ITU-T H.274 视频编码增强信息标准解析

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"视频编解码VSEI/H274 version1文档" 本文档主要讨论的是国际电信联盟（International Telecommunication Union, ITU-T）的H.274标准，这是针对编码移动视频的一种增强信息消息协议。H.274标准是ITU-T H系列音频与多媒体系统的一部分，其目的是提高视频编解码的效率和质量，特别是在移动通信和网络传输中。 H.274标准属于“Infrastructure of audiovisual services – Coding of moving video”类别，即视听服务基础设施中的运动图像编码。它的核心目标是提供一种灵活的补充增强信息（Versatile Supplemental Enhancement Information）消息，用于编码视频比特流。这样的信息有助于在编码过程中更有效地处理和传输视频数据，提升视频的压缩性能和解码时的图像质量。 H.274标准位于H.240到H.259子系列之下，这个子系列专注于运动视频的编码。这个系列包括了众多与视频编码相关的其他推荐标准，如H.261、H.263、H.264（也称为AVC，高级视频编码）、H.265（也称为HEVC，高效率视频编码）等，这些标准都在不断地演进，以适应更高的分辨率、更高的帧率以及更严苛的带宽限制。 H.274标准与其他H系列标准共同构建了一个全面的框架，涵盖了从系统层面的特性（如H.100-H.199），到传输、复用和同步（H.200-H.219），再到通信程序（H.230-H.239）等多个方面。这些标准旨在确保不同设备和系统之间的兼容性和互操作性，使得音频和视频服务能够在全球范围内顺畅地进行。此外，H系列还包括了与视听服务相关的终端设备标准（H.280-H.299）、多媒体服务目录服务架构（H.300-H.349）、服务质量架构（H.350-H.359），以及针对远程呈现、沉浸式环境、虚拟现实和扩展现实的规范（H.360-H.369）。这表明H.274标准不仅关注视频编码本身，还关注如何在各种复杂场景下实现高效、高质量的视频通信。 H.274标准的实施对于视频编解码器的开发者和应用者来说至关重要，因为它提供了在编码视频流时发送额外信息的方法，这些信息可以用于错误检测和恢复，提高视频的鲁棒性，或是在有限带宽条件下优化用户体验。因此，理解并正确应用H.274能够显著提升视频通信系统的整体性能。

6 Rec. ITU-T H.274 (08/2020)

The mathematical operators used in this Specification are similar to those used in the C programming language. However,

the results of integer division and arithmetic shift operations are defined more precisely, and additional operations are

defined, such as exponentiation and real-valued division.

Numbering and counting conventions generally begin from 0, e.g., "the first" is equivalent to the 0-th, "the second" is

equivalent to the 1-th, etc.

5.2 Arithmetic operators

addition

−

subtraction (as a two-argument operator) or negation (as a unary prefix operator)

multiplication, including matrix multiplication

exponentiation

Specifies x to the power of y. In other contexts, such notation is used for superscripting not intended

for interpretation as exponentiation.

integer division with truncation of the result toward zero

For example, 7 / 4 and −7 / −4 are truncated to 1 and −7 / 4 and 7 / −4 are truncated to −1.

division in mathematical equations where no truncation or rounding is intended

f( i )

i=x

summation of f( i ) with i taking all integer values from x up to and including y

x % y

modulus

Remainder of x divided by y, defined only for integers x and y with x >= 0 and y > 0

5.3 Logical operators

x && y Boolean logical "and" of x and y

x | | y Boolean logical "or" of x and y

! Boolean logical "not"

x ? y : z if x is TRUE or not equal to 0, evaluates to the value of y; otherwise, evaluates to the value of z.

5.4 Relational operators

> greater than

>= greater than or equal to

< less than

<= less than or equal to

= = equal to

!= not equal to

When a relational operator is applied to a syntax element or variable that has been assigned the value "na" (not applicable),

the value "na" is treated as a distinct value for the syntax element or variable. The value "na" is considered not to be equal

to any other value.

5.5 Bit-wise operators

& bit-wise "and"

When operating on integer arguments, operates on a two's complement representation of the integer

value. When operating on a binary argument that contains fewer bits than another argument, the shorter

argument is extended by adding more significant bits equal to 0.

| bit-wise "or"

Rec. ITU-T H.274 (08/2020) 7

When operating on integer arguments, operates on a two's complement representation of the integer

value. When operating on a binary argument that contains fewer bits than another argument, the shorter

argument is extended by adding more significant bits equal to 0.

^ bit-wise "exclusive or"

When operating on integer arguments, operates on a two's complement representation of the integer

value. When operating on a binary argument that contains fewer bits than another argument, the shorter

argument is extended by adding more significant bits equal to 0.

x >> y arithmetic right shift of a two's complement integer representation of x by y binary digits

This function is defined only for non-negative integer values of y. Bits shifted into the most significant

bits (MSBs) as a result of the right shift have a value equal to the MSB of x prior to the shift operation.

x << y arithmetic left shift of a two's complement integer representation of x by y binary digits

This function is defined only for non-negative integer values of y. Bits shifted into the least significant

bits (LSBs) as a result of the left shift have a value equal to 0.

5.6 Assignment operators

= assignment operator

++ increment, i.e., x++ is equivalent to x = x + 1; when used in an array index, evaluates to the value of the

variable prior to the increment operation

− − decrement, i.e., x− − is equivalent to x = x − 1; when used in an array index, evaluates to the value of the

variable prior to the decrement operation

+= increment by amount specified, i.e., x += 3 is equivalent to x = x + 3, and x += (−3) is equivalent

to x = x + (−3)

−= decrement by amount specified, i.e., x −= 3 is equivalent to x = x − 3, and x −= (−3) is equivalent

to x = x − (−3).

5.7 Range notation

x = y..z x takes on integer values starting from y to z, inclusive, with x, y, and z being integer numbers and z

being greater than y.

5.8 Mathematical functions

Abs( x ) = 

x ; x >= 0

x ; x < 0

(1)

Asin( x ) trigonometric inverse sine function, operating on an argument x that is

in the range of −1.0 to 1.0, inclusive, with an output value in the range of

−π÷2 to π÷2, inclusive, in units of radians (2)

Atan( x ) trigonometric inverse tangent function, operating on an argument x, with

an output value in the range of −π÷2 to π÷2, inclusive, in units of radians (3)

Atan2( y, x ) =













Atan 󰇡

󰇢 ; x > 0

Atan 󰇡

󰇢  π

Atan 󰇡

󰇢  

;

x < 0 && y >= 0

x < 0 && y < 0





;

x = = 0 && y >= 0

otherwise

(4)

Ceil( x ) smallest integer greater than or equal to x. (5)

Rec. ITU-T H.274 (08/2020) 9

5.10 Variables, syntax elements and tables

Syntax elements in the syntax tables are represented in bold type. Each syntax element is described by its name (all lower

case letters with underscore characters), and one descriptor for its method of coded representation. The decoding process

behaves according to the value of the syntax element and to the values of previously decoded syntax elements. When a

value of a syntax element is used in the syntax tables or the text, it appears in regular (i.e., not bold) type.

In some cases, the syntax tables and semantics use the values of other variables derived from the values of syntax elements.

Such variables appear in the syntax tables, or text, named by a mixture of lower case and upper case letter and without any

underscore characters. Variables starting with an upper case letter are derived for the decoding of the current syntax

structure and all depending syntax structures. Variables starting with an upper case letter could, in some cases, be used in

the decoding process for later syntax structures without mentioning the originating syntax structure of the variable.

Variables starting with a lower case letter are only used within the clause in which they are derived.

In some cases, "mnemonic" names for syntax element values or variable values are used interchangeably with their

numerical values. Sometimes "mnemonic" names are used without any associated numerical values. The association of

values and names is specified in the text. The names are constructed from one or more groups of letters separated by an

underscore character. Each group starts with an upper case letter and could contain more upper case letters.

NOTE – The syntax is described in a manner that closely follows the C-language syntactic constructs.

Functions that specify properties of the current position in the SEI message payload data are referred to as syntax functions.

These functions are specified in clause 6.3 and assume the existence of a pointer with an indication of the position of the

next bit to be read by the decoding process from the payload data. Syntax functions are described by their names, which

are constructed as syntax element names and end with left and right round parentheses including zero or more variable

names (for definition) or values (for usage), separated by commas (if more than one variable).

Functions that are not syntax functions (including mathematical functions specified in clause 5.8) are described by their

names, which start with an upper case letter, contain a mixture of lower and upper case letters without any underscore

character, and end with left and right parentheses including zero or more variable names (for definition) or values (for

usage) separated by commas (if more than one variable).

A one-dimensional array is referred to as a list. A two-dimensional array is referred to as a matrix. Arrays can either be

syntax elements or variables. Subscripts or square parentheses are used for the indexing of arrays. In reference to a visual

depiction of a matrix, the first subscript is used as a row (vertical) index and the second subscript is used as a column

(horizontal) index. The indexing order is reversed when using square parentheses rather than subscripts for indexing. Thus,

an element of a matrix s at horizontal position x and vertical position y could be denoted either as s[ x ][ y ] or as s

. A

single column of a matrix could be referred to as a list and denoted by omission of the row index. Thus, the column of a

matrix s at horizontal position x could be referred to as the list s[ x ].

A specification of values of the entries in rows and columns of an array could be denoted by { {...} {...} }, where each

inner pair of brackets specifies the values of the elements within a row in increasing column order and the rows are ordered

in increasing row order. Thus, setting a matrix s equal to { { 1 6 } { 4 9 }} specifies that s[ 0 ][ 0 ] is set equal to 1,

s[ 1 ][ 0 ] is set equal to 6, s[ 0 ][ 1 ] is set equal to 4, and s[ 1 ][ 1 ] is set equal to 9.

Binary notation is indicated by enclosing the string of bit values by single quote marks. For example, '01000001' represents

an eight-bit string having only its second and its last bits (counted from the most to the least significant bit) equal to 1.

Hexadecimal notation, indicated by prefixing the hexadecimal number by "0x", is used in some cases instead of binary

notation when the number of bits is an integer multiple of 4. For example, 0x41 represents an eight-bit string having only

its second and its last bits (counted from the most to the least significant bit) equal to 1.

Numerical values not enclosed in single quotes and not prefixed by "0x" are decimal values.

A value equal to 0 represents a FALSE condition in a test statement. The value TRUE is represented by any value different

from zero.

5.11 Text description of logical operations

In the text, a statement of logical operations as would be described mathematically in the following form:

if( condition 0 )

statement 0

else if( condition 1 )

statement 1

...

else /* informative remark on remaining condition */

statement n

10 Rec. ITU-T H.274 (08/2020)

is typically described in the following manner:

... as follows / ... the following applies:

– If condition 0, statement 0

– Otherwise, if condition 1, statement 1

– ...

– Otherwise (informative remark on remaining condition), statement n

Each "If ... Otherwise, if ... Otherwise, ..." statement in the text is introduced with "... as follows" or "... the following

applies" immediately followed by "If ... ". The last condition of the "If ... Otherwise, if ... Otherwise, ..." is always an

"Otherwise, ...". Interleaved "If ... Otherwise, if ... Otherwise, ..." statements can be identified by matching "... as follows"

or "... the following applies" with the ending "Otherwise, ...".

In the text, a statement of logical operations as would be described mathematically in the following form:

if( condition 0a && condition 0b )

statement 0

else if( condition 1a | | condition 1b )

statement 1

...

else

statement n

is typically described in the following manner:

... as follows / ... the following applies:

– If all of the following conditions are true, statement 0:

– condition 0a

– condition 0b

– Otherwise, if one or more of the following conditions are true, statement 1:

– condition 1a

– condition 1b

– ...

– Otherwise, statement n

In the text, a statement of logical operations as would be described mathematically in the following form:

if( condition 0 )

statement 0

if( condition 1 )

statement 1

is typically described in the following manner:

When condition 0, statement 0

When condition 1, statement 1

5.12 Processes

Processes are used to describe the decoding of syntax elements. A process has a separate specification and invoking. All

syntax elements and upper case variables that pertain to the current syntax structure and depending syntax structures are

available in the process specification and invoking. A process specification might also have a lower case variable explicitly

specified as input. Each process specification has explicitly specified an output. The output is a variable that can either be

an upper case variable or a lower case variable.

When invoking a process, the assignment of variables is specified as follows:

– If the variables at the invoking and the process specification do not have the same name, the variables are explicitly

assigned to lower case input or output variables of the process specification.

– Otherwise (the variables at the invoking and the process specification have the same name), assignment is implied.

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洌泉_就这样吧

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