30-05-2012, 10:54 AM
High-Definition Multimedia Interface
[attachment=23452]
HDMI communication channels
HDMI has three physically separate communication channels, which are the DDC, TMDS, and the optional CEC
The HDMI cable and connectors carry four differential pairs that make up the TMDS data and clock channels.
Audio, video and auxiliary data is transmitted across the three TMDS data channels.
A TMDS clock, typically running at the video pixel rate, is transmitted on the TMDS clock channel
HDMI connector
There are 3 Types of HDMI connector, Type A , B and C. All three connectors carry all required HDMI signals, including a TMDS link.
The Type B connector is slightly larger and carries a second TMDS link, which is necessary to support very high resolution displays using dual link.
The Type C connector carries the same signals as the Type A but is more compact and intended for mobile applications.
The HDMI connector provides a pin allowing the transmitter to supply +5.0 Volts to the cable and receiver.
All HDMI transmitters shall assert the +5V Power signal whenever the transmitter is using the DDC or TMDS signals
HDMI Link
The HDMI link operates in one of three modes:
Video Data Period - the active pixels of an active video line are transmitted
Data Island period - audio and auxiliary data are transmitted using a series of packets.
This auxiliary data includes InfoFrames and other data describing the active audio or video stream or describing the transmitter.
Control period- It is used when no video, audio, or auxiliary data needs to be transmitted. It is required between any two periods that are not control periods.
Video Data on HDMI
Video data can have a pixel size of 24, 30, 36 or 48 bits. Color depths greater than 24 bits are defined to be “Deep Color” modes.
Video at the default 24-bit color depth is
carried at a TMDS clock rate equal to the pixel clock rate.
Video Pixels Video Data Coding is such that the 8 bits converted to 10 bits by HDMI transmitter.
The video pixels can be encoded in either RGB, YCBCR 4:4:4 or YCBCR 4:2:2 formats.
Deep Color modes are optional though if an HDMI transmitter or receiver supports any Deep Color mode*, it shall support 36-bit mode.
AVI Infoframe
An InfoFrame packet carries one InfoFrame. The InfoFrame provided by HDMI is limited to 30 bytes plus a checksum byte.
HDMI transmitter shall always transmit an AVI InfoFrame at least once per two video fields if the transmitter supports.
The AVI InfoFrame shall be transmitted even while such a transmitter is transmitting RGB and non pixel-repeated video.
For AVI infoframe format refer : Section 8.2 in HDMI 1.3 specification
[attachment=23452]
HDMI communication channels
HDMI has three physically separate communication channels, which are the DDC, TMDS, and the optional CEC
The HDMI cable and connectors carry four differential pairs that make up the TMDS data and clock channels.
Audio, video and auxiliary data is transmitted across the three TMDS data channels.
A TMDS clock, typically running at the video pixel rate, is transmitted on the TMDS clock channel
HDMI connector
There are 3 Types of HDMI connector, Type A , B and C. All three connectors carry all required HDMI signals, including a TMDS link.
The Type B connector is slightly larger and carries a second TMDS link, which is necessary to support very high resolution displays using dual link.
The Type C connector carries the same signals as the Type A but is more compact and intended for mobile applications.
The HDMI connector provides a pin allowing the transmitter to supply +5.0 Volts to the cable and receiver.
All HDMI transmitters shall assert the +5V Power signal whenever the transmitter is using the DDC or TMDS signals
HDMI Link
The HDMI link operates in one of three modes:
Video Data Period - the active pixels of an active video line are transmitted
Data Island period - audio and auxiliary data are transmitted using a series of packets.
This auxiliary data includes InfoFrames and other data describing the active audio or video stream or describing the transmitter.
Control period- It is used when no video, audio, or auxiliary data needs to be transmitted. It is required between any two periods that are not control periods.
Video Data on HDMI
Video data can have a pixel size of 24, 30, 36 or 48 bits. Color depths greater than 24 bits are defined to be “Deep Color” modes.
Video at the default 24-bit color depth is
carried at a TMDS clock rate equal to the pixel clock rate.
Video Pixels Video Data Coding is such that the 8 bits converted to 10 bits by HDMI transmitter.
The video pixels can be encoded in either RGB, YCBCR 4:4:4 or YCBCR 4:2:2 formats.
Deep Color modes are optional though if an HDMI transmitter or receiver supports any Deep Color mode*, it shall support 36-bit mode.
AVI Infoframe
An InfoFrame packet carries one InfoFrame. The InfoFrame provided by HDMI is limited to 30 bytes plus a checksum byte.
HDMI transmitter shall always transmit an AVI InfoFrame at least once per two video fields if the transmitter supports.
The AVI InfoFrame shall be transmitted even while such a transmitter is transmitting RGB and non pixel-repeated video.
For AVI infoframe format refer : Section 8.2 in HDMI 1.3 specification