ITU-R+BT+656视频标准
BT656标准
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。
基于FPGA的ITU-656标准视频解码及存储系统设计
基于FPGA的ITU-656标准视频解码及存储系统设计王水鱼;李艳婷【摘要】本文主要从视频图像采集系统出发,针对基于FPGA视频采集系统中需要实时显示和高效存储视频数据的问题,设计了视频解码和SDRAM存储模块.在整个系统中使用CCD摄像头将采集到的模拟信号经解码芯片ADV7181B解码后,转换为数字信号,并使用乒乓存储方法存储在SDRAM中,以方便提供给后期其他操作.在分析了视频解码及SDRAM的基本原理和主要参数的基础上,利用Verilog语言实现了将有效视频数据分离出来并串行输出,同时也将图像分辨率调整为符合VGA显示的像素大小.另一方面通过乒乓缓存也保证了实时性、高速度的数据存储.最后,经过Modelsim仿真验证,证明了本设计的有效性.【期刊名称】《微型机与应用》【年(卷),期】2016(035)007【总页数】4页(P25-27,29)【关键词】视频解码;ITU-656;SDRAM;乒乓缓存【作者】王水鱼;李艳婷【作者单位】西安理工大学自动化与信息工程学院,陕西西安710048;西安理工大学自动化与信息工程学院,陕西西安710048【正文语种】中文【中图分类】TP274.2视频图像采集系统应用非常广泛，随着计算机通信技术的不断发展，FPGA以其高性能、低开发成本等优点广泛应用于视频和图像处理领域[1]，因此,更加深入地研究基于FPGA的实时图像采集系统, 对于视频监控系统、高性能的图像处理等都具有极其重要的作用。
本文主要研究的内容是基于FPGA的视频采集及显示系统中的视频解码和视频数据存储的问题，对于提取有效视频数据流和高效实时存储大量数据具有显著性的意义。
图1为视频图像采集的系统框图，主要由I2C配置模块、ITU-656视频解码模块、SDRAM控制器模块、视频格式转化模块和VGA控制器模块组成[2]。
为了使视频数据能实时、高速的显示，视频解码模块和SDRAM控制模块就显得尤为重要。
bt656标准
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。
BT656数据结构
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。
ITU-R BT.601 656
– NTSC制
• 720×480
– 640x480 – 320x240（320x262），LCD实验 – 352x288，CMOS Sensor实验
ITU-R BT.601 数字化
• 数据量
– 4:2:2的格式采样，10Bit量化
• 13.5×10+6.75×10+6.75×10=270Mbps
• 色差信号抽样频率
– 6.75MHz（4:2:2） – 3.375MHz（4:1:1和4:2:0）
ITU-R BT.601 数字化
• 每行采样样本N
– PAL
• 13.5MHz/(625x25)=864
– NTSC
• 13.5MHz/(525x29.97)=858
• 每一扫描行的有效样本数
– 720 – ITU-R BT.601规定采样时间是53.3333us
ITU-R BT.656
• 525/60 （NTSC）和625/50 （PAL）系统 的帧划分方法和数据流的特性
– 《Blackfin双核处理器与应用开发》图6-8、图 6-9、表6-9。 – 参考陈喆翻译的《嵌入式媒体处理》 P.134~.97FPS（精确来说是 60FPS（场速率）/1.001）？
– 是避免4.5MHz处的干扰而提出的 – NTSC经过调查研究后，于1954年决定从30FPS更改 为29.97FPS – 因为干扰跳动频率出现在颜色副载波（3.5795MHz） 和声音载波（4.5MHz）之间，以及颜色副载波和视频 亮度信号的高频之间 – 选择水平频率fH=15734.25Hz（其286次谐波频率为 4.5MHz，其227.5倍频率为3.5795MHz），可将干扰 最小化 – 垂直频率从而变成了fH/525=29.97Hz
ITU-RBT.656-5建议书使用ITU-RBT.601建议书422比例工
第1部分 接口的数字信号格式
1
接口总体说明
此接口在单一源与单一目的地间提供了一种单向互连。（注-使用信号路由器后则可为 多个目的地。）
第2节描述了该接口的数字信号格式。
数据信号使用 8或10比特编码字的二进制信息（见注1）。这些信号为：
5
表2 视频计时基准码
数据比特编号
9 (MSB) 8 7 6 5 4 3 2
1（注 2） 0
第一个字 (3FF) 1 1 1 1 1 1 1 1 1
1
第二个字 (000) 0 0 0 0 0 0 0 0 0
0
第三个字 (000) 0 0 0 0 0 0 0 0 0
0
注 1 – 显示的值为推荐10比特接口使用的值。 注 2 – 为与现有的8比特接口相匹配，比特D1和D0的值没有定义。
2.2 视频数据格式 八个最重要比特全设为1或全设为0的数据字被保留用于数据辨别，因此可用的256个
8比特字中仅有254个，或可用的1 024个10比特字中的1 016个可用于表述信号值。 视频数据字按下述顺序表示为27 Mword/s的复用：
CB, Y, CR, Y, CB, Y, CR, 等
其中字序CB, Y, CR是指共站亮度和色差抽样，而紧接着的Y字对应下一亮度抽样。
国际电联无线电通信全会，
考虑到
a) 电视广播公司和节目制作商在数字演播室标准中的明显优势，数字演播室标准拥有 525行和625行系统通用的最大数目的有效参数值；
b) 全世界兼容的数字方法将允许开发具备许多共同特点的设备，允许运行的经济性， 并促进节目的国际交流；
ITR-U BT.656视频标准中文说明
国际电信联盟无线电通信部门656-3号建议书：工作在ITU-R BT.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。
建议凡在电视演播室里需要分量编码数字视频信号接口的地方，这些接口和通过它们的数据流应符合规定比特并行和比特串行实施的如下说明：1引言本建议描述了运行在525行或625行制式并符合ITU-RBT．601建议(部分A)中所规定的4：2：2编码参数的数字电视设备的互连方法。
第一部分描述两种接口通用的信号格式。
第二部分描述比特并行接口的专有特性。
第三部分描述比特串行接口的专有特性。
补充资料在附件l中。
第一部分：接口的通用信号格式1，接口的一殷描述接口为在单一信号源与单一终点之间提供单向互连。
并行和串行接口通用的单一信号格式在第2节中描述。
数据信号采取编码成8比特字(也可任选10比特字’)的二进制信息的形式。
这些信号是：1：视频信号，2：定时基准信号，3：辅助信号。
2，视频数据表1场间隔定义注1：信号F和V在数字行的开始时与有效视频定时基准码同步改变状态。
注2：行数的定义见ITU-RBT．470建议。
关于ITU BT 601与ITU BT656的一点基础知识
使用BT.656并行接口传输4路CIF格式视频的数据结构。
视频处理器的输出是灵活多变的，可以改变处理器的输出数据结构来同时传送4路252×288像素的视频信号。BT.656并行接口传输的有效视频数据流为720×586，正好可以分割为4个360×288像素的空间来传输4路352×288像素的视频数据。多余的空间用固定数据“8010”进行填充。
CCIR601号建议的制定，是向着数字电视广播系统参数统一化、标准化迈出 的第一步。在该建议中，规定了625和525行系统电视中心演播室数字编码的基 本参数值。601号建议单独规定了电视演播室的编码标准。它对彩色电视信号的编 码方式、取样频率、取样结构都作了明确的规定。规定彩色电视信号采用分量编码。所谓分量编码就是彩色全电视信号在转换成数字形式之前，先被分离成亮度信号和色差信号，然后对它们分别 进行编码。分量信号（Y、B -- Y、R -- Y）被分别编码后，再合成数字信号。
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。
它规定了编码方式。对亮度信号和两个色差信同时，规定在数字编码时，不使用A/D转换的整个动态范围，只给亮度信号分配220个量化级，黑电平对应于量化级16，白电平对应于量化级235。为每个色差信号分配224个量化级，色差信号的零电平对应于量化级128。
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)。
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BROADCASTING DIVISION Application NoteThe digital Video Standardaccording toITU-R BT. 601/656Products:CCVS+COMPONENT GENERATOR SAFCCVS GENERATOR SFFDIGITAL VIDEO COMPONENT ANALYSER VCA7BM19_0E2Leveldiagram at the input of an A/D converter for theanalogue component signals Y , C B , CRE YE CB E CR255/1023 (FF.C h)0/0 (00.0 h)235/940 (EB.0 h)16/64 (10.0 h)1-0.50/0 (00.0 h)3Example for digital synchronizing signalsin the parallel interface (10 bit )black points indicate the value 1 , white points 0XY within EAV is DA.0 ( 11011010 00)XY within SAV is C7.0 ( 1100011100 ) this significatesthis line an active one in an even field4Data format and timing relationship with theanalogue video signal1716 T (525)5structure of digital synchronizing signalscode word bit number9876543210 first word ( FF.C) second word ( 00.0) third word ( 00.0) fourth word( XY.0)1111111111000000000000000000001F V HP3P2P1P00F = 0 first field F = 1 second field V = 0 or 1 ( in VBI )H = 0 in SAV H = 1in EAVP0, P1, P2, P3 see table of control bits6Table of values for V, F in VBIThe values of V and F change within the transmission of the EAV signal at the start of each digital line.The line numbers count according to ITU-R BT. 470; the number of the digital line changes at the reference point 0H .7Table of controlbitsconst. F V H P3 P2 P1 P0 const. const. XY.0level dec. 1 0 0 0 0 0 0 0 0 0 80.0 128.0active SAV 1 0 0 1 1 1 0 1 0 0 9D.0 151.01st fieldpicture EAV 1 0 1 0 1 0 1 1 0 0 AB.0 171.0VBI SAV 1 0 1 1 0 1 1 0 0 0 B6.0 182.0EAV 1 1 0 0 0 1 1 1 0 0 C7.0 199.0active SAV 1 1 0 1 1 0 1 0 0 0 DA.0 218.02nd fieldpicture EAV 1 1 1 0 1 1 0 0 0 0 EC.0 236.0VBISAV 1 1 1 1 0 0 0 1 0 0 F1. 0 241.0EAV8Signal Timing and Levels(parallel interface)dataclockt dtTECL level timing reference for data and clock Clock-to-data Timing (at source)-0.8 V-1.6 V-0.8 V-1.6 V>>><<<clock period (625):T = 1/ (1728 x f H ) = 37.037 ns clock period (525):T = 1/ (1716 x f H ) = 37.037 ns clock pulse width:t = 18.52 ± 3 ns data timing - sending end: t d = 18.5 ± 3 nsf H = line frequencyvariation of data timing - sending end in SAF and SFF :18.5 ± 10 ns9Connector contact assignmentsThe connector's contacts, numbered in the standard manner depicted below must be assigned in accordance with the following tableContactAssignment ContactAssignment 1clock14clock return 2system ground 15system ground 3data 9 (MSB)16data 9 return 4data 817data 8 return 5data 718data 7 return 6data 619data 6 return 7data 520data 5 return 8data 421data 4 return 9data 322data 3 return 10data 223data 2 return 11data 124data 1 return 12data 025data 0 return13chassis ground1 2 3 4 5 6 7 8 9 1 0 11 12 1314 15 16 17 18 19 20 21 22 23 24 25Connector containing male pins (plug)10Serial System ParametersITEM 4 : 2 : 2 (D1) 4 x f SC PAL (D2) 4 x f SC NTSC (D2)total bit rate Mb / s 270.0177.3143.2resolution10 (8) bit / wordchannel coding scrambled NRZI by G(x) = ( x 9 + x 4 + 1) ( x + 1)serial sync word 3FF, 000, 000 hex (10 bit)order oftransmission LSB firstnominal signal level800 mV ± 10% (terminated)code limitation000 through 003 and 3FC through 3FFshall not appear in any data words11serial 270 Mbit / sec Diagram of transmitter and receiver linep a r a l l e l /s e ri a l D a t a In pu tS c a m bl e r N R Z /NR Z I E C L Ou tpu t75 O h m 75 O h m c a b l e equali se r S i g n a l -pro ces s o rN R Z I /N RZDes c r a m bler O u t p u tBu ffers e r i a l /para lle l12serial 270 Mbit / sec222111x 9 + x 4 + 1Outputx + 1Output x + 1Output(complementary)18 bit18 bit 19 bit 19 bit 19 bit 19 bitSignal for Testing the Cable EqualiserPathological Signals for 10 bit Serial Interface13serial 270 Mbit /sec 111x 9 + x 4 + 1Output x + 1Output x + 1Output(complementary)20 bit Signal for Testing the PLL in the Receiver19 bit 19 bit 20 bit20 bit 20 bitPathological Signals for 10 bit Serial Interface14SAF / SFF Signalgroup ITU-R BT. 601 (Option)Signaloverviewaccording to ITU-R BT. 8011519PATHOL.SIGNAL Y=198h C=300h 39RAMP CR20 PATHOL.SIGNAL Y=110h C=200h16Pathological Signals1. Pathological Signals for Cable Equalizers in the Serial Digital InterfacePossible word combinations to generate a stress pattern for cable equalization . HexValidityNo. chroma luminance 4 : 2 : 2 D11st sample 2nd sample 10 bit 8 bit1 200 h 331 h yes no2300 h 198 h yes yes3180 h 0CC h yes yes40C0 h 066 h yes no5060 h 033 h yes no6230 h 019 h yes no7318 h 0CC h yes yes818C h 006 h yes no2. Pathological Signals for Genlock of PLL in the Serial Digital Interface Possible word combinations to generate a stress pattern for genlock of PLL. Hex ValidityNo. chroma luminance 4 : 2 : 2 D11st sample 2nd sample 10 bit 8 bit1 200 h 110 h yes yes2100 h 088 h yes yes3080 h 044 h yes yes4040 h 022 h yes no5020 h 011 h yes no6210 h 008 h yes yes7108 h 004 h yes yes17SDI Check Pattern (serial digital interface)<>H activeperiod 300, 198 (values in hex) C, Y(for cable equalizer)200, 110 (values in hex) C, Y(for PLL)18frequency jitter0maxQuartz PLL LC PLL 1 KHz 200 KHz 10 KHz 2 MHz up to 270 MHzPLL follows the datajitter, no errors occurwithin a jitter range of some clock periods ( UI * )PLL follows only partwise the datajitter, a rest-jitter remains,errors occur while reclocking the datathis frequency range isoutside the PLL lockingbandwidth and thereforeis this jitter not trans-ferred to the regeneratedclock>Jitter of a Serial Digital Interface Signalfrequency jitter0max Quartz PLL LC PLL 1 KHz 200 KHz 10 KHz 2 MHz up to 270 MHz>^< 0.5 UI** UI = Unit Interval (clock period), at 270 Mbit/s 1UI = 3.7 ns19Technical Data for Option S.F - Z1Standard ITU-R BT. 601 / 656 (4:2:2)SMPTE 125M / 259 MSystems 625 lines/50 Hz and 525 lines/60 Hz Signals according to ITU-R BT. 801pathological signals for SDIall SAF/SFF signalsParallel output 27 Msamples/seclevel ECL levelrise/fall time (20/80%)< 5 nsclockpulse width 18.5 ns ± 3nsdelay clock/data 18.5 ns ± 3 nsclock/data shifting ± 10 nsconnector 25 pin SUB D (ISO 2110 - 1980)Serial output 270 Mbit / sec acc. D1 formatlevel VPP = 800 mV ± 10% @ 75 Ωrise/fall time (20/80%)0.75....1.5 ns output impedance 75Ωreturn loss ≥ 15 dB within 10... 270 MHzconnector BNC20The SAF/SFF option "CCIR 601" has advanced possibilities:l parallel and two serial outputswith 8 / 10 bit resolution and27 Msamples / sec and 270 Mbit / secl the 10 th bit has additional funktion in all threecomponents Y, Cb, Cr :- toggle bit for quantization noise measuring- settable to 0 or 1 for measuring thescaling factor mV / LSBl adjustable rise / fall times of signaltransitions allow precisemeasurement of luma / chroma delayl output and variation in amplitude, timing and phase ofall SAF / SFF testsignals( testpatterns, ZONE PLATES, linearities...)including the self generated onesl special ITU-R BT. 601 testsignals are- signals according to ITU-R BT. 801- all pathlogical signalsl no PC needed for changing the signals´- amplitude in Y, Cb, Cr independently fromeachother- timing with the PHASE/TIME menu or usingfeatures of SIGNAL EDITSo you are able to test DSP machines ( trick mixers,frame stores ...) also at the limits of the system.ITU-R BT. 60121l the amplitude limits are- max. 254 dec / FE hex for 8 bit1019 dec / 3FB hex for 10 bit- min. 1 dec / 01 hex for 8 bit4 dec / 04 hex for 10 bitl editing the H frequency allows changing the numberof auxilliary data between EAV and SAV to check the sychronizing digital equipment.l the onscreen comparision of the digital signal andthe composite or component signal showsimmediately defects and differences of the DSPl the vertical blanking interval ( VBI ) is not influencedby the coding according to ITU-R BT. 601; the inserted VITS are part of the digital data. This is most useful fortesting the influence of DSP in digital machines in the VBI.。