What is HDMI?
HDMI is the successor to the old SCART system. SCART was a purely analogue way of connecting video signals to a TV or monitor. HDMI stands for High Definition Multimedia Interface. Moreover, HDMI is used to transmit digital video and sound data between devices. Display devices can include TVs or Projectors. While transmission devices include Blu-ray players, PCs, and Laptops. AV receivers also often have many HDMI inputs.
HDMI was deveoped as a universal standard so that different makes of equipment could be connected together. The connector itself is much smaller that SCART and can handle high definition video data as well as embedded audio. Since the connector came out in 2002 there have been many upgrades so that the cable can now handle 10K video data
HDMI cable types
There are different types of HDMI cable for different used. Standard HDMI cables originally were rated for 720p or 1080i, both now largely obsolete. These had a data rate of up to 5Gbps. there are also specialist HDMI cables for automotive use that have better shielding. High speed HDMI 2.0 can handle 4K images at up to 10Gbps.
High speed HDMI cables support 4K video Known as UltraHD. Moreover the standard supports HDR as well as an expanded colour gamut. Up to 10Gbps is possible.
Ultra High-speed cables are capable of 10K video as well as HDR support and a data rate up to 48Gbps. This is known as HDMI 2.1. The cables can also relay Ethernet signals at up to 100Mb per second.
What are the different types of HDMI connector?
To complicate matters, there are four types of HDMI connector, Standard, Mini, Micro and Automotive. The standard connector is used to connect source devices to integrated amplifiers and preamps. While the mini connector is used by some tablets and DSLR cameras.
HDMI 2.1
The Chord C-View HDMI 2.1 cable
The Chord company are renowned for their quality HDMI cables and the C-View HDMI 2.1 cable is a well priced example of a high performing cable. as mentioned below, the high data rates of HDMI 2.1 demand a well shielded cable and a quailty gold plated plug.
The HDMI 2.1 specification has a much higher bandwidth, at 48GBPS than previous versions. Hence it needs a cable with improved performance. 2.0 also added metadata for HDR and HLG. HLG stands for Hybrid Log Gama and is used by broadcasters to save bandwidth by combining SDR and HRD signals into one DataStream. Metadata is used by the sending and receiving devices so that the receiving device knows what settings to use.
HDMI 2.1 is now capable of handling 10K content at 120fps along with Dynamic HDR video codecs such as Dolby Vision and HDR10+.
Chord Epic HDMI AOC 8K 48Gbps Cable
The Chord Epic HDMI AOC 8K 48Gbps Cable is one of the highest quality HDMI 2.1 cables available. it does not used copper cables but an optical fibre link. Each plug has a built in transceiver that converts the electrical signal into light and then reconverts it at the other end. As a result long cable runs are possible with no signal degradation.
Variable Refresh Rates (VRR)
HDMI 2.1 has support for variable Refresh Rates (VRR). With variable refresh rates the display continuously adapts to the supplied frame rate. This reduces tearing and stutter particularly with games. The range of frame rates can be between 30 to 144 Hertz resulting in smoother motion.
Auto Low Latency Mode (ALMM)
Another piece of metadata sent by a device, onto the HDMI 2.1 lead, involves gaming consoles. These send a signal that indicates gaming material is being shown. As a result the display automatically switches to low latency mode. Latency refers to the delay of a video signal caused by the transmission method any lag can result in tearing and stutter. This is a particularly noticeable with gaming content that has a lot of fast movement. As a result the ALLM signal switches the display into gaming mode for a much smoother image.
What is eARC?
eARC is another feature of HDMI 2.1. eARC allows for high quality HD audio to be sent via the HDMI 2.1 lead. TV sound can be sent to your soundbar or AV receiver, if they have a compatible eARC enabled input. Your sending device may need to be configured to allow this. High quality audio sources include Dolby Atmos and DTS sound. eARC will also allow your TV remote handset to control the volume of your soundbar, active speaker or AV receiver.
What is source based Tone Mapping (SBTM)
Put simply Source based tone mapping (SBTM) is used by a source device to optimise the image brightness and colour settings that are sent to the display device. In the days of tube televisions(CRT), the transmitted video standard was fixed and optimized for the limited brightness and colour gamut of CRT displays. Nowadays there is a much wider range of display technologies, not to mention HDR.
Modern video source signals can be a mixture of SDR, HDR, graphics and other image information. This can can confuse the display device. As a result the two way capability of the HDMI 2.1 cable is used. the display device “talks” to the source device and tells it what it’s capabilities are. The SBMT processor in the source device then adapts the supplied video signal to make best use of the display’s capabilities.