BT656

RECOMMENDATION ITU-R BT.656-4*Interfaces for digital component video signals in 525-lineand 625-line television systems operating at the 4:2:2level of Recommendation ITU-R BT.601 (Part A)(Question ITU-R 42/6)(1986-1992-1994-1995-1998)The ITU Radiocommunication Assembly,consideringa) that there are clear advantages for television broadcasting organizations and programme producers in digital studio standards which have the greatest number of significant parameter values common to 525-line and 625-line systems;b) that a worldwide compatible digital approach will permit the development of equipment with many common features, permit operating economies and facilitate the international exchange of programmes;c) that to implement the above objectives, agreement has been reached on the fundamental encoding parameters of digital television for studios in the form of Recommendation ITU-R BT.601;d) that the practical implementation of Recommendation ITU-R BT.601 requires definition of details of interfaces and the data streams traversing them;e) that such interfaces should have a maximum of commonality between 525-line and 625-line versions;f) that in the practical implementation of Recommendation ITU-R BT.601 it is desirable that interfaces be defined in both serial and parallel forms;g) that digital television signals produced by these interfaces may be a potential source of interference to other services, and due notice must be taken of No. 964 of the Radio Regulations (RR),recommendsthat where interfaces are required for component-coded digital video signals described in Recommendation ITU-R BT.601 (Part A) in television studios, the interfaces and the data streams that will traverse them should be in accordance with the following description, defining both bit-parallel and bit-serial implementations.* Radiocommunication Study Group 6 made editorial amendments to this Recommendation in 2003 in accordance with Resolution ITU-R 44.1 IntroductionThis Recommendation describes the means of interconnecting digital television equipment operating on the 525-line or 625-line standards and complying with the 4:2:2 encoding parameters as defined in Recommendation ITU-R BT.601 (Part A).Part 1 describes the signal format common to both interfaces.Part 2 describes the particular characteristics of the bit-parallel interface.Part 3 describes the particular characteristics of the bit-serial interface.Supplementary information is to be found in Annex 1.PART 1Common signal format of the interfaces1 General description of the interfacesThe interfaces provide a unidirectional interconnection between a single source and a single destination.A signal format common to both parallel and serial interfaces is described in § 2.The data signals are in the form of binary information coded in 8-bit or, optionally, 10-bit words (see Note 1). These signals are:signals,– video– timing reference signals,signals.– ancillaryNOTE 1 – Within this Recommendation, the contents of digital words are expressed in both decimal and hexadecimal form. To avoid confusion between 8-bit and 10-bit representations, the eight most significant bits are considered to be an integer part while the two additional bits, if present, are considered to be fractional parts.For example, the bit pattern 10010001 would be expressed as 145d or 91h, whereas the pattern 1001000101 is expressed as 145.25d or 91.4h.Where no fractional part is shown, it should be assumed to have the binary value 00.Eight-bit words occupy the left most significant bits of a 10-bit word, i.e. bit 9 to bit 2, where bit 9 is the most significant bit.data2 Videocharacteristics2.1 CodingThe video data is in compliance with Recommendation ITU-R BT.601 Part A, and with the field-blanking definition shown in Table 1.Field interval definitions2.2 Video data formatThe data 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.The video data words are conveyed as a 27 Mword/s multiplex in the following order:C B , Y , C R , Y , C B , Y , C R , etc.where the word sequence C B , Y , C R , refers to co-sited luminance and colour-difference samples and the following word, Y , corresponds to the next luminance sample.2.3 Interface signal structureFigure 1 shows the ways in which the video sample data is incorporated in the interface data stream. Sample identification in Fig. 1 is in accordance with the identification in Recommendation ITU-R BT.601 (Part A).625 525V-digital field blankingField 1 Start(V = 1) Line 624 Line 1Finish (V = 0) Line 23 Line 20 Field 2 Start (V = 1) Line 311 Line 264Finish (V = 0) Line 336 Line 283 F-digital field identification Field 1 F = 0 Line 1 Line 4 Field 2F = 1Line 313Line 266NOTE 1 – Signals F and V change 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.470. Note that digital line number changes state prior to O H as described in Recommendation ITU-R BT.601 (Part A).NOTE 3 – 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.Last sample Sample dataFirst sampleReplaced bytiming referencesignalReplaced by digital blanking dataReplaced by timing referencesignalEnd of active videoStart of active videoNote 1 – Sample identification numbers in parentheses are for 625-line systems where these differ from those for 525-line systems. (See also Recommendation ITU-R BT.803.)Composition of interface data streamD012.4Video timing reference codes (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. 1.Each timing reference signal consists of a four word sequence in the following format: FF 00 00 XY. (Values are expressed in hexadecimal notation. FF 00 values are reserved for use in timing reference signals.) The first three words are a fixed preamble. The fourth word contains information defining 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 in Table 2.Video timing reference codesBits P 0, P 1, P 2, P 3, have states dependent on the states of the bits F, V and H as shown in Table 3. At the receiver this arrangement permits one-bit errors to be corrected and two-bit errors to be detected.TABLE 3 Protection bits2.5 Ancillary dataThe ancillary signals should comply with Recommendation ITU-R BT.1364.Data bit number First word (FF) Second word (00) Third word (00) Fourth word (XY) 9 (MSB) 1 0 0 18 1 0 0 F 7 1 0 0 V 6 1 0 0 H 5 1 0 0 P 3 4 1 0 0 P 2 3 1 0 0 P 1 2 1 0 0 P 0 1 (Note 2) 1 0 0 00 1 0 0 0 NOTE 1 – The values shown are those recommended for 10-bit interfaces.NOTE 2 – For compatibility with existing 8-bit interfaces, the values of bits D 1 and D 0 are not defined.F = 0 during field 1;1 during field 2 V = 0 elsewhere;1 during field blanking H = 0 in SAV;1 in EAVP 0, P 1, P 2, P 3: protection bits (see Table 3) MSB: most significant bitTable 1 defines the state of the V and F bits.F V H P 3 P 2 P 1 P 00 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 12.6 Data words during blankingThe data words occurring during digital blanking intervals that are not used for the timing reference code or for ancillary data are filled with the sequence 80.0h, 10.0h, 80.0h, 10.0h etc. corresponding to the blanking level of the C B, Y, C R, Y signals respectively, appropriately placed in the multiplexed data.PART 2Bit-parallel interface1 General description of the interfaceThe bits of the digital code words that describe the video signal are transmitted in parallel by means of eight (optionally, ten) conductor pairs, where each carries a multiplexed stream of bits (of the same significance) of each of the component signals, C B, Y, C R, Y. The eight pairs also carry ancillary data that is time-multiplexed into the data stream during video blanking intervals. An additional pair provides a synchronous clock at 27 MHz.The signals on the interface are transmitted using balanced conductor pairs. Cable lengths of up to 50 m (–;~ 160 feet) without equalization and up to 200 m (–;~650 feet) with appropriate equalization may be employed.The interconnection employs a twenty-five pin D-subminiature connector equipped with a locking mechanism (see § 5).For convenience, the bits of the data word are assigned the names DATA 0 to DATA 9. The entire word is designated as DATA (0-9). DATA 9 is the most significant bit. Eight-bit data words occupy DATA (2-9).Video data is transmitted in NRZ form in real time (unbuffered) in blocks, each comprising one active television line.format2 DataThe interface carries data in the form of eight (optionally, ten) parallel data bits and a separate synchronous clock. Data is coded in NRZ form. The recommended data format is described in Part 1.signal3 Clock3.1 GeneralThe clock signal is a 27 MHz square wave where the 0-1 transition represents the data transfer time. This signal has the following characteristics:Width: 18.5 ± 3 nsJitter: Less than 3 ns from the average period over one field.NOTE 1 – This jitter specification, while appropriate for an effective parallel interface, is not suitable for clocking digital-to-analogue conversion or parallel-to-serial conversion.3.2 Clock-to-data timing relationshipThe positive transition of the clock signal shall occur midway between data transitions as shown in Fig. 2.4 Electrical characteristics of the interface4.1 GeneralEach line driver (source) has a balanced output and the corresponding line receiver (destination) a balanced input (see Fig. 3).Although the use of ECL technology is not specified, the line driver and receiver must be ECL-compatible, i.e. they must permit the use of ECL for either drivers or receivers.All digital signal time intervals are measured between the half-amplitude points.Timing referenceClock period (625):T =11 728 fH= 37 nsClock period (525):T =1H= 37 nsClock pulse width:Data timing – sending end: f : line frequencyH t = 18.5 ± 3 ns t = 18.5 ± 3 nsFIGURE 2Clock-to-data timing (at source)dD024.2 LogicconventionThe A terminal of the line driver is positive with respect to the B terminal for a binary 1 and negative for a binary 0 (see Fig. 3).Line driver and line receiver interconnection(source)characteristics4.3 Linedriver4.3.1Output impedance: 110 Ω maximum.4.3.2Common mode voltage: –1.29 V ± 15% (both terminals relative to ground).4.3.3Signal amplitude: 0.8 to 2.0 V peak-to-peak, measured across a 110 Ω resistive load.4.3.4Rise and fall times: less than 5 ns, measured between the 20% and 80% amplitude points, with a 110 Ω resistive load. The difference between rise and fall times must not exceed 2 ns.4.4 Line receiver characteristics (destination)4.4.1Input impedance: 110 Ω± 10 Ω.4.4.2Maximum input signal: 2.0 V peak-to-peak.4.4.3Minimum input signal: 185 mV peak-to-peak.However, the line receiver must sense correctly the binary data when a random data signal produces the conditions represented by the eye diagram in Fig. 4 at the data detection point.4.4.4Maximum common mode signal:± 0.5 V, comprising interference in the range 0 to 15 kHz (both terminals to ground).4.4.5Differential delay: Data must be correctly sensed when the clock-to-data differential delay is in the range between ± 11 ns (see Fig. 4).Idealized eye diagram correspondingto the minimum input signal levelminT V = 11 ns = 100 mVminminNote 1 – The width of the window in the eye diagram, within whichdata must be correctly detected comprises ± 3 ns clock jitter, ± 3 nsdata timing (see § 3.2), ± 5 ns available for differences in delaybetween pairs of the cable. (See also Recommendation ITU-R BT.803.)D045 Mechanical details of the connectorThe interface uses the 25 contact type D subminiature connector specified in ISO Doc. 2110-1980, with the contact assignment shown in Table 4.Connectors are locked together by two UNC 4-40 screws on the cable connectors, which go in female screw locks mounted on the equipment connector. Cable connectors employ pin contacts and equipment connectors employ socket contacts. Shielding of the interconnecting cable and its connectors must be employed (see Note 1).NOTE 1 – It should be noted that the ninth and eighteenth harmonics of the 13.5 MHz sampling frequency (nominal value) specified in Recommendation ITU-R BT.601 (Part A) 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. Emission levels for related equipment are given in CISPR Recommendation: “Information technology equipment – limits of interference and measuring methods”, Doc. CISPR/B (Central Office) 16. Nevertheless, RR No. 964 prohibits any harmful interference on the emergency frequencies. (See also Recommendation ITU-R BT.803.)Contact assignmentsPART 3Bit-serial interface1General description of the interfaceThe multiplexed data stream of 10-bit words (as described in Part 1) is transmitted over a single channel in bit-serial form. Prior to transmission, additional coding takes place to provide spectral shaping, word synchronization and to facilitate clock recovery (see Note 1).NOTE 1 – Previous versions of this Recommendation have described a serial interface based on an 8B9B word-mapping technique. Due to implementation difficulties this technique is no longer recommended.In addition to the 10-bit interface based on scrambling described in this revision of the Recommendation, there exists an 11-bit word format (10B1C) in which the eleventh bit is the complement of the least significant bit (LSB) of the scrambled data word.Contact Signal line 1 Clock 2 System ground A 3 Data 9 (MSB) 4 Data 8 5 Data 7 6 Data 6 7 Data 5 8 Data 4 9 Data 310 Data 2 11 Data 1 12 Data 0 13 Cable shield 14 Clock return 15 System ground B 16 Data 9 return 17 Data 8 return 18 Data 7 return 19 Data 6 return 20 Data 5 return 21 Data 4 return 22 Data 3 return 23 Data 2 return 24 Data 1 return 25 Data 0 returnNOTE 1 – The cable shield (contact 13) is for the purpose of controlling electromagnetic radiationfrom the cable. It is recommended that contact 13 should provide high-frequency continuity to the chassis ground at both ends and, in addition, provide DC continuity to the chassis ground at the sending end. (See also Recommendation ITU-R BT.803.)Rec. ITU-R BT.656-4112 CodingThe uncoded 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, andG2(x) =x + 1 to produce a polarity-free NRZI sequence.transmission3 OrderofThe least significant bit of each 10-bit word shall be transmitted first.4 LogicconventionThe signal is transmitted in NRZI form, for which the bit polarity is irrelevant.medium5 TransmissionThe bit-serial data stream can be conveyed using either a coaxial cable (see § 6) or fibre-optic bearer (see § 7).6 Characteristics of the electrical interfacedrivercharacteristics(source)6.1 Line6.1.1 Output impedanceThe line driver has an unbalanced output with a source impedance of 75 Ω and a return loss of at least 15 dB over a frequency range of 5-270 MHz.6.1.2 Signal amplitudeThe peak-to-peak signal amplitude lies between 800 mV ± 10% measured across a 75 Ω resistive load directly connected to the output terminals without any transmission line.6.1.3 d.c. offsetThe d.c. offset with reference to the mid-amplitude point of the signal lies between +0.5 and –0.5 V.6.1.4 Rise and fall timesThe rise and fall times, determined between the 20% and 80% amplitude points and measured across a 75 Ω 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.6.1.5 JitterThe output jitter is specified as follows:Output jitter (see Note 1) f1= 10 Hzf3= 100 kHzf4= 1/10 of the clock rateA1= 0.2 UI (UI; unit interval) (see Note 2)A2= 0.2 UI12 Rec. ITU-R BT.656-4NOTE 1 – 1 UI and 0.2 UI correspond to 3.7 ns and 0.74 ns.Specification of jitter and jitter measurements methods shall comply with Recommendation ITU-R BT.1363 (Jitter specifications and jitter measurement methods of bit-serial signals conforming to Recommendations ITU-R BT.656, ITU-R BT.799 and ITU-R BT.1120).NOTE 2 – 0.2 UI for timing jitter is often used in other specifications. There are considerations in specifying 1 UI for timing jitter.6.2 Line receiver characteristics(destination)6.2.1 Terminating impedanceThe cable is terminated by 75 Ω with a return loss of at least 15 dB over a frequency range of 5-270 MHz.6.2.2 Receiver sensitivity (see Note 1)The line receiver must sense correctly random binary data when either connected to a line driver operating at the extreme voltage limits permitted by § 6.1.2 or when connected via a cable having a loss of 40 dB at 270 MHz and a loss characteristic of 1 / f.NOTE 1 – Parameters defined in § 6.1.5, 6.2.2 and 6.2.3 are target values and may be refined in the future with regard to practical implementations of the system.6.2.3 Interference rejection(see Note 1)When connected directly to a line driver operating at the lower limit specified in § 6.1.2, the line receiver must sense correctly the binary data in the presence of a superimposed interfering signal at the following levels:d.c. ± 2.5 VBelow 1 kHz: 2.5 V peak-to-peak1 kHz to 5 MHz: 100 mV peak-to-peakAbove 5 MHz: 40 mV peak-to-peakNOTE 1 – Parameters defined in § 6.1.5, 6.2.2 and 6.2.3 are target values and may be refined in the future with regard to practical implementations of the system.6.2.4 Input jitterInput jitter tolerances needs to be defined. Input jitter is measured with a short cable (2 m). Specification of jitter and jitter measurements methods shall comply with Recommendation ITU-R BT.1363 (Jitter specifications and jitter measurement methods of bit-serial signals conforming to Recommendations ITU-R BT.656, ITU-R BT.799 and ITU-R BT.1120).Rec. ITU-R BT.656-413 6.3 Cables and connectors6.3.1 CableIt is recommended that the cable chosen should meet any relevant national standards on electromagnetic radiation.NOTE 1 – It should be noted that the ninth and eighteenth harmonics of the 13.5 MHz sampling frequency (nominal value) specified in Recommendation ITU-R BT.601 (Part A) 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. Emission levels for related equipment are given in CISPR Recommendation: “Information technology equipment – limits of interference and measuring methods” (Doc. CISPR/B (Central Office) 16). Nevertheless, RR No. 964 prohibits any harmful interference on the emergency frequencies. (See also Recommendation ITU-R BT.803.)6.3.2 Characteristic impedanceThe cable used shall have a nominal characteristic impedance of 75 Ω.6.3.3 Connector characteristicsThe connector shall have mechanical characteristics conforming to the standard BNC type (IEC Publication 169-8), and its electrical characteristics should permit it to be used at frequencies up to 850 MHz in 75 Ω circuits.7 Characteristics of the optical interfaceSpecifications for the characteristics of the optical interface should comply with general rules of Recommendation ITU-R BT.1367 (Serial Digital Fiber Transmission Systems for Signals Conforming to Recommendations ITU-R BT.656, ITU-R BT.799 and ITU-R BT.1120).To make use of this Recommendation the following specifications are necessary:Rise and fall times < 1.5 ns (20% to 80%)Output jitter (see Note 1) f1 = 10 Hzf3= 100 kHzf4= 1/10 of the clock rateA1= 0.135 UI (UI; unit interval)A2= 0.135 UIInput jitter needs to be defined. Input jitter is measured with a short cable (2 m).NOTE 1 – Specification of jitter and jitter measurements methods shall comply with Recommendation ITU-R BT.1363 (Jitter specifications and jitter measurement methods of bit-serial signals conforming to Recommendations ITU-R BT.656, ITU-R BT.799 and ITU-R BT.1120).14 Rec. ITU-R BT.656-4Annex 1Notes concerning interfaces for digital video signalsin 525-line and 625-line television systems1 IntroductionThis Annex includes supplementary information on subjects not yet fully specified, and indicates studies in which further work is required.2 DefinitionsInterface is a concept involving the specification of the interconnection between two items of equipment or systems. The specification includes the type, quantity 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 data word, and successive data words, are sent consecutively via a single channel.interfaces3 ParallelAppropriate coding of the clock signal, such as the use of an alternating parity (AP) coding, has been shown to extend the interconnection distance by reducing the effects of cable attenuation.To permit correct operation with longer interconnection links, the line receiver may incorporate equalization.When equalization is used, it may conform to the nominal characteristic of Fig. 5. This characteristic permits operation with a range of cable lengths down to zero. The line receiver must satisfy the maximum input signal condition of § 4.4 of Part 2 of this Recommendation.interfaces4 SerialThe 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, while preference would go to optical 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 interconnections 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 itself.Rec. ITU-R BT.656-41520181614121086420110210–1FIGURE 5Line receiver equalization characteristic for small signalsR e l a t i v e g a i n (d B )Frequency (MHz)D05Development work is ongoing on the subject of serial interfaces. In the context of the European RACE projects, for example, fibre optic routing systems which can accept a variety of input formats are assembled as part of a pilot installation. 5Interference with other servicesProcessing 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. In particular, attention is drawn in the present Recommendation to the fact that the ninth and eighteenth harmonics of the 13.5 MHz sampling frequency (nominal value) specified in Recommendation ITU-R BT.601 (Part A) 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 such related equipment are given in CISPR Recommendation: “Information technology equipment – Limits of interference and measuring methods”, Doc. CISPR/B (Central Office) 16.In the case of the bit-parallel interface, work carried out by the Canadian Broadcasting Corporation (CBC) indicates that, with a correct shielding of the cables, no interference problem with other services is to be expected. Radiation levels should comply with the limits given in Table 5. These limits are equivalent to those of the FCC in the United States of America.16 Rec. ITU-R BT.656-4TABLE 5Limits of spurious emissionsTransmission by optical fibres eliminates radiation generated by the cable and also prevents conducted common-mode radiation, but the performance of coaxial cable can also be made near-perfect. It is believed that the major portion of any radiation would be from the processing logic and high-power drivers common to both methods. Due to the wideband, random nature of the digital signal, little is gained by frequency optimization. 6 ConclusionFurther studies are required on the practical methods required to ensure acceptably low levels of radiated interference from the digital signals.Frequency (MHz) Maximum field strength at 30 m(dB(µV/m))30-88 30 88-216 50 216-1 00070。

ITU BT 601建议及与ITU BT656 的区别1、ITU-R BT.601介绍1982年CCIR(International Radio Consultative Committee国际无线电咨询委员会)制定了彩色视频数字化标准，称为CCIR 601标准，现改为ITU-R BT.601标准（601-4:1994.7. / 601-5:1995.10）。

该标准规定了彩色视频转换成数字图像时使用的采样频率，RGB和YCbCr两个彩色空间之间的转换关系等。

其中的ITU = International Telecommunication Union(联合国)国际电信联盟，R = Radiocommunication Sector无线电部，BT = Broadcasting service (television)广播服务(电视)。

为了便于国际间的节目交换，为消除数字设备之间的制式差别,和为 625行电视系统与 525行电视系统之间兼容，向着数字电视广播系统参数统一化、标准化迈出，在 1982年 2月国际无线电咨询委员会(CCIR)第 15次全会上，通过了 601号建议，确定以分量编码为基础, 即以亮度分量Y、和两个色差分量R-Y、 B-Y 为基础进行编码,作为电视演播室数字编码的国际标准,601号建议单独规定了电视演播室的编码标准。

该标准规定:(1).不管是PAL制，还是 NTSC制电视,Y、R-Y、B-Y三分量的抽样频率分别为13.5MHz、6.75MHz、6.75MHz。

(2). 抽样后采用线性量化，每个样点的量化比特数用于演播室为10bit, 用于传输为8bit。

(3). Y、R-Y、B-Y三分量样点之间比例为4:2: 2。

在 1983年 9月召开的国际无线电咨询委员会(CCIR)中期会议上，又作了三点补充：(1). 明确规定编码信号是经过γ预校正的 Y、(R-Y)、B-Y)信号；(2). 相应于量化级 0和 255的码字专用于同步， l到 254的量化级用于视频信号;(3). 进一步明确了模拟与数字行的对应关系，并规定从数字有效行末尾至基准时间样点的间隔，对 525行、 60场／秒制式来说为 16个样点，对 625行、 50场/秒制式则为 12 个样点。

BT656简介凡是做模拟信号采集的，很少不涉及BT.656标准的，因为常见的模拟视频信号采集芯片都支持输出BT.656的数字信号，那么，BT.656到底是何种格式呢？本文将主要介绍标准的 8bit BT656（4:2:2）YCbCr SDTV（标清）数字视频信号格式，主要针对刚刚入门模拟视频采集的初学者入门之用。

1. 帧的概念（Frame）一个视频序列是由N个帧组成的，采集图像的时候一般有2种扫描方式，一种是逐行扫描（progressive scanning），一种是隔行扫描（interlaced scanning）。

对于隔行扫描，每一帧一般有2个场（field），一个叫顶场（top field），一个叫底场（bottom field）。

假设一帧图像是720行，那么，顶场就包含其中所有的偶数行，而底场则包含其中所有的奇数行。

2. 场的概念（field）注意，上面提到顶场和底场，用的是“包含”二字，而不是说完全由后者组成，因为在BT.656标准中，一个场是由三个部分组成的：场 = 垂直消隐顶场（First Vertical Blanking） + 有效数据行（Active Video） + 垂直消隐底场（Second Vertical Blanking）对于顶场，有效数据行就是一帧图像的所有偶数行，而底场，有效数据行就是一帧图像的所有奇数行。

顶场和底场的空白行的个数也有所不同，那么，对于一个标准的 8bit BT656（4:2:2）SDTV（标清）的视频而言，对于一帧图像，其格式定义如下：由上图可以知道，对于PAL制式，每一帧有625行，其中，顶场有效数据288行，底场有效数据也是288行，其余行即为垂直消隐信号。

为什么是288行？因为PAL制式的SDTV 或者D1的分辨率为 720*576，即一帧有576行，故一场为288行。

由上图我们还可以知道，顶场有效数据的起始行为第23行，底场有效数据的起始行为第335行。

标题：BT656标准：视频接口的重要里程碑引言：在数字化时代，视频接口的发展对于图像和视频的传输至关重要。

BT656标准作为一项重要的视频接口标准，在多种应用领域中发挥着关键作用。

本文将详细介绍BT656标准的定义、特点和应用，并探讨其对于视频传输的重要意义。

一、BT656标准的定义BT656标准是指由国际电信联盟（ITU）制定的一项视频接口标准。

它规定了视频数据的传输格式、时序和电气特性等方面的标准，以确保视频信号的高质量传输和兼容性。

二、BT656标准的特点1. 数据格式：BT656标准采用了基于8位并行数据的格式，每个像素的亮度和色度信息被分开传输，以保证图像的清晰度和色彩还原度。

2. 时序要求：BT656标准定义了视频数据传输的时序要求，包括场同步、行同步和像素时钟等信号的生成和传输顺序，以确保视频信号的同步和稳定性。

3. 电气特性：BT656标准规定了视频信号的电平范围、阻抗匹配和信号线的布线要求，以提高信号传输的稳定性和抗干扰能力。

4. 兼容性：BT656标准与其他视频标准具有良好的兼容性，可以与不同设备之间的视频接口进行连接和互操作。

三、BT656标准的应用1. 数字摄像机：BT656标准被广泛应用于数字摄像机领域，用于将摄像机采集的视频信号传输到后续处理设备或存储介质中，保证图像的清晰度和色彩还原度。

2. 显示设备：BT656标准也被应用于各类显示设备，如液晶显示屏、投影仪等，用于接收和显示来自不同来源的视频信号，以提供高质量的图像展示效果。

3. 视频采集卡：BT656标准在视频采集卡中得到广泛应用，用于将外部视频信号输入到计算机中进行处理和编辑，满足多媒体应用的需求。

4. 视频传输系统：BT656标准还可以用于视频传输系统，如监控系统、视频会议系统等，通过标准化的接口实现视频信号的传输和共享。

四、BT656标准的重要意义1. 提高传输质量：BT656标准的采用可以有效提高视频信号的传输质量，保证图像的清晰度、色彩还原度和稳定性。

标准BT.656并行数据结构BT.656并行接口除了传输4:2:2的YCbCr视频数据流外，还有行、列同步所用的控制信号。

如图3所示，一帧图像数据由一个625行、每行1 728字节的数据块组成。

其中，23～311行是偶数场视频数据，336～624行是奇数场视频数据，其余为垂直控制信号。

BT.656每行的数据结构如图4所示。

图4中，每行数据包含水平控制信号和YCbCr。

视频数据信号。

视频数据信号排列顺序为Cb-Y-Cr-Y。

每行开始的288字节为行控制信号，开始的4字节为EAV信号(有效视频结束)，紧接着280个固定填充数据，最后是4字节的SAV信号(有效视频起始)。

SAV和EAV信号有3字节的前导：FF、FF、00；最后1字节XY表示该行位于整个数据帧的位置及如何区分SAV、EAV。

XY字节各比特位含义见图5。

图5中，最高位bit7为固定数据1；F=0表示偶数场，F=1表示奇数场；V=0表示该行为有效视频数据，V=1表示该行没有有效视频数据；H=0表示为SAV信号，H=1表示为EAV信号；P3～P0为保护信号，由F、V、H信号计算生成；P3=V异或H；P2=F异或H；P1=F异或V；P0=F异或V异或H。

*****************************************************************************************************ITU-R601/656 原名CCIR601/656,是国际电信协会提出的一个视频标准。

名词解释：BT.656 : This ITU recommendation defines a parallel interface (8-bit or 10-bit, 27 MHz) and a serial interface (270 Mbps) for the transmission of 4:3 BT.601 4:2:2 YCbCr digital video betweenpro-video equipment.国际电信联盟无线电通信部门656-3号建议书：工作在ITU-RBT.601建议（部分A）的4:2:2级别上的525行和625行电视系统中的数字分量视频信号的接口国际电联无线电通信全会考虑到：a)对于电视广播机构和节目制作者，在525行和625行系统的数字演播室标准方面有最多个数的相同重要参数有明显好处；b)一种世界范围兼容的数字方法将会使设备的开发具有许多共同特点，运行会更经济，并便于国际间节目’的交换；c)为实现上述目标，已以ITU-RBT．601建议的形式对数字电视演播室的基本编码参数达成了协议；d)ITU-RBT．601建议的实际实施要求规定接口和通过接口的数据流的细节；e)这些接口在525行和625行两型问应该具有最大的共同性；f)在ITU-RBT．601建议的实际实施中，希望对接口的串行和并行两种形式都作出规定；g)这些接口所产生的数字电视信号有可能是对其它业务的潜在干扰源，必须对无线电规则No．964给予应有的注意。

常用视频信号接口与处理方法总结刘学满2010-4-13 一、视频接口概述视频接口，从颜色空间、数字/模拟、分离/复合（适用于模拟信号）、并行/串行（适用于数字信号）、单端/差分等类别可以分为如下几种，见下表：二、模拟视频信号接口1．接口设计模拟信号由于其电压范围很小，如果接口电路设计不当，很可能造成最终的信号质量下降。

因此需要注意以下几个事项：1）阻抗匹配：通常为75Ω，包括发送端，接收端以及传输路径上的阻抗。

2）隔直电容：为了防止不同设备间地电压差对信号造成的影响，此电容不宜过大或者过小。

3）滤波网络：尽可能地消除低频和高频纹波。

4）地平面：根据理论，地平面分隔可以防止数字信号对模拟地干扰，但从实际经验来看，分隔成小的地平面后，实际上会造成环流（AD9883资料中有叙述）。

因此大部分情况下，还是用同一个地。

多层地平面，以及多打过孔，保持地电平的稳定是非常必要的。

5）PCB走线：等长是需要的，而且要确保三个器件经过不同的选择器/缓冲器之后的延时也相差不多，否则很难保证采样相位。

6）ESD保护：如果视频接口经常插拔，就需要加ESD保护二极管。

2．视频ADC完成模拟信号到数字信号的转换，在使用过程中需要注意的主要问题有：1）A/D是否支持交流耦合方式输入2）A/D内部是否有信号增益调整功能3）是否支持差分输入4）A/D内部是否有PLL等器件，采样相位是否可调整5）A/D输出的信号格式（24bit RGB，YCbCr）6）是否支持SOG或者SOY等同步信号输入模拟信号在A/D转换时，通常需要进行一些调整，以达到最佳显示效果：1）调整黑电平位置和最大辐值，通常可以配置A/D芯片有关offset和gain的寄存器，经过此番调整之后，实际上是校准了RGB三色，同时提高了灰度等级。

2）调整PLL锁相环，以达到合适的采样频率，并保证PLL在各种温度条件下均能稳定工作。

3）调整采样起始点和终止点，确保有效信号不丢失。

浅谈光端机在安防视频监控中的作用体现光端机发展概述自2001年以来，随着宽带数字光传输器件技术以及数字视频技术的飞速发展，数字视频光端机开始走向市场并逐渐取代了模拟光端机市场，迎来了数字视频光端机高速发展的时代，并呈现出技术成熟、性能优越、应用面广、需求旺盛的局面。

近年来，随着安防市场需求的变化，视频光端机的技术创新和产品变革呈现出了更强的应用性：(1)为适应高速公路外场监控的需要，级联型链路式光端机取代传统的点到点光端机大量应用；(2)为了满足公安三四级联网的应用，单纤传输双向视频、音频、数据、电话、E1、以太网等的多功能光端机应运而生；(3)随着平安城市建设规模的不断扩大，光纤资源紧缺的问题暴露出来，光端机厂家又及时推出了汇聚光端机产品。

目前，安防视频光端机呈现出高速发展的势头，其应用也大幅增长，核心编解码技术及关键技术都有很大提高和创新，实际应用中存在的技术瓶颈和问题都得到了很大的完善。

本文重点从视频光端机的编解码技术、技术创新及应用情况等进行分析探讨。

光端机原理及编码光传输系统由三部分组成：光源(光发送机)、传输介质、检测器(光接收机)其中光源和检测器的工作都是由光端机完成的。

光端机就是将多个E1(一种中继线路的数据传输标准，通常速率为 2.048MbPS，此标准为中国和欧洲采用)信号变成光信号并传输的设备(它的作用主要就是实现电-光和光-电转换)。

光端机主要有模拟光端机和数字光端机两种：1、模拟光端机模拟光端机采用了PFM调制技术实时传输图像信号，是目前使用较多的一种。

发射端将模拟视频信号先进行PFM调制后(一般有调频、调相、调幅几种方式，从而把模拟光端机分成调频、调相、调幅等几种光端机)，再进行电-光转换，光信号传到接收端后，进行光-电转换，然后进行PFM解调，恢复出视频信号。

由于采用了PFM调制技术，其传输距离很容易就能达到30Km左右，有些产品的传输距离可以达到60Km，甚至上百公里。

BT656BT601BT1120协议以及DM365DM355DM6467上使用的Y...YUV是被欧洲电视系统所采用的一种颜色编码方法（属于PAL），是PAL和SECAM模拟彩色电视制式采用的颜色空间。

在现代彩色电视系统中，通常采用三管彩色摄影机或彩色CCD摄影机进行取像，然后把取得的彩色图像信号经分色、分别放大校正后得到RGB，再经过矩阵变换电路得到亮度信号Y和两个色差信号R－Y（即U）、B－Y （即V），主要的采样格式有YCbCr 4:2:0、YCbCr 4:2:2、YCbCr 4:1:1和YCbCr 4:4:4。

其中YCbCr 4:1:1 比较常用，其含义为：每个点保存一个 8bit 的亮度值(也就是Y值)，每 2x2 个点保存一个 Cr 和Cb 值, 图像在肉眼中的感觉不会起太大的变化。

所以，原来用 RGB(R，G，B 都是 8bit unsigned) 模型，1个点需要 8x3=24 bits（如下图第一个图），（全采样后，YUV仍各占8bit）。

按4:1:1采样后，而现在平均仅需要8+(8/4)+(8/4)=12bits（4个点，8*4（Y）+8(U)+8(V)=48bits）, 平均每个点占12bits(如下图第二个图)。

这样就把图像的数据压缩了一半。

ITU-R BT.601和ITU-R BT.656国际电信联盟（International Telecommunication Union）无线通信部门（ITU-R）制定的标准。

严格来说，ITU-R BT.656应该是隶属ITU-R BT.601的一个子协议。

ITU-R BT.601是演播室数字电视编码参数标准，而ITU-R BT.656 则是ITU-R BT.601附件A中的数字接口标准，用于主要数字视频设备(包括芯片)之间采用27Mhzs并口或243Mbs串行接口的数字传输接口标准。

BT.656并行接口除了传输4:2:2的YCbCr视频数据流外，还有行、列同步所用的控制信号。

BT1120与BT656的区别视频数据格式BT656接口使用的是8位或者10位4：2：2 YCbCr数据，为了能够处理HDTV数据传输，有些设计使用16位或者20位YCbCr的接口（本质上是两个BT656数据流，一个为数据Y,一个为数据CbCr）,或者使用时钟的两个边沿传输数据。

BT1120与BT656的区别BT656主要是针对PAL/NTSC等标清视频。

时钟频率是27MHz。

注意采样频率灰度为12.5MHz，色度为6.25MHz。

随着高清视频的发展的需要，又推出了BT1120标准，它与BT656是类似的，只不过时钟频率更高了，以适合高清视频的传输。

601是SDTV的数据结构 656是SDTV的interface709是HDTV的数据结构 1120是HDTV的interface从ITU-R BT1120文档上可知，BT1120支持的是1080p：文档定义一帧为1 125 总行数和1 080 有效行；每行有效像素为1920图像频率60、 50、 30、 25 和 24Hz包括逐行、隔行和帧分段传输；在60、 30和24 Hz系统中，也包括这些值除以1.001的图像频率，文档规定对于10位接口对应于数字量化级0(10)至3(10)和1 020(10)至1 023(10)的数据字保留用于数据标识目的，不得作为图像数据出现。

下面是逐行扫描系统帧结构SAV和EAV称为定时基准码，定时基准码由 4 个字的序列组成，前 3 个字为固定前缀，第 4个字运载的信息定义出场识别（F）、场/帧消隐期（V）和行消隐期（H）。

使用SAV和EAV来指示视频时序，可以减少视频传输的引脚数量。

注1 —EAV和SAV中（F/V/H）的值反映F、V和H比特的状态；该值以F、V、H组成的3比特字用二—十进制记数（BCD）表示（F 对应MSB，H对应LSB）。

例如，数值3代表的比特为F=0、V=1和H=18bit辅助数据EAV终端和SAV始端之间的水平消隐间隔可被应用于传送辅助数据包。

BT656是一种视频传输标准，它定义了一种将数字视频信号转换为并行视频信号的接口。

在BT656标准中，数字视频信号以并行的方式传输，每个像素的颜色信息被分割成几个字节，并以并行方式传送。

"8位"和"12位"是指BT656接口中每个像素的颜色深度。

深度表示每个像素所占用的位数，决定了颜色的细节和精度。

在8位颜色深度下，每个像素的颜色信息使用8个二进制位来表示。

这意味着每个像素可以有256种可能的颜色选择。

8位颜色深度适合于一般的视频应用，如普通的图像和视频播放。

而在12位颜色深度下，每个像素的颜色信息使用12个二进制位来表示。

这意味着每个像素可以有4096种可能的颜色选择，相比于8位颜色深度，颜色精度更高，图像显示更细腻。

12位颜色深度适合于需要更高图像质量的应用，如高清视频、专业图形处理等。

需要注意的是，BT656接口的具体配置和使用可能会因设备和应用而有所不同，这只是对8位和12位颜色深度的基本解释。

BT.656NTSC制式彩条⽣成模块（verilog）BT.656 NTSC制式彩条⽣成模块(verilog)1.知识储备隔⾏扫描是将⼀副图像分成两场扫描，第⼀场扫描第1,2,5,7...等奇数⾏，第⼆场扫描2，4,6,8...等偶数⾏，并把扫奇数⾏的场称为奇数场，扫偶数⾏的场称为偶数场，⼀幅图像经过两次扫描即可。

由左到右的扫描称为⾏扫描，由上到下的扫描称为场扫描。

对于标准的8bit BT656(YUV4:2:2)标清制式来说，⼀帧图像的格式定义如下：⼀⾏是由4个部分组成：⾏ = 结束码（EAV） + ⽔平消隐（Horizontal Vertical Blanking） + 起始码（SAV） + 有效数据（Active Video）注意：实际的⼯程中彩条每⼀⾏像素点的排列并不是这样的，⽽是(SAV Code ->Active video->EAV Code->Blanking video)2.代码分析TPG端⼝说明：reset_in：由SDI播出⼯程内部信号提供。

pclk_in:与播出时钟tx_usrclk对接。

data_out:输出图像数据。

tx_sd_ce:门控时钟（SD-SDI,5/6/5/6）并且初识化像素位置pixels=1,⾏位置lines=1,即图像扫描的初始位置。

彩条中各种⾊彩值设定（忽略⼗进制的数字，部分有误），同时定义了⽤来存储当前颜⾊的寄存器cur_color定义常数，总共有多少⾏，多少列（1716 ，525）彩条颜⾊分配函数，通过像素点的位置来分配当前位置的颜⾊。

有效像素点的排列如下图所⽰：pixels初始值为1，则01：Cb10：Y11：Cr00：Y01：Cb通过pixels[0],pixels[1:0]来分割cur_color,得到colorValue.以下always块⾥⾯是⾏扫描和场扫描控制，当⼀⾏扫描完成后，pixels回到初始位置，line加1.根据⾏来控制F,V的值：每⼀⾏的像素排列，⼀定要注意顺序SAV（FF,00,00,XY）,接下来的是Active video,然后是EAV（FF,00,00,XY），最后是Blankingvideo,⽤80,10填充。

图 1 去隔行处理与图像缩放 SCALER 电路分别使用单独的集成电路示图液晶彩电去隔行处理和 SCALER 电路介绍（二）笙马介新二、常见去隔行、SCALER 芯片介绍液晶彩电中的去隔行处理与图像缩放 SCALER 电 路的配置方案一般有两大类：一种是去隔行处理与 图像缩放 SCALER 电路分别使用单独的集成电路，如 图 1 所示；第 2 种电路配置方案是将去隔行处理、SCALER 电路集成在一起(如图 1 所示)，也 就是说， 它们是作为一个整体而存在的，我们一般将此类芯 片称为“视频控制芯片”。

随着集成电路的发展，视频 控制芯片开始将 A/D 转换器、TMDS 接收器(接收 DVI 接口信号)、OSD (屏显电路)、MCU 、LVDS 发送器等集 成在一起，为便于区分，这样的芯片我们称其为“主 控芯片”。

现在，已有一些主控芯片开始集成有数字视频 解码电路，此类芯片我们一般称其为“全功能超级芯片”，由全功能 超级芯片构 成 的 液 晶 彩 电 是 最 为 简 洁 的一种。

下面简要介绍在液晶彩 电 中 比 较 常 用 的 几 种 去 隔 行、SCALER 芯片。

1.视频控制芯片 PWl232 BT656 数据格式(4∶2∶2)YUV 视频信号的输入，完成处理后以 24 bit 并行传输的 4∶4∶4 数字逐行信号 输出。

PWl232 内含运动检测和降噪电路、电影模式检测 电路、视频标度器、去隔行处理电路、视频增强电路、彩 色空间变换器、显示定时、行场同步定时等电路。

其中， PWl332 内部的去隔行处理电路用以将隔行扫描的视 频信号转换为逐行扫描的视频信号，内部的可编程视 频增强器用以提高图像的鲜明度，并可完成对亮度、对 比度、色调、色饱和度的控制。

图 3 所示为 PWl232 内部 电路框图。

与 PWl232 功 能 类 似 的 还 有 PWl226、PWl230、 PWl231、PWl235 等，其中，PWl226、PWl230、PWl235 内含 D／A 转换器，除可输出数字视频信号外，还可以输出 介绍PWl232 是 Pixelworks (像素科技)公司生产的扫描 格式变换电路，可接受标准 隔 行 ITU-RBT601 或 ITU-R图 2 去隔行处理、SCALER 电路集成为一块视频控制芯片示图图 3 PW1232 内部电路框图18 ( 总 594 页 ) 家电检修技术 2014 年第 10 期厂家 ︵ 专 家 ︶ 论 坛模拟视频信号。

基于无线2.4G的井下彩色视频传输与显示装置设计与实现崔业梅;丁帮俊;杨焕峥;吴建军【摘要】无线2.4G井下彩色视频传输与显示装置包括两个部分，井下无线发送端和井上无线接收端。

无线发送端主要包含摄像头、2.4G FM调制模块，可以将摄像头采集的模拟视频信号通过FM调制方式以2.4GHz的频率无线发射，无线接收端主要包含2.4GHz的FM解调模块、视频解码电路、液晶屏及驱动电路、单片机系统，可以将2.4G的模拟视频信号接收下来后经过FM解调，送入视频解码电路进行解码后经液晶屏驱动电路送液晶屏显示，单片机系统分别对视频解码芯片和液晶屏显示芯片寄存器进行配置。

该系统拥有较好的微波抗干扰能力，能供选取的频道数多，各频道间不容易进行互相干扰，当信号功率为1W时，直线有效传输距离500米以上，能把深井图像清晰、稳定的传输到地面，该无线视频传输与显示装置具有稳定、可靠的特点。

【期刊名称】《制造业自动化》【年(卷),期】2014(000)016【总页数】5页(P145-149)【关键词】视频监控;2.4GHz频率;FM调制;RTC6701;TVP5150【作者】崔业梅;丁帮俊;杨焕峥;吴建军【作者单位】无锡商业职业技术学院物联网技术学院，无锡214153;无锡商业职业技术学院物联网技术学院，无锡214153; 江苏省无线传感系统应用工程技术开发中心，无锡214153;无锡商业职业技术学院物联网技术学院，无锡214153; 江苏省无线传感系统应用工程技术开发中心，无锡214153;无锡商业职业技术学院物联网技术学院，无锡214153; 江苏省无线传感系统应用工程技术开发中心，无锡214153【正文语种】中文【中图分类】TP391.410 引言市场上的无线视频传输与显示装置一般是来源于移动型网络（Wi-Fi/3G/4G）的远程监控系统，功能很强大，采集视频信号并即时上传到服务器，但需要依靠现有网络的支持，需要服务器等设备，系统有一定的依赖性和复杂性[1]，在有些没有常规网络覆盖的地区，在一些矿井、矿道内部进行无线视频传输并不适用，没有传输信号。