An Overview of Current Display Interfaces

HDMI

After the DDWG failed to agree on a specification for a consumer version of the

DVI specification, Silicon Image formed a new consortium to develop a digital

interface specifically for the consumer TV market, this time with six leading CE

companies. The result was the High Definition Multimedia Interface, or HDMI.

HDMI is essentially a single link of the TMDS electrical interface (as used in the DVI

standard), plus a standard (and Silicon Image proprietary) method of carrying

digital audio signals within the video data stream. Like DVI, HDMI also supports the

Intel High Definition Content Protection (HDCP) copy-protection scheme. As in DVI,

HDCP support is technically optional, but basically required for products in the CE

market and HDMI implementations. HDMI is semi-compatible with single-link DVI,

as DVI cannot provide the embedded audio features of HDMI and does not support

HDMI’s Consumer Electronics Control (CEC) channel, a one-line serial data bus for

the control of CE products (such as DVD players, etc.) from the TV or other output

device.

As was the case with DVI, HDMI (up to the 1.2 specification revision) provides

support for up to 165 MHz pixel rates, or about 4.8 Gbit/sec. raw data capacity.

The HDMI 1.3 spec approximately doubled this capacity and also introduced a

more compact version of the connector, for portable CE products, the HDMI-C. The

most recent version, HDMI 1.4, provided some additional capacity increase and

improved support for certain audio and video formats, including stereo (“3D”)

video.

Figure 3. HDMI Connector

Table 3. HDMI Connector Pinout

Signal

TMDS Data 2+

TMDS Data 0 shield

DDC Clock (SCI)

TMDS Data 2 shield

TMDS Data 0-

DDC Data (SDA)

TMDS Data 2-

TMDS Clock+

DDC/CEC ground

TMDS Data 1+

TMDS Clock shield

+5 VDC

TMDS Data 1 shield

TMDS Clock 1-

Hot Plug Detect (HPD)

TMDS Data 1-

CEC

TMDS Data 0+

Reserved (no connect)