INTERNATIONAL TELECOMMUNICATION UNION
`
`CCITT
`
`THE INTERNATIONAL
`TELEGRAPH AND TELEPHONE
`CONSULTATIVE COMMITTEE
`
`T.81
`(09/92)
`
`TERMINAL EQUIPMENT AND PROTOCOLS
`FOR TELEMATIC SERVICES
`
`INFORMATION TECHNOLOGY –
`DIGITAL COMPRESSION AND CODING
`OF CONTINUOUS-TONE STILL IMAGES –
`REQUIREMENTS AND GUIDELINES
`
`Recommendation T.81
`
`Ex. 2004
`Netflix v. Realtime
`IPR2018-01630
`
`

`

`Foreword
`
`the field of
`in
`the United Nations Specialized Agency
`is
`ITU (International Telecommunication Union)
`telecommunications. The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent
`organ of the ITU. Some 166 member countries, 68 telecom operating entities, 163 scientific and industrial organizations
`and 39 international organizations participate in CCITT which is the body which sets world telecommunications
`standards (Recommendations).
`
`The approval of Recommendations by the members of CCITT is covered by the procedure laid down in CCITT Resolution
`No. 2 (Melbourne, 1988). In addition, the Plenary Assembly of CCITT, which meets every four years, approves
`Recommendations submitted to it and establishes the study programme for the following period.
`
`In some areas of information technology, which fall within CCITT’s purview, the necessary standards are prepared on a
`collaborative basis with ISO and IEC. The text of CCITT Recommendation T.81 was approved on 18th September 1992.
`The identical text is also published as ISO/IEC International Standard 10918-1.
`
`___________________
`
`CCITT NOTE
`
`In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication
`administration and a recognized private operating agency.
`
`All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or
`mechanical, including photocopying and microfilm, without permission in writing from the ITU.
`
`ITU 1993
`
`ª
`

`

`Contents
`
`Introduction..............................................................................................................................................................
`
`1
`
`2
`
`3
`
`4
`
`5
`
`6
`
`7
`
`Scope ............................................................................................................................................................
`
`Normative references.....................................................................................................................................
`
`Definitions, abbreviations and symbols .........................................................................................................
`
`General .........................................................................................................................................................
`
`Interchange format requirements ...................................................................................................................
`
`Encoder requirements ...................................................................................................................................
`
`Decoder requirements ...................................................................................................................................
`
`Annex A – Mathematical definitions........................................................................................................................
`
`Annex B – Compressed data formats........................................................................................................................
`
`Annex C – Huffman table specification....................................................................................................................
`
`Annex D – Arithmetic coding ..................................................................................................................................
`
`Annex E – Encoder and decoder control procedures................................................................................................
`
`Annex F – Sequential DCT-based mode of operation...............................................................................................
`
`Annex G – Progressive DCT-based mode of operation.............................................................................................
`
`Annex H – Lossless mode of operation ....................................................................................................................
`
`Annex J – Hierarchical mode of operation................................................................................................................
`
`Annex K – Examples and guidelines........................................................................................................................
`
`Annex L – Patents....................................................................................................................................................
`
`Annex M – Bibliography..........................................................................................................................................
`
`Page
`
`iii
`
`1
`
`1
`
`1
`
`12
`
`23
`
`23
`
`23
`
`24
`
`31
`
`50
`
`54
`
`77
`
`87
`
`119
`
`132
`
`137
`
`143
`
`179
`
`181
`
`CCITT Rec. T.81 (1992 E)
`
`i
`
`

`

`Introduction
`
`This CCITT Recommendation | ISO/IEC International Standard was prepared by CCITT Study Group VIII and the Joint
`Photographic Experts Group (JPEG) of ISO/IEC JTC 1/SC 29/WG 10. This Experts Group was formed in 1986 to
`establish a standard for the sequential progressive encoding of continuous tone grayscale and colour images.
`
`Digital Compression and Coding of Continuous-tone Still images, is published in two parts:
`
`–
`
`–
`
`Requirements and guidelines;
`
`Compliance testing.
`
`This part, Part 1, sets out requirements and implementation guidelines for continuous-tone still image encoding and
`decoding processes, and for the coded representation of compressed image data for interchange between applications.
`These processes and representations are intended to be generic, that is, to be applicable to a broad range of applications for
`colour and grayscale still images within communications and computer systems. Part 2, sets out tests for determining
`whether implementations comply with the requirments for the various encoding and decoding processes specified in Part
`1.
`
`The user’s attention is called to the possibility that – for some of the coding processes specified herein – compliance with
`this Recommendation | International Standard may require use of an invention covered by patent rights. See Annex L for
`further information.
`
`The requirements which these processes must satisfy to be useful for specific image communications applications such as
`facsimile, Videotex and audiographic conferencing are defined in CCITT Recommendation T.80. The intent is that the
`generic processes of Recommendation T.80 will be incorporated into the various CCITT Recommendations for terminal
`equipment for these applications.
`
`In addition to the applications addressed by the CCITT and ISO/IEC, the JPEG committee has developped a compression
`standard to meet the needs of other applications as well, including desktop publishing, graphic arts, medical imaging and
`scientific imaging.
`
`Annexes A, B, C, D, E, F, G, H and J are normative, and thus form an integral part of this Specification. Annexes K, L
`and M are informative and thus do not form an integral part of this Specification.
`
`This Specification aims to follow the guidelines of CCITT and ISO/IEC JTC 1 on Rules for presentation of CCITT |
`ISO/IEC common text.
`
`

`

`INTERNATIONAL STANDARD
`
`ISO/IEC 10918-1 : 1993(E)
`CCITT Rec. T.81 (1992 E)
`
`CCITT RECOMMENDATION
`
`ISO/IEC 10918-1 : 1993(E)
`
`INFORMATION TECHNOLOGY – DIGITAL COMPRESSION
`AND CODING OF CONTINUOUS-TONE STILL IMAGES –
`REQUIREMENTS AND GUIDELINES
`
`1
`
`Scope
`
`This CCITT Recommendation | International Standard is applicable to continuous-tone – grayscale or colour – digital still
`image data. It is applicable to a wide range of applications which require use of compressed images. It is not applicable to
`bi-level image data.
`
`This Specification
`
`–
`
`–
`
`–
`
`specifies processes for converting source image data to compressed image data;
`
`specifies processes for converting compressed image data to reconstructed image data;
`
`gives guidance on how to implement these processes in practice;
`
`specifies coded representations for compressed image data.
`–
`NOTE – This Specification does not specify a complete coded image representation. Such representations may include
`certain parameters, such as aspect ratio, component sample registration, and colour space designation, which are application-
`dependent.
`
`2
`
`Normative references
`
`The following CCITT Recommendations and International Standards contain provisions which, through reference in this
`text, constitute provisions of this CCITT Recommendation | International Standard. At the time of publication, the
`editions indicated were valid. All Recommendations and Standards are subject to revision, and parties to agreements
`based on this CCITT Recommendation | International Standard are encouraged to investigate the possibility of applying
`the most recent edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers
`of currently valid International Standards. The CCITT Secretariat maintains a list of currently valid CCITT
`Recommendations.
`
`–
`
`CCITT Recommendation T.80 (1992), Common components for image compression and communication –
`Basic principles.
`
`3
`
`Definitions, abbreviations and symbols
`
`3.1
`
`Definitions and abbreviations
`
`For the purposes of this Specification, the following definitions apply.
`
`abbreviated format: A representation of compressed image data which is missing some or all of the table
`3.1.1
`specifications required for decoding, or a representation of table-specification data without frame headers, scan headers,
`and entropy-coded segments.
`
`3.1.2
`
`AC coefficient: Any DCT coefficient for which the frequency is not zero in at least one dimension.
`
`(adaptive) (binary) arithmetic decoding: An entropy decoding procedure which recovers the sequence of
`3.1.3
`symbols from the sequence of bits produced by the arithmetic encoder.
`
`(adaptive) (binary) arithmetic encoding: An entropy encoding procedure which codes by means of a recursive
`3.1.4
`subdivision of the probability of the sequence of symbols coded up to that point.
`
`application environment: The standards for data representation, communication, or storage which have been
`3.1.5
`established for a particular application.
`
`CCITT Rec. T.81 (1992 E)
`
`1
`
`

`

`ISO/IEC 10918-1 : 1993(E)
`
`3.1.6
`
`3.1.7
`
`arithmetic decoder: An embodiment of arithmetic decoding procedure.
`
`arithmetic encoder: An embodiment of arithmetic encoding procedure.
`
`baseline (sequential): A particular sequential DCT-based encoding and decoding process specified in this
`3.1.8
`Specification, and which is required for all DCT-based decoding processes.
`
`3.1.9
`
`binary decision: Choice between two alternatives.
`
`3.1.10
`
`3.1.11
`
`3.1.12
`
`bit stream: Partially encoded or decoded sequence of bits comprising an entropy-coded segment.
`block: An 8 ·
` 8 array of samples or an 8 ·
`
` 8 array of DCT coefficient values of one component.
`
`block-row: A sequence of eight contiguous component lines which are partitioned into 8 ·
`
` 8 blocks.
`
`3.1.13
`
`byte: A group of 8 bits.
`
`byte stuffing: A procedure in which either the Huffman coder or the arithmetic coder inserts a zero byte into
`3.1.14
`the entropy-coded segment following the generation of an encoded hexadecimal X’FF’ byte.
`
`carry bit: A bit in the arithmetic encoder code register which is set if a carry-over in the code register overflows
`3.1.15
`the eight bits reserved for the output byte.
`
`ceiling function: The mathematical procedure in which the greatest integer value of a real number is obtained
`3.1.16
`by selecting the smallest integer value which is greater than or equal to the real number.
`
`3.1.17
`
`class (of coding process): Lossy or lossless coding processes.
`
`code register: The arithmetic encoder register containing the least significant bits of the partially completed
`3.1.18
`entropy-coded segment. Alternatively, the arithmetic decoder register containing the most significant bits of a partially
`decoded entropy-coded segment.
`
`3.1.19
`
`coder: An embodiment of a coding process.
`
`3.1.20
`
`coding: Encoding or decoding.
`
`3.1.21
`
`coding model: A procedure used to convert input data into symbols to be coded.
`
`3.1.22
`
`(coding) process: A general term for referring to an encoding process, a decoding process, or both.
`
`3.1.23
`
`colour image: A continuous-tone image that has more than one component.
`
`3.1.24
`
`columns: Samples per line in a component.
`
`3.1.25
`
`component: One of the two-dimensional arrays which comprise an image.
`
`3.1.26
`
`compressed data: Either compressed image data or table specification data or both.
`
`3.1.27
`
`compressed image data: A coded representation of an image, as specified in this Specification.
`
`3.1.28
`
`compression: Reduction in the number of bits used to represent source image data.
`
`conditional exchange: The interchange of MPS and LPS probability intervals whenever the size of the LPS
`3.1.29
`interval is greater than the size of the MPS interval (in arithmetic coding).
`
`(conditional) probability estimate: The probability value assigned to the LPS by the probability estimation
`3.1.30
`state machine (in arithmetic coding).
`
`conditioning table: The set of parameters which select one of the defined relationships between prior coding
`3.1.31
`decisions and the conditional probability estimates used in arithmetic coding.
`
`context: The set of previously coded binary decisions which is used to create the index to the probability
`3.1.32
`estimation state machine (in arithmetic coding).
`
`3.1.33
`
`3.1.34
`
`continuous-tone image: An image whose components have more than one bit per sample.
`data unit: An 8 ·
`
` 8 block of samples of one component in DCT-based processes; a sample in lossless processes.
`
`2
`
`CCITT Rec. T.81 (1992 E)
`
`

`

`ISO/IEC 10918-1 : 1993(E)
`
`3.1.35 DC coefficient: The DCT coefficient for which the frequency is zero in both dimensions.
`
`3.1.36 DC prediction: The procedure used by DCT-based encoders whereby the quantized DC coefficient from the
`previously encoded 8 ·
` 8 block of the same component is subtracted from the current quantized DC coefficient.
`
`(DCT) coefficient: The amplitude of a specific cosine basis function – may refer to an original DCT coefficient,
`3.1.37
`to a quantized DCT coefficient, or to a dequantized DCT coefficient.
`
`3.1.38
`
`decoder: An embodiment of a decoding process.
`
`3.1.39
`image.
`
`decoding process: A process which takes as its input compressed image data and outputs a continuous-tone
`
`default conditioning: The values defined for the arithmetic coding conditioning tables at the beginning of
`3.1.40
`coding of an image.
`
`dequantization: The inverse procedure to quantization by which the decoder recovers a representation of the
`3.1.41
`DCT coefficients.
`
`differential component: The difference between an input component derived from the source image and the
`3.1.42
`corresponding reference component derived from the preceding frame for that component (in hierarchical mode coding).
`
`3.1.43
`decoded.
`
`differential frame: A frame in a hierarchical process in which differential components are either encoded or
`
`(digital) reconstructed image (data): A continuous-tone image which is the output of any decoder defined in
`3.1.44
`this Specification.
`
`(digital) source image (data): A continuous-tone image used as input to any encoder defined in this
`3.1.45
`Specification.
`
`3.1.46
`
`(digital) (still) image: A set of two-dimensional arrays of integer data.
`
`discrete cosine transform; DCT: Either the forward discrete cosine transform or the inverse discrete cosine
`3.1.47
`transform.
`
`downsampling (filter): A procedure by which the spatial resolution of an image is reduced (in hierarchical
`3.1.48
`mode coding).
`
`3.1.49
`
`encoder: An embodiment of an encoding process.
`
`3.1.50
`data.
`
`encoding process: A process which takes as its input a continuous-tone image and outputs compressed image
`
`entropy-coded (data) segment: An independently decodable sequence of entropy encoded bytes of compressed
`3.1.51
`image data.
`
`(entropy-coded segment) pointer: The variable which points to the most recently placed (or fetched) byte in
`3.1.52
`the entropy encoded segment.
`
`3.1.53
`
`entropy decoder: An embodiment of an entropy decoding procedure.
`
`entropy decoding: A lossless procedure which recovers the sequence of symbols from the sequence of bits
`3.1.54
`produced by the entropy encoder.
`
`3.1.55
`
`entropy encoder: An embodiment of an entropy encoding procedure.
`
`entropy encoding: A lossless procedure which converts a sequence of input symbols into a sequence of bits
`3.1.56
`such that the average number of bits per symbol approaches the entropy of the input symbols.
`
`extended (DCT-based) process: A descriptive term for DCT-based encoding and decoding processes in which
`3.1.57
`additional capabilities are added to the baseline sequential process.
`
`forward discrete cosine transform; FDCT: A mathematical transformation using cosine basis functions which
`3.1.58
`converts a block of samples into a corresponding block of original DCT coefficients.
`
`CCITT Rec. T.81 (1992 E)
`
`3
`
`

`

`ISO/IEC 10918-1 : 1993(E)
`
`frame: A group of one or more scans (all using the same DCT-based or lossless process) through the data of one
`3.1.59
`or more of the components in an image.
`
`frame header: A marker segment that contains a start-of-frame marker and associated frame parameters that are
`3.1.60
`coded at the beginning of a frame.
`
`3.1.61
`
`frequency: A two-dimensional index into the two-dimensional array of DCT coefficients.
`
`3.1.62
`
`(frequency) band: A contiguous group of coefficients from the zig-zag sequence (in progressive mode coding).
`
`full progression: A process which uses both spectral selection and successive approximation (in progressive
`3.1.63
`mode coding).
`
`3.1.64
`
`grayscale image: A continuous-tone image that has only one component.
`
`hierarchical: A mode of operation for coding an image in which the first frame for a given component is
`3.1.65
`followed by frames which code the differences between the source data and the reconstructed data from the previous
`frame for that component. Resolution changes are allowed between frames.
`
`hierarchical decoder: A sequence of decoder processes in which the first frame for each component is followed
`3.1.66
`by frames which decode an array of differences for each component and adds it to the reconstructed data from the
`preceding frame for that component.
`
`hierarchical encoder: The mode of operation in which the first frame for each component is followed by frames
`3.1.67
`which encode the array of differences between the source data and the reconstructed data from the preceding frame for
`that component.
`
`horizontal sampling factor: The relative number of horizontal data units of a particular component with respect
`3.1.68
`to the number of horizontal data units in the other components.
`
`3.1.69 Huffman decoder: An embodiment of a Huffman decoding procedure.
`
`3.1.70 Huffman decoding: An entropy decoding procedure which recovers the symbol from each variable length code
`produced by the Huffman encoder.
`
`3.1.71 Huffman encoder: An embodiment of a Huffman encoding procedure.
`
`3.1.72 Huffman encoding: An entropy encoding procedure which assigns a variable length code to each input symbol.
`
`3.1.73 Huffman table: The set of variable length codes required in a Huffman encoder and Huffman decoder.
`
`3.1.74
`
`image data: Either source image data or reconstructed image data.
`
`interchange format: The representation of compressed image data for exchange between application
`3.1.75
`environments.
`
`interleaved: The descriptive term applied to the repetitive multiplexing of small groups of data units from each
`3.1.76
`component in a scan in a specific order.
`
`inverse discrete cosine transform; IDCT: A mathematical transformation using cosine basis functions which
`3.1.77
`converts a block of dequantized DCT coefficients into a corresponding block of samples.
`
`Joint Photographic Experts Group; JPEG: The informal name of the committee which created this
`3.1.78
`Specification. The “joint” comes from the CCITT and ISO/IEC collaboration.
`
`3.1.79
`coding).
`
`latent output: Output of the arithmetic encoder which is held, pending resolution of carry-over (in arithmetic
`
`3.1.80
`
`less probable symbol; LPS: For a binary decision, the decision value which has the smaller probability.
`
`level shift: A procedure used by DCT-based encoders and decoders whereby each input sample is either
`3.1.81
`converted from an unsigned representation to a two’s complement representation or from a two’s complement
`representation to an unsigned representation.
`
`4
`
`CCITT Rec. T.81 (1992 E)
`
`

`

`ISO/IEC 10918-1 : 1993(E)
`
`lossless: A descriptive term for encoding and decoding processes and procedures in which the output of the
`3.1.82
`decoding procedure(s) is identical to the input to the encoding procedure(s).
`
`lossless coding: The mode of operation which refers to any one of the coding processes defined in this
`3.1.83
`Specification in which all of the procedures are lossless (see Annex H).
`
`3.1.84
`
`lossy: A descriptive term for encoding and decoding processes which are not lossless.
`
`3.1.85 marker: A two-byte code in which the first byte is hexadecimal FF (X’FF’) and the second byte is a value
`between 1 and hexadecimal FE (X’FE’).
`
`3.1.86 marker segment: A marker and associated set of parameters.
`
`3.1.87 MCU-row: The smallest sequence of MCU which contains at least one line of samples or one block-row from
`every component in the scan.
`
`3.1.88 minimum coded unit; MCU: The smallest group of data units that is coded.
`
`3.1.89 modes (of operation): The four main categories of image coding processes defined in this Specification.
`
`3.1.90 more probable symbol; MPS: For a binary decision, the decision value which has the larger probability.
`
`non-differential frame: The first frame for any components in a hierarchical encoder or decoder. The
`3.1.91
`components are encoded or decoded without subtraction from reference components. The term refers also to any frame in
`modes other than the hierarchical mode.
`
`non-interleaved: The descriptive term applied to the data unit processing sequence when the scan has only one
`3.1.92
`component.
`
`3.1.93
`
`parameters: Fixed length integers 4, 8 or 16 bits in length, used in the compressed data formats.
`
`3.1.94
`
`point transform: Scaling of a sample or DCT coefficient.
`
`3.1.95
`
`precision: Number of bits allocated to a particular sample or DCT coefficient.
`
`3.1.96
`
`predictor: A linear combination of previously reconstructed values (in lossless mode coding).
`
`probability estimation state machine: An interlinked table of probability values and indices which is used to
`3.1.97
`estimate the probability of the LPS (in arithmetic coding).
`
`probability interval: The probability of a particular sequence of binary decisions within the ordered set of all
`3.1.98
`possible sequences (in arithmetic coding).
`
`(probability) sub-interval: A portion of a probability interval allocated to either of the two possible binary
`3.1.99
`decision values (in arithmetic coding).
`
`3.1.100 procedure: A set of steps which accomplishes one of the tasks which comprise an encoding or decoding
`process.
`
`3.1.101 process: See coding process.
`
`3.1.102 progressive (coding): One of the DCT-based processes defined in this Specification in which each scan
`typically improves the quality of the reconstructed image.
`
`3.1.103 progressive DCT-based: The mode of operation which refers to any one of the processes defined in Annex G.
`
`3.1.104 quantization table: The set of 64 quantization values used to quantize the DCT coefficients.
`
`3.1.105 quantization value: An integer value used in the quantization procedure.
`
`3.1.106 quantize: The act of performing the quantization procedure for a DCT coefficient.
`
`3.1.107 reference (reconstructed) component: Reconstructed component data which is used in a subsequent frame of a
`hierarchical encoder or decoder process (in hierarchical mode coding).
`
`CCITT Rec. T.81 (1992 E)
`
`5
`
`

`

`ISO/IEC 10918-1 : 1993(E)
`
`3.1.108 renormalization: The doubling of the probability interval and the code register value until the probability
`interval exceeds a fixed minimum value (in arithmetic coding).
`
`3.1.109 restart interval: The integer number of MCUs processed as an independent sequence within a scan.
`
`3.1.110 restart marker: The marker that separates two restart intervals in a scan.
`
`3.1.111 run (length): Number of consecutive symbols of the same value.
`
`3.1.112 sample: One element in the two-dimensional array which comprises a component.
`
`3.1.113 sample-interleaved: The descriptive term applied to the repetitive multiplexing of small groups of samples from
`each component in a scan in a specific order.
`
`3.1.114 scan: A single pass through the data for one or more of the components in an image.
`
`3.1.115 scan header: A marker segment that contains a start-of-scan marker and associated scan parameters that are
`coded at the beginning of a scan.
`
`3.1.116 sequential (coding): One of the lossless or DCT-based coding processes defined in this Specification in which
`each component of the image is encoded within a single scan.
`
`3.1.117 sequential DCT-based: The mode of operation which refers to any one of the processes defined in Annex F.
`
`3.1.118 spectral selection: A progressive coding process in which the zig-zag sequence is divided into bands of one or
`more contiguous coefficients, and each band is coded in one scan.
`
`3.1.119 stack counter: The count of X’FF’ bytes which are held, pending resolution of carry-over in the arithmetic
`encoder.
`
`3.1.120 statistical conditioning: The selection, based on prior coding decisions, of one estimate out of a set of
`conditional probability estimates (in arithmetic coding).
`
`3.1.121 statistical model: The assignment of a particular conditional probability estimate to each of the binary
`arithmetic coding decisions.
`
`3.1.122 statistics area: The array of statistics bins required for a coding process which uses arithmetic coding.
`
`3.1.123 statistics bin: The storage location where an index is stored which identifies the value of the conditional
`probability estimate used for a particular arithmetic coding binary decision.
`
`3.1.124 successive approximation: A progressive coding process in which the coefficients are coded with reduced
`precision in the first scan, and precision is increased by one bit with each succeeding scan.
`
`3.1.125 table specification data: The coded representation from which the tables used in the encoder and decoder are
`generated and their destinations specified.
`
`3.1.126 transcoder: A procedure for converting compressed image data of one encoder process to compressed image
`data of another encoder process.
`
`3.1.127 (uniform) quantization: The procedure by which DCT coefficients are linearly scaled in order to achieve
`compression.
`
`3.1.128 upsampling (filter): A procedure by which the spatial resolution of an image is increased (in hierarchical mode
`coding).
`
`3.1.129 vertical sampling factor: The 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.
`
`3.1.130 zero byte: The X’00’ byte.
`
`3.1.131 zig-zag sequence: A specific sequential ordering of the DCT coefficients from (approximately) lowest spatial
`frequency to highest.
`
`3.1.132 3-sample predictor: A linear combination of the three nearest neighbor reconstructed samples to the left and
`above (in lossless mode coding).
`
`6
`
`CCITT Rec. T.81 (1992 E)
`
`

`

`3.2
`
`Symbols
`
`The symbols used in this Specification are listed below.
`
`ISO/IEC 10918-1 : 1993(E)
`
`A
`
`AC
`
`ACji
`
`Ah
`
`Al
`
`Api
`
`APPn
`
`B
`
`B2
`
`BE
`
`BITS
`
`BP
`
`BPST
`
`BR
`
`Bx
`
`C
`
`Ci
`
`Cu
`
`Cv
`
`CE
`
`C-low
`
`Cmi
`
`CNT
`
`CODE
`
`probability interval
`
`AC DCT coefficient
`
`AC coefficient predicted from DC values
`
`successive approximation bit position, high
`
`successive approximation bit position, low
`
`ith 8-bit parameter in APPn segment
`
`marker reserved for application segments
`
`current byte in compressed data
`next byte in compressed data when B = X’FF’
`
`counter for buffered correction bits for Huffman coding in the successive approximation
`process
`
`16-byte list containing number of Huffman codes of each length
`
`pointer to compressed data
`
`pointer to byte before start of entropy-coded segment
`
`counter for buffered correction bits for Huffman coding in the successive approximation
`process
`
`byte modified by a carry-over
`
`value of bit stream in code register
`
`component identifier for frame
`
`horizontal frequency dependent scaling factor in DCT
`
`vertical frequency dependent scaling factor in DCT
`
`conditional exchange
`
`low order 16 bits of the arithmetic decoder code register
`
`ith 8-bit parameter in COM segment
`
`bit counter in NEXTBYTE procedure
`
`Huffman code value
`
`CODESIZE(V)
`
`code size for symbol V
`
`COM
`
`Cs
`
`Csi
`
`CT
`
`Cx
`
`CX
`
`dji
`
`djik
`
`D
`
`comment marker
`
`conditioning table value
`
`component identifier for scan
`
`renormalization shift counter
`
`high order 16 bits of arithmetic decoder code register
`
`conditional exchange
`
`data unit from horizontal position i, vertical position j
`
`dji for component k
`
`decision decoded
`
`CCITT Rec. T.81 (1992 E)
`
`7
`
`

`

`ISO/IEC 10918-1 : 1993(E)
`
`Da
`
`DAC
`
`Db
`
`DC
`
`DCi
`
`DCk
`
`DHP
`
`DHT
`
`DIFF
`
`DNL
`
`DQT
`
`DRI
`
`E
`
`EC
`
`ECS
`
`ECSi
`
`Eh
`
`EHUFCO
`
`EHUFSI
`
`EOB
`
`EOBn
`
`EOBx
`
`in DC coding, the DC difference coded for the previous block from the same component;
`in lossless coding, the difference coded for the sample immediately to the left
`
`define-arithmetic-coding-conditioning marker
`
`the difference coded for the sample immediately above
`
`DC DCT coefficient
`
`DC coefficient for ith block in component
`
`kth DC value used in prediction of AC coefficients
`
`define hierarchical progression marker
`
`define-Huffman-tables marker
`
`difference between quantized DC and prediction
`
`define-number-of-lines marker
`
`define-quantization-tables marker
`
`define restart interval marker
`
`exponent in magnitude category upper bound
`
`event counter
`
`entropy-coded segment
`
`ith entropy-coded segment
`
`horizontal expansion parameter in EXP segment
`
`Huffman code table for encoder
`
`encoder table of Huffman code sizes
`
`end-of-block for sequential; end-of-band for progressive
`
`run length category for EOB runs
`
`position of EOB in previous successive approximation scan
`
`EOB0, EOB1, ..., EOB14
`
`run length categories for EOB runs
`
`EOI
`
`Ev
`
`EXP
`
`FREQ(V)
`
`Hi
`
`Hmax
`
`HUFFCODE
`
`HUFFSIZE
`
`HUFFVAL
`
`i
`
`I
`
`end-of-image marker
`
`vertical expansion parameter in EXP segment
`
`expand reference components marker
`
`frequency of occurrence of symbol V
`
`horizontal sampling factor for ith component
`
`largest horizontal sampling factor
`
`list of Huffman codes corresponding to lengths in HUFFSIZE
`
`list of code lengths
`
`list of values assigned to each Huffman code
`
`subscript index
`
`integer variable
`
`Index(S)
`
`index to probability estimation state machine table for context index S
`
`j
`
`J
`
`8
`
`subscript index
`
`integer variable
`
`CCITT Rec. T.81 (1992 E)
`
`

`

`ISO/IEC 10918-1 : 1993(E)
`
`JPG
`
`JPGn
`
`k
`
`K
`
`Kmin
`
`Kx
`
`L
`
`Li
`
`Li(t)
`
`La
`
`marker reserved for JPEG extensions
`
`marker reserved for JPEG extensions
`
`subscript index
`
`integer variable
`
`index of 1st AC coefficient in band (1 for sequential DCT)
`
`conditioning parameter for AC arithmetic coding model
`
`DC and lossless coding conditioning lower bound parameter
`
`element in BITS list in DHT segment
`
`element in BITS list in the DHT segment for Huffman table t
`
`length of parameters in APPn segment
`
`LASTK
`
`largest value of K
`
`Lc
`
`Ld
`
`Le
`
`Lf
`
`Lh
`
`Lp
`
`LPS
`
`Lq
`
`Lr
`
`Ls
`
`LSB
`
`m
`
`mt
`
`M
`
`Mn
`
`length of parameters in COM segment
`
`length of parameters in DNL segment
`
`length of parameters in EXP segment
`
`length of frame header parameters
`
`length of parameters in DHT segment
`
`length of parameters in DAC segment
`
`less probable symbol (in arithmetic coding)
`
`length of parameters in DQT segment
`
`length of parameters in DRI segment
`
`length of scan header parameters
`
`least significant bit
`
`modulo 8 counter for RSTm marker
`
`number of Vi,j parameters for Huffman table t
`
`bit mask used in coding magnitude of V
`
`nth statistics bin for coding magnitude bit pattern category
`
`MAXCODE
`
`table with maximum value of Huffman code for each code length
`
`MCU
`
`MCUi
`
`MCUR
`
`minimum coded unit
`
`ith MCU
`
`number of MCU required to make up one MCU-row
`
`MINCODE
`
`table with minimum value of Huffman code for each code length
`
`MPS
`
`MPS(S)
`
`MSB
`
`more probable symbol (in arithmetic coding)
`
`more probable symbol for context-index S
`
`most significant bit
`
`M2, M3, M4, ... , M15
`
`designation of context-indice