HDMI Splitter shares video

HDMI Splitter shares video …

The HDMI Splitter does the opposite of what the HDMI “Switcher Box” that I covered in my last blog entry does – the Ying and Yang effect. Also known as a HDMI Distribution Amplifier, the HDMI Splitter allows a user to display the same HD image and listen to the same audio from one HDMI source on multiple targets such as LED/LCD TVs or projectors. This effect is sometimes referred to as “Mirroring”. One place where this is done a lot is in home Theater system. But, even more common is there usage in local electronic stores such as Best Buy. In these stores where they have many TVs on display you will notice that most of them are showing the same images. This is done with the use of the HDMI Splitter.

There is a strong correlation between the increase growth in the number of HDMI Splitters on the market and the popularity of High Definition sources, displays and availability of HDMI devices such as Blue Ray players and video gaming consoles. Over the years, there has also been tremendous improvements with regards to functionality for these devices. They track well with new functionality in the HDMI standard. For example, there are a lot of Splitters that has 3D and 1080P video resolution support. Like any other HDMI device there are limits to the allowable Splitter configurations due to system loss. However, it is not uncommon to have a bunch of HDMI Splitters cascaded together to display HD images on up to 64 devices simultaneously with minimal losses. In general, you can find Splitters available in 2, 4 or 8 port configurations. There is an active (require a separate power supply) and a passive version. The consensus is that the passive one is useless and should be avoided. Splitters have CE, FCC, and UL certifications. In some situations such as a consumer electronic show or even a home theater, long wire routes might be needed. In these cases, as with standard HDMI cabling, it is more cost effective to use Cat5e/Cat6 cables. Consequently, a CAT5e/CAT6 HDMI Splitter is used for these types of hook ups.

Conceptually, when you think splitter, the mind might visualize something like a headphone. While that would be representative, it would be a very simple form of this device. Contrary to your visual, like the HDMI Switch, the Splitter device is relatively complex. Beyond the need to make sure the HDMI signal is not degraded while it is being transmitted and shared, there is also a need to manage and account for all the back and forth communication that takes place between the signal device and the display. The information that is being communicated is called extended display identification data (also known as EDID) as documented in the HDMI specification. In a typical two device communication scenario, EDID is sent from the display to the source device to tell the source device what kind of data to send. By itself, that scenario is challenging enough, now add more than one display in the mix and the complexity is magnified. The original source has to communicate back and forth between the new Splitter source and all the displays that are connected to the splitter. Support for HDCP (High Definition Content Protection) which protects the multimedia content from being pirated and guarantees the content makes it to the display, adds an additional layer that needs to be managed by the splitter as well.

So, what are some of things one should consider before buying a HDMI Splitter?

1. The splitter will be limited by the display device with the lowest resolution. For example, if your source device transmits 1080p HD but one TV display 1080p and the second TV displays 720p, both TVs will only display in 720p even though the source device is capable of transmitting 1080p video.

2. It is recommended that you buy an active Splitter device. The passive ones are cheap and does not work as well. So, save yourself the headache and your money.

3. Try to keep the cable length between your source device and displays shorter than 50 feet. Anything more than that, will require some type of restoration/amplification device.

4. Make sure to only buy a splitter that is HDMI authorized testing center (ATC) certified. This will limit your options. But, should allow you to buy with more confidence.

5. Finally, try to buy from a vendor/manufacture that will allow you to return the device if you are not satisfied.

In the following section “Tech Talk”, I will get a little bit more technical about the HDMI Splitter and conceptually what is inside it.

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Inside the HDMI Splitter, basically, you have what is know as a DEMULTIPLEXER. This component is used in the Electronic Engineering world for expanding a single signal into multiple destinations (it might also be referred to as parallel drivers). I can go deep into the details of Boolean equations, logic diagram and truth tables to explain the digital behavior of a DEMULTIPLEXER but, I will save that for another time. Although, it is really not that complex since the expansion is not conditional. Anyway, instead, I will use a highway analogy to convey the point.

Imagine you have a one (1) lane highway that expands into three (3). This is a magical highway that allows the same car that enters via the single lane to exit and travel down the 3 new expanded lanes. By the nature of how the highway is constructed, the process outlined above is done automatically. So, fundamentally, the DEMULTIPLEXER behaves opposite to the MULTIPLEXER.

Also, some of these devices have repeater circuitry to help restore any signal loss that might have occurred as a result of Demultiplexing the digital signals.

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