Samsung LNT4669F Training Manual page 150

What is HDMI? Attachment
Operating Modes Overview
The HDMI link operates in one of three modes: Video Data Period, Data Island
period, and Control period. During the Video Data Period, the active pixels of
an active video line are transmitted. During the Data Island period, audio and
auxiliary data are transmitted using a series of packets. The Control period is
used when no video, audio, or auxiliary data needs to be transmitted.
A Control Period is required between any other two periods.
Video Data Periods use transition minimized coding to encode 8 bits per
channel, or 24 bits total per pixel.
Data Island Periods are encoded using a similar transition minimized coding,
TMDS Error Reduction Coding (TERC4), which transmits 4 bits per channel,
or 12 bits total per pixel clock period.
During Control Periods, 2 bits per channel, or 6 bits total are encoded per pixel
clock using a transition maximized encoding. These 6 bits are HSYNC, VSYNC,
CTL0, CTL1, CTL2 and CTL3. Near the end of every Control Period,
a Preamble, using the CTLx bits, indicates whether the next Data Period is
a Video Data Period or a Data Island Period.