1. 像素时钟频率
The HDMI specification defines the protocols, signals, electrical interfaces and mechanical requirements of the standard. An HDMI connection can either be single-link (type A/C) or dual-link (type B) and can have a video pixel rate of 25 MHz to 340 MHz (for a single-link connection) or 25 MHz to 680 MHz (for a dual-link connection).
2. 支持的video format, audio format。不支持subtitle：
To ensure baseline compatibility between different HDMI sources and displays (as well as backward compatibility with the electrically compatible DVI standard) all HDMI devices must support the sRGB color space at 8 bits per component.[49]
For digital audio, if an HDMI device supports audio, it is required to support the baseline format: stereo (uncompressed) PCM. Other formats are optional, with HDMI allowing up to 8 channels of uncompressed audio at sample sizes of 16-bit, 20-bit and 24-bit, with sample rates of 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz and 192 kHz.[52]
The HDMI standard was not designed to pass closed caption data (for example, subtitles) to the television for decoding. in that format.
3. HDMI 1.3 cable definition:
HDMI 1.3 defines two cable categories: Category 1-certified cables, which have been tested at 74.5 MHz (which would include resolutions such as 720p60 and 1080i60), and Category 2-certified cables, which have been tested at 340 MHz (which would include resolutions such as 1080p60 and 2160p30). This labeling guideline for HDMI cables went into effect on October 17, 2008
4. HDMI 1.4 cable definition:
- Standard HDMI Cable – up to 1080i and 720p
- Standard HDMI Cable with Ethernet
- Automotive HDMI Cable
- High Speed HDMI Cable – 1080p, 4K, 3D and deep color
- High Speed HDMI Cable with Ethernet
5. DDC
The Display Data Channel (DDC) is a communication channel based on the I²C bus specification.[83]
The DDC channel is actively used for High Definition Content Protection.
6. CEC
Consumer Electronics Control (CEC) is an HDMI feature designed to allow the user to command and control up-to ten CEC-enabled devices, that are connected through HDMI,[100]
It is a one-wire bidirectional serial bus that uses the industry-standard AV.link protocol to perform remote control functions. CEC wiring is mandatory, although implementation of CEC in a product is optional.
Trade names for CEC are Anynet+ (Samsung); Aquos Link (Sharp); BRAVIA Link and BRAVIA Sync (Sony); HDMI-CEC (Hitachi); E-link (AOC); Kuro Link (Pioneer); CE-Link and Regza Link (Toshiba); RIHD (Remote Interactive over HDMI) (Onkyo); RuncoLink (Runco International); SimpLink (LG); HDAVI Control, EZ-Sync, VIERA Link (Panasonic); EasyLink (Philips); and NetCommand for HDMI (Mitsubishi).[113]
The following is a list of HDMI-CEC commands:
- One Touch Play: allows devices to switch the TV to use it as the active source when playback starts
- System Standby enables users to switch multiple devices to standby mode with the press of one button
- Preset Transfer: transfers the tuner channel setup to another TV set
- One Touch Record allows users to record whatever is currently being shown on the HDTV screen on a selected recording device
- Timer Programming allows users to use the electronic program guides (EPGs) that are built into many HDTVs and set-top-boxes to program the timer in recording devices like PVRs and DVRs
- System Information: checks all components for bus addresses and configuration
- Deck Control allows a component to interrogate and control the operation (play, pause, rewind etc.), of a playback component (Blu-ray or HD DVD player or a Camcorder, etc.)
- Tuner Control allows a component to control the tuner of another component
- OSD Display: use the OSD of the TV set to display text
- Device Menu Control allows a component to control the menu system of another component by passing through the user interface (UI) commands
- Routing Control: control the switching of signal sources
- Remote Control Pass Through allows remote control commands to be passed through to other devices within the system
- Device OSD Name Transfer: transfer the preferred device names to the TV set
- System Audio Control allows the volume of an AV receiver, integrated amplifier or pre-amplifier to be controlled using any remote control from a suitably-equipped device(s) in the system
7. ARC和HEC (1.4 defined)
ARC就是可以把HDMI中的audio route到功放（av receiver上），这样就省了一根线（从media source连到功放的线）。配合CEC，美好的蓝图就是将所有设备都通过HDMI连接起来，然后一切就都搞定了。
HDMI 1.4 introduces two features called ARC (Audio Return Channel) and HEC (HDMI Ethernet Channel).[114]
ARC is an audio link meant to replace other cables between the TV and the A/V receiver or speaker system.[79]
HEC provides a bidirectional Ethernet communication at 100 Mbit/s.[114]