Thomas, It all depends on how fast the HDMI signal degrades in the cable. And how much the chipset inside the camera boosts the signal to get it true.
Okee a little lesson in HDMI cables and how it works.
How does HDMI transport the digital video: The video portion of HDMI is carried by 3 separate differential pairs. Each pair transports 1 of 3 uncompressed native digital R,G, B signals from source ( dvd player, set top box) to the sink ( HDTV display). A unique protocol, T.M.D.S.( transmission minimized differential signaling), is used to transport the digital data. Each pixel is represented by 24 bits ( 8 bits each for each of the primary colors). The T.M.D.S. protocol then "calculates" and stuffs 2 extra bits to the video data stream in order to create a digital stream with minimum transitions ( lower EMI, lower interference) and also minimize long strings of '1' and '0' which can cause detection errors.
A fourth differential pair, called the TMDS clock provides the pixel clock for timing the data stream. The maximum TMDS single link pixel clock rate is 165 MHz.
What is the data rate of a single link HDMI connection: The maximum pixel clock rate is 165MHz and each of the 3 TMDS video streams carries 10 bits. Therefore the aggregate data rate is 3 x 10 x 165MHz = 4.95Gbps.
How many pins are included in the HDMI connector: There are 19 individual pins in the HDMI connector. There are 3 pairs of TMDS signals which carry all the digital audio and video signals.
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http://www.octavainc.com/HDMI%20deciphered.htmWell So the HDMI signal is Digital. 0 and 1. But a lot of them running together and in high speeds (up to 5Gbps)
That means that a lot of info is going trough your cable.. Remember from the early days if you had a very thin composite cable or had some power cable's running close to it.. You could see that in your analog picture? Well that is distortion.. Distortion and loss of quality has to do with a few factors..
-1 Cable quality Cables with very low impendence have better success. Also more copper means better signal. (more copper is often more expensive cable)
-2 Cable shield It all depends on how well the shield is that is made around the cable. Some manufactures cut cost here by just putting a few strands of aluminum wire or foil around the cable. The idea behind the shield is to minimize the influence from outside (magnetic distortion caused by
other wiring)
-3 Cable Length The longer the cable, the more distortion and cable resistance there is.
-4 Cable driver inside camera This is a big deal.!! Camera's like GoPro, handycams, consumer products do have HDMI. The problem is this HDMI output was never meant for long cable runs. These products have been designed with the consumer in mind. Dad who filmed his son on his first bicycle run. A party or whatever.. They plug the camera into there HDMI TV in the living room with a
short cable and everything works just fine!! Now a new world opened up with HDMI enabled video mixers. So people can use "cheap" camcorders as input device to your mixer and do your thing with it. But HDMI was never designed for cables longer then 10 meters.. HDMI was designed for in the living room. Set-top box to TV. Cable length 1.80 meters... Those consumer camera's were never designed for long cables.. They were designed to put your camera next to the tv to watch the footage back.
-5 Receiver Error handling Because with every meter of HDMI cable the signal degrades and ones and zero's starting to get lost. There is an error handling inside HDMI. It tries to give you the best picture as long as possible.. But if too much of the packets get lost or "unreadable" the signal will go black, stutter, give errors, or digital noise.. (Depending on the chipset behind it)
-6 Bandwith Also bandwith of the signal has some to do with it. As 1080P /1080I needs a lot more data to transmit as 720P or other resolutions.. And higher speeds means more loss of bits..
Noise distortion pattern on HDMIReading an Eye Diagram
The eye diagram is a valuable tool for analyzing the quality of a digital signal. It consists of the signal’s oscilloscope display, repetitively sampled to present an “at-a-glance” depiction of its behavior. It is particularly useful in evaluating how well an interconnect maintains signal integrity over distance.
As with any interconnect, signal attenuation and interference in an HDMI cable will increase over distance, until at a certain length the signal-to-noise ratio becomes unacceptable. As the signal degrades, the “eye” begins to collapse. Once the eye collapses into the mask (the area that describes the minimally acceptable opening for a signal to be recovered by the receiver of the signal – the HDTV or projector), then the signal is not strong enough to pass HDMI compliance.
eye diagram
The eye diagram on the left shows a robust, undistorted digital signal that does not encroach in the mask (gray area in the center). Notice the large area of undisturbed black space in the center of each sample, indicating that the signal is strong and noise is low. Note how signal noise and attenuation has closed down the “eye” and the signal has started to encroach on the mask.
Maximum length can vary widely based on the cable’s materials (i.e., copper or fiber), the quality of its construction, the quality of the HDMI receiver chip, and the presence or absence of active electronics in the transmission path. As well, a cable ability to successfully pass an HDMI signal depends on its bandwidth capability
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http://www.hdmi.org/installers/eyediagram.aspxWhat does an extender do? Well this difference what is used inside the extender...
Some extenders only have drivers inside.. What it does, is gain the input signal
AND noise and output it again..
Other extenders do have advanced re-clocking and cable equalization inside. They decode the signal. Clean it up. (get rid of the noise) and output a clean signal again. (most of the times these extenders are the expensive ones as there is a lot more inside then just a signal booster.)
End conclusion: HDMI is designed for SHORT distances. And the performance of a HDMI connection has a lot of variables why it does or does not work.. Then why do we use it in the first place??
Because we can! And it is cheap.. Because 95% of the devices worldwide with a HDMI connection is designed and build for consumer purpose. For use in your living room or with your computer..
And yes SDI is also relies on good cables, good shielding from distortion, error handling and re-clocking. But it is an industry standard. Designed to work with long runs of cable. Designed to handle high quality video. Designed with a sturdy connector..
SDI is not a cheap solution compared to HDMI. But it is designed for the broadcast industry. And is proven to work!