What is HDMI (High Definition Multimedia Interface)?

HDMI or High Definition Multimedia Interface is the uncompressed encrypted digital Audio and Video standard supported for the industry to replace the scart.

What is HDMI?

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

Properties

It allows multi-channel digital audio to be used in a single cable as well as computerized, advanced or high definition video. It is independent of various DTV standards such as ATSC, DVB (-T, -S, -C), which is nothing but an encapsulation of MPEG format data.

After being sent to a decoder, uncompressed video data is obtained and can be in high definition. These data are encoded in TMDS format for digital transmission.

It also includes 8 channels of uncompressed digital audio. Starting with 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.

The High-Definition Interface is a standard for transmitting uncompressed digital video and audio from one computer to another. It would be a digital and copyright protected 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-resolution video and multi-channel digital audio in addition to remote control signals.

Until wireless connection arrives, HDMI is considered to be the connection of the future since 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 important support, there is also support from the entertainment industry such as Fox, Universal, Warner Bros, and Disney.

Connectors and Compatibility

Although it may seem otherwise, there are multiple connectors. The most common and used can be found in 19-pin Type A and practically all equipment carrying this type of port. However, a 29-pin Type B was created and prepared for future displays with much higher resolution than what is available. Not currently used.

The Type C cable, like MiniUSB, which is more common, also designed for portable devices such as camcorders or photos, is 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 to a screen with HDMI input to a device with DVI. However, an adapter is required. Of course, only the image will be acquired. The sound and signal of the remote control disappear.

When you want to buy cables, you will definitely find a huge price difference between them. In general, it can be said that any of these services under normal conditions and when long cables are not working. Like other signals, this 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 that can control several devices with one remote when they are connected via HDMI. This is called CEC (Consumer Electronics Control) and the latest equipment is already supported.

Of course, you should be careful, because each manufacturer calls this feature with a different name, which sometimes causes errors.

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

The operation of the CEC is not complicated: the system normally identifies the display, the connected items, configures them appropriately and becomes able to control them with a single button or remote control. Almost all manufacturers adopt this functionality in multimedia equipment for the living room.

Versions

Since the 1.0 standard was established in December 2002, several updates were made up to 1.3. You may have heard about 1.3a and 1.3b features, but these are unrelated to the consumer.

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

Higher versions are fully compatible with the previous ones, but it is currently not possible to upgrade to higher versions of the standard, as existing updates require both Hardware and Firmware modifications. The only equipment prepared for this type of update is the Playstation 3 console, as it already has the necessary hardware items. In fact, it was the first device to use version 1.3.

   HDMI 1.0 (2002)

It is the only digital audio/video link cable with a maximum bit rate of 4.9 Gbit/s. Supports up to 165 channels/second and 8 channels 192 kHz/24 bit audio in video mode (1080p60 Hz or UXGA).

   HDMI 1.2 (2005)

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

   HDMI 1.3 (2006)

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

   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 an improvement in the resolution we call the starting weapon FullHD today. This new feature can send videos up to 4096 × 2160 at 24 fps or 3840 × 2160 at 30 fps and is known for XHD.

It also introduces new feature enhancements in expanded color support, where the new HDMI can bring more true colors to television, especially when a video camera is connected.

The sound also goes through improvements. There is now an audio return channel that requires less cable to have a surround sound system connected to the television.

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

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

This forward-looking step is vital today because both televisions and reproduction equipment see the Internet connection as logical and include an Ethernet port or even a WiFi connection.

In a team of 1.4, we wouldn’t need extra Ethernet connectivity because it would combine video, audio and Internet connectivity to the television anywhere with the same cable.

   HDMI 2.0 (2013)

HDMI 2.0, 32 audio channels, two simultaneous video streams, Rec. The 2020 color space has been enhanced in 3D and super wide 21:9 aspect ratio at 25 fps.

   HDMI 2.0a (2015)

Added support for high dynamic range (HDR) metadata with version 2.0a.

   HDMI 2.1 (2017)

Added support for Ultra high-speed cables by adding ARC support for 4K 120p, 8K, stage Dynamic HDR and high-end surround sound (eARC).

Version Comparison Chart

Advantages and Disadvantages

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

And it is a two-way link, which makes self-structuring 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 their control over copyright, thanks to HDCP.

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

Connectors

The standard Type A connector has 19 pins. Type B, a higher resolution version, has also been identified, but its use has not yet been generalized.

Type B has 29 pins that allow carrying an expanded video channel for high-resolution displays. The latter is designed for higher resolutions than 1080p format, i.e. a larger image size.

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

Also, without the use of HDCP, video quality and resolution can be artificially degraded by the signal source to prevent end-user viewing or mostly copy-protected content. HDMI Type B is backward compatible, similar to the trial DVI connection.

Technical Specifications

   TMDS Channel

It has audio, video and auxiliary data.

Signaling method: Single connection (HDMI type A) or double connection (HDMI type B) according to DVI 1.0 specifications.

Video pixel frequency: 25 MHz – 165 MHz (type A) or 330 MHz (type B). Video formats below 25MHz are transmitted using a pixel repeat 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, 96kHz, 176.4 kHz, 192 kHz.

Audio channels: up to 8.

   Copy Protection

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

For this, if each device manufacturer with HDMI produces equipment that allows copying from the consortium, it will be withdrawn and included in a blacklist and after that, it will not be able to transfer audio-video content to other manufacturers’ HDMI equipment.

Cable Length

HDMI features do not define the maximum cable length. As with all cables, the signal attenuation rises very much after a certain length. Instead, HDMI sets the minimum power level.

Different materials and build quality will allow cables of different lengths. In addition, the highest performance requirements must be met to support the highest resolution video formats and/or HDTV standard format ratio framework.

Signal attenuation and interference caused by cable interference can be compensated using the Adaptive Equalizer.

HDMI 1.3 defines two cable categories:

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, a 5 meter (~16 ft) wire can be easily and inexpensively produced according to category 1 specifications. Higher build quality can reach 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) that can be used to expand HDMI to 100 meters or more. Some companies also offer amplifiers, equalizers, and repeaters that can chain multiple HDMI cable standards, not triggers.

High Definition HDMI and Optical Media Players

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

It can carry HDMI 1.3, DD +, TrueHD and DTS-HD bitstreams in compressed format. This feature allows preprocessing or audio/video reception with the decoder required to decrypt data but has a limited utility for HD DVD and Blu-ray.

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

Multichannel LPCM can be carried over an HDMI 1.1 connection. Audio playback is the same as HDMI 1.3 resolution, while the audio/video receiver supports multiple LPCM audio channels via HDMI and supports HDCP.

However, most cheaper AV receivers do not support HDMI audio and are often labeled as HDMI gateway devices. It can also be used on consoles like Playstation 3 and Xbox 360.

Review

The main criticism of the HDMI connector is that the device using it is designed to encrypt the data so that the user does not copy the transmitted audio-video content.

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

It is also criticized by mounting systems, in particular, for the absence of any locking mechanisms or warranties in its connectors.

The connectors are easily removed by mistake, and worse, the plug and connector are more susceptible to physical or electrical damage. You may have locking mechanisms with the participation of third parties in HDMI, but they are few and expensive.

Subtitle Issues

While an HDMI display is allowed to define a native mode for video capable of extending the active line 21, most MPEG decoders cannot work with digital video formats that only contain additional lines and send only vertical bleach.

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

Although not standardized, it is possible to transmit a specific portion of the content in text form from source to destination using CEC commands or InfoFrame packages.

However, since there is no standard format for such data, this is likely to work only between sources and destinations from the same manufacturer. This exception goes against the standardization task of HDMI, which focuses in part on interoperability.

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

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