**ISO/IEC 10918-1 : 1993(E)**

Ta

j

AC entropy table destination selector for *j*th component in scan

Tb

arithmetic conditioning table destination identifier

Tc

Huffman coding or arithmetic coding table class

Td

j

DC entropy table destination selector for *j*th component in scan

TEM

temporary marker

Th

Huffman table destination identifier in DHT segment

Tq

quantization table destination identifier in DQT segment

Tq

i

quantization table destination selector for *i*th component in frame

U

DC and lossless coding conditioning upper bound parameter

V

symbol or value being either encoded or decoded

V

i

vertical sampling factor for *i*th component

V

i,j

*j*th value for length *i* in HUFFVAL

V

max

largest vertical sampling factor

V

t

temporary variable

VALPTR

list of indices for first value in HUFFVAL for each code length

V1

symbol value

V2

symbol value

x

i

number of columns in *i*th component

X

number of samples per line in component with largest horizontal dimension

X

i

*i*th statistics bin for coding magnitude category decision

X1, X2, X3, ... , X15

designation of context-indices for coding of magnitude categories in the arithmetic coding

models

XHUFCO

extended Huffman code table

XHUFSI

table of sizes of extended Huffman codes

X'values'

values within the quotes are hexadecimal

y

i

number of lines in *i*th component

Y

number of lines in component with largest vertical dimension

ZRL

value in HUFFVAL assigned to run of 16 zero coefficients

ZZ(K)

*K*th element in zig-zag sequence of quantized DCT coefficients

ZZ(0)

quantized DC coefficient in zig-zag sequence order

**4**

**General**

The purpose of this clause is to give an informative overview of the elements specified in this Specification. Another

purpose is to introduce many of the terms which are defined in clause 3. These terms are printed in *italics* upon first usage

in this clause.

**12**

**CCITT Rec. T.81 (1992 E)**