In recent years, HDMI has gradually replaced DVI or VGA and become the major audio/video transmission interface for all kinds of computers, smart TVs, over-the-top devices and blu-ray players. In response to this market trend which there is a wide variety of HDMI cables with significant difference in price and visual perception, how to make the best choice for all your purchasing HDMI cables is the important lesson. To help the consumers or buyers understand the quality of HDMI cables in the market, Allion (Allion Labs, Inc.) particularly analyzes the quality and performance of various types of HDMI cables.
First, we focus on the Japan marketplace and select 20 different branding models of HDMI cables with HDMI certification. The range of our selection includes all global and local brands, and the price is ranged from 450 JPY to 15,000 JPY. Through a series of cable and connector tests that implement the professional validation and competitive analysis, we expect to further perceive the current HDMI’s quality and to analyze the correlation between the price and quality. Also, Allion’s competitive analysis test report can be used as the useful reference with hi-tech and in-depth performance analytics to all the consumers and buyers.
For the test coverage, we not only refer to the HDMI specifications, but also further extend 5 test items based on our abundant HDMI testing experiences at the high-precision Allion cable assemblies and connector testing center. The test purpose is not just a basic check of HDMI test, but to characterize the existing HDMI cables must have both quality and performance according to the real user scenarios which might happen in daily life. With the test results of 20 HDMI cables; finally, we made the completive analysis in-between. The detailed test items include:
1. Eye Diagram Test
2. Attenuation/Insertion Loss Test
3. EMI Test
4. Insertion & Withdrawal Force Test
5. Durability Test
Due to the different technical principles and test conditions of these 5 test items, we would make a brief introduction for each theoretical basis, and analyze the test results. Particularly, we will set up the judging criteria for each test item to comply with the requirements for the competitive analysis of 20 HDMI cables.
1. Eye Diagram Test
Eye diagram, in which a digital data signal from a receiver is repetitively sampled and applied to the vertical input while the data rate is used to trigger the horizontal sweep, is a time series analysis tool for evaluating the performance of HDMI cables. As shown in Table II, the pattern looks like a series of eyes between a pair of rails. It is an experimental tool for the evaluation of the combined effects of channel noise and inter-symbol interference on the performance of a baseband pulse-transmission system. A completed open eye pattern corresponds to a good signal quality. When the eye diagram of a cable touches the border and narrowed down the black space, it indicates the cable’s performance is not stable or is worse, which may cause noise, mosaics, random screen flash, unexpected pause or event blank screen on the screen display.
Based on the HDMI specifications to test the eye diagram of 20 HDMI cables, we would check the high speed data transmit quality and make sure the cable can transmit video and audio data with troubles. The test result is shown in Table III. Most of HDMI cables can pass the eye diagram test with high criteria, but the rest of them are unstable. Therefore, we can say that it is still a critical issue for the quality of HDMI cables in the market. The root cause of unstable performance may be due to its low copper content, resulting in the high impedance. If the design of anti-interference is poor; besides, different cable signals will interfere with each other and cause the loss of frequency accuracy.
2. Attenuation /Insertion Loss Test
Attenuation is also referred to as Insertion Loss, which means the loss of signal strength at the far end of a line compared to the signal that was introduced into the line. This loss is due to the electrical impedance, quality or length of the cable & connectors. Compared with short-length cable, long-length cable usually has more signal loss, resulting in failed connection or instability, so the screen flash or audio distortion would be happened easily during video/audio transmission (In this case, we use 2-meter-long cables for testing). In addition, the poor impedance and match between cable and connector would also decrease the signal amplitude. Measuring the insertion loss of a cable can help us realize how well the cable design is. Take Table IV as an example, we can see that the limit line value (the red line) represents the normal signal amplitude according to the HDMI specifications. When the amplitude is lower than the limit line value, we could determine that it has poor cable quality.
Referring to HDMI specifications for the basic requirement of limit line value, we measure the difference of test line and limit line @ 825MHz, 2475MHz, 4125MHz and 5100MHz frequency. Summary of all value (Result value = Limited line value -test line value) for all 4 lanes and compare the result value. As shown in Table V, the higher value means lower attenuation, and the top 20% of the value of HDMI cables includes Vodka, Panasonic, Hypertools and Victor.JVC.
3. EMI Test
Electromagnetic Interference (EMI) is the disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. In addition to harming human being’s safety and body, the disturbance may also interrupt, obstruct, or otherwise degrade or limit the effective performance of other wireless devices such as cell phone or frequency modulation. If the isolated coverage of the cable is not enough, it is easy to have the electromagnetic leakage. Thus, the purpose of EMI test not only can protect the consumer’s safety, but also ensures the cable’s quality and performance without any interference. Especially, HDMI Licensing, LLC defines a base limit line for EMI test result. Beyond HDMI LLC’s requirement, we suggest to tighten the EMI test requirement for stricter criteria. If the test result exceeds the red limit line, the EMI test is failed. As shown in Table VI, the normal test result should be lower than the red limit line to comply with the requirement of EMI specifications.
One interesting discovery is that all 20 cables failed to meet the EMI requirement. Thus, we compare both horizontal and vertical emission result value of each tested cable with EMI limit line for in-between quality analysis because the EMI test results are still different from cable to cable. If the amplitude exceeds the red limit line less, it represents that its EMI issue is not very serious. If the amplitude exceeds the limit line much more; conversely, the further EMI validation and fine-tune are relatively urgent and crucial. The test result is shown in Table VII, and we can still find that most cables’ EMI test results are poor. This result represents that EMI issues in the whole industry are very critical; beside, EMI test should be relied on the specialized lab like Allion to involve in testing, validating and consulting and to find out the most efficient ways to reduce unstable EMI issues.
4. Insertion & Withdrawal Force Test
Insertion and withdrawal force test is very important for a cable product because of its close relationship between the consumers and their user scenarios, including user’s touch, feeling and power which would generate the physical forces for connection and separation of two paired parts. The test purpose is to ensure that the external forces of insertion and withdrawal won’t cause interruption for the connected cable and connector. When insertion or withdrawal force is too large, it will increase friction and raise the possibility of damaging the HDMI receptacle on the device. Conversely, the contact of connected devices is too poor to produce display interference and noise if insertion or withdrawal force is too weak. Therefore, we would like to simulate the insertion and withdrawal forces through the equipment to understand whether the design of connector’s mechanical structure can deal with such tests without any broken, inconvenience and functional failure.
For the judging criteria, we will define the intermediate force is the best for the cable and connector. Referring to HDMI specification for the insertion and withdrawal forces requirement, the insertion force is up to criteria within 44.1N, so we take the middle value 22.05N (+/- 10%) as the best force. On the other hand, the withdrawal force range of HDMI specification is defined from 9.8N (the minimum) to 39.2N (the max), so we take the middle value 24.5N (+/- 10%) as the best force. According to Table VIII, we can find that the insertion and withdrawal force of Supra’s and Sanwa’s cables are intermediate and stable, that will have not been influenced their functionalities for a long time.
5. Durability Test
Durability test is another consumer-related test to ensure the cable could be multi-paired with different devices and still function properly, it’s also known as the cable’s life or duration. This test can evaluate the damage caused by normal wear and tear of the cable after a period of continuous use, confirming the cable and connectors can meet the functional requirements of its declaration. The test is to apply multiple insertion and withdrawal forces on the tested cable, and see if it can avoid the damage to indirectly affect the signal transmission. According to HDMI specifications, the minimum requirement of durability test is 10,000 cycles. In this test case, we will set the durability test up to 15,000 cycles and measure the insertion and withdrawal forces again after the previous 15,000 cycle. If the HDMI cable durability can support 15,000 cycles with the stable and intermediate force, it is able to indicate the HDMI cable has higher quality and the test would not harm its internal components or structures. The test result is shown in Table IX. Most cables have their basic durability and meet the requirement of HDMI specifications; especially, Amazon, PCI, MotionTech and Pioneer have relatively outstanding performance.
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According to the test results overview in Table X, we can find out an unusual phenomenon. Although it is generally considered the high-price device would adopt better component to achieve the best quality and performance; but the assumption is not true, many low-price cables followed HDMI specifications to production are able to achieve good level in performance. In other words, the consumers or buyers need to shop around or seek specialized lab’s competitive analysis test report to get the best one while purchasing the related cable and connector.
In the competitive analysis test report, we find out that the 20 cables selected from Japan market have their significant differences in performance. The product design and validation methods should be more integrated, and should be conducted by specialized lab’s validation, consultant and fine-tuning to ensure the best quality and the worthy of C/P value. As a global leading engineering validation & consulting company, Allion announced the grand opening of its newly-established cable assemblies and connector testing center approved by USB-IF, which is able to provide the complete compliance testing service for cable assemblies and connectors adopting USB 2.0 and USB 3.0 specification. In addition, we are also the authorized test laboratory for HDMI cable products. This new facility is capable of performing all these major validation categories such as high-frequency signal, mechanical characteristic, electrical characteristic and environmental change on mainstream technologies including HDMI (connector), DisplayPort, MHL, SATA and more. With the establishment of our all-embracing service scope, we hope to see many well-development products with quality, performance and cost/price into the market, so that the consumers can be able to obtain the maximum benefits. In the future, we will continue to make further competitive analysis for all kind of mainstream technological products for all your reference.
(Note: Some test data presented herein is related to Allion’s self-developed criteria and won’t be disclosed in details. For further test proposal or report content as reference, please contact Allion.)