Today’s new digital video formats like HDMI and DVI provide uncompressed digital audio and video with a sharp, crystal-clear image quality. No more flickering and blurry pictures. However, even the best inventions have their limitations. Digital video signals require a huge amount of bandwidth to be transmitted properly. Using low-quality cabling or distribution equipment may lead to problems. Here are the five most common:

Problem #1: Black screen (no picture at all).

Possible cause:

1. Bad cable or one that’s too long, causing either the video signals or EDID/HDCP control signals not to be transmitted properly. Make sure that you use good-quality, high-speed HDMI® cables—they don’t even have to be expensive ones—or try an HDMI extender.
2. HDCP is unsupported. Does the display support HDCP? DVI displays usually don’t.

Problem #2: “Sparkles” in the picture.
Usually caused by:
Too long or inferior HDMI cable. Use a video extender, and/or buy quality HDMI cables from a reputable supplier.

Problem #3: RGB color tint.

Usually caused by:

A color encoding issue, a common problem when using a DVI display with an HDMI source. If you’re using a splitter or an extender between your source and the link, make sure it handles EDID correctly—all Black Box® HDMI products do. If possible, force the source (for instance, a Blu-ray player) to output HDMI video with RGB color encoding instead of Component (YPbCr) video encoding.

Problem #4: White noise, or just “snow,” for a picture.

Usually caused by:
An HDCP issue. This is actually what the encrypted video looks like. It happens when your display (or any active component, like an extender or a splitter, used in the transmission) doesn’t support HDCP. The display, in turn, isn’t able to decrypt the video stream. Be sure to use equipment that supports HDCP.

Problem #5: Flickering, unstable, or blinking image.

Can be caused by:
Electromagnetic or radio frequency interference (EMI/RFI), bad cable, or cable that’s too long. These all can cause issues with HDCP or the video signal, resulting in flickering or the video randomly disappearing then reappearing after a second. The solution: Use certified high-speed HDMI cables instead of standard HDMI cables, or if you need to transmit longer distances, try an extender from Black Box. If you’re already using an extender, try changing to shielded CAT6 solid-core bulk cable.

When VGA (Video Graphics Array) was introduced by IBM® in 1987 for PC video display, it was a huge improvement over the earlier EGA DB9 connector. VGA, the basic format, supports resolutions up to 640 x 480 with 256 colors. You can find it on many video cards and computer monitors.

SVGA (Super VGA), EGA, and later formats continued the drive to provide ever-sharper images and greater color depth. Plus, over the years, VESA standards have brought structure and interoperability to a market that was becoming a mixture of often incompatible SVGA graphics cards.

Later formats supported even higher resolutions—oftentimes, rivaling those of digital 1080i and 1080p displays. These later formats include SXGA (1280 x 1024), UXGA (1600 x 1200) and WUXGA (1920 x 1200).

Other analog video connectors:

Composite video—Typically presented as a yellow RCA connector, the analog Composite interface has been the standard interface for consumer TV equipment. As its name suggests, Composite video has the luminance (black and white), chrominance (color) and sync pulses combined in one signal.

S-Video—Also called Y/C video, S-Video was introduced to overcome some shortfalls associated with Composite video. It’s a less encoded video format, transmitting color (C) and luminance (Y) information separately to produce a sharper image.

Component video—This YCbCr connector separates the signal more than S-Video for less interference and improved video. In addition to Y (luminance) signals, it transmits color information as two signals: B-Y (Blue minus luminance, also called Cb or Pb) and R-Y (Red minus luminance, also called Cr or Pr).

Go Long! Alternatives to analog video cable extension

Extending video long distances isn’t often possible or practical using standard VGA or coax cabling. With Composite, Component, and other analog video cabling, frequency losses result in deteriorated video quality. Generally, with these cables, the shorter distance the better.

Extenders that extend analog video over UTP copper or fiber optic cable solve this problem, enabling you to use backbone or horizontal wiring for your long-distance extensions. Depending on the extender model, video input can be VGA, Component, S-Video, Composite, or BNC coax. They’re a great alternative to using analog video or coax cables, which often can’t be easily pulled through tight conduits and can be more difficult to terminate. What’s really nice is, in most buildings, copper or fiber cabling is already installed to service data communications.

Fiber-based extenders provide higher bandwidth and interference-free extensions at distances much farther than copper-type CATx extenders. But there’s the matter of cost. CATx extenders that use cabling and connectors cost considerably less than fiber cabling components.

Another thing to consider: Coax- or VGA-cabled extension installations usually require a separate RS-232 or other line for transmitting the control signal for the display—yet another cable to fit into the conduit. CATx cable, however, delivers both the video and control signals through a single transmission medium.

But what if you have long runs of coax installed? An extender like the MediaCento RF that uses low-cost RF cabling to broadcast video to remote HDTV screens may be the answer. Supporting both VGA and Component video source input, the MediaCentro RF encodes and modulates signals for single-channel RF transmission over existing coax wiring. The QAM tuner at the screen enables the reception of the high-definition MediaCentro RF channel, so no set-up box or other piece of hardware is required.

Resources

Buyer’s Guide: Analog Extenders

Simplify the routing of high-resolution video between multiple sources and DVI display devices with new DVI-D Matrix Switches (XPT-DVI4X4, XPT-DVI4X8, XPT-DVI8X4, XPT-DVI8X8). Available in 4 x 4, 4 x 8, 8 x 4, and 8 x 8 matrix port configurations, these DVI single-link switches help you save time because they eliminate having to disconnect and reconnect different DVI video sources for output to LCDs, plasma screens, and projectors.

Any input can be directed to any output, making the switches ideal for point-to-point and multipoint applications. They’re particularly ideal for frequently rerouting source input for output to multiple digital signage screens. Switch ports electronically from a remote RS-232 RS-232 console or from an Ethernet TCP/IP network, or manually using front-panel buttons.

These switches support resolutions up to 1920 x 1200 at 60 Hz, including HDTV resolutions of 720p, 1080i, and 1080p. Deploy them for high-definition video switching in multimedia conference rooms, healthcare imaging applications, and command and control centers with a number of high-resolution monitors.

They can also be used with the newest panels featuring EDID capabilities, with each input port on devices supporting EDID emulation. Plus, they support HDCP feed-through in point-to-point applications.

What’s more, the switches also enable you to set up extended DVI cabling runs to source devices. A built-in equalizer preserves video quality on switch-to-source runs as long as 114.8 feet (35 m), for instance, from the switch to servers or media players backracked in a secure room.

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