the components in an image

3.1.60

scan header

marker segment that contains a start-of-scan marker and associated scan parameters that are coded at the beginning of a scan

3.1.61

superbox

box that carries other boxes as payload data

3.1.62

table specification data

coded representation from which the tables used in the encoder and decoder are generated and their destinations specified

3.1.63

(uniform) quantization

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

3.1.64

upsampling

procedure by which the spatial resolution of a component is increased

3.1.65

vertical sampling factor

relative number of vertical data units of a particular component with respect to the number of vertical data units in the other components in the frame

3.1.66

zero byte

0x00 byte

3.1.67

zig-zag sequence

specific sequential ordering of the DCT coefficients from (approximately) lowest spatial frequency to highest