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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HDMI Switcher Box Shares HDTV

HDMI Switcher Box shares HDTV

The HDMI Switcher box is a good solution for creating additional HDMI input ports. For older HDTVs or other displays with one HDMI port, a HDMI Switcher box can be used to share a single port. It is like a selector switch from the old days that allowed the sharing of a single computer monitor with multiple computers. Obviously, there is a lot more complexity to a HDMI switch box. For example, almost all of them have remote control that allows the user to control them in the same way a TV is controlled.

So, what would be a typical scenario where a HDMI Switcher Box is used. Lets say you have a HD video camera, PSP video game and a Blue Ray player. Your HDTV only has one HDMI port. Instead of spending thousands of dollars on a newer HDTV with many more HDMI ports, you can simply purchase a 3-to-1 HDMI switch box for much less and would work perfectly for this situation. The hook up is simple, you would need to purchase a HDMI Cable for each source (i.e., the PSP game, Blue Ray Player, etc …) that connects to one of the HDMI inputs on the Switcher box and a HDMI Cable to connect the output of the switch box to the HDMI input port on the HDTV.

Here is an example of a pretty good HDMI switcher box from Amazon:

Like HDMI itself, most of the HDMI switch boxes on the market are kind of smart – meaning they have some level of automation. It will detect which source is the last one to be powered on and give that one priority to the HDTV display. There is usually some type of LED indicator to show which source is selected at any one time. Also, the user has the ability to override the automatic behavior with the remote control. They can manually select which source to show on the HDTV.

As a general matter, most HDMI Switcher boxes have similar features and construction. There are too many manufacturers to mention and I am not in the practice of pushing one brand over the next. But, there are certainly functions and features you can compare to make an informed buying decision. In terms of HDMI Cable versions, there is pretty good compatibility between the latest standard and high-speed HDMI Cables and most of the switches on the market. The thing to be mindful of is that there are a few HDMI features that are Not supported yet: the Ethernet channel and Audio Return. Some of the lower end devices do not come with IR receivers or remote. That might be a reason to stay away from those types. Another thing to look out for is whether the HDMI switch box comes with its own power supply are whether it is powered from the HDMI Cable. My suggestion is to stay away from devices that don’t have an independent power source. They tend to not work as well.

Here are a couple of issues that you might run into and how to debug them:

1) There is no picture present:

  • Check that all connectors are connected well.
  • Check that the HDMI cable is not damaged.
  • Check that the power of the HDMI Switcher is on.
  • If there is a reset button try to reset the device.

2) HDTV could not show in 1080p resolution:

  • Make sure the content, source devices (Blue Ray Player, etc …) fully supports 1080p.
  • Make sure your HDMI cables are capable of transmitting 1080P video signal.

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

 

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Inside the HDMI switch box, basically, you have what is know as a MULTIPLEXER. This component is used in the Electronic Engineering world for selecting between different signal sources. I can go deep into the details of Boolean equations, logic diagram and truth tables to explain the digital behavior of a MULTIPLEXER but, I will save that for another time. Instead, I will use a highway analogy to convey the point.

Imagine you have a three (3) lane highway that merges into one (1). The merging process is controlled by traffic lights. Therefore, at the point of merger, the incoming lane that has a green light is allowed to merge into the single exiting lane. If one incoming lane has the green light then the other two incoming lanes will see a RED light. The lights can be controlled automatically by sensors in the lanes or they can be controlled manually by a traffic cop. That is the essence of how a Multiplexer and the HDMI Switcher box works.

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

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