1、 Rec. ITU-R BT.799-4 1 RECOMMENDATION ITU-R BT.799-4*Interface for digital component video signals in 525-line and 625-line television systems operating at the 4:4:4 level of Recommendation ITU-R BT.601*(Question ITU-R 42/6) (1992-1994-1995-1998-2007) Scope This Recommendation covers the data struct
2、ure and dual link serial interface for 525/625-line digital signals as defined in Recommendation ITU-R BT.601-5. The ITU Radiocommunication Assembly, considering a) that there are clear advantages for television broadcasting organizations and programme producers in digital studio standards which hav
3、e the greatest number of significant parameter values common to 525-line and 625-line systems; b) that in implementing the above objectives, agreement was reached on the fundamental encoding parameters of digital television for studios in the form of Recommendation ITU-R BT.601; c) that the worldwid
4、e compatible digital approach has permitted the development of equipment with many common features, permitting operating economies and facilitating the international exchange of programmes; d) that the practical implementation of Recommendation ITU-R BT.601 or complex digital studio processes requir
5、es definition of details of an interface at the 4:4:4 level and the data streams traversing them; e) that such an interface should have a maximum of commonality between 525-line and 625-line versions, recognizing a) that in the practical implementation of Recommendation ITU-R BT.601 it is desirable
6、that a serial interface be defined, recommends 1 that where an interface for the 4:4:4 level is required for component-coded digital video signals conforming to Recommendation ITU-R BT.601 in television studios, the interface and the data streams that will traverse them should be in accordance with
7、Annex 1, defining the bit-serial implementation. *This Recommendation should be brought to the attention of ITU-T Study Group 9. *Recommendation ITU-R BT.601-6 - Studio encoding parameters of digital television for standard 4:3 and wide-screen 16:9 aspect ratios. 2 Rec. ITU-R BT.799-4 Annex 1 1 Intr
8、oduction Part 1 in this Annex describes the digital signal format of the interface. Part 2 in this Annex describes the particular characteristics of the bit-serial interface. The particular characteristics of the bit-parallel interface are to be found in Appendix 1 attached to this Annex for informa
9、tion. The interface for the 4:4:4 level is based on the use of the serial interface already developed for use at the 4:2:2 level and described in Recommendation ITU-R BT.656. Whereas at the 4:2:2 level a single interface carries a multiplex of a wideband luminance and two lower-bandwidth colour-diff
10、erence video signals, at the 4:4:4 level a pair of signal representations is used, each carrying a multiplex of two wideband video signals; this gives capacity for carrying the green, blue and red primary signals or, alternatively, the luminance and two colour-difference signals, together with a fou
11、rth wideband signal such as an associated key signal. In this case the signal is at the “4:4:4:4” level. The interfaces for the 4:4:4 level have been specified for 10-bit (see Note 1) data words according to Recommendation ITU-R BT.601. Only two devices will be connected together at one time through
12、 one interface. NOTE 1 Within this Recommendation, the contents of digital words are expressed in hexadecimal form of 10-bit representation. For example, the bit pattern 10010001 is expressed as 245h.Eight-bit words occupy the left most significant bits of a 10-bit word, i.e. bit 9 to bit 2, where b
13、it 9 is the most significant bit. PART 1 Digital signal format of the interface 1 Introduction The interface consists of two unidirectional interconnections between one device and another. The interconnections carry the data corresponding to the television signal and associated data. The two interco
14、nnections are referred to as: link A and link B. The data signals are carried in the form of binary information coded in ten-bit words. These signals are: the video signals themselves, digital blanking data, timing reference signals, ancillary data signals. These signals are time-multiplexed. Rec. I
15、TU-R BT.799-4 3 2 Video data signals 2.1 Coding characteristics The video data signals are derived by coding of the analogue video signal components in accordance with the 4:4:4 level of Recommendation ITU-R BT.601, with the field-blanking definition shown in Table 1. 2.2 Video data format The data
16、words in which the eight most significant bits are all set to 1 or are all set to 0 are reserved for data identification purposes and consequently only 254 of the possible 256 8-bit words or 1 016 of the possible 1 024 10-bit words may be used to express a signal value. TABLE 1 Field interval defini
17、tions 625 525 V-digital field blanking Field 1 Start (V = 1) Line 624 Line 1 Finish (V = 0) Line 23 Line 20 Field 2 Start (V = 1) Line 311 Line 264 Finish (V = 0) Line 336 Line 283 F-digital field identification Field 1 F = 0 Line 1 Line 4 Field 2 F = 1 Line 313 Line 266 NOTE 1 Signals F and V chang
18、e state synchronously with the end of active video timing reference code at the beginning of the digital line. NOTE 2 Definition of line numbers is to be found in Recommendation ITU-R BT.1700. Note that digital line number changes state prior to OHas described in Recommendation ITU-R BT.601. NOTE 3
19、Designers should be aware that the “1” to “0” transition of the V-bit may not necessarily occur on line 20 (283) in some equipment conforming to previous versions of this Recommendation for 525-line signals. 2.3 Multiplex structure The video data words are conveyed in two separate 27 Mword/s data-st
20、reams. The multiplex sequence is: for links carrying colour primaries link A: B0G0R0G1B2G2R2G3B4. link B: B1K0R1K1B3K2R3K3B5. 4 Rec. ITU-R BT.799-4 where R, G and B represent the red, green and blue signal data words, and K represents the key signal data words, if present. The first sample of the di
21、gital active line shall be B0for link A and B1for link B. The distribution of the red, green, blue and key signals between link A and link B is shown in Fig. 1a); for links carrying luminance and colour-difference signals link A: CB 0 Y0CR 0 Y1CB2 Y2CR2. link B: CB1 K0CR1 K1CB3 K2CR3. where Y, CBand
22、 CRrepresent the luminance and colour-difference signals respectively, and K represents the key signal data words, if present. The first sample of the digital active line shall be CB 0 for link A and CB1 for link B. The distribution of the luminance, colour-difference and key signals between link A
23、and link B is shown in Fig. 1b). 2.4 Interface signal structure Figure 2 shows the ways in which the video sample data is incorporated in the interface data stream. Sample identification in Fig. 2 is in accordance with the identification in Recommendation ITU-R BT.601. FIGURE 1 Link contents when us
24、ed for R, G, B, K and Y, CR, CB, K signals 2.5 Video timing reference signals (SAV, EAV) There are two timing reference signals, one at the beginning of each video data block (start of active video, SAV) and one at the end of each video data block (end of active video, EAV) as shown in Fig. 2. Each
25、timing reference signal consists of a four word sequence in the following format: 3FF 000 000 XYZ. (Values are expressed in hexadecimal notation. Words 3FF, 000 are reserved for use in timing reference signals.) The first three words are a fixed preamble. The fourth word contains information defined
26、 field 2 identification, the state of field blanking, and the state of line blanking. The assignment of bits within the timing reference signal is shown below in Table 2. Bits P0, P1, P2, P3, have states dependent on the states of the bits F, V and H as shown in Table 3. At the receiver this arrange
27、ment permits one-bit errors to be corrected and two-bit errors to be detected. Rec. ITU-R BT.799-4 5 2.6 Ancillary data The ancillary signals should comply with Recommendation ITU-R BT.1364. 2.7 Data words during blanking During digital blanking the luminance or R, G, B sample values should be set t
28、o black, level 40h, and the colour-difference samples set to zero, level 200h. The key samples should be set to peak white, level EB.0h, when not carrying a key signal. FIGURE 2 Composition of the data multiplex and position of the timing reference signals, EAV and SAV (shown here for link A carryin
29、g Y, CR, CBas an example) 6 Rec. ITU-R BT.799-4 TABLE 2 Video timing reference signal Data bit number First word (3FF) Second word (000) Third word(000) Fourth word (XYZ) 9 (MSB) 1 0 0 1 8 1 0 0 F 7 1 0 0 V 6 1 0 0 H 5 1 0 0 P34 1 0 0 P23 1 0 0 P12 1 0 0 P01 (Note 2) 1 0 0 0 0 1 0 0 0 NOTE 1 The val
30、ues shown are those recommended for 10-bit interfaces. NOTE 2 For compatibility with existing 8-bit interfaces, the values of bits D1 and D0 are not defined. F = 0 during field 1,1 during field 2V = 0 elsewhere,1 during field blankingH = 0 in SAV,1 in EAVP0, P1, P2, P3: protection bits (see Table 3)
31、 MSB: most significant bit Table 1 defines the state of the V and F bits. TABLE 3 Protection bits in the timing reference signal F V H P3P2P1P00 0 0 0 0 0 0 0 0 1 1 1 0 1 0 1 0 1 0 1 1 0 1 1 0 1 1 0 1 0 0 0 1 1 1 1 0 1 1 0 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 1 Rec. ITU-R BT.799-4 7 PART 2 Bit-serial inter
32、face 1 General A serial interface is an interface in which the bits of a data word, and successive data words, are sent consecutively via a single transmission channel. The serial interface is capable of carrying video, audio, and ancillary data. It may also be used for carrying packetized data in a
33、ccordance with Recommendation ITU-R BT.1364. The transmission of signals can be achieved in both electrical form, using coaxial cable, and in optical form using an optical fibre. Coaxial cables would probably be preferred for connections of medium length (e.g. 300 m), while preference would go to op
34、tical fibres for very long connection lengths. It is possible to implement a system for detection of the occurrence of errors at the receiving end of the connection and thus automatically monitoring its performance. In a fully integrated digital installation or system it may be useful for all interc
35、onnections to be transparent to any appropriate digital stream, irrespective of the message content. Thus, although the interface will be used to transmit a video signal, it should be “transparent” to the message content, i.e. it should not base its operation on the known structure of the message it
36、self. The multiplexed data stream of 10-bit words (as described in Part 1) is transmitted over two links in bit-serial form. Prior to transmission, additional coding takes place to provide spectral shaping, word synchronization and to facilitate clock recovery. The 10-bit data for each link is trans
37、ferred across the interface as a serial data-stream in unbalanced form and at an impedance of 75 . 2 Link-to-link timing relationship The interface must operate correctly when the electrical lengths of the two interconnections between line sender and receiver differ by up to 10 ns. 3 Coding The unco
38、ded serial bit-stream is scrambled using the generator polynomial G1(x) G2(x), where G1(x) = x9+ x4+ 1 to produce a scrambled NRZ signal, and G2(x) = x + 1 to produce a polarity-free NRZI sequence. 4 Order of transmission The least significant bit of each 10-bit word shall be transmitted first. 5 Lo
39、gic convention The signal is transmitted in NRZI form, for which the bit polarity is irrelevant. 8 Rec. ITU-R BT.799-4 6 Transmission medium The bit-serial data-stream can be conveyed using either a coaxial cable ( 7) or fibre optic bearer ( 8). 7 Characteristics of the electrical interface 7.1 Line
40、 driver characteristics (source) 7.1.1 Output impedance The line driver has an unbalanced output with a source impedance of 75 and a return loss of at least 15 dB over a frequency range of 5-270 MHz. 7.1.2 Signal amplitude The peak-to-peak signal amplitude lies between 800 mV 10% measured across a 7
41、5 resistive load directly connected to the output terminals without any transmission line. 7.1.3 DC offset The DC offset with reference to the mid amplitude point of the signal lies between +0.5 and 0.5V. 7.1.4 Rise and fall times The rise and fall times, determined between the 20% and 80% amplitude
42、 points and measured across a 75 resistive load connected directly to the output terminals, shall lie between 0.75 and 1.50 ns and shall not differ by more than 0.50 ns. 7.1.5 Jitter The output jitter is specified as follows: output jitter (see Note 1) f1= 10 Hz f3= 1 kHz f4= 1/10 of the clock rate
43、A1= 0.2 UI (UI; unit interval) A2= 0.2 UI NOTE 1 1 UI corresponds to 3.7 ns 0.2 UI corresponds to 0.74 ns. Specification of jitter and jitter measurements methods shall comply with Recommendation ITU-R BT.1363 (Jitter specifications and for methods jitter measurement of bit-serial signals conforming
44、 to Recommendations ITU-R BT.656, ITU-R BT.799 and ITU-R BT.1120). 7.2 Line receiver characteristics (destination) 7.2.1 Terminating impedance The cable is terminated by 75 with a return loss of at least 15 dB over a frequency range of 5 to 270 MHz. 7.2.2 Receiver sensitivity The line receiver must
45、sense correctly random binary data either when connected directly to a line driver operating at the extreme voltage limits permitted by 7.1.2, or when connected via a cable having a loss of 40 dB at 270 MHz and a loss characteristic of 1/ f. Rec. ITU-R BT.799-4 9 7.2.3 Interference rejectionWhen con
46、nected directly to a line driver operating at the lower limit specified in 7.1.2, the line receiver must correctly sense the binary data in the presence of a superimposed interfering signal at the following levels: DC 2.5 V below 1 kHz: 2.5 V peak-to-peak 1 kHz to 5 MHz: 100 mV peak-to-peak Above 5
47、MHz: 40 mV peak-to-peak. Specification of jitter and jitter measurements methods shall comply with Recommendation ITU-R BT.1363. 7.3 Cables and connectors 7.3.1 Cable It is recommended that the coaxial cable chosen should meet any relevant national standards on electromagnetic radiation. NOTE 1 Proc
48、essing and transmission of digital data, such as digital video signals at high data rates produces a wide spectrum of energy that has the potential to cause cross-talk or interference. It should be noted that the ninth and eighteenth harmonics of the 13.5 MHz sampling frequency (nominal value) speci
49、fied in Recommendation ITU-R BT.601 fall at the 121.5 and 243 MHz aeronautical emergency channels. Appropriate precautions must therefore be taken in the design and operation of interfaces to ensure that no interference is caused at these frequencies. Permitted maximum levels of radiated signals from digital data processing equipment are the subject of various national and international standards, and it should be noted that emission levels for related equipment are given in CISPR Recommendation: “Information technology equipment limits
