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The world of audio and video transmission has incredibly changed since its beginnings when Thomas Edison invented the first phonograph in 1877. The mechanical means of reproducing and playing back the produced analog sine wave signal has immensely evolved since those days, the same as the means used to transmit those signals. What began with strictly sound waves soon expanded to video sinusoidal waves with the invention of the first TV in 1927. With both of that sine-wave technological advancement, the world was introduced to analog technology.
The Analog Signal
When you get an audible 1000 Hertz tone coming from a speaker and traveling through the air, what you hear is the mechanical transformation of an electrical sine wave through the speaker cone via its electromagnet into a vibration of the air molecules at 1000 cycles per second. The electrical sine-wave activating the speaker, in this case, is a voltage alternating from a positive to a negative value and back again at a rate of 1000 times every second (or cycling at 1000 Hz) as shown in the drawing of Figure 1 below. Insert Fig. 1 Here:
Viewed through the screen of a signal generator or an oscilloscope, you would see a horizontal line at the 0-volt line across the center of the screen. All values above the line are positive voltages and the ones below are read as negative, a sine wave appearing on the screen snaking from above the 0-volt mark and then sliding down to the negative side of the 0 mark in a sinusoidal pattern would provide you with the amplitude of the sine wave while the divisions on the timeline would indicate the time duration of a cycle (1 milliseconds for a 1kHz signal).
The starting point of the sine wave going up to its peak then back down to intersect the 0 mark line and down to the negative peak of the sine wave and back up to where it intersects the 0 mark again is 1 full sine wave or 1 cycle. In Figure 1, the positive amplitude of the first half of the cycle can be read at +5 volts while the negative half of the cycle is at -5 volts. Changing the frequency of the sine wave would alter the tone while a change in the voltage level would change its volume level.
All communication systems were once based strictly on analog signals which presented itself with several disadvantages such as noise and distortion often caused by external interference. Such effects were found to be worse over long-distance transmissions where it also suffered increased generation loss leaving it that much more exposed to undesirable signal interference. In most applications, analog signals are usually of lower quality than digital signals, but certain of their advantages still benefit some applications that interface with sound, pressure, light, and temperature.
The Digital Technology
Without deeply involving yourself in the slightly more complex world of digital communication, the following description should provide you with a basic understanding of the general concept of how digital technology works and how to work with it, its various distribution systems and accessories, while handling a digital signal and routing it from a transmitter to several locations throughout your home or at work.
Instead of gradual alternations such as with a sine wave, digital signals are generated as instantaneous transitions in voltages between 0V and either 1.8V, 3.3V, or 5V. These quick and sudden pulses make the digital signal appear as the “square wave” as shown in the drawing of Figure 2 below. Insert Fig. 2 Here:
The instant that the voltage jumps up to 1.8 volts or higher, the vertical spike triggers a “1” bit, and after a pre-determined lapse of a few microseconds when it suddenly drops straight below 1.8 volts, a “0” bit is then triggered. The number of bits processed during 1 second of data processing determines the “bitrate” (the measure of its speed per second), and you should also know that a higher bitrate usually means better quality—eg. 1 megabit per second (Mbps) equals 1 million bits per second.
Not to Confuse Mbps with MBps – 2 very common terms are used in digital communication; Mbps and MBps. Even though they are spelled the same way except for the capital “B” in the second abbreviation, they are 2 very distinct and different systems of measurements—the same way that someone who weighs 185 pounds can interpret his weight as 84 kg instead—the weight is the same, just read differently!
Similarly, MBps (or Megabytes per second) is 8 times greater than Mbps (or Megabits per second). So 1MBps equals 8Mbps, and all the difference is between a Capital or a Lowercase letter “b”. Make sure to avoid mixing the two of them up!
To get back to our digital signals, let’s differentiate standard-definition, HD, and 4K video signals:
1 – A standard-definition digital video, for instance, runs in a range between 5 to 20 Mbps (or 5000 Kbps to 20,000 Kbps).
2a – HD (definition) video quality (of 720p resolution) is still popular even while providing only about half the quality with only half as many pixels as a Full HD video—populating the screen at 1.5Mbps to 6.0Mbps (the difference mainly caused by the rate at which different frames appear on the screen per second or fps).
2b – While the HD 720p signal requires a speed of about 1.5 Gbps, the HD 1080p which is referred to as “Full HD”, will require a speed of 4Gbps to 8Gbps. The faster bitrates will provide a 1920 x 1080p Full HD Video signal with the best HD quality video signal processing over 2 million bits of information every second.
3 – Last but not least, the 4K and 8K videos now readily available have bitrates of between 8Mbps and 14Mbps. So now where the HD 1080p processes 2 million bits of information per second, a 4K or 8K video signal will be up to 14 million bits inside the same time frame!
The Downside of Digital Signals
The downside of digital signals is that as the bitrate increases, the frequency response on the cable that carries it must also be increased as the signal’s wavelength decreases correspondingly. The shorter the wavelength, the more critical the response of the cable will become critical in the degradation of the signal. The characteristic impedance of the cable and its tolerances become more important as the degradation of the digital signal or waveform is directly affected by the impedance match between the cable, the source, and the load.
So the importance of very good quality cables is critical for reliable results. But while any cables will always cause a certain amount of degradation of the digital signals, it should be said that the receiver picking up the signal can somewhat reconstitute the original bitstream and provide a perfect reception by rendering the waveform distortions and degradation, noises, and jitters present in the signal. The threshold where a digital signal can be perfectly rendered, however, and where the signal is lost is extremely small and cable specifications must be duly respected.
But the difference between perfect rendering of a digital signal and total loss of signal can be surprisingly small; one can reach a threshold where the digital signal begins to fall apart, and not long after that threshold, find that there is no signal at all.
HDMI Splitter or HDMI Switch?
As you search online for HDMI splitters, you’ll also get a lot of hits for HDMI switches, which are completely different devices performing a completely different purpose from what you’re trying to achieve. An HDMI switch is required when you lack HDMI input connectors at your TV set to hook up many HDMI devices when your TV set only offers 1 or 2 HDMI connections.
For instance, let’s say that from time to time, you want to stream HDMI signals from different sources such as a cable box or satellite, a Bluray player, a Playstation, a laptop, or a PC on your HDTV without always having the burden of unplugging and switching cables from one device to another. The solution is installing an HDMI switch with enough input ports to accommodate the number of devices that need to be accessed from time to time (4 devices in this case) and one output port to feed the signal into your HDTV. HDMI Splitters, however, serve a different purpose.
How HDMI Splitters Can Work for You.
For the sake of simplifying its description, a basic splitter has only one HDMI input port into which the device you’re streaming from is plugged through an HDMI cable. This device feeding into the splitter can be your cable box, satellite, Bluray player, Playstation, etc.
This same splitter also provides you with 2, 3, 4, 6, or more output ports from which the same signal that is fed into the single HDMI input is reproduced at each one of the splitter’s output ports. With the use of HDMI cables, each output port can then be fed into as many TV receivers and projectors. HDMI splitters are available in both hardwired and wireless transmissions. While the wireless units transmit using WiFi and Bluetooth technologies, the hardwired splitters need to be physically connected through a hardwired setup.
Pros and Cons
The wired setup through HDMI cabling has a few setbacks. Made up of small-gauge (24 and 28 AWG conductors) twisted pairs of wires packed into a slim profile, the cable ends up with a very poor impedance tolerance. The impedance variations throughout HDMI cables create a serious degradation of the signal over longer distances, leaving it to perform best for shorter distances only—50 feet usually being the longest at which they are manufactured is not a common length and is usually hard to find making the 25 feet lengths and much more common.
The input of the splitter goes connected directly to the HDMI output from the cable box (or the Bluray player, the projector, etc.) with a short HDMI cable. One of the HDMI outputs of the splitter is then connected to an HDMI input of your HDTV, while the rest of the multiple outputs can be connected through longer HDMI cables to other TV screens in other different parts of the house. You can then stream a Movie or TV show on any one of the connected screens, but every screen is limited to broadcast exactly what is playing at the source.
Splitters also come as either “passive splitters” or “active splitters”. As opposed to passive splitters, active splitters are powered through a power outlet providing a stronger signal for multiple HDMI outlet ports and making them better at sending signals over longer distances. Passive splitters are only suitable for short drops and are frequently susceptible to choppy and breaking-up signal transmissions.
A clean installation of such setups will require some in-wall wiring and fishing from one room to another and even to a different floor of the house. Fishing cables up into ceilings, under floors, and around doors will often end up in a very long cable, thus increasing the risks of a downgraded or poor signal.
Alternative Setup through Piggybacking with Cat 6.
One effective solution for cable-length limitations for HDMI signal is with the use of a HDMI over Ethernet “extender”—the extender consisting of a “sender” unit at one end (Figure 3a and 3b) and a “receiver” unit (Figure 4a and 4b) at the other end of the setup, both units connected through Cat 5e or Cat 6 cables. The sender’s input HDMI port is also connected to the source box (cable box or game box) using a short HDMI cable and the receiver’s HDMI output to the LCD TV, also with an HDMI cable. Insert Figures 3a & 3b and Figures 4a & 4b together Here:
You can find sender and receiver units available as small boxes that can sit close to the unit it is connected to through HDMI cables and then joined together through network cables as shown in Figure 5. But HDMI extenders are also sold as integrated units within wallplates that can be made inconspicuous with the network cables running inside the walls in the house. Those wall plate extenders are more expensive, however, but only require low-voltage installations. Insert Figure 5 Here:
Although Cat 5e networking cables have been extensively used for Ethernet networking in the past, the Cat 6 is the new favored AV cable for quality setups because of its higher bandwidth performance. The extenders create a direct bridge between the HDMI and the Ethernet cables also providing transmission distances of up to 150 feet (45 meters) when powered from an external source voltage.
Communication between the TV and the Cable Box
Now that you know how to bring an HDMI signal to your room at the opposite end of the house, you’ll most probably want to avoid having to run back to the cable box every time you want to switch channels. You just have to make sure that you get an extender with an IR control. The IR controls come in pairs, of which one is a transmitter (TX) and the other is the receiver (RX). Both units come attached to a certain length of cable and a mono jack plug connector.
With a setup equipped with IR control, you’ll first need to plug the TX unit into the jack plug of the sender unit of the HDMI extender, aiming the little window at the IR window of the signal source box (either cable box or game box). At your LED TV, locate the mono jack plug on the HDMI extender, and plug in the RX unit of the IR control. You can then aim it in the direction where you’ll be sitting and secure it on the frame of your TV with a 2-sided piece of tape. All you have left to do is aim your remote at the IR control to turn on the TV box and choose what you want to watch.
You have now acquire enough information to let you choose the system you want to use and how you intend to lay it out around the house to distribute your signal to every room you want. In the meantime, you can follow some of our links on “The Types of HDMI Cables Explained” or perhaps pinpointing a faulty HDMI cable to get your system up and running.