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HDMI (High-Definition Multimedia Interface) is a compact audio/video interface for transferring uncompressed video data and compressed or uncompressed digital audio data from a HDMI-compliant source device to a compatible computer monitor, video projector, digital television, or digital audio device.[1] HDMI is a digital replacement for existing analog video standards.

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  2. 2. What is HDMI • HDMI – High-Definition Multimedia Interface* – Allows for transmission of digital audiovisual content on the same physical link (DVD player, TV’s, set top boxes etc…) – Digital interface defined around DVI1.0 specification and backwards compatible with DVI – Command and control data (DDC) • Content Protection via HDCP (High Definition Content Protection) • Administered by HDMI * LLC (Limited Liability Corporation) – Licensing and Royalty fees apply • Transfer rate depends on display mode. – Spec range 25MHz to 340MHz (dense spectrum of frequencies) – Max speed is a product decision. IBX, CPT max: 222.5MHz
  3. 3. HDMI Overview EDID ROM HDMI Sink (Rx) HDMI Transmitter Video Audio Control/Status TMDS Channel 0 HDMI Receiver TMDS Channel 1 Display Data Channel (DDC) HDMI Source (Tx) Video Audio Control/Status TMDS Clock Channel TMDS Channel 2 HDMI Cable CEC HPD Main Link: 250Mbps to 3.4Gbps per channel, 25-340MHz sideband clock RGB or YCbCr 444 or 422, TMDS and TERC4 encoding 3.3V Rx termination, ~500mV swing based on DVI 1.0 Spec accounts for AC coupling tolerance on Sink (not Source) DDC: 100 KHz, I2C format, 3.3 - 5V HPD: Hot Plug Detect, 2 - 5V CEC: Optional 400 Hz bus, 2.5 – 3.3V (We do not support CEC)
  4. 4. HDMI Overview DDC Display Data Channel (HDMI) transmitter A device with an HDMI output. (HDMI) receiver A device with an HDMI input. TMDS clock is used by the receiver as a frequency reference for data recovery on the three TMDS data 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
  5. 5. HDMI Overview – HDMI carries a VESA DDC channel. The DDC is used for configuration and status exchange between a single transmitter and a single receiver. » The DDC is used by the transmitter to read the receiver’s Enhanced Extended Display Identification Data (E-EDID) in order to discover the receiver’s configuration and capabilities. – The optional CEC protocol provides high-level control functions between all of the various audiovisual products in a user’s environment.
  6. 6. HDMI Overview • 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
  7. 7. HDMI Overview
  8. 8. 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.
  9. 9. 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.
  10. 10. HDMI Frame Composition •Example frame: 1280x1024 resolution •Vertical and horizontal blanking filled by control sequences – Color depth control information – TERC4 encoding used – HDMI specific controls •Pixel periods filled with TMDS-encoded active pixel data •Quick pixel clock Calculation: •HT*VT*Refresh Rate •1440*1054*60=91.0656MHz
  11. 11. EDID Extended display identification data • HDMI transmitter shall read the EDID and first CEA Extension to determine the capabilities supported by the receiver. • HDMI transmitter shall check the E-EDID for the presence of an HDMI Vendor Specific Data Block within the first CEA Extension to determine whether it is an HDMI/DVI device. • All the receiver supports 640 * 480P video format by default.
  12. 12. Hot-Plug detect • An HDMI receiver shall assert high voltage level on its Hot Plug Detect pin when the E- EDID is available for reading. • HDMI receiver shall indicate any change to the contents of the E-EDID by driving a low voltage level pulse on the Hot Plug Detect pin.
  13. 13. HDMI Usage History: HDMI is based on DVI • HDMI is REQUIRED BY SPEC to interoperate with DVI – Simple cable adapter is all that is allowed • DVI = Digital Visual Interface; used on PC’s (and some TV’s) • Almost identical electrical spec, same coding and clocking • HDMI connector is smaller than DVI, but same digital signals • HDMI adds audio packets, “info frames”, compliance testing Interface to Consumer Electronics displays (TV) • Set-top box to TV • DVD player to TV • Input to DVD burner (Content protection application) Interoperate with DVI • HDMI on DVD player to DVI on PC display • DVI on PC to HDMI display OR External Cable LCD Monitor DVI HDMI HDCP CE TV
  14. 14. Red 1TMDS Red TMDS CLK Green 1TMDS Green Blue 1TMDS Blue Red 2 Green 2 Blue 2 Red 3 Green 3 Blue 3 Red 4 Green 4 Blue 4 10-bit TMDS Code 10-bit TMDS Code 10-bit TMDS Code 10-bit TMDS Code Red 5 Green 5 Blue 5 10-bit TMDS Code TMDS Code and Clock HPD •HDMI main link is called the “TMDS Channel” – Three “TMDS” differential data lanes • Red, Green, Blue each have a lane • 10 bit “TMDS” coded data – TMDS is only used on HDMI and DVI – TMDS Clock lane • Clock is 1/10 bit rate – We send TMDS clock as a data pattern: 0000011111
  15. 15. HDMI TMDS Clock to Pixel Relationship TMDS Clock is 1/10 bit transfer rate 8 Bit Per Component Example: • 8 bits per color = 24 bits per pixel • Each 8 bit color value is coded as a 10-bit TMDS code, mapped to one Tx lane • TMDS clock runs at 1/10 the serialized bit rate, so … • 1 TMDS clock = 1 pixel For 1600x1200@24bpp, 60Hz refresh, pixel clock ~162MHz TMDS Clock = 162MHz; Bit rate per lane = 1.62GT/s Red 1TMDS Red TMDS CLK Green 1TMDS Green Blue 1TMDS Blue Red 2 Green 2 Blue 2 Red 3 Green 3 Blue 3 Red 4 Green 4 Blue 4 10-bit TMDS Code 10-bit TMDS Code 10-bit TMDS Code 10-bit TMDS Code Red 5 Green 5 Blue 5 10-bit TMDS Code Pixel 1 Pixel 2 Pixel 3 Pixel 4 Pixel 5
  16. 16. HDMI/DVI Main Link Topology – DC coupled to Rx 3.3V termination • Process scaling issues • Back-power issues for Tx – Signal amplitude is the same for all modes / speeds / channels • No power or EMI savings for short cables • Signal integrity suffers at higher speed HDMI or DVI “Spec” Tx HDMI TV Or DVI MONITOR AVcc = 3.3V RT = 50ohmsRT MOTHER BOARD HDMI SOURCE SINK HDMISource CONNECTOR ~11” Trace HDMISink CONNECTOR 2m – 15m Cable (TYP)HDMI CABLE TMDS Data or Clock Lane: Electrical Spec and Compliance Testing at Connectors
  17. 17. HDMI* Connector Design HDMI Type A 14 mm(W) x 5 mm(H) 37 mm(W) x 10 mm(H) DVI1.0 Connector HDMI Type C 10.5 mm(W) x 2.5 mm(H) • HDMI main link, HPD and DDC signals match single channel DVI • HDMI type A and C connectors have the same signals • Type C targets small form factors • HDMI type B connectors are not in use