1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T T.4TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2003) SERIES T: TERMINALS FOR TELEMATIC SERVICES Standardization of Group 3 facsimile terminals for document transmission ITU-T Recommendation T.4 ITU-T Rec. T.4 (07/2003) i ITU-T Recommendation T.4 S
2、tandardization of Group 3 facsimile terminals for document transmission Summary This Recommendation defines the characteristics of Group 3 facsimile terminals which enable black and white documents and also optionally colour documents to be transmitted on the general switched telephone network, inte
3、rnational leased circuits and the Integrated Services Digital Network (ISDN). Group 3 facsimile terminals may be operated manually or automatically and document transmission may be requested alternatively with telephone conversation. The procedures used by Group 3 facsimile terminals are defined in
4、ITU-T Rec. T.30. This revised version consolidates features previously approved as amendments to the text as well as recently approved capabilities, including: support of all standardized image resolutions; support of mixed raster content for black and white images; definitions for transmission of s
5、YCC colour space using facsimile protocol. Source ITU-T Recommendation T.4 was approved by ITU-T Study Group 16 (2001-2004) under the ITU-T Recommendation A.8 procedure on 14 July 2003. ii ITU-T Rec. T.4 (07/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nations special
6、ized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a w
7、orldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down i
8、n WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication adm
9、inistration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory pro
10、visions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention
11、 to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others out
12、side of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the l
13、atest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. T.4 (07/2003) iii CONTENTS Page 1 Scanning track 1 2 Di
14、mensions of terminals. 1 3 Transmission time per total coded scan line. 2 3.1 Minimum transmission time of total coded scan line. 2 3.2 Maximum transmission time of total coded scan line 3 3.3 Error correction mode. 3 4 Coding scheme 3 4.1 One-dimensional coding scheme 3 4.2 Two-dimensional coding s
15、cheme . 8 4.3 Extended two-dimensional coding scheme 14 4.4 Progressive bi-level image compression 14 5 Modulation and demodulation 16 6 Power at the transmitter output. 17 7 Power at the receiver input . 17 8 Implementation of terminals. 17 9 File transfer mode. 17 10 Character mode. 17 11 Mixed mo
16、de 17 12 64 kbit/s option . 17 13 Continuous-tone colour and gray-scale modes. 18 14 Secure communication mode 18 15 Lossless transmission mode of one bit per colour, palette-colour, continuous-tone colour and gray-scale images using ITU-T Rec. T.43 18 16 Mixed Raster Content. 18 17 Continuous-tone
17、colour mode (sYCC) . 18 Annex A Optional error correction mode . 18 A.1 Introduction 18 A.2 Definitions 18 A.3 Message format 18 Annex B Optional file transfer mode 22 B.1 Introduction 22 B.2 Definitions 22 B.3 Normative references 22 B.4 Definition of the different file transfer modes 23 B.5 Coding
18、 of the file description. 24 B.6 Message format Blocks structure 26 B.7 Protocol aspects 27 iv ITU-T Rec. T.4 (07/2003) Page Annex C Optional character mode 28 C.1 Introduction 28 C.2 Definitions 28 C.3 Normative references 29 C.4 Graphic character set Repertoire and coding. 29 C.5 Page format. 30 C
19、.6 Control functions 30 C.7 Message format Blocks structure 31 C.8 Protocol aspects 33 C.9 Imaging process 33 Annex D Optional mixed mode 34 D.1 Introduction 34 D.2 Definitions 34 D.3 Facsimile Control Field (FCF) . 34 D.4 Frame numbering 34 D.5 Facsimile data field. 35 D.6 Character coded data fiel
20、d 35 D.7 Graphic character set 35 D.8 Page format. 35 D.9 Control functions 36 D.10 End Of Retransmission (EOR) . 36 Annex E Optional continuous-tone colour mode 36 E.1 Introduction 36 E.2 Definitions 36 E.3 References 37 E.4 Definition of different multilevel image transfer modes 37 E.5 Coding of t
21、he image description. 37 E.6 Data format. 38 Annex F Facsimile Group 3 64 kbit/s option F G3F 44 F.1 Introduction 44 F.2 Terminal characteristics for G3F 44 F.3 Protocol set . 45 F.4 Basic procedure for the interchange of Group 3 64 kbit/s option F facsimile document. 47 F.5 Interworking . 53 Annex
22、G Transmission of colour and gray-scale images using lossless coding scheme 54 G.1 Introduction 54 G.2 Definition of image type and mode of operation 55 G.3 Data format. 57 ITU-T Rec. T.4 (07/2003) v Page Annex H Mixed Raster Content (MRC) mode for G3 facsimile 58 H.1 Scope 58 H.2 References 58 H.3
23、Definitions 58 H.4 Conventions 58 H.5 Image representation 58 H.6 Layer Transmission Order 62 Annex I Optional continuous-tone colour mode (sYCC) . 63 I.1 Introduction 63 I.2 Definitions 63 I.3 References 63 I.4 Continuous-tone colour image transfer mode 64 I.5 Coding of the image description. 64 I.
24、6 Data format. 64 Appendix I Guaranteed reproducible area for Group 3 terminals conforming to this Recommendation 65 Appendix II Repertoire of box-drawing characters for character mode of Group 3 terminals . 67 vi ITU-T Rec. T.4 (07/2003) Introduction This Recommendation defines the characteristics
25、of Group 3 facsimile terminals which enable documents to be transmitted on the general switched telephone network, international leased circuits and the Integrated Services Digital Network (ISDN). These terminals enable black and white documents to be transmitted and also optionally colour documents
26、. Group 3 facsimile terminals may be operated manually or automatically and document transmission may be requested alternatively with telephone conversation. The procedures to enable Group 3 facsimile terminals to communicate using the above capabilities are defined in ITU-T Recommendation T.30. ITU
27、-T Rec. T.4 (07/2003) 1 ITU-T Recommendation T.4 Standardization of Group 3 facsimile terminals for document transmission 1 Scanning track The message area should be scanned in the same direction in the transmitter and receiver. Viewing the message area in a vertical plane, the picture elements shou
28、ld be processed as if the scanning direction were from left to right with subsequent scans adjacent and below the previous scan. 2 Dimensions of terminals NOTE The tolerances on the factors of cooperation are subject to further study. 2.1 The following dimensions shall be used for ISO A4, ISO B4, IS
29、O A3, North American Letter (215.9 279.4 mm) and Legal (215.9 355.6 mm): a) a standard resolution of 3.85 lines/mm 1% in vertical resolution; b) optional higher resolution of 7.7 lines/mm 1% and 15.4 lines/mm 1% in vertical direction; c) 1728 black and white picture elements along the standard scan
30、line length of 215 mm 1%; d) optionally, 2048 black and white picture elements along a scan line length of 255 mm 1%; e) optionally, 2432 black and white picture elements along a scan line length of 303 mm 1%; f) optionally, 3456 black and white picture elements along a scan line length of 215 mm 1%
31、; g) optionally, 4096 black and white picture elements along a scan line length of 255 mm 1%; h) optionally, 4864 black and white picture elements along a scan line length of 303 mm 1%. Optionally: 1) continuous-tone and colour images may be transmitted using Group 3 facsimile terminals as described
32、 in Annex E; 2) multilevel and bi-level data resulting from the coding of continuous-tone and colour images and text/line-art respectively, may be transmitted on the same page as described in Annex H (Mixed Raster Content); 3) continuous-tone colour images (sYCC) may be transmitted using Group 3 fac
33、simile terminals as described in Annex I. All of the dimensions of Group 3 may be used with the procedures identified in options “1“, “2“ and “3“. Non-square resolutions (i.e., those that do not have the same horizontal and vertical resolution values), such as 8 3.85 lines/mm or 300 pels/25.4 mm 600
34、 lines/25.4 mm, are not supported by Annex E, H and/or Annex I. 2.2 The following dimensions for inch-based resolutions shall be used. The optional inch-based resolution requirements and their picture elements are given in Table 1. Specific values for the number of pels per line are given in Table 1
35、 for all the Group 3 resolutions for ISO A4, ISO B4, ISO A3, North American Letter and Legal. An alternative standard resolution of 200 pels/25.4 mm horizontally 100 lines/25.4 mm vertically may be implemented provided that one or more of 200 pels/25.4 mm 200 lines/25.4 mm, 300 pels/25.4 mm 300 line
36、s/25.4 mm, 400 pels/25.4 mm 400 lines/25.4 mm, 600 pels/25.4 mm 600 lines/25.4 mm, 1200 pels/25.4 mm 1200 lines/ 25.4 mm, 300 pels/25.4 mm 600 lines/25.4 mm, 400 pels/25.4 mm 800 lines/25.4 mm and 600 pels/25.4 mm 1200 lines/25.4 mm are included. 2 ITU-T Rec. T.4 (07/2003) 2.3 Input documents up to
37、a minimum of ISO A4 size should be accepted. NOTE The size of the guaranteed reproducible area is shown in Appendix I. 3 Transmission time per total coded scan line The total coded scan line is defined as the sum of data bits plus any required fill bits plus the end-of-line (EOL) bits. For the optio
38、nal two-dimensional coding scheme as described in 4.2, the total coded scan line is defined as the sum of data bits plus any required fill bits plus the EOL bits plus a tag bit. To handle various printing methods, several optional minimum total coded scan line times are possible in addition to the 2
39、0 milliseconds standard. Table 1/T.4 Number of picture elements along a scan line Resolution Horizontal (pels/25.4 mm) Vertical (lines/25.4 mm) Tolerance ISO A4, North American Letter/Legal ISO B4 ISO A3 Horizontal 100 Vertical 100 1% 864/219.46 mm 1024/260.10 mm 1216/308.86 mm Horizontal 200 Vertic
40、al 200 1% 1728/219.46 mm 2048/260.10 mm 2432/308.86 mm Horizontal 300 Vertical 300 1% 2592/219.46 mm 3072/260.10 mm 3648/308.86 mm Horizontal 300 Vertical 600 1% 2592/219.46 mm 3072/260.10 mm 3648/308.86 mm Horizontal 400 Vertical 400 1% 3456/219.46 mm 4096/260.10 mm 4864/308.86 mm Horizontal 400 Ve
41、rtical 800 1% 3456/219.46 mm 4096/260.10 mm 4864/308.86 mm Horizontal 600 Vertical 600 1% 5184/219.46 mm 6144/260.10 mm 7296/308.86 mm Horizontal 600 Vertical 1200 1% 5184/219.46 mm 6144/260.10 mm 7296/308.86 mm Horizontal 1200 Vertical 1200 1% 10 368/219.46 mm12 288/260.10 mm 14 592/308.86 mmNOTE T
42、he resolutions 200 pels/25.4 mm 200 lines/25.4 mm and 8 7.7 lines/mm can be considered as being equivalent. Similarly, the resolutions 400 pels/25.4 mm 400 lines/25.4 mm and 16 15.4 lines/mm can be considered also as being equivalent. Consequently, conversion between mm-based terminals and inch-base
43、d terminals is not required for the communications in these cases. However, communication between these resolutions will cause the distortion and the reduction of reproducible area. Non-square resolutions are applicable only to black and white images. 3.1 Minimum transmission time of total coded sca
44、n line The minimum transmission times of the total coded scan line should conform to the following: 1) Alternative 1, where the minimum transmission time of the total coded scan line is the same both for the standard resolution and for the optional higher resolution: a) 20 milliseconds recommended s
45、tandard; ITU-T Rec. T.4 (07/2003) 3 b) 10 milliseconds recognized option with a mandatory fall-back to the 20 milliseconds standard; c) 5 milliseconds recognized option with a mandatory fall-back to the 10 milliseconds option and the 20 milliseconds standard; d) 0 millisecond recognized option with
46、a mandatory fall-back to the 5 milliseconds option, the 10 milliseconds option and the 20 milliseconds standard, and an optional fall-back to the 40 milliseconds option; e) 40 milliseconds recognized option. 2) Alternative 2, where the minimum transmission time of the total coded scan line for the o
47、ptional higher resolution is half of that for the standard resolution (see Note). These figures refer to the standard resolution: a) 10 milliseconds recognized option with a mandatory fall-back to the 20 milliseconds standard; b) 20 milliseconds recommended standard; c) 40 milliseconds recognized op
48、tion. The identification and choice of this minimum transmission time is to be made in the pre-message (phase B) portion of T.30 control procedure. NOTE Alternative 2 applies to terminals with printing mechanisms which achieve the standard vertical resolution by printing two consecutive, identical h
49、igher resolution lines. In this case, the minimum transmission time of the total coded scan line for the standard resolution is double the minimum transmission time of the total coded scan line for the higher resolution. The minimum transmission time for the optional resolutions of 15.4 lines/mm and 400 lines/25.4 mm can be a quarter of that for the standard resolution. 3.2 Maximum transmission time of total coded scan line The maximum transmission time of any total coded sca
