Have a correct understanding of HD cables and HD 2.1 specifications

HD cables are the most important transmission cables in home theaters, capable of transmitting both images and audio. However, HD cables are also the most difficult type of cable to understand. Especially when compared with traditional video cables and audio cables, the structure and usage of HD cables are more complex. Many audio-visual enthusiasts have only a superficial understanding of HD cables. Moreover, when manufacturers introduce HD cable products, their statements and labels vary, which further deepens many people's misunderstandings about HD. This article aims to clarify the ins and outs of HD cables and the HD 2.1 specification through simple words.

In fact, there is no HD 2.1 version cable

First of all, the first concept is that HD "cables" themselves do not have the distinction between version 2.0 and version 2.1. In fact, they are just a simple physical transmission channel. Unless it is specially designed, there are no chips or protocols inside the general HD cable connector. There are a total of 19 transmission channels inside the HD cable body. If you check the HD connector, you will see that there are 19 pins, and each pin is a transmission channel. This has remained the same since the HD cable was introduced and has not changed.

So, what's the deal with that so-called HD version? The significance of the HD version lies in what version the HD transmission chip configured for the playback signal source (such as a Blu-ray player) and the HD receiving/processing chip configured for the receiving device (such as a television) are. For instance, the HD2.1 specification supports 8K/60Hz video. To achieve this, both the Blu-ray player and the TV must be equipped with an HD2.1 chip to be able to transmit 8K/60Hz video. As long as either party's version is insufficient, it is impossible to transmit 8K/60Hz. The HD cable merely serves as a signal transmission channel in it.

To be more specific, there is a channel in HD that is responsible for EDID (Extended Display Identification Data), which is the identification function between the transmission end and the receiving end. This is what players commonly call the "handshake" of the equipment. After the handshake is successful, Only then will the transmission mode, bandwidth, and supported functions be determined. Then how does the HD cable transfer data? Among the 19 channels inside HD, there are four "groups" responsible for the transmission of a large amount of audio and video information. These four groups are composed of every three channels (for example, channels 1 to 3 form a group), so these four groups occupy 12 channels inside, and these 12 channels are also known as high-speed transmission channels. The remaining 7 channels are used for other functions, such as the aforementioned EDID handshake identification, HDCP copyright protection mechanism, CEC linkage control, and the ARC/eARC audio return channel to be discussed this time, etc.

Then, if the physical structure (the number of channels) of HD cables remains unchanged, why can HD cables transmit a larger amount of data as the version of HD improves? This is because the higher the version of the HD transmission and reception chip, the more advanced the compression and transmission technology will be adopted.

For example, before HD version 2.1, its four main transmission channels adopted the TMDS (Transition Minimized Differential Signaling) technology. After HD version 2.1, it was changed to the new FRL (Fixed Rate Link) technology. The amount of information that each channel using FRL technology can transmit can be 6, 8, 10 and 12Gbps. After adding up the four groups, The transmission rates of HD 2.1 can be 24, 32, 40 and 48Gbps. The common claim that "HD 2.1 claims a maximum transmission rate of 48Gbps" comes from this.

So, if there is an HD cable produced in the 1.4 version era, but due to its good workmanship, it can theoretically work normally in the HD 2.1 version environment. Then why do we still care about the quality of HD cables? This is theoretical. In practical situations, the more data an HD cable needs to transmit, the better its anti-attenuation and anti-interference capabilities must be. Otherwise, information loss or transmission failure may occur. In other words, the better the HD cable is designed and the better the materials used, the more it can withstand the transmission test of new versions and high-data volume environments.