存档

2012年1月 的存档

HDMI之CEC

2012年1月10日
HDMI之CEC已关闭评论

The bus, known as the consumer electronics control (CEC) bus, is the basis for a new level of automatic control in HDMI-interfaced systems. With the recent release of a CEC compliance test specification and commercial CEC test equipment, consumer electronic companies are now poised to implement CEC in their products. In fact, new CECenabled products are expected to begin shipping in April 2006.

The basic technology of the CEC bus originated in Europe, on the SCART interface, where it’s been used with great success for many years. HDMI borrows and improves on the basic SCART technology, allowing AV products to discover and communicate with one another across a system. CEC makes possible global controls, which build on existing point-topoint E-DDC-based "plug & play" automation to minimize the number of IR remotes and key-presses required for basic operation of a system.

CEC assumes that all AV source products in a system are directly or indirectly connected to a “root” display. HDMI connections form an upside-down tree, with a display as the “root”, switches as “branches”, and various source products as “leaf” nodes. For example, CEC allows users to connect a mix of AV products, place a DVD into the player, press PLAY, and let CEC handle the rest.

CEC will automatically power-on the appropriate products, route the DVDplayer’s audio output through the AVR to attached speakers, and route the player’s motion picture to the Digital TV. Likewise, selecting a channel on the set-top-box will cause television audio to replace movie audio on the speakers and a TV picture to replace the motion picture on the Digital TV. Further, pressing the RECORD button on the recording device will cause the television program on the "root" to be automatically routed to and recorded on that device. In short, CEC enables automatic equipment discovery and simple "one touch" operation in HDMI-interfaced systems.

The CEC bus is a one-wire, “party line” that connects up to ten (10) AV devices through standard HDMI cabling. The CEC protocol includes automatic mechanisms for physical address (topology) discovery, (product type based) logical addressing, arbitration, retransmission, broadcasting, and routing control. Message opcodes support both device specific (e.g. set-top-box, DTV, and player) and general features (e.g. for power, signal routing, remote control pass-through, and on-screen display).

IT技术 ,

HDMI之EDID

2012年1月10日
HDMI之EDID已关闭评论

      EDID(Extended Display Identification DATA,即扩展显示识别数据), 最初是为PC显示器设置的优化显示格式而设计的规范,存储在显示器中专用的1Kb的EEROM存储器中(即EDID数据结构是128Bytes),数字电视HDMI接口,遵从并且扩展了此规范。

     同PC主机和显示器通过DDC数据线访问存储器中数据,以确定显示器的显示属性(如分辨率、纵横比等)信息一样,在数字电视上,也沿用HDMI接口的DDC数据线访问EDID存储器,以确定数字电视的相关显示属性,关键是128Byte是PC显示器的标准,已不能满足数字电视视频标准的要求,因此需要对数据结构进行扩展,由于EDID标准并没有相应的规范,按照EIA/CEA-861-B标准规范对EDID数据进行编程。(VESA已经有相关的规范出台, 新的标准也是配合了EIA/CEA-861-B标准规范而已, 且需付费才能获取)

HDMI接口在数字电视中的EDID数据结构,与PC显示器的最大区别是编程数据可以是128Byte的倍数,它不仅规定数字电视显示的格式,也规定数字视频信号和数字音频信号,基本的128Byte以外的数据都是附加数据,在基本数据的第127个字节定义EDID的附加数据块数量。在EDID数据编程中,根据数字电视的显示属性要求,有两个关键环节必须注意:

  第一,如果数字电视的显示是固定格式,则在首选Timing Mode字节中必须选择相应的定义;

  第二,数字电视的标准显示属性应在第一段详细Timing Mode字节中完成数据编程。
数字电视HDMI的EDID读取,因为有CEA的数据在附加数据块里,信号源必须满足E-DDC标准,才能读取EDID数据。

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HDMI之HPD

2012年1月10日
HDMI之HPD已关闭评论

    HPD(Hot Plug Detection),在HDMI的一对联接中,为热插拔的实现而设计的。简单地说,当发送端接入接受端时,接受端会回应HPD信号给发送端,进而发送端会启动DDC通道,而读取接受端EDID的信息,然后进行HDCP的交互,如果双方认证成功,则视频、音频正常工作,否则联接失败,不同系统会有不同的处理。

    例如,如果EDID信息不支持HDMI,则发送端只发送视频信息,而没有音频信息,这时候的HDMI就只相当于DVI了;如果HDCP认证不成功,有的系统会出现雪花屏幕和噪音,有的系统会由高分辨率(1080I、720P)降低为低分辨率(480I、480P)而输出,这样一来,HDTV就不再是HD 了,而变成了普通的SD。

    An Important element to proper interpretation of EDID is "Hot Plugging". The following presents a recommendation for achieving consistent results during a Hot Plugging event.

    DVI 1.0 define a HPD signal function that indicates to the host whether a  monitor is connected. HPD is designed to be powered by the DDC +5V coming from the host, and to be independaent of whether the monitor is powered or not. In this way, a host device can detect the monitor and read its characteristics from EDID without the monitor being powered. On a PC, this feature allows the system to load the correct display configuration without delaying the boot process.

    In short, in this context, HPD serves as an indication that the EDID is available to be read, however HPD may also have alternative uses. It does no imply any other state of readiness. The relevant definitions from the DVI 1.0 specification are:

    a. HPD – Signal is driven by monitor to enable the system to identify the presence of a monitor;

    b. The monitor is required to provide a voltage of greater than +2.4V on the HPD pin of the connector only when the EDID data structure is available to be read by the host.

    Implementation Notes: As an example for hot plug support, a simple monitor implementation of HPD support could be a pull up resistor to the EDID power supply. After HPD goes active, the host is only expected to read EDID and determine that a valid display mode is available and supported.

    Note — Whenever the EDID information in a device changes for any reason(e.g. if the EDID was updated, or is capable of dynamically changing its information content), the receiving device pulses HPD low for at least 100ms. This recommendation follows from the HDCP repeater implementation requirement that HDCP repeater pulse HPD low for at least 100ms to indicate the connection of new device or disconnection of an existing one.

    这里只是概要的谈谈,后续将会对其联系EDID和HDCP详述。

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HDMI引脚定义

2012年1月10日
HDMI引脚定义已关闭评论

   为了方便大家查阅资料,以及各位DIY玩家对HDMI接口作进一步改造特此将A型、B型、A型转DVI、B型转DVI接口的各个针脚定义归纳出来。

A型 HDMI 接口
 

 

针脚 信号类型定义
1 TMDS 数据2+
2 TMDS 数据2 屏蔽线
3 TMDS 数据2
4 TMDS 数据1+
5 TMDS 数据1 屏蔽线
6 TMDS 数据1–
7 TMDS 数据0+
8 TMDS 数据0 屏蔽线
9 TMDS 数据0–
10 TMDS 时钟信号+
11 TMDS 时钟信号 屏蔽线
12 TMDS 时钟信号–
13 CEC
14 保留针脚 (如探测设备是否正在运行)
15 SCL
16 SDA
17 DDC/CEC 接地
18 + 5V
19 热插拔监测

B型 HDMI 接口

针脚 Signal
1 TMDS 数据2+
2 TMDS 数据2 屏蔽线
3 TMDS 数据2-
4 TMDS 数据1+
5 TMDS 数据1 屏蔽线
6 TMDS 数据1-
7 TMDS 数据0+
8 TMDS 数据0 屏蔽线
9 TMDS 数据0-
10 TMDS 时钟信号+
11 TMDS 时钟信号 屏蔽线
12 TMDS 时钟信号-
13 TMDS 数据5+
14 TMDS 数据5 屏蔽线
15 TMDS 数据5-
16 TMDS 数据4+
17 TMDS 数据4 屏蔽线
18 TMDS 数据4-
19 TMDS 数据3+
20 TMDS 数据3 屏蔽线
21 TMDS 数据3-
22 CEC
23 保留针脚 (如探测设备是否正在运行)
24 保留针脚 (如探测设备是否正在运行)
25 SCL
26 SDA
27 DDC/CEC 接地
28 +5V
29 热插拔监测

A型 HDMI 接口转DVI-D接口

HDMI针脚 信号类型定义 Wire DVI-D针脚
1 TMDS 数据2+ A 2
2 TMDS 数据2 屏蔽线 B 3
3 TMDS 数据2- A 1
4 TMDS 数据1+ A 10
5 TMDS 数据1 屏蔽线 B 11
6 TMDS 数据1- A 9
7 TMDS 数据0+ A 18
8 TMDS 数据0 屏蔽线 B 19
9 TMDS 数据0- A 17
10 TMDS 时钟信号+ A 23
11 TMDS 时钟信号 屏蔽线 B 22
12 TMDS 时钟信号- A 24
13 CEC N.C. N.C.
14 保留针脚 N.C. N.C.
15 SCL C 6
16 DDC C 7
17 DDC/CEC 接地 D 15
18 +5V 5V 14
19 热插拔监测 C 16
20 不连接 4
21 不连接 5
22 不连接 12
23 不连接 13
24 不连接 20
25 不连接 21
26 不连接 8
HDMI针脚 信号类型定义 Wire DVI-D针脚
1 TMDS 数据2+ A 2
2 TMDS 数据2 屏蔽线 B 3
3 TMDS 数据2- A 1
4 TMDS 数据1+ A 10
5 TMDS 数据1 屏蔽线 B 11
6 TMDS 数据1- A 9
7 TMDS 数据0+ A 18
8 TMDS 数据0 屏蔽线 B 19
9 TMDS 数据0- A 17
10 TMDS 时钟信号+ A 23
11 TMDS 时钟信号 屏蔽线 B 22
12 TMDS 时钟信号- A 24
13 TMDS 数据5+ A 21
14 TMDS 数据5 屏蔽线 B 19
15 TMDS 数据5- A 20
16 TMDS 数据4+ A 5
17 TMDS 数据4 屏蔽线 B 3
18 TMDS 数据4- A 4
19 TMDS 数据3+ A 13
20 TMDS 数据3 屏蔽线 B 11
21 TMDS 数据3- A 12
22 CEC N.C. N.C.
23 保留针脚 N.C. N.C.
24 保留针脚 N.C. N.C.
25 SCL C 6
26 DDC C 7
27 DDC/CEC 接地 D 15
28 +5V 5V 14
29 热插拔监测 C 16
不连接 N.C. 8

B型 HDMI 接口转 DVI-D接口

HDMI针脚 信号类型定义 Wire DVI-D针脚
1 TMDS 数据2+ A 2
2 TMDS 数据2 屏蔽线 B 3
3 TMDS 数据2- A 1
4 TMDS 数据1+ A 10
5 TMDS 数据1 屏蔽线 B 11
6 TMDS 数据1- A 9
7 TMDS 数据0+ A 18
8 TMDS 数据0 屏蔽线 B 19
9 TMDS 数据0- A 17
10 TMDS 时钟信号+ A 23
11 TMDS 时钟信号 屏蔽线 B 22
12 TMDS 时钟信号- A 24
13 TMDS 数据5+ A 21
14 TMDS 数据5 屏蔽线 B 19
15 TMDS 数据5- A 20
16 TMDS 数据4+ A 5
17 TMDS 数据4 屏蔽线 B 3
18 TMDS 数据4- A 4
19 TMDS 数据3+ A 13
20 TMDS 数据3 屏蔽线 B 11
21 TMDS 数据3- A 12
22 CEC N.C. N.C.
23 保留针脚 N.C. N.C.
24 保留针脚 N.C. N.C.
25 SCL C 6
26 DDC C 7
27 DDC/CEC 接地 D 15
28 +5V 5V 14
29 热插拔监测 C 16
不连接 N.C. 8

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