The reason is that my friend used a 20-meter HDMI cable, and then found that the signal attenuation was serious, so I would like to introduce some knowledge about HDMI cable.
HDMI (High Definition Multimedia Interface) is an all-digital video and sound transmission interface, which can transmit uncompressed audio and video signals. HDMI can be used in set-top boxes, DVD players, personal computers, video games, integrated amplifiers, digital audio and televisions. HDMI can send audio and video signals at the same time. Because the audio and video signals use the same line, the installation difficulty of the system line is greatly simplified.
1 and the development of HDMI
From the official release of the standard version of HDMI 1.0 on February 9, 2002 to the latest release of HDMI2. 1 on June 9, 2007, the whole development of HDMI has been nearly 20 years. See the following table for specific development specifications:
2.3 different HDMI interfaces
From left to right, there are HDMI (type A), mini-HDMI (type C) and micro-HDMI (type D).
HDMI (type a): used in HDMI 1.0 version, with a total of 19 pins, with a specification of 4.45 mm× 13.9 mm, which is the most common HDMI connector specification, with point-to-point to DVI single-link transmission. Before HDMI 1.2a, the maximum transmission capacity was 165MHz, so the maximum transmission specification can only be1600x1200 (TMDS162.0mhz).
Mini-HDMI(C TYPE C): commonly known as mini-HDMI, it is applied to the version of HDMI 1.3, with the total pin 19, which can be said to be a reduced version of HDMI Type A, with the specification of 2.42 mm× 10.42 mm, but the definition of the pin has changed. Mainly used in portable devices, such as DV, digital cameras, portable multimedia players, etc. Due to the limited size, some graphics cards will use mini-HDMI, and users must use an adapter to convert it into a standard size A, and then connect the monitor.
Microhdmi (type D): It is suitable for HDMI version HDMI 1.4, with a total of 19 pins, and the specification is 2.8 mm×6.4 mm, but the pin definition has been changed. The new Micro HDMI interface will be about 50% smaller than the current 19 pin MINI HDMI interface, which can bring the highest resolution support of 1080p and the fastest transmission speed of 5GB to portable devices such as cameras and mobile phones.
This paper introduces the interfaces of A, C and D, so is there a B? The answer is yes, but no product uses this interface, so I won't introduce it here.
3. Comparison with DP
These two kinds of interfaces are the mainstream digital interfaces now, and there are many in comparison. Let's talk about it briefly today.
Due to the late release of DP, it has a little advantage in benchmarking their latest standards, but the main products on the market at present are HDMI2.0 and DP 1.4. HDMI2. 1 has produced some corresponding products, such as TV sets and graphics cards, while DP2.0 is said to be listed in 2020, but it has not been seen yet.
In daily use, the popularity of HDMI is relatively high, and it is easy to find HDMI interfaces for TVs, computer monitors, set-top boxes, etc. Personally, considering that HDMI has patent fees, major manufacturers should prefer free DP, and the development of DP may be better in the future.
4. Transmission distance
The main influencing factors are the material itself (gold, silver, gold, copper), the thickness of the material and the bandwidth of the transmission signal.
In the past, copper cores were common. Generally, the transmission of 1080P does not exceed 15m, and 4K does not exceed 5m. It should be noted that sometimes HDMI transmission will pass through the matrix. If the input+output exceeds 20m, the matrix has no amplification function and the signal is likely to be attenuated.
Now there is an optical fiber HDMI cable, which mainly has the following advantages:
The transmission distance is long, up to 300 meters.
Free from external electromagnetic interference
Light volume and weight
5. Other frequently asked questions:
When using HDMI cable, it is necessary to avoid excessive bending and winding of the cable. If you take a pipe, use 25% of the pipe and use it at the corner.
If inserted, then choose a gold-plated connector to reduce poor contact;
Some HDMI cables over 20 meters have signal amplification, so it is divided into positive and negative signals, so pay attention to output and output;
Try to use finished wires. Although HDMI connectors can also be soldered, there are many and dense pins, which are prone to problems. '
HDMI can transmit audio. Pay attention to the audio output when connecting to a computer. You need to add an audio de-embedding device to extract audio separately.