The ABCs of HDMI Cables

Digital standards and technologies improve at an exhilarating pace. Newer and better technology is a good thing, but the downside is that many of us amass a huge variety of cables and connectors over time. Knowing how, when, and why to pick one connection type over another can be overwhelming.

Fortunately, as we move into an increasingly digital world, options are getting simpler and more straightforward, so a little information can go a long way towards clarifying your best choice. HDMI is the gold standard today, but not all HDMI cables are created equal.

What is HDMI?

HDMI stands for “High Definition Multimedia Interface.” Just as the name suggests, HDMI functions by passing high-quality audio and video signals. Unlike the DVI interface that came before it, HDMI can send uncompressed video signals along with either compressed or uncompressed audio signals using a single cable (DVI could only send video). This versatility allows the user to simplify their setup by using only one cable for both audio and video without sacrificing signal quality.

HDMI cables also carry a Consumer Electronics Control (CEC) signal that allows HDMI-connected devices to control each other. The CEC signal enables the use of a single remote control to operate all the connected devices. Some HDMI cables are available with an Ethernet channel as well, which allows high-speed bidirectional data transfer.

HDMI Connector Overview

The HDMI standard includes five types of connectors, referred to as types A-E:

1. Type A: This is the standard HDMI connector (13.90 x 4.45mm), available on virtually all HD TVs. It has 19 pins, the bulk of which carry video, audio, and timing data and are assigned in groups of three: a positive/negative pair with a pin that acts as an interference shield between them. The remaining pins carry information like the CEC signal. There is enough bandwidth to carry all modes of video up to 4K. These connectors are compatible with the older DVI-D connector.

2. Type B: This type was designed as a dual-link version to increase data speeds but was never implemented. Single-link HDMI speed eventually outstripped the speeds possible in the dual-link concept.

3. Type C: Often referred to as “mini HDMI,” this connector is considerably smaller (10.42 x 2.42mm) and retains the 19-pin configuration, though it swaps the position of the positive signals with their corresponding shields.

4. Type D: Known as “micro HDMI” and roughly the same size as a micro-USB connector (5.83 x 2.20mm), Type D also has 19 pins, but a configuration different from either Types A or C.

4. Type E: Used in automotive applications, Type E has locking tabs to keep the cable inserted during vibration in its environment. It also features a shell to protect against environmental hazards like moisture and dirt.

HDMI Pinout

The standard Type A connector has, as mentioned above, 19 pins. Below is how a 19-pin HDMI Type A connector works:

- Pins 1-3 carry Data channel 2 (+/ground or data shield/- respectively)

- Pins 4-6 carry Data channel 1 (+/ground or data shield/- respectively)

- Pins 7-9 carry Data channel 0 (+/ground or data shield/- respectively)

- Pins 10-12 carry the clock channel that synchronizes the signals (+/ground or data shield/- respectively)

- Pin 13 is a CEC channel allowing devices to control each other

- Pin 14 has no current use

- Pins 15-16 carry the Display Data Channel (DDC) which communicates extended display ID information

- Pin 17 is the data shield for pins 13, 15, and 16

- Pin 18 is a low-voltage power supply (5v)

- Pin 19 is the Hot Plug Detect, and it monitors power and plug/unplug events

Mini HDMI Type C: In the Type C “mini” plug, the overall pinout is the same, but each pair’s positive signals exchange places with the corresponding shield/ground (pins 1 and 2 change places, for example). Additionally, the ground for CEC/DDC is on pin 13, CEC data is on pin 14, and the additional pin is on 17.

Micro HDMI Type D: The Type D “micro” plug also rearranges the order of the pins but retains the same number of pins as well as their same basic functions.

Note that the (relatively) new USB-C connector has an HDMI-compatible alternate mode. This mode does not require active converters. Instead, the HDMI protocol’s full functions are mapped directly to the pins of the USB-C, allowing a native connection with USB-C devices.