ISO/IEC TR 19566-1:2016 情報技術— JPEGシステム—パート1：コードストリームとファイル形式を使用した情報のパッケージ化 | ページ 5

2.1.1

backward compatibility

inclusive of the old specification within the new specification

Note 1 to entry: Any devices implementing the new standard can also interpret all data compliant with the old version of the standard. However, an old device only compliant with the old version of the standard might not be able to interpret the data compliant with the new version of the standard.

2.1.2

bit stream

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

2.1.3

box

structured collection of data describing the image or the image decoding process

Note 1 to entry: See B.2 for the definition of boxes.

2.1.4

box-based file format

file format whose composing elements are well-defined, hierarchically structured boxes

2.1.5

byte

group of 8 bits

2.1.6

coder

embodiment of a coding process

2.1.7

coding

umbrella term that defines both the encoding/compression of a signal as well as the decoding/decompression of a signal

2.1.8

coding model

procedure used to convert input data into symbols to be coded

2.1.9

coding process

process which transforms compressed data into a continuous-tone image and/or a continuous-tone image into its compressed representation

Note 1 to entry: It presents thus an umbrella term for “encoding process” and “decoding process”.

2.1.10

compression

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

2.1.11

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, for example, red, green and blue.

2.1.12

continuous-tone image

image whose components have more than one bit per sample

2.1.13

decoder

embodiment of a decoding process

3.1.14

decoding process

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

2.1.15

dequantization

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

2.1.16

downsampling

procedure by which the spatial resolution of a component is reduced

2.1.17

encoder

embodiment of an encoding process

2.1.18

encoding process

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

2.1.19

entropy-coded (data) segment

independently decodable sequence of entropy encoded bytes of compressed image data

2.1.20

entropy decoder

embodiment of an entropy decoding procedure

2.1.21

entropy decoding

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

2.1.22

entropy encoder

embodiment of an entropy encoding procedure

2.1.23

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

2.1.24

forward compatibility

only compliant with the old specification but able to interpret the new specification

Note 1 to entry: Although devices only compliant with the old version of the standard are nevertheless able to interpret the data conforming with the new standard, it is possible that the obtained results are not as good as when using a device compliant with the new version of the standard.

2.1.25

grayscale image

continuous-tone image that has only one component

2.1.26

high dynamic range

image or image data comprised of more than eight bits per sample, coded in floating point representation

2.1.27

intermediate dynamic range

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

2.1.28

Joint Photographic Experts Group

JPEG

informal name of the committee which created this part of ISO/TR 19566

2.1.29

JPEG standards

collection of ISO/IEC/ITU standards developed by the Joint Photographic Experts Group for still imaging application as listed in the Bibliography

2.1.30

JPEG Systems

common elements of a system layer for JPEG standards

2.1.31

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)

2.1.32

lossless coding

mode of operation which refers to any one of the coding processes defined in this part of ISO/TR 19566 in which all of the procedures are lossless

2.1.33

lossy

descriptive term for encoding and decoding processes which are not lossless

2.1.34

low-dynamic range

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

2.1.35

marker

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

2.1.36

marker segment

marker together with its associated set of parameters

2.1.37

metadata

additional data associated with the image data beyond the image data

2.1.38

minimum coded unit

MCU

smallest group of data units that is coded

2.1.39

pixel

collection of sample values in the spatial image domain having all the same sample coordinates

2.1.40

point transform

scaling of a sample or DCT coefficient by a factor

2.1.41

precision

number of bits allocated to a particular sample or DCT coefficient

2.1.42

procedure

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

2.1.43

quantization value

integer value used in the quantization procedure

2.1.44

quantize

act of performing the quantization procedure for a DCT coefficient

2.1.45

sample

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

2.1.46

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.

2.1.47

table specification data

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

2.1.48

(uniform) quantization

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

2.1.49

upsampling

procedure by which the spatial resolution of a component is increased

2.1.50

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

2.1.51

zero byte

0x00 byte