The Big Question: Are all HDMI® cables the same …?
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The only way this question can be answered satisfactorily is to fully understand the issues surrounding the technology and the manufacture of HDMI cables.
1) The HDMI® cable - Manufacturing
In general, the majority of HDMI cables are manufactured to very similar specifications and therefore offer the same basic performance. These cables are usually sourced from factories in Asia. So what you get is a generic cable in a variety of different guises carrying different branding.
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2) The HDMI® cable - Bandwagon
HDMI® (High-Definition Multimedia Interface) was designed in 2002 and production of consumer HDMI products started in late 2003. In the last few years there has been an explosion in the number of cable brands offering HDMI cables at premium prices. These cables are often accompanied by ambiguous performance claims and technological buzzwords. Many consumers have bought these products and have been left disappointed. This has sparked a hot debate as to whether Premium HDMI cables are worth the money they command. This issue has been further complicated by the advocates of ideology such as "Digital is 1’s and 0’s and therefore the system will work perfectly or not work at all".
3) The Digital Myths and Misconceptions
‘Contrary to popular belief, transmission of Digital Audio and Video is by no means perfect. The very fact that extensive use of error correction is employed; is a testimony in its self'.
During transmission, digital signal suffers from data corruption/loss due to a variety of reasons, these include bandwidth limitations, jitter, signal attenuation, crosstalk, external EMI (Electro Magnetic Interference) etc. To counteract these problems digital processing systems employ error correction and/or error reduction techniques.
‘Real world’ digital signal
The common misconception is that since a digital signal comprises of 1’s and 0’s, the device will therefore work perfectly or not work at all. An ideal theoretical square wave has instantaneous transitions between the High (logic 1) and Low (logic 0) levels. In practice, this is never achieved because of physical limitations of the system.
‘It is scientifically impossible to transmit an undistorted ideal square wave through a transmission channel/medium.’
The limitations of digital signal processors and cables create timing errors known as jitter, which remove portions of the signal and replace them with noise and distortion. Cables tend to round off the square waveforms of the signal, making them less clear to the processor, thus increasing jitter. This rounding effect varies greatly among cables and truly superior HDMI cables can make great improvements in imaging and sound quality.
Another important point to remember is that the digital signal degrades as the length of the HDMI cable increases due to bandwidth limitations.
What is Jitter?
Jitter is the deviation in or displacement of some aspect of the pulses in a high-frequency digital signal. In other words, Jitter is when a signal varies in time or amplitude outside of a mathematical ideal. Jitter is the dominant cause of signal error in a digital system.
The images below (screen shots courtesy of Techtronic) show a relatively clean digital signal and a signal with severe Jitter.
The HDMI technology explained: READ MORE
5) Evaluation of HDMI® cables - Audio and Video
It is relatively easy to evaluate the sound quality of a HDMI® cable, whilst the assessment of video can be made difficult due to the ‘Processing Engine’ present in a display device which manipulates the data to try and compensate for errors and missing data in the video stream. The result is often ‘acceptable’ performance but still far from the best HD experience that the screen or projector is capable of.
The net effect of all this is that whilst the ‘Processing Engine’ may allow a basic performance from a poor HDMI cable, the extra processing can also negate the benefits from a good HDMI cable!
What’s more, the design and quality of a ‘Processing Engine’ is manufacturer specific and even varies between model ranges, this adds further complications to the evaluation process.
Here are some pointers to allow you to properly assess a HDMI cable:
*A Blu-ray disc can be mastered at difference bit rates. The general rule is; the higher the bit rate the better the picture and audio quality. In addition, the bit rate varies from movie to movie and also changes between scenes, a complex fast scene will use higher bit rate.
An objective evaluation of HDMI cables is a very complex affair and requires highly developed technical skill and experience. In short, only purchase a premium HDMI cable from a manufacturer that offers comprehensive information and full technical specification about their product.
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Why use WireWorld HDMI® cables?
Digital video and audio signals are continuous streams of data, which are quite fragile, since the digital processor must remain perfectly locked onto the timing of the signal to avoid data losses.
WireWorld HDMI cables utilize unique designs specifically developed to minimize jitter by providing sharper, cleaner leading edges on the digital waveform. At each price level, they provide the lowest jitter and the widest bandwidth, producing distinct improvements in clarity, image focus, smoothness and dynamic contrast.
WireWorld - History of Innovation
In January 2004, WireWorld introduced the Starlight® 5, the world's first upgrade HDMI cable. WireWorld was able to achieve this milestone due to its unique position of being an innovative technology company with foresight. READ MORE
WireWorld Series 7 HDMI cables: CLICK HERE
This article is intended to provide a basic overview of the HDMI technology, digital transmission and other associates issues specific to Audio Video industry. Due to the nature of this article every aspect of digital data transmission has not been included.
“HDMI, the HDMI Logo, and High-Definition Multimedia Interface are trademarks or registered trademarks of HDMI Licensing, LLC in the United States and other countries."