Lies in HDMI specifications

Products in this post

No items found.
All information about this project is available in a special website section.
We thank you for your attention!
No items found.
Click image to zoom

1. Our equipment fully* supports** the HDMI standard***

HDMI is the most basic standard for digital video transmission.

"Acceptable" quality is HDMI 1.4, "good" quality is HDMI 2.0. All standards above 2.0 are redundant, at least for now. Also, HDMI at a lower quality than Display Port wins in reliability, which is why professional equipment uses HDMI. By 2016, 100% of new TVs with resolutions higher than HD had an HDMI connector.

The HDMI 2.0 standard has many parameters:

- Resolution, 4K@60 or 5K@30 or 8K@30 (4:2:0)

- HDR support for 1080p@60, 4K60 (4:2:0)

- Widescreen aspect ratios 21:9, 2:1

- CEC, unified control signal

- Audio, up to 768kHz, 24-bit, 32 channels

- 3D

- Ethernet

🧐 In practice, compliance with the HDMI 2.0 standard is guaranteed to mean: 4K resolution at 60 frames and 4:2:0 color subsampling; audio up to 192 kHz 24-bit 2 channels. All other parameters are optional, but these two are sufficient for professional use.

Good HDMI equipment manufacturers list all supported parameters and all technologies in the specifications to avoid surprises during installation.

2. Our equipment fully* supports** HDR technology***

HDR - high dynamic range. This technology allows the display to increase brightness locally. HDR is often used in bright night scenes in movies or when the sun, fire, or explosion is shown on the screen.

In technical terms, HDR is a wider color range, extra bits for extra brightness. Color is 8 bits; a signal with HDR requires 10 or 12 bits. Most budget segment custom displays use a conversion: it takes HDR 10 bits and converts it to 8.

To support extended dynamic range, all elements of the system must work with it:

- A source, computer, or media player with HDR support at the output end

- The content, video file, or web player must contain HDR information

- Cables, extenders must transmit 10-12 color bits

- Display with 10–12-bit HDR support; specific HDMI port on the display must support this mode

- The display must have a peak brightness many times higher than the nominal value; this is the point of HDR technology.

🧐 The "HDR-compatible" label on the equipment does not mean that it supports this standard. It's a marketing ploy, meaning the device takes an HDR signal as input and quietly converts it to regular 8 bits. The source sends HDR, but the HDR-compatible device simply ignores the extra 2 bits of brightness.

🧐 HDR 10 bit (8bit + FRC) is also an example of a marketing ploy. The sentence has a cherished number 10, but it stands for "8 + FRC". FRC stands for Frame Rate Control, meaning that the monitor receives a 10-bit HDR signal and plays back 8 bits digitally enhanced. The effect is like HDR, suitable for inexpensive TVs, but is not HDR.

Good manufacturers do not specify HDR support for equipment where it is emulated or limited to compatibility only. Therefore, the choice of HDMI devices with HDR support is quite narrow.

3. Our extenders transmit the video signal* without delay**

Video signal transmission is always delayed. A 0 ms transmission delay is physically impossible, but it is unnecessary in practice. During transmission, time is lost to encoding/decoding in the extender.

Human reaction time is on the order of 250 ms, and reaction time of cyber athletes reaches 100-120 ms. The minimum perceived latency a human can hear and see is 15-30 ms.

The monitor and the extender give the delay or input lag from the computer or set-top box to the monitor. Consumer segment monitor introduces 30-70 ms of delay; gamer and professional models are closer to 10-30 ms.

🧐 A "latency-free" HDMI extender is a device that transmits a signal faster than 30ms. The main consumer quality of lag-free video transmission is the ability to work comfortably with a mouse or trackpad. For this purpose, it is enough to keep the transmission speed within some known limits.

Where manufacturers specify "latency free", it is there. Still, it is less than all other equipment in the chain and will not be noticeable (e.g., 8ms).

4. Our equipment fully* supports** 4K***

4K resolution is a marketing designation for all resolutions around 4 thousand pixels wide. It's usually 3840×2160 resolution, precisely four (2×2) FullHD screens, and a 16:9 aspect ratio.

16:9 is an excellent usable ratio for a monitor, but they're changing it both ways now. Laptops with modern interfaces are moving toward "square" 16:10 and 3:2. Home TVs show us movies and clips in "wide" theater format, and that's 21:9 or 18:9. All these resolutions can be "about 4,000 pixels" wide, too.

🧐 Resolution is always counted in pixels, not in marketing terms. Strictly speaking, 4K is only 3840×2160, not 4096×2160. This is the resolution "4K" is meant in the HDMI standard.

Good manufacturers list all supported resolutions clearly and precisely in the specifications list, with frame rates for each resolution.

5. Our extenders transmit video without modification* or conversion**

The HDMI standard involves connecting the source to the receiver with a cable. This cable must be made to a specific HDMI standard, with HDMI connectors, between devices with HDMI ports. Extenders, converters, active cables, or scalers do not exist in this formula. These devices came later to extend the standard's capabilities.

- An HDMI cable is 19 individual conductors and pins on a connector. A twisted pair network cable is only 8 conductors.

- A passive HDMI 2.0 standard cable can theoretically be 30 feet long; LAN cable for IP networks is limited to 400 feet.

- Twisted pair typically supports speeds up to 10Gbps, HDMI 2.0 is 18Gbps for 4K resolution.

Signal conversion is inevitable when transmitting HDMI through an extender. Even installation equipment standards that advertise "perfect quality" as HDbaseT convert the HDMI signal at the transmitter and decode it at the receiver.

🧐 All active extenders compress the HDMI signal from 18Gbps to more acceptable values. The transmission accuracy is determined by the quality of the codec algorithm. If the conversion retains ≥95% of the 4:4:4:4 3840×2160 signal, the difference will not be noticeable when viewing.

Good manufacturers use and constantly improve their transmission algorithms to preserve video quality when properly connected. When using a lower-quality cable than required by the instructions, the equipment usually continues to work at the expense of reduced picture quality. Dynamic conversion allows you to adapt to deteriorating conditions and improve reliability.

Sign up for my newsletter

Kevin Gibbs

Hi! I'm Kevin! I am a very curious engineer :))
I'm the website founder and author of many posts.

I invite you to follow exciting experiments, research, and challenges.
Let's go on to new knowledge and adventures!

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.