1、 Report ITU-R BT.1088-2(11/2009)Interfaces for digital video signalsin 525-line and 625-linetelevision systemsBT SeriesBroadcasting service(television)ii Rep. ITU-R BT.1088-2 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the
2、radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regiona
3、l Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submiss
4、ion of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Repo
5、rts (Also available online at http:/www.itu.int/publ/R-REP/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and rel
6、ated satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management Note: This ITU-R Report was appr
7、oved in English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2010 ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rep. ITU-R BT.1088-2 1 REPORT ITU-R BT.1
8、088-2 Interfaces for digital video signals in 525-line and 625-line television systems (1986-1990-2009) Preface Introduction/purpose Readers of this Report should be aware that the text in this Report is the original text generated during the development of the SDTV digital interfaces. It is has bee
9、n retained as an historic record of the digital interface development. Many of the concepts and technical parameters developed during the 1982 to 1986 time-frame have changed, readers are advised to consult the latest ITU-R Recommendations before implementing digital interfaces. Reference is made to
10、 the International Radio Consultative Committee (CCIR), the year 1920 saw the beginning of sound broadcasting at the improvised studios of the Marconi Company, and in 1927, the CCIR was established at a conference held in Washington D.C. The International Telephone Consultative Committee (CCIF, set
11、up in 1924), the International Telegraph Consultative Committee (CCIT, set up in 1925) and the CCIR were made responsible for coordinating the technical studies, tests and measurements being carried out in the various fields of telecommunications, as well as for drawing up international standards. I
12、n 1989 the CCIR was reorganized into the International Telecommunication Union (ITU), over time, the Union was streamlined into three Sectors, corresponding to its three main areas of activity: Telecommunication Standardization (ITU-T), Radiocommunication (ITU-R) and Telecommunication Development (I
13、TU-D). Today the ITU-R has the responsibility for broadcasting services. The broadcasting and related industries depend 100% on the interfaces and their derivatives that were proposed back pre-1986. In 1986 in Houston Texas the first digital serial interface as we know it today was demonstrated at a
14、 trade show, since that time the serial interface which originally ran at 270 Mbit/s (an interim interface ran at 243 Mbit/s, this interface had only very limited use) has been extended to 3 Gbit/s. The serial interface has also been adapted to carry almost any data signal in addition to the uncompr
15、essed video signals that was the original intent. Further treatment of the characteristics of the serial interfaces as implement can be found in EBU Tech. 3283. The following text is presented as an historic record of the digital interface development, along with a copy of the original Recommendatio
16、ns CCIR 601 and 656. The original Recommendation CCIR 656 was never implemented on a widespread basis as it was constrained to 8-bit operation. A later version, Recommendation ITU-R BT.656-2 replaced the 8/9 code mapping with scrambled NRZ coding. It is the scrambled NRZ version of the serial digita
17、l interface that found very widespread implementation. The original Recommendation CCIR 601 was originally called CCIR-AA/11 and was approved in 1982. The attached Recommendation CCIR 601-1 has been restored using the original text along with any errors that may have been in this text. 1 Introductio
18、n Recommendation CCIR 656 specifies interfaces for digital studio equipment, in conformity with the basic parameter values contained in Recommendation CCIR 601. 2 Rep. ITU-R BT.1088-2 This Report summarizes the contributions received on digital video interfaces which provided the basis for Recommend
19、ation CCIR 656, it includes supplementary information on the subject, and indicates areas in which further studies are required. 2 Definitions Interface is a concept involving the specification of the interconnection between two items of equipment or systems. The specification includes the type, qua
20、ntity and function of the interconnection circuits and the type and form of the signals to be interchanged by these circuits: a parallel interface is an interface in which the bits of a data word are sent simultaneously via separate channels; a serial interface is an interface in which the bits of a
21、 data word, and successive data words, are sent consecutively via a single channel. A parallel-serial (hybrid) interface is an interface in which portions of a data word are sent consecutively via separate channels. 3 Primary encoding format There are features of the basic data organization which ar
22、e common to the three types of interface defined above and which are the subject of Part I of Recommendation CCIR 656. They comprise: the organization of the video data into words and blocks; the timing reference codes providing video synchronization; ancillary data signal structure; data signals du
23、ring blanking intervals; details of the multiplexing. 3.1 Blanking and synchronization considerations CCIR, 1982-86a, b, and c agreed on the form and use of timing reference signals. Each timing reference signal consists of a four-word sequence. The first three words are a fixed preamble. The fourth
24、 word contains information defining: first or second field identification; state of field blanking; state of line blanking; error protection data. CCIR, 198286d proposed that only one timing reference signal should be used, located at the end of each line-blanking period. This identification signal
25、includes a clock burst (for a bit-serial interface), indication of the initial point of the data frame, field-blanking period and first and second field periods. End-of-line information will be obtained by counting clock pulses. The EBU CCIR, 1982-86e suggested that additional codes be included in t
26、he data stream and that the beginning and end of the digital active line will be identified in the de-multiplexed Y, CR, CBdata streams. It further proposed that these codes be included at the 4:4:4 level for both Y, CR, CBand R, G, B signals in digital form. CCIR, 1982-86f stated that the timing re
27、ference (digital synchronization) codes inserted into the parallel code should be easily usable in a serial code. Proposals for 525-line and 625-line differ in their definition of digital field-blanking intervals. CCIR, 1982-86b, c, and d stated that only 9 lines in both fields 1 and 2 belong to the
28、 field-blanking interval. CCIR, 1982-86a and f specify the digital field-blanking interval of 24 lines (field 1) and 25 lines (field 2). It may be advisable to shorten the digital field-blanking interval so as to allow for complex vertical filtering, though this problem needs further study. Rep. ITU
29、-R BT.1088-2 3 Amongst other considerations CCIR, 1982-86g drew attention to the fact that “timing reference signals” should be referred to as “timing reference codes”. In those data words occurring during digital blanking intervals that are otherwise unspecified, the OIRT CCIR, 1982-86e proposed th
30、at the digital codes equivalent to blanking level for Y, CR, CBbe included in the appropriate locations in the multiplex. 3.2 Ancillary signals Provision is made for ancillary data signals to be inserted synchronously into the video multiplex during both horizontal and vertical blanking intervals. I
31、t is noted that digital video tape recorders (see Recommendation CCIR 657) do not record any of the horizontal blanking intervals or some lines in the vertical blanking intervals. For that reason the EBU has allocated only four vertical blanking lines for ancillary signals. The unrecordable blanking
32、 periods can be used to transfer data between other studio equipment if required. CCIR, 1982-86 d and f contain some details of the ancillary signals. CCIR, 1982-86a, band c propose the ancillary data signal format. Time-code is an essential ancillary signal for control of post-production processes
33、and the synchronization of video and audio. Four formats are currently recognised, IEC format IEC Pub. 461 in the vertical interval and longitudinal forms, audio time code in accordance with Recommendation CCIR 647 and time code associated with the R-DAT audio recording format. Ancillary data format
34、s to include this information in the vertical interval are a current study in a number of Administrations and offer possibilities to maintain the synchronism of video and audio through various processes CCIR, 1986-1990a). Recommendation CCIR 656 specifies only a timing reference code ANC; the data f
35、ield following the ANC is left unspecified. There have been discussions about various packet formats for the ancillary data. Some information with higher priority and predetermined format might have a fixed data packet length and probably also a fixed time slot in the data stream. Less important anc
36、illary data not having a predetermined format might have variable packet length. (CCIR 1986-1990b mentions digital line numbers as possibly useful information which should be considered as an ancillary signal. The document contains a proposal for two modes of digital line numbering. In addition one
37、method for introduction of respective code words into the video data is proposed. The study of the requirements for sound signals is included in Decision 60 to ensure that any possible effects upon the associated sound signals caused by the video interface parameters will be duly considered. Except
38、for the need to control the relative delay between the video and the sound, no such effects have been identified. 4 Parallel interfaces A number of proposals CCIR, 1982-86a, b, c, d and f suggested using eight conductor pairs, where each should carry, in NRZ format, a multiplex stream of bits (of th
39、e same significance) of each of the component signals, namely, Y, CR, CB. The eight pairs should also carry timing reference information and may carry ancillary signals that are time-multiplexed into the data stream during video blanking intervals. A ninth pair would provide a synchronous clock at 2
40、7 MHz. These proposals, with CCIR, 1982-86e, contributed to the preparation of Recommendation CCIR 656 (see also EBU, 1983). 4 Rep. ITU-R BT.1088-2 The signals on the interface may be transmitted using balanced conductor pairs for a distance of up to 50 m without equalization and up to 200 m with ap
41、propriate equalization CCIR, 1982-86a. Appropriate coding of the clock signal, such as the use of an alternating parity (AP) coding, has been shown to extend this distance by reducing the effects of cable attenuation CCIR, 1982-86h. 5 Serial interfaces CCIR, 1982-86d gives an example of a data seque
42、nce using 216 Mbit/s multiplexing. Particular attention is paid to ease of clock extraction and word synchronization by the inclusion of words within the data stream which generate clock bursts. CCIR, 1982-86f refers to channel coding and states that transmission should be effected via 75 Q coaxial
43、cables for distances up to 1 km. CCIR, 1982-86e contains a detailed consideration of the special requirements for a serial interface and proposes in Annex I a draft Recommendation for a bit-serial interface for the 4:2:2 level of Recommendation CCIR 601. This contributed to the preparation of Recomm
44、endation CCIR 656 (see also EBU, 1985). In CCIR, 1982-86e the transmission of signals is considered in both electrical form, using coaxial cable, and in optical form using an optical fibre. The special requirements for bit-serial signal transmission between studios, or between equipments in a studio
45、 are given as: low cost and low complexity coupled with high reliability; very low intrinsic error rate in the transmission due to the very short distances; multiple outputs for monitoring and distribution; rapid recovery from errors introduced by switching of the transmission path, the video source
46、 or signal interruptions; full compatibility with the format of the bit-parallel interface and signal code commonality of both electrical and optical implementations of the bit-serial interface; usable over a range of distances from zero to at least 500 m, with a minimum of adjustments and extremely
47、 low error rates; applicable to a range of cable types. These requirements are confirmed in CCIR, 1982-86i, which also points out that in the implementation of a digital video installation, preference would normally be given to the parallel interface for short connection lengths and that recourse wo
48、uld be made to the serial interface mainly in the case of long or complex connection paths, where the cost of the interface terminal equipment would not override the saving in the physical support of the connection itself. Coaxial cables would probably be preferred for connections of medium length,
49、while preference would go to optical fibres for very long connection lengths. This contribution also suggests that the code used should be structured so as to permit the redundant bits to be employed to implement a system for measuring the BER at the receiving end of the connection and thus automatically monitoring its performance. It further suggests that in a fully integrated digital installation or system it may be useful for all interconnections to be transparent to any appropriate digital stream, irrespective of
