What is HDMI (High Definition Multimedia Interface)?

HDMI, or high-definition multimedia interface, is the uncompressed encrypted digital audio and video standard supported by the industry to replace the cart.

What is HDMI?

DVB-T Tuner provides an interface between digital audio and video sources such as a Blu-ray player, Tablet PC, computer, or receiver and a compatible digital audio/video monitor such as a Digital Television (DTV).

Properties

It allows the use of computerized, enhanced, or high-definition video as well as multi-channel digital audio in a single cable. It is independent of various DTV standards such as ATSC and DVB (-T, -S, -C), which is nothing more than an encapsulation of MPEG format data.

After being sent to a decoder, uncompressed video data is obtained and can be high definition. This data is encoded in TMDS format to be transmitted digitally.

It also contains eight channels of uncompressed digital audio. Starting from version 1.2, it can use up to 8 single-bit audio channels. Super Audio CDs use 309-bit audio.

HDMI is one of the most used words today when talking about TVs, reproductive equipment, and even computer screens or the same computer equipment.

High Definition Multimedia Interface is a standard for transmitting uncompressed digital video and audio from one computer to another. It would be a digital and copyrighted version of Scart.

Therefore, it does not require two cables to connect two computers with this type of connection. A single cable is all it takes to carry high-definition video and multi-channel digital audio in addition to remote control signals.

Until wireless connectivity came along, HDMI was considered the connectivity of the future, as it was not created by industry leaders such as Hitachi, Panasonic, Philips, Sony, Thomson (RCA), Toshiba, Samsung, and Silicon Image. In addition to the most prominent support, there is also the support of the entertainment industry, such as Fox, Universal, Warner Bros, and Disney.

Connectors and Compatibility

Although it may seem otherwise, there are several connectors. The most common and used is the Type A, with 19 pins, and can be found in practically all equipment that carries this type of port. However, a Type B with 29 pins was created and is intended for future screens with much higher resolution than the current ones. It is not currently used.

The more common is the Type C cable, like the MiniUSB, which is also designed for portable devices such as video cameras or stills, smaller but still has 19 pins.

It is compatible with DVI equipment. This means that we can connect an HDMI source to a device with a DVI connection or a device with DVI to a screen with HDMI input. However, an adapter is required. Of course, only the image will be obtained. The sound and signal of the remote control are lost.

When you want to buy a cable, you will definitely find a significant price difference between them. In general, it can be said that any of them serve in normal conditions, and long cables do not work. Like other signals, this one loses distance.

CEC (Consumer Electronics Control)

In addition to uncompressed video and audio, the connection can send information from the remote control.

This turns into something magical, being able to control several devices with a single remote control when connected via HDMI. This is called CEC (Consumer Electronics Control), and the latest equipment supports it.

Of course, you have to be careful because each manufacturer calls this feature by a different name, which sometimes leads to errors.

For example, Sony calls it Bravia Sync Theater. Samsung calls it Anynet +. Panasonic calls it Bravia Link or EZsync, while LG calls it SimpLink.

The operation of CEC is not complicated. The system typically identifies the elements connected to the screen. It configures them accordingly and allows you to control them with a single button or remote control. Almost all manufacturers have adopted this functionality in their multimedia equipment for the living room.

What are the HDMI Versions?

Since the 1.0 standard was established in December 2002, there have been several updates up to 1.3. You may have heard about the 1.3a and 1.3b specifications, but these are of no interest to the consumer.

This is the 1.3 standard. It introduced a number of improvements for laptops, including an increase in bandwidth to 340 MHz (10.2 Gbit/s) in late 2010, support for Dolby TrueHD, DTS-HD, TrueHD and DTS-HD audio, and the introduction of the Type-C connector.

The higher versions are fully compatible with their predecessors. However, the current updates require both Hardware and Firmware modifications. It is not currently possible to upgrade to higher versions of the standard. The only equipment prepared for such an update is the Playstation 3 console, as it already has the necessary hardware elements. In fact, it was the first device to use version 1.3.

1) HDMI 1.0 (2002)

It is the only digital audio/video connection cable with a maximum bit rate of 4.9 Gbit/s. It supports up to 165 channels/second in video mode (1080p60 Hz or UXGA) and eight channels of 192 kHz/24-bit audio.

2) HDMI 1.2 (2005)

Support for One Bit Audio used in Super Audio CDs adds up to 8 channels to this specification. Type A is available for PC connectors.

3) HDMI 1.3 (2006)

Bandwidth increased to 340 MHz (10.2 Gbit/s), and support for Dolby TrueHD and DTS-HD was added. TrueHD and DTS-HD are low-loss audio formats used on HD-DVD and Blu-ray Discs. The specification also features a new mini-connector format for camcorders.

4) HDMI 1.4 (2009)

It is a cable that can send not only high-definition video and audio but also data and 3D video. It also provides the starting gun with an improvement in the resolution that we call today FullHD. This new specification can send video with a resolution of up to 4096 × 2160 at 24 fps or 3840 × 2160 at 30 fps, known as XHD.

It also introduces new specification improvements in extended color support, with which the new HDMI can bring more real colors to television, especially when a video camera is connected.

The audio also undergoes improvements. There is now an audio return channel that requires fewer cables to have a surround sound system connected to the television.

A curiosity that 1.4 brings is being able to see high-definition video on the move. The new specification is about maintaining quality despite vibrations or noise. You can think of high definition directly in cars and public transport.

One of the most exciting innovations offered by the 1.4 specification is the possibility of sending and receiving data via an Ethernet connection built into the cable at speeds of up to 100 Mbps.

This forward step is vital today because both televisions and reproductive equipment see the Internet connection as something logical and includes an Ethernet port or even a WiFi connection.

In a 1.4 team, we would not need an additional Ethernet connection. With the same cable, video, audio, and Internet connection can be combined anywhere on the television.

5) HDMI 2.0 (2013)

HDMI 2.0 has been enhanced to deliver 4K frame rates without the need for new cables, with 32 audio channels, two simultaneous video streams, Rec. 2020 color space, 3D at 25 fps, and a super-wide 21:9 aspect ratio.

6) HDMI 2.0a (2015)

Version 2.0a added support for high dynamic range (HDR) metadata.

7) HDMI 2.1 (2017)

They added support for ultra-high-speed cables, providing 4K 120p, 8K, scene dynamic HDR, and ARC support for high-end surround sound (eARC).

Version Comparison Chart

HDMI Advantages and Disadvantages

The advantage of this connection is evident to the consumer since we only need one cable to send uncompressed video and audio from one device to another. In addition, as we see with HDMI CEC, the use of the equipment is greatly simplified.

It is a two-way connection, which makes self-configuration and easy control a reality. Because we can say that different teams can not only receive information but also send it at the same time and communicate with each other. And let’s not forget the quality it offers us.

In the case of industry, the main advantage is the control they have over the copyright, thanks to HDCP.

As for the disadvantages, in addition to those derived from the signal control, we see that the connection between the port and the equipment is very sensitive to accidental disconnections since it is not currently fixed to the cable and the equipment but is connected.

Connectors

The standard HDMI Type A connector has 19 pins. A higher resolution version, Type B, has also been defined. However, its use has not yet been generalized.

Type B has 29 pins, allowing it to carry an extended video channel for high-resolution displays. The latter is designed for resolutions higher than 1080p, meaning a larger image size.

HDMI Type A is backward compatible with the single DVI connection used by modern computer monitors and graphics cards. This means that a DVI source can be connected to an HDMI monitor using a suitable adapter or cable and vice versa. However, this means that audio and HDMI, remote control features, cannot be used.

Additionally, without the use of HDCP, the signal source can artificially degrade video quality and resolution to prevent the end user from viewing or often copy-protected content. HDMI Type B is similarly backward compatible with the trial DVI connection.

Technical Specifications

1) TMDS Channel

It has audio, video, and auxiliary data.

Signaling method: According to DVI 1.0 specifications, single link (HDMI type A) or dual-link (HDMI type B) is the best option.

Video pixel frequency: 25 MHz – 165 MHz (type A) or 330 MHz (type B). Video formats below 25 MHz are transmitted using a pixel repetition scheme. Regardless of frequency, up to 24 bits per pixel can be transmitted.

Pixel coding: RGB 4:4:4, YCbCr 4:2:2, YCbCr 4:4:4.

Audio sampling rates: 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz.

Audio channels: Up to 8.

2) Copy Protection

The HDMI connection is designed so that you cannot make copies of the audio and video content transmitted according to the HDCP 1.10 specifications.

For this, every device manufacturer with HDMI, if they produce equipment that allows copying, will be withdrawn from the consortium and will be included in a blocklist, and from then on, other manufacturers will not be able to transmit audio-video content to them on HDMI equipment.

3) Cable Length

The HDMI specification does not specify a maximum cable length. As with all cables, signal attenuation becomes very high after a certain length. Instead, HDMI specifies a minimum power level.

Different materials and build quality will allow for various lengths of cable. Additionally, the highest performance requirements must be met to support the highest resolution video formats and the HDTV standard format rate framework.

Signal attenuation and noise caused by cable interference can be compensated by using an adaptive equalizer.

HDMI 1.3 defines two categories of cables:

Category 1: Standard or HDTV.

Category 2 Higher speed or higher than HDTV to reduce confusion about which cables support which video formats.

Using 28 AWG, approximately 5 meters (~16 ft) of wire can be quickly and inexpensively manufactured to Category 1 specifications. Higher build quality can achieve lengths of 12 to 15 meters (~39 to 49 feet).

It also enables cables (fiber optic or Cat-5 dual cable instead of copper standard) to be used to extend HDMI to 100 meters or more. Some companies also offer amplifiers, equalizers, and repeaters that can daisy chain multiple HDMI cable standards, not triggers.

High-Definition HDMI and Optical Media Players

Both were released in 2006, and Blu-ray Discs and HD DVDs offer the new hi-fi audio features that HDMI needs for the best results. Dolby Digital Plus (DD+), Dolby TrueHD, and DTS-HD Master Audio use higher bit rates that exceed the capabilities of TOSLINK.

HDMI 1.3 can carry DD+, TrueHD, and DTS-HD bitstreams in compressed form. This feature allows for pre-processing or audio/video ingestion with the necessary codec to decode the data. However, it has limited utility for HD DVD and Blu-ray.

HD DVD and Blu-ray enable interactive audio, where the content on the disc tells the player to combine multiple audio sources before output. Accordingly, most players will decode the audio internally and only process the LPCM audio output.

Multi-channel LPCM can be carried over an HDMI 1.1 connection. Audio playback is the same at HDMI 1.3 resolution, while the audio/video receiver supports multiple channels of LPCM audio over HDMI and supports HDCP.

However, many cheaper AV receivers do not support HDMI audio. They are often labeled as HDMI pass-through devices. They can also be used on consoles such as the Playstation 3 and Xbox 360.

Review

The main criticism of the HDMI connector is that it is designed in such a way that the device using it encrypts the data in question, preventing the user from copying the audio-video content being transmitted.

Another criticism is that the connectors are not as robust as previous display connectors. Currently, most HDMI-enabled devices use surface mount connectors rather than through-holes or stiffener connectors, making them more susceptible to damage from external forces. Passing over a cable connected to an HDMI port can easily damage that port.

It has also been criticized, particularly by mounting systems, for the lack of any locking mechanism or warranty on its connectors.

The connectors can be easily removed by accident, and worse, the plug and connector are more prone to physical or electrical damage. You can get locking mechanisms with third-party involvement in HDMI, but these are few and expensive.

Subtitle Issues

Although it is permissible for an HDMI display to define a native mode for video that can extend to cover active lines 21, most MPEG decoders cannot work with digital video formats that include additional lines and only send vertical bleaching.

Even if possible, closed caption characters must somehow be encoded into the pixel values ​​on line 21. In this case, there must be a logical receiver on the display to decode the building codes and subtitles.

Although not standardized, a particular portion of the content in text form can be transmitted from source to destination using CEC commands or InfoFrame packets.

However, since there is no standard format for this type of data, this is likely to only work between sources and destinations from the same manufacturer. This exception runs counter to HDMI’s standardization mission, which is partly focused on interoperability.

Of course, closed captions could be carried in a future extension of the HDMI specification.