ISO/IEC 21122-2:2024 情報技術 — JPEG XS 低遅延軽量画像符号化システム — Part 2:プロファイルとバッファ モデル | ページ 6

3.1

blanking codestream fragment

placeholder codestream fragment representing blanking periods

3.2

buffer model

combination of a decoder model (3.8) and a channel model (3.4) whose behaviour can be defined by a set of parameters

3.3

buffer model instance

specific configuration of a buffer model (3.2) specified by the assignment of well-defined values to the buffer model parameters

3.4

channel model

model describing the temporal behaviour of the transmission channel (3.26) connecting an encoder and a decoder

3.5

coded codestream fragment

continuous sequence of bits in the codestream containing exactly one packet body and a well-defined number of packet headers, markers and marker segments

3.6

codestream fragment

either coded codestream fragment (3.5) or blanking codestream fragment (3.1)

3.7

cycle

clock cycle

single clock period of an encoder or decoder clocked implementation

3.8

decoder model

combination of a decoder unit (3.10) and a decoder smoothing buffer (3.9)

3.9

decoder smoothing buffer

memory buffer that is used to level out changes in the number of bits read by a decoder unit (3.10) per time unit

3.10

decoder unit

module reading a variable number of bits (from the smoothing buffer) per time unit to generate decoded output pixels at a fixed output rate

3.11

encoder model

combination of an encoder unit and an encoder smoothing buffer (3.12)

3.12

encoder smoothing buffer

memory buffer that is used to level out changes in the number of bits generated by an encoder unit (3.13) per time unit

3.13

encoder unit

module transforming a sequence of input pixels with constant rate into a conforming codestream, producing a bit sequence with variable number of bits generated per time unit

3.14

fill level

number of bits stored in the encoder or decoder smoothing buffer (3.9)

3.15

horizontal blanking period

timespan expressed in units of the grid point sampling rate between the last pixel of an image line — not being the last line of an image — and the first pixel of the next image line

3.16

level

defined set of constraints on the number of decoded samples to be processed by an encoder or decoder, both in the spatial and temporal dimensions

Note 1 to entry: The same set of levels is defined for all profiles. Individual implementations may, within the specified constraints, support a different level for each supported profile (3.19)

3.17

nominal bits per pixel value

mean number of bits allocated per encoded pixel which is used to derive the sublevel constraints by assuming an image with well-defined dimensions and frame rate derived from the level

3.18

pixel

samples of all components at a single sampling grid point (3.20)

3.19

profile

specified subset of the codestream syntax together with admissible parameter values

3.20

sampling grid point

position on the sample grid, specified by integer horizontal and vertical offset relative to the origin of the sample grid

3.21

smoothing buffer unit

level- and sublevel-dependent number of bits by which the smoothing buffer size of the decoder model is specified

3.22

start of transmission

SoT

time at which the transmission channel starts transmission relative to the start of encoding of the first codestream fragment of a codestream

3.23

sublevel

defined set of constraints on the amount of codestream bits to be processed by an encoder or decoder, per unit of time, per column, and per image

Note 1 to entry: The same set of sublevels is defined for all profiles. Individual implementations may, within the specified constraints, support a different sublevel for each supported profile

3.24

TDC disabled codestream

codestream that contains zero SLI markers

Note 1 to entry: See ISO/IEC 21122-1.

3.25

TDC enabled codestream

codestream that contains one or more SLI markers

Note 1 to entry: See ISO/IEC 21122-1.

3.26

transmission channel

facility transferring bits from a source entity to a target entity

3.27

transmission channel capacity

maximum number of bits per time unit that a transmission channel (3.26) can transfer from a source entity to a target entity

3.28

vertical blanking period

timespan expressed in units of the grid point sampling rate between the last line of an image — including the horizontal blanking periods  (3.15) — and the first line of the next image