Audio, Video

HDBaseT 101 – Part 1

Fundamentals and requirements.
Figure 1

According to a 2015 survey, nearly 40% of integrators are already deploying or working with HDBaseT technology, and that number is expected to grow. HDBaseT allows AV displays to be installed using the same materials and skills currently used for a LAN infrastructure, creating big opportunities and a new source of revenue for datacom installation experts. By understanding the finer points of this convergence, datacom contractors can become AV experts for their customers.

Here, we’ll answer some common (and not so common) questions about the capability of HDBaseT technology, and we’ll provide an overview of cabling system requirements for supporting high-density, digital audiovisual distribution for signals up to 4K and beyond.

What is HDBaseT?

HDBaseT is a technology that enables faster, simpler installations of large-format displays. This is accomplished by using a single category-rated cable to carry the high-bandwidth signals required for high-resolution displays across distances up to 150 meters.

HDBaseT is widely adopted as a reliable, plug-and-play HDMI extension method. With an HDBaseT AV signal extender, you can turn a tested, certified datacom permanent link into an IT/AV channel that is more reliable and flexible than traditional HDMI cables or multi-conductor systems.

HDBaseT is compatible with 4K video, but the distance at which the HDMI signal is extended can vary based on the HDBaseT class, the strength of the HDMI signal and the specific implementation of the HDBaseT technology by the manufacturer. Common video signals include 1080p and 4K (2160p):

  • 4K (2160p)
    • horizontal pixel count of about 4000 pixels
    • frame is progressively scanned
    • frame refreshed typically 30 or 60 times per second (fps)
    • DCI: Digital Cinema Initiatives movie projection industry standard (4096 pixels wide by 2160 pixels high in a 1.9:1 aspect ratio)
    • UHD: television/consumer standard (3840 pixels wide by 2160 pixels high in a 16:9 or ~1.78:1 aspect ratio = 2160p)
  • 1080p
    • 1920 pixels wide by 1080 pixels high (16:9 aspect ratio)
    • frame is progressively scanned
    • frame refreshed typically 30 or 60 times per second (fps)

HDMI Signals

HDMI 1.4 transfers uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source to a compatible display. These signals support high-speed networking, audio return, 3D video formats, 4K (2160p) video resolution at 30 frames per second (fps), real-time signaling of content and additional color spaces for enhanced digital photography and computer graphics.

Released in 2013, HDMI 2.0 transmits 4K (2160p) resolution at 60fps for four times greater pixel count over 1080p/60fps. In addition to being backward compatible with earlier HDMI versions, HDMI 2.0 features:

  • transmission of High Dynamic Range (HDR) video bandwidth up to 18Gbps
  • up to 32 audio channels for a multi-dimensional immersive audio experience
  • up to 1536kHz audio sample frequency for the highest audio fidelity
  • wide-angle theatrical 21:9 video aspect ratio
  • simultaneous delivery of dual video streams and multi-stream audio to multiple users on the same screen.

Figure 1 compares the 1080p and 4K (2160p) resolution.

HDBaseT Classifications

HDBaseT 1.0 was initially introduced as a point-to-point connectivity standard, and defined the 5Play feature set (video, audio, control, Ethernet and power). HDBaseT 2.0 adds several enhancements, including expanding it as a multipoint-to-multipoint technology, as well as supporting multi-stream and daisychain. HDBaseT 2.0 also includes USB for multi-touch and KVM applications; improved performance for 4K (UHD) video with enhanced error correction, and fiberoptics as a means of transmitting HDBaseT for longer distances.

For more information about HDBaseT classifications and specifications, go to www.hdbaset.org.

  • HDBaseT 1.0 Class A: HDBaseT 1.0 Class A extenders carry a 1080p/60fps HDMI 1.4 signal to a display, extending full 5Play audio, video, power, control and Ethernet signals up to 100 meters. Because of the extra data received, the distance for a 4K UHD 2160p/30fps signal is typically shorter at 70 meters (depending on manufacturer), and the refresh rate is only 30fps. This potential limitation must be considered when designing an extender solution. The choice of extender can limit the ability to easily upgrade from 1080p to 4K resolution. (See Figure 2.)
  • HDBaseT 1.0 Class B: HDBaseT 1.0 Class B extenders carry a 1080p/60fps HDMI 1.4 signal to a display, extending audio, video, power and control signals up to 70 meters. Again, because of the extra data required, the distance for a 4K UHD 2160p/30fps signal is typically shorter at 40 meters. Be sure to check manufacturer’s specifications. (See Figure 3.)
  • HDBaseT 2.0: HDBaseT 2.0, combined with HDMI 2.0, can extend higher-resolution signals at greater distances. HDBaseT 2.0 can extend a 1080p/60fps HDMI 2.0 signal or a 4K UHD 2160p 60fps HDMI 2.0 signal to a display, extending 5Play audio, video, power, control and Ethernet, plus USB 2.0 signals up to 100 meters. (See Figure 4.)

Alternatively, for longer reach, HDBaseT 2.0 can be used to extend 1080p 60fps HDMI 2.0 5Play audio, video, power, control, Ethernet and USB signals up to 150 meters. (See Figure 5.)

Other capabilities of HDBaseT 2.0 include daisychaining and multi-streaming. For more information about these features and to see how different manufacturers implement these technologies, go to www.hdbaset.org/certification. (See Figure 6.)

Transmitters With Integrated Projectors

An HDBaseT transmitter can be paired with the latest HDBaseT-integrated projectors, and the technology is evolving to better accommodate IT/AV devices. Several manufacturers now offer projectors with an integrated HDBaseT receiver and HDBaseT port. This allows you to directly connect an HDBaseT transmitter to the projector, eliminating the need for an HDBaseT extender receiver. (See Figure 7.)

Although HDBaseT-integrated devices offer additional network flexibility, there are limitations to consider. Devices, such as the integrated projector, typically are not capable of supporting Power over HDBaseT (PoH), meaning that these devices cannot power the HDBaseT transmitter from the receiver end, which could limit network layout and organization options.

Other considerations include control (IR, USB, RS232 and IP) compatibility, which should be confirmed prior to specification. For more information about device control compatibility and features, go to www.hdbaset.org/certification. (See Figure 8.)

Cabling Requirements

HDBaseT enables the transmission of AV signals at speeds up to 18Gbps and a frequency of 500MHz (HDBaseT 2.0). TIA UTP cable specifications define the frequency capability for Cat5e at 100MHz, Cat6 at 250MHz and Cat6a at 500MHz. When driving a PAM-16 signal (similar to 10GBASE-T) more than 100 meters, signal strength and complexity are greatly increased, causing alien crosstalk (AXT, signal crosstalk from one cable to another).

AXT is created in a channel by other cables and connectivity outside and in close proximity of one another. In Figure 9, there are six disturbers around one victim. The signals carried by the outside disturbers impact signals transported by the victim.

Unfortunately, AXT cannot be predicted effectively, and therefore cannot be reduced or eliminated through noise cancellation techniques within active equipment. AXT can only be controlled through design and installation of proper cable and connectivity.

Leviton conducted a series of tests to verify the capability of different category channels, cable and connector types. Testing concentrated on the effectiveness of the extenders at their maximum distance capability (shorter distances may have better performance) and was conducted using 1080p/60fps video sources. (See Figure 10.)

Cat5 Channels: No HDBaseT Support

Although Cat 5e channels can carry HDBaseT signals in a point-to-point link, they do not support HDBaseT in real-world, high-density installations with adjacent data or HDBaseT channels. Using Cat 5e UTP cable in these applications led to signal dropouts and total link loss because the channels are not designed to resist alien crosstalk.

  • Test Configuration A: 100m Cat5e UTP cable (6 around 1 bundle):
    • Victim = HDBaseT 1.0 extension channel 1080p/60fps
    • Disturbers = multiple HDBaseT 1.0 extension channels 1080p/60fps
  • Results
    • Cat5e channels can carry HDBaseT 1.0 1080p signals in a single point-to-point isolated channel.
    • Cat5e channels do not support HDBaseT signals in high-density installations bundled with adjacent HDBaseT channels.
    • When a Cat5e UTP channel is tested with one adjacent HDBaseT disturber, the HDBaseT extender attempts to connect, but never succeeds.
    • Cat5e channels are not designed for 300MHz signals and are not optimized for resistance to alien crosstalk.

Cat5e cabling of all types is not designed to deal with AXT. This report shows the results of testing two Cat5e links for AXT margin, one victim and one disturber. Adding a single disturber results in signal loss. (See Figure 11.)

We will conclude this discussion next month.

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