Samsung LNT4669F Training Manual page 144

What is HDMI? Attachment
HDMI system architecture is defined to consist of Sources and Sinks. A
given device may have one or more HDMI inputs and one or more HDMI
outputs. Each HDMI input on these devices shall follow all of the rules for
an HDMI Sink and each HDMI output shall follow all of the rules for an
HDMI Source.
As shown HDMI block diagram the HDMI cable and connectors carry four
differential pairs that make up the TMDS data and clock channels. These
channels are used to carry video, audio and auxiliary data. In addition,
HDMI carries a VESA DDC channel. The DDC is used for configuration and
status exchange between a single Source and a single Sink. The optional
CEC protocol provides high-level control functions between all of the
various audiovisual products in a user's environment.
Audio, video and auxiliary data is transmitted across the three TMDS data
channels. The video pixel clock is transmitted on the TMDS clock channel
and is used by the receiver as a frequency reference for data recovery on
the three TMDS data channels. Video data is carried as a series of 24-bit
pixels on the three TMDS data channels. TMDS encoding converts the 8
bits per channel into the 10 bit DC-balanced, transition minimized
sequence which is then transmitted serially across the pair at a rate of 10
bits per pixel clock period.