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HDMI


贡献者:sylar    浏览:7822次    创建时间:2009-06-08

HDMI简介Top

  HDMI,英文全称是High Definition Multimedia Interface,中文名称是高清晰多媒体接口的缩写。2002年4月,日立、松下、飞利浦、索尼、汤姆逊、东芝和Silicon Image七家公司联合组成HDMI组织。HDMI能高品质地传输未经压缩的高清视频和多声道音频数据,最高数据传输速度为5Gbps。同时无需在信号传送前进行数/模或者模/数转换,可以保证最高质量的影音信号传送。
  HDMI不仅可以满足目前最高画质1080P的分辨率,还能支持DVD Audio等最先进的数字音频格式,支持八声道96kHz或立体声192kHz数码音频传送,而且只用一条HDMI线连接,免除数字音频接线。同时HDMI标准所具备的额外空间可以应用在日后升级的音视频格式中。足以应付一个1080p的视频和一个8声道的音频信号。而因为一个1080p的视频和一个8声道的音频信号需求少于4GB/s,因此HDMI还有很大余量。这允许它可以用一个电缆分别连接DVD播放器,接收器和PRR。此外HDMI支持EDID、DDC2B,因此具有HDMI的设备具有“即插即用”的特点,信号源和显示设备之间会自动进行“协商”,自动选择最合适的视频/音频格式。
  HDMI 和 DVI 接口与DVI相比HDMI接口的体积更小,而且可同时传输音频及视频信号。DVI的线缆长度不能超过8米,否则将影响画面质量,而HDMI最远可传输15米。只要一条HDMI缆线,就可以取代最多13条模拟传输线,能有效解决家庭娱乐系统背后连线杂乱纠结的问题。
  优点:
  HDMI规格的接口在保持高品质的情况下能够以数码的形式传输未经压缩的高分辨率视频和多声道音频的数据。 其卓越性能超越了以往所有的产品。
  HDMI规格的连接器采用单线连接,取代了产品背后的复杂的线缆。
  采用HDMI规格接口的线缆没有长度的限制。比如:DVI的线缆长度不能超过8米,否则将影响画面质量,而符合HDMI规格的产品则没有这个问题。
  HDMI规格可搭配宽带数字内容保护(HDCP),以防止具有著作权的影音内容遭到未经授权的复制。
What is HDMI?Top
  ????Digital interface defined around DVI 1.0 that transmits video and audio on the same physical channel.
  ????Interface defined for use in the consumer market space.
  ????Requires separate licensing from that of DDWG’s DVI.
  ????Allows DVI/HDMI products to be sold in consumer products
  ????Supports the use of HDCP copy protection.
  ????Utilizes VESA’s Display Data Channel to read E-EDID from a display.
  ????Defines a different connector from that used on DVI.
  ????Supports optional CEC (Consumer Electronics Control), which allows high level control of all A/V products in a user environment.
  DVI 1.0: The Physical Interface
  ????Digital Visual Interface (DVI) was developed by a group called the Digital Display Working Group or DDWG for the PC market.
  ????The interface is a high speed digital serial interface based on Transition Minimized Differential Signaling or TMDS.
  ????Source synchronous architecture. Uses a separate channel to transmit the clock.
  ????Used to provide variable data rates to handle the various VESA supported display resolutions.
  ????A complete connection from the source to the sink devices uses three data channels (RGB/YCbCr) and a clock.
  HDMI = DVI + Audio
  ????Using the DVI physical link to transmit video/graphics
  ????Audio is added as a logical layer to the DVI phy.
  ????Digital audio processed into packets of data
  ????These packets are scheduled for transmission during existing horizontal and vertical blanking times within a frame.
  ????In addition, HDMI implements a packet called an infoFrame.
  ????InfoFramesare structures defined in the EIA-861B specification
  ????EIA-861B is spec for DTV and uncompressed high speed digital interfaces.
  What is HDMI Data?
  ????There are three categories of data that is transmitted via an HDMI link.
  ????Video Data –Video pixel data (8b data encoded to 10b), and Guard Bands (fixed 10b pattern)
  ????Data Island –Packet data, which can be either audio samples or Infoframes(TERC4 encoded, 4b encoded to 10b) as well as its own Guard Band (fixed 10b pattern).
  ????Control –Control period coding, in which we find HSYNC, VSYNC (2b to 10b encoding) and a Preamble (used to determine whether subsequent data is video or data island)
  Transmission of Video/Graphics
  ????HDMI transmits 24bit pixel data via three separate channels.
  ????Pixel rates supported are 25MHz to 165MHz.
  ????This is exactly the same as single link DVI 1.0
  ????Also supports video rates below 25MHz e.g. 13.5MHz for 480i NTSC signals.
  ????Achieves this through a “pixel-repetition”scheme.
  ????Can handle pixel data in RGB, YCbCr(4-4-4), YCbCr(4-2-2) formats.
  ????In all cases 24 bits of data per pixel clock are transmitted.
  Transmission of Audio
  ????Basic Audio is provided via an IEC60958 audio stream at 33kHz, 44.1kHz, or 48kHz.
  ????Accommodates any normal stereo audio stream.
  ????Optionally this stream can be sent as a single channel at 192kHz.
  ????Can support IEC61937 compressed formats as found in surround-sound, Dolby Digital, etc. at rates up to 192kHz.
  Infoframes and HDMI
  ????EIA/CEA-861B specifies a special packet called an infoframe
  ????HDMI sources and sinks are expected to use two basic infoframes.
  ????AVI (Auxiliary Video Information) Infoframe
  ????Communicates Colorimetry, Picture aspect ratio, Pixel-Repetition factor, RGB or YCbCrindicator, and others specified within 861B standard.
  ????Audio Infoframe
  ????Communicates, Channel count, Coding Type, Sample size, Sample frequency, Channel allocation and other audio specific information.
  ????There are other types of infoframes that are supported by the 861B standard, but are optional with respect to HDMI specification.
HDMI测试规范Top
  HDMI测试规范的规范细节请参考:《HDMI一致性测试规范1.1》,《HDMI规范1.1》,《HDCP规范1.1》;
  一.HDMI输出兼容性测试:
  1. 和HDMI接口电视的兼容性:同时传输音频和视频;
  2. 和DVI接口电视的兼容性:只传输视频;
  3. 和HDMI接口的功放的兼容性:只传输音频;
  判断标准:HDMI接口可以传输的音频支持“任何能通过S/PDIF输出的压缩数字音频”和“2/6/8声道,32-192KHZ采样率的未压缩的数字音频”,可以输出“I2S(一种数字传输界面,时差性能要优于S/PDIF,适合短距离通讯)和SPDIF的音频”;它总能获得CD的音频质量;HDMI接口可以传输的视频支持“高清1080I”,“高清720P”,“普通隔行”和“普通逐行”(目前后两种我们没有支持),同时支持NTSC和PAL电视制式;可以根据接受端可以接受的视频状态自动输出“YUV”或“RGB”编码的视频格式;
  二.HDMI端口插拔可靠性测试:
  1.接口热插拔可靠性:在碟机和接受端都工作的状态下,插拔HDMI接口,两端的设备是否工作正常,HDMI输出的音视频功能是否正常;
  2.ESD 测试
  3.接口插拔寿命测试:多次插拔HDMI接口,测试HDMI接口寿命;判断标准:热插拔时接受端能正常输出HDMI的音视频信号,源端系统需仍正常工作;接口插拔寿命最少需要5000次以上;
  三.HDMI输出的可靠性测试:
  1.源输出端驱动能力测试;
  2.连接线的衰减特性测试;
  3.高频和大容量数据传输可靠性;
  判断标准:最长可以传输30米,保证声音图像正常;大容量DVD(多字幕,多通道)碟片播放画面的流畅性;
  4.开机,待机时,HDMI是否输出正常。
  四.HDMI连接线和接口的检测标准:
  请参考HDMI接口和连接线的供应商的检测标准;
  五.非正常工作状态下HDMI端口输出测试:
  1.高低温状态:
  2.高低压状态:
  3.长时间工作状态:
  判断标准:具体的温度,电压和工作时间的参数参考普通碟机;在这些状态下,需要HDMI接口的音视频功能正常工作;
  六.HDMI输出端口功能测试:
  1.HDMI端口支持1080I,720P的高清格式视频输出;
  2.HDMI端口支持各种压缩和非压缩的数字音频输出;
  3.自动侦测接受设备的屏幕比例;判断标准:在同样的片源下,HDMI高清输出图像效果应该比CVBS和普通色差“更清晰,无闪烁,细节的表现力上更强,色彩更逼真”(可以用高清晰的JPEG图片或DVD效果演示碟来演示);如果接受的电视设备可以解码由HDMI输出的数字音频信号,接受端应该有声音输出;HDMI输出端可以自动调整输出的宽高比来适应接受设备。


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开放分类
接口    数字介面    信号传输    

参考资料
1.The World Leader in High-Performance Signal Processing Solutions 2.http://www.zhaolong.net.cn 3.http://www.soeol.com/info/news/2008/5-12/2008512214631.html 4.http://www.soeol.com/info/news/2008/6-17/2008617145517.html 5.http://www.soeol.com/info/news/2008/6-17/2008617151701.html 6.http://www.soeol.com/info/news/2008/6-17/2008617153107.html 7.http://www.soeol.com/info/news/2008/5-12/2008512214942.html

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