Video Extenders Information

When working with video signals, the location where the video will be displayed is often physically removed from the location of the signal source. The greater the distance between the source and the display locations, the greater the loss of the signal strength. Video extenders overcome these issues, minimizing video degradation and extending the range of common video transmission techniques.
 

Source: Pixabay

 

How Video Extenders Work

 
Signals that transmit video signals are typically not designed to transmit signals long distances. Using standard cables and video transmission standards, the signal will degrade and noise will be increased as the length of transmission increases. This noise can appear as blurriness, blinking screens, or overall low quality video. Video extenders allow video signals to be transferred long distances while maintaining a high-quality signal.
 
To transmit the signal over a greater distance while maintaining signal quality, video extenders need some source of power. This power typically comes from three main sources:
  • Local power
  • USB power
  • Power over cable
With a source of power, video extenders then either boost or convert the video signal. Boosting the signal allows it to travel further using the same protocol. While this method can be very effective, for large distances it often makes sense to convert the signal to a different format. 
 
With a transmitter and receiver, the source signal is converted into a signal type that can be transmitted more easily. Once the modified signal is received by the receiver, it is converted back to the original signal to be displayed.
 
 

Source: Pixabay

 

Specifications

 
Choosing the right video extender depends on the particular application. Common specifications include:
  • Power source
  • Transmission range
  • Video resolution
  • Audio transmission
  • Control transmission
  • Cable type
 
The desired format is important to ensure the signal can be extended and that the video extender will be compatible with both the source and the display. The most common formats where video extenders are used include the following.
  • HDMI
  • DisplayPort
  • DVI
  • VGA
  • Component video
  • Wireless
 

Types

 
Because of how often the need for video extenders occurs, many different solutions exist to address the problem. Here are some of the more common ones.
 

Active Cables

 
Some cables have built-in boosters to allow the video signal to travel longer distances without excessive degradation. Sometimes called a repeater, the circuitry to boost the signal is usually either in the middle of the cable or on the receiving end of the cable. Because of the added circuitry, active cables are often one-way only cables. The ends are clearly marked to determine which is the sending and which is the receiving end.
 

Active Optical Cables (AOCs)

 
Instead of boosting the signal, these types of cables convert the signal from electrical signals to light pulses. The light allows the packets of data to be transmitted using fiber optic cable. Fiber optics allow for high transmission speed with low signal degradation. The receiving end of the AOC converts the light pulses back into an electrical signal that the receiving device can use.
 

CATx Video Extenders

 

Source: Public domain

 
While fiber optics transmit data at high rates with low degradation, Cat5e or Cat6 cable is much less expensive. CATx video extenders transmit the signal via a CATx cable, allowing the signal to reach distances of over 295 ft. Instead of boosting the signal, these video extenders convert the signal so that it can be transmitted over CATx cables. On the receiving end, another device decodes the signal so that the video can be displayed properly.
 

AV Over IP Extenders

 
While CATx video extenders use CATx cables to transmit video signals, they do not follow IP standards to move the signal around. AV over IP extenders follow TCP/IP standards to distribute audio, video, and control signals meaning any equipment designed to work with that standard will work, such as network switches. These types of extenders can pass the video signal to many different displays in an efficient manner.
 

HDBaseT Video Extenders

 

Source: HDBaseT/CC BY-SA 4.0

 
With the ability to transmit video data up to 328 ft, the HDBaseT standard offers a simple method for extending video. HDBaseT uses 5Play to transmit uncompressed digital video and audio over a single Cat6 or above cable. Because HDBaseT is an industry standard, any equipment designed to work with that standard is compatible, regardless of manufacturer.
 

Fiber Video Extenders

 
Fiber provides a low latency method of transmitting video signals up to 1,000 ft with single mode fiber and over 6.2 miles with multimode fiber. Because fiber video extenders use light instead of electrical signals to transmit data, they are unaffected by electromagnetic interference and crosstalk.
 

Wireless Video Extenders

 
For ease of installation, wireless video extenders can be hard to beat. Capable of sending 1080p, 4k video, and 7.1 channel audio signals up to 165 ft, wireless video extenders provide a flexible, quick to install solution for extending video. While most manufacturers recommend the transmitter and receiver be placed within line of sight, the signal can transmit through walls but the signal may degrade. Transmission in a single room, like a conference room, typically works just fine.
 

Features

 
Certain video extenders have built-in features to prevent signal degradation and increase the range of the video being transmitted. Some features to look for are:
 

Color Space

 
The range of colors represented in a video image is referred to as color space. Two primary color spaces used in digital video are RGB and YCbCr. Each color uses a certain number of bits (color depth) to determine the correct shading and gradation and each color space has a curtain number of colors available (gamut). With the human eye only able to distinguish around 10 million different colors, anything over 24-bit color is adequate for most applications.
 

Chroma Subsampling

 
Reducing the amount of data being transmitted is called compression. Too much compression will distort the image and reduce the quality of the signal. Applying the correct amount of compression allows for faster transmission rates with no noticeable reduction in video quality.
 
Chroma subsampling takes advantage of the fact that the human eye is more sensitive to changes in brightness than changes in color. Because each pixel contains both brightness (luma) and color (chroma) data, reducing the amount of chroma data reduces the overall signal. Chroma subsampling allows pixels to share color data with adjacent pixels using a three digit representation.
  • The first digit is the number of pixels in each row being sampled
  • The second digit indicates the number of pixels in the top row with color information
  • The third digit indicates the number of pixels in the bottom row with color information
 

Source: Chroma Subsampling/ CC BY-SA 3.0

High Dynamic Range (HDR)

 
Dynamic range refers to the variations in brightness a signal contains. As displays advance, the range of brightness levels they can produce pushes the need for better video signals. HDR digital signals contain enough variation in brightness to support modern HDR compatible displays. If the display is designed to accept an HDR signal, the video extender should be able to transmit this signal or the video quality will be below what the display is capable of showing.
 

Source: Pixabay

 

Applications

 
Video extender applications occur frequently from consumer devices up to large commercial or industrial display applications.
 

Media Closets

 
With the increasing popularity of streaming and other media devices, many new homes are built with dedicated media closets. Devices in this room generate the source of the video signal, but the display may be located quite a far distance from the source. HDMI extenders are often used in this scenario.
 

Projectors

 
Whether in a conference room or large auditorium, the display projecting video is often physically mounted far from the source of the signal. Video extenders are critical for transmitting the signal with low latency and little degradation.
 

Informational Displays

 
Whether used in business settings to display information to customers or used in an industrial setting to display critical metrics to workers, video extenders are often needed to distribute this information. Video extenders that use TCP/IP protocols are often used in these scenarios so that the same signal can be sent to many different displays in different locations.
 

Closed-Circuit Monitoring

 
When monitoring a CCTV network, many video sources must transmit video signals back to a central location. Video extenders allow cameras located far from the control room to still transmit high quality video.
 

Standards

 
Knowing the common standards involving video extenders ensures compatibility between equipment.
 

HDBaseT

 
An industry standard used to ensure compatibility, HDBaseT ensures that any two HDBaseT supported devices will work at the highest possible version of their shared featured set. Regardless of the manufacturer, HDBaseT ensures the equipment will work together as designed. Choosing equipment that is HDBaseT compliant helps ensure installation is easier and provides flexibility in specifying equipment.
 

High-Bandwidth Digital Content Protection (HDCP)

 
This anti-piracy protocol is designed to protect copyright laws. To protect data from cyber criminals, data is encrypted and can only be decrypted with a key. This key requires authentication from both transmitting and receiving products. 

 

Related Information

 
 

References

 
 
 
 
 
 
 
 
 
 
 

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