HDMI Protocol : PinOut, Features, Specifications, Components & Its Applications

A digital interface is a medium that allows seamless communication between electronic devices, applications, or systems. It acts as a protocol to translate complex digital data into understandable formats for users. One of the most popular examples of a digital interface in multimedia systems is the HDMI (High-Definition Multimedia Interface) protocol, which this article discusses in detail.

What is the HDMI Protocol?

HDMI or High-Definition Multimedia Interface, is a digital interface or a standard protocol used to transmit high-quality digital video and audio signals between devices like monitors, gaming consoles, TVs, and other devices like laptops and DVD players. Additionally, HDMI cables can transmit both compressed and uncompressed audio & video signals through a single interface by carrying both signals.

How does the HDMI Protocol Work?

The HDMI protocol uses TMDS (Transition Minimized Differential Signaling) to work by transmitting uncompressed digital audio and video data above a single cable with auxiliary and control data using a variety of periods and link modes. This protocol includes the HPD (Hot Plug Detect) pin used for detection of connection, the EDID (Extended Display Identification Data) for exchange of device ability & the optional CEC (Consumer Electronics Control) to control various devices through a single remote.

The working of this protocol follows as;

• When a device is connected, the HPD pin signals the source that a display is available.
• After that, the source & display devices can exchange EDID data to know each other’s abilities by ensuring compatibility and avoiding the transmission of unsupported signals.
• An authentication procedure establishes a shared key to guard digital content and encrypt the data stream between the devices by avoiding piracy.

Pin Configuration:

The HDMI protocol includes 19 pins, which are explained below.

• Pins 1-9 (TMDS Data2+, Data2-, Data1 shield, Data0+, Data0-): These pins are used for TMDS data transmission.
• Pin 10-12 (TMDS CLK+, CLK Shield & CLK-): These pins are used for the transmission of TMDS CLK, which is a pixel CLK.
• Pin-13 (CEC): It is a consumer electronics control pin that allows connected HDMI devices like Blu-ray players, AV receivers, and TVs to control one another.
• Pin-14 (Reserved Pin): This pin’s function can be changed based on the specific version of HDMI, particularly from 1.3 to 1.4.
• Pins 15 & 16 (SCL & SDA): These pins are based on I2C protocol transmission.
• Pin- 17 (GND): It is a ground pin.
• Pin-18 (+5V power): This pin provides +5V power to the HDMI.
• Pin-19 (HPD): This pin is used to set up the connection.

Features

The features of the HDMI protocol include the following.

• The HDMI protocol transmits uncompressed and high-quality digital audio & video data over a single cable by supporting a variety of resolutions & audio formats.
• It provides higher bandwidth to support 4K, 8K, and beyond higher resolutions & refresh rates with the most recent standards by providing up to 96 Gbps.
• Current HDMI versions support HDR content to provide a wider range of contrast and colors.
• HDMI is backward-compatible with earlier devices, which allows faultless integration with a variety of systems.
• Additionally, it is electrically compatible through DVI, allowing simple passive adapters to be utilized.
• The CEC (Consumer Electronic Control) allows for two-way communication between devices. Moreover, it allows many features similar to one-touch control, where a single remote can work with various HDMI-connected devices.
• ARC (Audio Return Channel) allows audio to be transmitted from a TV to an AV receiver or soundbar via a similar HDMI cable which eliminates the need for a separate audio cable.
• Enhanced ARC (eARC) provides higher bandwidth for superior audio formats.
• The HEC feature includes high-speed range networking to an HDMI link by allowing IP applications & internet-enabled devices to utilize the connection of HDMI for networking.
• HDMI uses the TMDS signaling method to reduce data signal transitions to help the sink device lock consistently to the data stream, and decreases interference by allowing for longer cables.
• The HDCP (High-bandwidth Digital Content Protection) is a copy-protection standard. So it is implemented to avoid unauthorized digital audio & video content copying, which is transmitted above an HDMI connection.

HDMI Specifications

The HDMI Specifications include the following.

• It has a Higher bandwidth, which supports refresh rates & higher resolutions.
• Resolution and Refresh Rates mainly include 1080p, 2160p, 10K, and 8K, with changing refresh rates for smooth motion.
• It supports different color spaces and depths, like wider BT.2020 and standard BT.709.
• It has high-fidelity uncompressed audio, several audio channels & dynamic lip-sync features.
• Newer standards simply support advanced High Dynamic Range formats for better color and contrast.
• Consumer Electronics Control allows a single remote for controlling multiple connected devices.
• It is available in different versions like HDMI 1.0, HDMI 2.0, HDMI 2.1, and HDMI 2.2.
• Cable Types are: Standard HDMI, High Speed HDMI, Premium High Speed, Ultra High Speed HDMI, and Ultra96 HDMI Cable
• HDMI 1.0 has 4.95 Gbps Max Bandwidth with 1080p @ 60Hz Max Resolution.
• HDMI 1.3 has 10.2 Gbps Max Bandwidth with 1440p @ 60Hz Max Resolution.
• HDMI 1.4 has 10.2 Gbps Max Bandwidth with 4K @ 30Hz Max Resolution.
• HDMI 2.0 has 18.0 Gbps Max Bandwidth with 4K @ 60Hz Max Resolution.
• HDMI 2.1 has 48.0 Gbps Max Bandwidth with 10K @ 120Hz Max Resolution.
• It uses TMDS for audio or video transmission.
• The Fixed Rate Link, or FRL in HDMI 2.1, replaces TMDS for high speeds.
• It includes three channels: audio, video, and auxiliary.
• It controls signals over Consumer Electronics Control (CEC) and Display Data Channel (DDC).
• HDMI supports video formats like RGB, YCbCr 4:2:2, 4:2:0, and 4:4:4 with up to 10K resolution with HDMI 2.1.
• Moreover, it supports Dolby Vision, HDR10 from HDMI 2.0+.
• Connectors like Type A (Standard), Type C (Mini), Type D (Micro), and Type E.

HDMI Protocol Components

The HDMI protocol includes different components, which include the HDMI cable & connector, TMDS, DDC, CEC, HPD, and eARC. All these components work together to transmit audio, video & control data between sources & sink devices. So these components allow the high-definition audio & video transmission, as well as the vital control & configuration data exchange between consumer electronics. The breakdown of each component is discussed below.

Cable & Connectors

The physical interface of HDMI includes a cable with a strong external jacket with 19 pins, which are set in three rows. Different connector types like Type A, C & D are designed mainly for a variety of devices.

TMDS (Transition Minimized Differential Signaling)

TMDS in the HDMI protocol is a technique that encodes & transmits digital data with differential signaling & a particular coding system to decrease EMI (electromagnetic interference). In addition, it maintains signal integrity over longer distances to ensure high precision for high-speed data transmission.  Moreover, this can be achieved by reducing signal transitions, which are vulnerable to noise & by sending two out-of-phase signal versions above twisted-pair wires. This allows the receiving device to remove the original data while avoiding most noise.

DDC (Display Data Channel)

The Display Data Channel in the HDMI protocol is an I2C communication channel. The main function of this is to allow a source device to find out & communicate with the capabilities of a sink device. The DDC reads the E-EDID (Enhanced Extended Display Identification Data), which includes data regarding the supported display modes, resolutions & characteristics of a sink device. Therefore, this data allows the source to regulate its output to match the capabilities of the sink to ensure proper display functionality by allowing brightness & contrast control features.

HPD (Hot Plug Detect)

In the HDMI protocol, Hot Plug Detect (HPD) is a signal that allows a source device to determine when a sink device has been connected or disconnected, triggering a communication sequence to read the sink’s Extended Display Identification Data (EDID). Therefore, the HPD signal is asserted by the sink device upon receiving +5V power through the HDMI cable, indicating readiness to establish a connection and exchange EDID information. This process enables plug-and-play functionality by allowing the source to automatically select the optimal audio and video settings for the display.

CEC (Consumer Electronics Control)

The HDMI-CEC is a feature that allows devices to connect through HDMI to converse and control each other, simplifying home entertainment setups by allowing a single remote to control many devices. This CEC facilitates some functions like One Touch Play. So, it is a device that turns on a TV & switches automatically to its input. A System Standby that turns off several devices through a single button press. Therefore, a core HDMI feature that needs support from both the TV & connected devices must often be enabled in the settings menu.

SCDC (Status and Control Data Channel)

The SCDC is an optional interface mainly for HDMI 2.0b & later versions that works over the I2C bus by connecting the source & sink devices. Additionally, it provides registers mainly for monitoring & controlling features like the TMDS CLK ratio & scrambling by allowing the devices to exchange essential operational data & status data beyond the typical CEC & DDC capabilities.

HEAC (HDMI Ethernet & Audio Return Channel)

HEAC or HDMI Ethernet Channel, introduced in HDMI 1.4, allows a single HDMI cable to carry bidirectional Ethernet data. Moreover, it allows IP-based applications & sharing an Internet connection between different devices. However, it also refers to the merged abilities of an HDMI cable to manage both HEC & ARC data. Thus, the HEC provides a bidirectional and high-speed data link for networking, whereas the ARC allows an audio signal to be transmitted upstream from a sink device to a source device.

Please refer to this link for the Difference between VGA and HDMI.

HDMI Versions

Advantages

The advantages of the HDMI protocol include the following.

• HDMI protocol transmits high-definition and uncompressed video signals, resulting in a flicker-free and crisp picture.
• This protocol carries multi-channel audio like DTS and Dolby Digital formats, which provide high-fidelity surround sound without requiring separate audio cables.
• In addition, HDMI carries both video and audio signals over a single cable to simplify connections and decrease cable clutter, and makes setup easier.
• It is a universal standard that is supported by a huge range of consumer electronics like game consoles, TVs, computers, Blu-ray players, projectors, etc.
• HDMI cables are simple to connect & don’t need complicated configuration, which makes them simple for most users.
• HDMI protocol supports some features like Consumer Electronics Control (CEC). Therefore, it allows you to control various devices from a single remote.
• Some HDMI cables have an Ethernet channel, which allows network connectivity between devices through the same cable.
• HDMI protocol helps future-proof your home entertainment system with newer standards support like HDR, Dolby Vision, 8K, 4K, etc.

Disadvantages

The disadvantages of the HDMI protocol include the following.

• Standard HDMI has a limited cable length.
• Authentication delays between devices can cause flashing screens or a blank screen when launching a connection.
• The signal can be influenced through electromagnetic interference, which can corrupt video quality, particularly over longer runs.
• The HDCP technology can cause compatibility problems and control the playback of protected content on certain configurations or devices.
• These are expensive compared to analog counterparts.
• The HDMI protocol lacks certain advanced capabilities, making it less suitable for broadcast or large-scale production environments.
• In addition, HDMI cables can face difficulties in the field termination.
• HDMI ports can be unsuccessful if subjected to common plugging & unplugging, which makes the cable less fit for stable use.

HDMI Protocol Applications

The applications of the HDMI protocol include the following.

• HDMI protocol connects and transmits uncompressed digital audio & video signals between electronic devices. It ensures a high-range digital pathway to display from the source.
• It connects display devices like projectors, computer monitors, and flat-panel TVs to audio or video sources.
• It is used in Blu-ray & DVD Players for high-fidelity audio & video playback to a well-matched display.
• It is used in gaming consoles to transmit high-definition game graphics & surround sound.
• It is used in set-top boxes of Cable & satellite to deliver high-quality TV channels to operators or viewers.
• The HDMI protocol connects desktop PCs and laptops to external projectors, televisions, and monitors.
• It is used in several modern camcorders and cameras to provide video output directly to displays.
• It is used in tablets and mobile phones to send video content to big screens.
• In addition, it is used in professional audio/video systems for event setups and presentations.
• This protocol is used in automotive systems to deliver HD quality to seatback displays or the dashboard.

Thus, this is an overview of the HDMI protocol, its working, and its applications. This is a powerful & versatile interface, used in the entertainment industry for high-definition multimedia connections. Moreover, this protocol has features like simple to simple-to-use, high-quality audio and video transmission capabilities & is compatible with other interfaces. It is used in a wide range of industries & settings. Moreover, it is a high-quality and dominant digital interface. In addition, it provides a single-cable solution to connect devices like gaming consoles, laptops, and TVs. Here is a question for you: What are the other versions of HDMI?