Hello, friends.

From this article, you will get the basic useful information about HDMI what it is, where and why it is used, what characteristics it has and what types it is. Why should you know this?

Now most of the multimedia equipment is connected through this interface, and it is possible that you also use it, perhaps without knowing it yourself. Also, after reading the article, you will be able to choose the right cables for connecting devices.

Introducing HDMI

This abbreviation means the phrase “ High definition Multimedia Interface ", which exactly translates as a multimedia interface high definition... It is used to send high-resolution digital video signals. As well as multi-channel copy-protected digital audio.

In simple terms, it is a channel for transmitting digital image and sound from one high definition device to another. This process is carried out using the appropriate cables. They can connect video cards and monitors, home theaters / game consoles and modern TVs, tablets / phones and computers, etc.

By the way, the connectors for the above gadgets differ in form factor (size): large equipment is usually connected, mini-HDMI - smartphones and some models of tablets, micro-HDMI - laptops, tablet PCs, etc. Each port contains approximately 19 pins.

Specifications

Consider the main features that distinguish this interface among the others:

• Data transfer rates range from 4.9 to 48 (new in 2017) Gbps.
• Capable of transmitting high definition, incompressible video, 3D TV signals, and 8 channels of digital audio.
• Displays a high-quality picture on screens with an aspect ratio of 16: 9, a resolution of 1920 × 1080 pixels or higher (up to 4K). So you can compare: TVs outdated by today's standards had the corresponding parameters of 4: 3 and 704 × 480 pixels.
• Hertz of supported resolutions in modern interfaces varies from 50/60 to 100 / 120Hz
• Supports Ethernet connection up to 100 Mbps.

About cables

Sectional cable includes:

• Outer cover;
• Wire braid for screening with the addition of a bare copper strand for soldering;
• Another screening layer of aluminum foil;
• Polypropylene sheath;
• Twisted pairs of the 5th category with a resistance of 100 Ohm, which are intended for transmitting information;
• Screening of the specified twisted pairs from external insulation and wires for soldering;
• Another twisted pair without screening, sharpened for SDA SCL signals;
• Additional conductors for control signals and power supply.

Length

The standard cable length is 10 meters. But you can lengthen it to the required size using external or built-in amplifiers-repeaters. They are not installed at the signal output, but closer to the receiver.

To avoid interference, some manufacturers equip their products with ferrite beads on one side and the other.

And keep in mind that the longer the cable, the more massive the conductor should be.

Types

There are 5 types of HDMI cables:

• Standard. Look for a budget option? Standart is for you. Used to connect not too demanding household appliances(DVD-player, satellite receiver, plasma and LCD panels, etc.).

It doesn't have super-quality work. Judge for yourself: it transmits a picture with a resolution of 1080i or 720p., The maximum bandwidth is 4.9 Gbps, the bandwidth (video streaming) is 165 megapixels, and the color depth is 24 bits.

• High speed. Do you own a Blu-ray / HDD player, widescreen or other advanced technology, or are you just a connoisseur of high-quality images? How to distinguish from the usual? Pay attention to the inscription "High Speed" on the plug, or on the cable itself.

Interacts with any format, including Deep Color and 3D. Features support for Audio Return Channel (Audio Return Channel) technology, which allows you to transfer audio without another cable. Note that receiving devices must also support it. These are usually labeled ARC.

It has the following parameters: it works with a resolution of 1080i and higher, the same number of bandwidths (in megapixels), a speed of 10.2 Gbps and a color depth of 48 bits.

• Standard with Ethernet. The same as in the first paragraph, only in addition there is an option to connect to the Internet.
• High speed Ethernet. I think it's understandable without explanation.

• Automotive version (Standard Automotive). A separate type of cable used to connect devices to the car media system.

Difference between HDMI and DVI

The predecessor to HDMI was the interface. Most likely, you also dealt with it when you connected the monitor to your first computer. But only video was transmitted through this channel. As you yourself can draw a conclusion. The main improvement in the HDMI interface is that it is capable of transmitting audio in addition.

But this is not the only difference from DVI. The modern port is also smaller. It also transmits only digital signals, unlike its outdated counterpart, which can work with analog data. Even the bandwidth of HDMI is higher than that of DVI (the latter operate at 3.4 Gbps).

That's all.

I look forward to seeing you more often as a guest of my blog.

In our daily "cable" work, there are requests for the repair of hdmi cables, thanks to which we have accumulated experience in situations in which the repair of hdmi cables is necessary. And regarding the questions of our customers who are just choosing an hdmi cable, we have accumulated a list of common questions that we are ready to answer to those people who just now have a need to purchase an HDMI cable.

In our practice, there was a situation when we were at the same object 2 times (while we were the second repairmen) - first we cut the cable from the receiver side, shortened it as much as possible and changed the connector, and the second time we shortened it as much as possible and replaced the connector already from side of the TV. There was only one problem - desynchronization of sound and image, sound dips. But expensive repair options were the only way out, because gross mistakes were made at the stage of cable laying:

• the cable was an ordinary Chinese cable from the market.
• the cable was embedded in the wall, and not laid in the cable duct.

As a result of our repair, the problems with sound were gone, but that “snow” and the impossibility of turning on a high resolution, inherent in a bad cable, remained.

HDMI cables are serious digital cables that are unforgiving in design and manufacture. We have repeatedly seen Chinese cables "in a cut" and we can say that they are cheaper than high-quality cables for obvious reasons - in such cables they save on everything - starting from the material, continuing with the number (!) Of conductors in the cable (yes, the Chinese manage to throw away the "extra" wires) and their cross-section and ending with the fragmentary shielding of the cable and the quality of the external insulation of the cable. See for yourself - the total thickness of the cables (on the left - a Supra HD5 hdmi cable, on the right - "ordinary Chinese cable"):

And here you can clearly see what the cables are made of: the Swedish cable is made of thick mono-core conductors in multilayer individual screens, and the representative of the Chinese team is made of thin veins in poor shielding and ... paper filler :):

But in the store you do not have the opportunity to cut the cable and look inside. And even if it were possible, how do you know if the cross section is enough to transmit a 4K signal?

Why won't my old HDMI cable work with my new TV?

It will do because the new HDMI standards are backward compatible. But it will be possible to use the "old" cable only with "old" content. If you don't want to use the capabilities of your new TV, an old cable will do the trick. But it was designed for the old standard, and most importantly - for the "old" bandwidth - information flow in new formats (4K resolution, multichannel sound) has grown significantly, for which the old cables were not designed. In addition, for some new functions (audio return channel), additional pairs in the cable are used, which are simply not physically present in the old ones.

But if we are used to answering these common questions, then for deeper questions we need answers from development engineers. Therefore, we within the framework and asked highly specialized questions to Swedish engineers who are engaged in digital cables Supra Cables, including HDMI. The answers give a deeper understanding of the processes taking place with the signal inside the hdmi cable, in particular, and in general, they answer the question "Why should I pay more for a cable from another manufacturer?"

How does the speed (signal bandwidth) of HDMI depend on the cross-section of the conductors in pairs?

Bandwidth is related to area cross section only indirectly - there is no direct relationship between the signal loss in the cable and the cross-section. The most harmful characteristic is the capacitance in the cable. Capacitance is also a complex quantity - it also depends on the size of the conductor and the distance between the conductive pairs and the screen and the insulating properties. At HDMI frequencies, the skin effect is more pronounced, i.e. the signal travels near the surface of the conductor. The conductor insulation acts like a sponge and charges when the signal rises and discharges while the signal falls. The figure below shows a schematic waveform with the indicated capacitive effect with an initial rectangular input waveform.

As you can see, as a result of the appearance of the capacitance, the square wave at the output is deformed and will not grow from 0 to 1 instantly, but will grow with a delay. But since the transmission bandwidth is wide, the effect on the useful signal is different at different frequencies. In the figure below, you can see how the cable affects the digital signal at different frequencies.

With an increase in the cross-section, the resistance R will be lower, and the capacitance C will charge somewhat faster. But still, C will continue to deform the square wave at a higher frequency. Time lag is what we call jitter. The problem the receiver gets is how to interpret correctly when the signal goes from 0 to 1 and vice versa. The overall output level will decrease with distance and the pivot point from 0 to 1 becomes more difficult to determine. Thus, the characteristic impedance of the cable must be a very carefully balanced RC filter. This is why, for example, S / PDIF (75 ohm), USB (90 ohm), and HDMI (100 ohm) cables have their own standard impedance that must be maintained to ensure digital signal integrity. See Figure 3 below) for the balancing effect of the impedance of the RC characteristic.

What is the difference between stranded and solid conductors in an HDMI cable?

Solid conductors create a stiffer cable that is subject to more material stress during handling and installation. But mono conductors allow us to have much better control over the size (diameter) of the conductor and therefore very even distribution of the insulation during the process of making conductors. It is thanks to this that we obtain precision indicators of both conductor resistance and insulation resistance. As a result, our HDMI cable outperforms many other brands, including even active HDMI cables! Yes, our cable is more rigid, but we prioritize performance over flexibility. It doesn't really matter how flexible the cable is if the end result is that the client doesn't see anything on the screen. Our experience (and our HDMI sales) shows that our customers also opt for excellent performance and are able to cope with the slight disadvantage of a harder-than-normal cable.

Why does the signal get weaker with increasing cable length? Distance-dependent damping

Any signal transmission destroys the signal, unless the conductor is theoretically cooled to 0 degrees Kelvin (- 273.16 Celsius) and transmitted through a vacuum - which is obviously not achievable in a domestic environment. The longer the cable runs, the more factors there are for signal degradation. All electrical signals contain small energy packets, and as long as the conductor cannot be cooled in a vacuum, there will be a loss of energy along the entire signal path. Finally, energy is lost critically, and the signal loses voltage to a point where the receiver can no longer recognize the signal or distinguish 0 from 1.

How does the maximum image frequency (at 4K resolution) depend on the length? Why does the frequency decrease with length?

As we already understood - the higher the frequency, the higher the losses associated with capacity. If you please, our HDMI cable (Supra Cables) cannot overcome basic physics, even though it offers superior signal integrity compared to many other branded cables. Figure 2 shows that when the frequency finally reaches very high levels (for example, at 4K Ultra), the inevitable capacitance and resistance beyond the critical length cannot be fed to the output stages in the transmitter, and the loss (attenuation) in the cable becomes large. This, by the way, is one of the reasons why some devices can transmit a signal even on cables that are poor in terms of performance. More stable output stages provide best performance compared to those that are not so well designed and where the cable loading (R and C) will degrade signal integrity faster. This is another important point - the ability to transfer content at high bandwidth is not exclusively a matter of HDMI cable! It is the harmony in the bundle of the transmitting device and the HDMI cable that is important. What actually happens at the other end of the cable above the cutoff is that the voltage drop at the end of the cable will be so significant and the phase shift will distort the square waveform (and therefore add jitter) to such an extent that the receiver cannot tell the difference between 1 and 0 and correct operation will be impossible. Do not forget that packets of electrical energy at the highest frequencies are converted into heat and generate capacitive stray currents, which, through the conductor insulation, affect the quality of signal transmission in adjacent pairs. This has been a problem for both PCs and supercomputers for a long time, prompting laboratory experiments with computers and quantum physics, where the use of quantum mechanics allowed latency-free transmissions. So far, this has been achieved only in experimental laboratories, but the physical boundaries of electricity today limit the growth of speeds and we will have to look for new solutions for high-speed data transmission in the next generations of HDMI.

Once, at an object with expensive repairs, we observed how, for the sake of design, when the brickwork was played up, the hdmi cable was laid between the bricks and was bent an unimaginable number of times. Unfortunately, we were not allowed to take a photo, and the electricians looked in bewilderment at the horror in our eyes - why shouldn't we do that ?? Therefore, we answer one more question about bending hdmi cables - why can't HDMI cables bend straight (or even worse - at an acute angle)

“When bending the cable, you must strive to maintain a minimum bend radius. With a large bend in a small arc, the insulation separating the conductors is compressed, the conductors are at new less favorable mutual distances, causing strong capacitance and thereby changing the balance of the RC characteristics of the cable. Over time, the conductors themselves suffer from physical stress, stretching the copper crystals and thereby changing the impedance of the conductor. Sharp bends should be avoided, allowing a generous curve rather than an acute angle. "

To summarize - hdmi cable requires increased care when choosing a routing route, does not tolerate negligence when passing corners and planes and will provide maximum performance only with the correct design of the cable itself, i.e. after a responsible choice. You bought an expensive TV / projector - why do you want to connect it with a cheap cable?

Seeming Abundance.
(The first part of the trilogy "HDMI 1.4")

With the release of the HDMI 1.4 specification, there were five types of HDMI cables at once. The purpose of this article is to help make sense of this abundance. I'll make a reservation right away that the material is intended for the reader who already has an idea of ​​what HDMI is. Therefore, I will focus on the most important features of its design and use, as well as a comparison with an HDMI 1.3 cable. By and large, there is no fundamental difference in the designs of the "old" 1.3 cable and the "new" 1.4 cable, and the differences that exist mainly relate to the cable with Ethernet, and most of the differences refer not to the cable as such, but to the new capabilities of the format itself , and is implemented in devices: signal sources and receivers. Moreover, some of these opportunities exist so far only on paper. The new classification should theoretically make it easier for the user to select the right cable, dividing cable products by data transfer rate and functionality.

(fig. 1)

In the near future, all manufacturers will switch to a standard designation system for all five types of manufactured products. Each product will be labeled according to its type. Standardized markings can be of several types: color, black and white, rectangular, round. The most important thing is that the presence of such a marking already determines that the cable belongs to the HDMI 1.4 category. In this case, the very designation "HDMI 1.4" may be absent!

1. Standard HDMI cable

A standard HDMI cable is designed to work with most common home components ( DVD players, satellite TV receivers, plasma and liquid crystal panels, etc.) and is designed to transmit image signals with a resolution of up to 1080i or 720p. In fact, this is an old friend, HDMI 1.3 "category 1", it is characterized by a reduced (in comparison with the cable "category 2") total bandwidth (by 3 channels - RGB) to 2.25 Gb / s and clock frequency up to 74 , 25 MHz.

ATTENTION! In some cases, at lengths of more than 2 - 3 meters, you can forget about the correct transmission of 1080p and higher signals when using such a cable.

The situation will depend on the quality of a particular cable specimen, but when using this type, no one promised a high data transfer rate. Visually, degradation of the image signal can be observed even at shorter lengths. This type of cable is primarily intended for connecting conventional signal sources and receivers.

2.Standard HDMI cable with Ethernet

This type of cable has the same capabilities as the standard HDMI cable discussed above (1080i or 720p), but is additionally equipped with a dedicated Ethernet HDMI data link and is designed to combine various components on a network at speeds up to 100 Mbps and link these components with the internet. Functionality HDMI Ethernet cables are available if both linked devices support HDMI Ethernet. It should be noted that this cable supports the Audio Return Channel (ARC). A typical diagram of Ethernet connections in an audio-video system is shown in the following figures (Fig. 2,3). This issue is discussed in more detail in the second part of the article.

Ethernet data link capabilities

Typical Component Connection without Ethernet HDMI (Figure 2)

Typical Component Connection with Ethernet HDMI (Figure 3)

3. Car HDMI cable

A new type of HDMI cable designed specifically for vehicles to withstand harsh environments such as vibration, high humidity and temperature extremes. Designed to connect various multimedia devices in cars. One of the possible schemes of use is shown in the figure below (Fig. 4).

The new HDMI E-type connector with a lock provides better fixation of the convector in the socket and prevents disconnection during operation. In fig. 5 shows a view of an E-type HDMI connector. There are no such devices in Russia today, not to mention the cable.

4. High Speed ​​HDMI Cable

The High Speed ​​HDMI cable is designed to connect high quality home components (Blu-ray players, HDD players, satellite TV receivers, plasma and LCD panels) and is designed to transmit image signals with a resolution of 1080p and higher (up to 4K - 4096 × 2160, 24Hz). The total bandwidth (for 3 channels - RGB) reaches 10.2 Gb / s, and the allowable clock frequencies - up to 340 MHz. Suitable for connecting ANY signal sources and receivers. Backward compatible with all types of HDMI when using Type A connectors. The main differences from the standard HDMI cable are in the cross-section and material of the four twisted pairs, the quality and construction of the dielectric of the twisted pairs, the shielding of the pairs, and the overall design. Naturally, all this is reflected in the final price of the product. From my point of view, this is the most suitable cable in most situations, provided that your components do not support HDMI 1.4 Ethernet or you do not intend to connect your home network and the Internet to your AV system in the future. This is a significantly higher quality cable compared to STANDART and STANDART with ETHERNET. The difference in image quality with a good HIGH SPEED cable versus a STANDART cable is usually noticeable even on inexpensive components.

5. High Speed ​​HDMI Cable with Ethernet

This type of cable has the same capabilities as the previous type of High Speed ​​HDMI cable, but has an additional dedicated Ethernet HDMI data link for linking various components on a network at speeds up to 100 Mbps and connecting those components to the Internet. HDMI Ethernet cable functionality is available if both linked devices support HDMI Ethernet. It is a versatile cable with every imaginable feature that the HDMI 1.4 specification can provide today. It makes sense to purchase with an "eye" for the future.

A few simple tips for choosing and using a cable.

First of all, let's decide on the choice of one of the four types of HDMI cable. The fundamental choice is between HIGH SPEED (more expensive and better) or STANDART (cheaper and somewhat worse). The rest is easier - you should decide whether you need an Internet connection or a local computer network of your components. In this case, the components MUST support HDMI 1.4 with Ethernet, or HDMI communication will not be possible. And again there are two options, differing in quality features - HIGH SPEED with ETHERNET (better) or STANDART with ETHERNET (cheaper).

The cable packaging can provide information about the guaranteed transmission range of the 1080p signal, and everything is simple: the further, the better. The conductors of the cable should be of the maximum cross-section, but this information is usually not indicated on the packaging. It is possible to assess the quality of the cable by some indirect signs. In general, the thicker and more rigid the cable, the better the sound and image transmission. This, at first glance, ambiguous criterion has a rather serious physical justification (about this in the second part of the article).

I would especially like to dwell on the choice of a cable for laying in a wall or ceiling: the technique is evolving very quickly and it makes sense to lay the cable only with the maximum bandwidth - HIGH SPEED or HIGH SPEED with ETHERNET.

Very important! Never connect components via HDMI while the equipment is on, it may damage it! Avoid sharp bends in the cable, as this leads to a change in the wave impedance and can in some cases disrupt the signal transmission.

FOR THOSE WHO WANTS TO LEARN MORE. PRICE OF THE QUESTION.
(The second part of the trilogy "HDMI 1.4")

This part will tell you about the characteristics and differences in HDMI cable designs.

The HDMI 1.4 standard clearly divides cables into two groups based on their characteristics. This division was in the past (in the HDMI 1.3 specification - "Category 1" and "Category2"), but not all manufacturers indicated this. This will now be called "STANDART" and "HIGH SPEED".

What is the difference in performance between "STANDART HDMI 1.4" and "HIGH SPEED HDMI 1.4"? Let's turn to the HDMI 1.4 specification. Examining table 1 (tab. 1), we see that a standard HDMI 1.4 cable is significantly inferior to a high-speed HDMI 1.4 cable in terms of frequency characteristics and, accordingly, information transfer rate.

Comparison of High Speed ​​HDMI 1.4 and Standard HDMI 1.4 cable

Tab. 1

In the diagram below (Fig. 5), this difference is expressed graphically. I draw your attention to the fact that in the overwhelming majority of cases, the total bandwidth is indicated, and it will be THREE times higher than that of each of the channels. Marketing!...

Table 2 provides a comparative analysis of the maximum physical capabilities of the format and cable HDMI 1.3 and HDMI 1.4 - highlighted in blue dotted line. As you can see, they are no different. Everything highlighted in brown dotted line refers to FORMAT capabilities. Hence the conclusion: there is no difference between a high-quality cable (no Ethernet) HDMI 1.3 and a high-speed (no Ethernet) HDMI 1.4.

We will dwell on the design differences and their influence in more detail later.

HDMI 1.4 cable with and without Ethernet: what's the difference?

If we look at the difference in design between a standard (or high-speed) HDMI 1.4 cable without Ethernet and a standard (or high-speed) cable with Ethernet, we will find that the latter has a 5th shielded twisted pair, wired to 14, 17 and 19 pins of the connector ( Table 3). The same pair carries the ARC (Audio Return Channel) signal.

In this photo (Fig. 6) you can clearly see the difference in the design of the HDMI 1.4 cable with Ethernet and HDMI 1.4 without Ethernet.

Standard HDMI cable and High speed HDMI cable

Table 4

A very interesting question is about the difference between the design of a standard HDMI 1.4 cable and a high-speed HDMI 1.4 cable, taking into account the fact that the pinout of the connectors and the number of physical conductors are the same (Table 4). In the meantime, let's see what some of the manufacturers offer, and what options for HDMI cable designs are used.

Variants appearance HDMI cable. Not yet labeled and without colorful packaging.

In the manufacturer's proposal, one of the specification options for manufacturing an HDMI cable looks like this:

Version: HDMI 1.3b / 1.4 (optional)
AWG: 30/28/26/24 (optional)
Plated: Gold / Nickel (optional)
Length: 1m to 20m (3FT to 60FT)
Braid: Black / White / Blue / Gray ... (optional)
Conductor: BC-Bare Copper, TC-Tin Copper, SC-Sliver Copper

As you can see, the manufacturer offers various options for cables, connectors, etc., in general, "any whim for your money." This is where a very important factor appears - the cost, with which the characteristics and, ultimately, the resulting quality of the cable are connected. Unfortunately, in a number of cases, firms - markers of cable products (ordering their goods from manufacturers) include a “free” margin in the final cost. As a result, the products high level, and very mediocre, can be close in price, and in some cases the price may not correspond to the quality at all. Largely because of such "paradoxes", the misconception is widespread that all cables are the same and that you do not need to overpay for some unknown reason. The cost of producing an HDMI cable can be very different due to the peculiarities of the technology from different manufacturers, in particular, due to manual soldering and its quality (do not forget about 38 pins).

Taking into account the mass production, they try to save on literally everything, primarily on copper, replacing it with cheaper aluminum and lowering the cross-section of copper conductive conductors. Some people also save on individual grounding conductors of twisted pairs, which significantly reduces the noise immunity of such a product. A 1080p signal over such a cable, depending on the source, receiver and external conditions, may not "pass" even five meters, with the declared fifteen. In some cases, the performance at long lengths, unfortunately, can only be verified empirically. The main difference between a standard HDMI 1.4 cable, in comparison with a high-speed one, is in the cross-sections of the twisted pairs, the precision of the cable construction, the quality of the copper, in the service conductors, dielectrics, screens, etc. As the cross-section of the conductors is increased to a certain limit, the signal transmission is improved. But along the way, there are limitations associated with the physical dimensions of the cable, its flexibility and the complexity of soldering. The cross-section of the conductors used in the HDMI cable usually does not exceed 24 AWG (0.205 mm2), very rarely 23.5 AWG (0.22 mm2), in some cases 22 AWG (0.32 mm2).

The precision of the twisted-pair cable production is very important for the data transfer rate. The uniformity and thickness of the dielectric, the observance of the diameters of the conductors are very important conditions for ensuring the normalized value of the characteristic impedance and minimizing signal reflections at the ends of the lines. The uniformity of the twisting pitch of twisted pairs greatly affects the noise immunity of the cable. The quality of shielding of twisted pairs determines the level of crosstalk of transmission channels of different nature and structure of signals, which ultimately determines the quality of video signal transmission. An external double shield allows to additionally protect twisted pairs and service conductors from external interference. Shielding cables in itself is a complex theoretical and practical problem. In general terms, for frequency ranges transmitted signals with which the HDMI standard works, the following points are true:

The thicker the wire and foil material, the better, as this provides an increase in conductivity.

Longitudinal foil installation is better than spiral installation, but it is quite stiff and difficult to bend.

An outer braid and foil, or double braid, shield is significantly better than a single shield, even if the two shielding layers are not insulated from one another.

Best configuration for braided and foil shielded cables where the braid is against the conductive side of the spiral foil.

The individual twisted pairs in a common shielded cable must be placed in individual shields to prevent capacitive crosstalk between the signal conductors, and the shields themselves must be isolated from each other.

It is desirable that the resistivity of the material of the conductors is minimal.

It follows from the above that a quality HDMI cable is almost impossible to make thin and flexible. In the photo below you can see the comparative thickness of three HDMIs (Fig. 8). Two high speed and one standard. Determining which one is standard, I think, will not be difficult ...

Fig. 8

Soldering also contributes to cable performance. It was not possible to experiment with the quality of soldering and its influence on the transmission of an HDMI signal, but I had to face a defective cable from different manufacturers and was surprised that the cable was, in principle, workable. In the photos below (Fig. 9) you can see various options for soldering a defective cable from different manufacturers (some of the photos are by the author). According to the opinions of the people related to trade, some part of the HDMI cable failed after 1-2 years. One of the most likely causes is poor soldering.

QED Reference HDMI

Thus, a high-quality HIGH SPEED HDMI cable is a rather complex structure that requires a high technological culture in its manufacture. Therefore, the choice of cable, especially for stationary, and even more hidden, wiring should not be approached according to the principle "the cheaper the better." Look at the cross-section of twisted pair conductors, many manufacturers indicate it and it is better if it is at least 0.205 mm2. It is desirable that all screens are copper. The photographs (Figure 10 and Figure 11) show two different designs of High Speed ​​HDMI cable. The price of these products is very close, but the complexity of the design and the quality of the materials used are different. In fig. 12 shows the typical stuffing of an HDMI Standard cable.

Examples of building a network, switching using an HDMI cable with Ethernet

Audio Return Channel (ARC) Capabilities

Connecting components without using the audio return channel capabilities (Figure 14).

Fig. 14

Connecting components using the audio return channel capabilities (Figure 15). Allows you to connect your TV to your home theater system using the TV's HDMI INPUT jack to send audio to the receiver. Let me remind you that both devices must support ARC. It is advisable to use HDMI 1.4 with Ethernet. True, the "normal" HIGH SPEED also works.

The Audio Return Channel supports Dolby Digital, DTS and PCM and is analogous to a standard S / PDIF connection. When using it, you do not need an additional cable to transfer sound from the TV to the home theater receiver.

SPECIALLY FOR THOSE WHO THINK THAT THE CABLE CANNOT AFFECT THE SIGNAL QUALITY. LEGEND ABOUT THE DIGIT.
(The final part of the "HDMI 1.4" trilogy)

Heated controversies on this topic constantly arise in various forums. Many people believe that the signal via HDMI cable may or may not be transmitted, because consists of 0 and 1. In fact, this is not entirely true. Let's dwell on some of the problems of signal transmission in HDMI (DVI) formats. First of all, one should not forget that ANY electrical signals, including “digital,” in the real world are analog, that is, changing continuously and for a certain, albeit sometimes very short time. The main difference between what is conventionally called "digital" signals from conventional "analog" is in a much wider spectrum of frequencies occupied by the former. In other words, over an HDMI cable (like any other), the signal is transmitted in analog form, that is, in the form of electric currents from very low (including direct current) to very high (many tens of GHz) frequencies. Without going into details, from an electrical point of view, when transmitting digital signals, one has to face the same problems as when transmitting analog signals: amplitude attenuation, edge roll-off (decrease in the level of high-frequency components), noise. When the useful signal is attenuated, distorted and enriched with interference, part of the information is lost. And since the means to control the correctness of data transmission (for example, checksum), unlike data transmission in a computer, are not used, then when a certain level of errors is reached, you can get distortions and interference that are clearly visible in the transmitted image ("blurring" of the image outline , "Wiggle" pixels, dots, stripes). This is where the influence of the cable manifests itself. I will cite some materials on this topic. They partially relate to the study of the problem of connecting via DVI, but all of the following can be safely attributed to HDMI, and to any other format for transmitting wideband signals.

There are many electromagnetic processes that affect the properties of the transmitted signal in a cable. For the first time, the influence of the cable line on the transmitted electrical signals was encountered when laying the first telegraph cable along the bottom of the English Channel. At first, the fifty-kilometer section of the cable was unable to transmit even the slow signals of the hand-held telegraph - so great were the attenuation and dispersion of the signal in it. To date, the problems of one and a half centuries ago, of course, have been resolved, but, nevertheless, similar physical processes manifest themselves on a different level. If we transmit a "digital" signal, then we must always determine the conditions for its "discreteness". When transmitting a signal, it is considered that if its voltage at the input of the receiver at a given time is higher than one certain level, the receiver considers that this is a "logical 1" level, if it is lower than another certain, then "logical 0". At the output of the source, the signal is a sequence of rectangular pulses, and when propagating through the cable, such a signal is distorted. Its attenuation occurs, i.e. decrease in amplitude (due to losses in conductors, losses on radiation and polarization processes in dielectrics), blockage of fronts (due to a finite bandwidth associated with frequency-dependent losses), distortion of the pulse shape as a result of dispersion, mutual influence of signals from different twisted pairs and external interference. In addition, resonance phenomena and signal reflections from inhomogeneities are possible in the cable, which also leads to distortion of the pulse shape ... If we connect the oscilloscope to the source connector, we will see more or less clear rectangular pulses... Further, as they propagate in the cable, they will gradually blur, their shape will be distorted. If the cable is too long or of poor quality, the signal at the input of the receiver will be very different from that which can be observed at the input of the cable. The distortion can be so great that the receiver will not be able to perceive such a signal by the criterion of its "discreteness". Interference can also have a large impact on the stability of digital signal transmission. The cardinal solution to the problem of protection against interference is the so-called "differential" (or "balanced") transmission. Each line uses two wires, one of which carries a direct signal, and the other carries its inverted copy. Thus, at any moment in time, the sum of such signals is ideally zero, and the difference is twice the signal at the input of each line. At the receiving end of the line, a special device is installed - a differential receiver, which subtracts one signal from another. Imagine now that two conductors carrying such signals are very close to each other. An external interfering field will create practically identical interference signals in these conductors - the so-called. common mode interference. The receiver will subtract them from one another, as a result, at its output, the interference signal will be close to zero, and the useful signal will be doubled. The operation of the differential line and receiver is well illustrated by the following figure (Fig. 16):

Fig. 16

The upper part of the figure shows the signals acting on the line. Shown in green is a useful signal in a direct conductor. Blue - in antiphase conductor, and red - a noise signal, the same for both conductors. The lower part of the figure shows the signal at the input of the differential receiver - you can see that the useful signal will be doubled, and the common mode noise signal will be practically zero. In order for the conductors to be located side by side, and external interference created in them as close signals as possible, twist the conductors into pairs, which are usually used to transmit broadband signals, are used. If such a pair is enclosed in an external screen, the line pickup will be reduced even more. The result is a cable with a sufficiently high noise immunity. This is how DVI and HDMI cables are designed to carry a very wide bandwidth of signals. The figure below (Figure 17) shows a simplified transmission line diagram for a single shielded twisted pair.

Fig. 17

The higher the maximum frequency of useful signals in the cable and the higher the frequency of possible external interference, the smaller must be the twist pitch of the pair and the smaller the distance between the conductors to ensure a given level of external interference impact on the line. But, on the other hand, these same parameters determine the line impedance, dispersion and losses in it. Therefore, there are certain optimal values ​​of the insulation thickness of the conductors and the twisting pitch, which, with good noise immunity, provide the required electrical parameters of the line. However, there is nothing perfect in the world, and even the best cables are still not ideally protected from interference (for a number of reasons, including manufacturing accuracy) and have a very definite attenuation. Therefore, disturbances, unfortunately, penetrate even shielded cables, and the inherent electrical parameters of the cables also affect the signal. What can this lead to? Let's look at the following figure (Fig. 18):

Fig. 18

The upper oscillogram shows the signal at the output of the data transmitter. The second is the signal at the output of the receiver when its input is directly connected to the output of the transmitter. It can be seen that the reconstructed signal has a precise reference to the time scale. The third oscillogram corresponds to what can be observed at the output of a long cable in conditions of large external interference and the presence of a mismatch in the characteristic impedance of the cable and the load. The last oscillogram shows what will be at the output of the signal receiver. The reconstructed signal, in addition to having received a time delay, also changes its duration and the location of the edges and falls in time, that is, randomly, depending on instantaneous interference, changes the instantaneous phase values. And this is jitter, the thunderstorm of all digital data transmission systems. Its appearance leads to the fact that a strict time grid is violated, which defines all processes of processing and conversion of signals in digital devices.

This results in visible and audible distortions in the picture and sound. Of course, in real conditions, interference and transmission distortions will not be as high as in the above example, but they are available in ANY case, only their level and properties directly depend on the properties and quality of the cable connecting the source and receiver of digital signals. Any hardware and software tools for jitter suppression have limitations in their application, and the quality of their work is directly related to its initial level - the larger the jitter value, the lower the efficiency of its suppression. In simple cases, a large level of jitter simply leads to a slight decrease in the quality of the image and sound, in "clinical" cases it can cause serious disruptions in the operation of digital systems. In differential transmission lines, jitter can occur not only under the influence of external factors. Any asymmetry in the cable, incl. and the difference in signal delays within the pair results in an in-phase signal component. In this case, the amplitude of the differential component decreases. Another problem is that differential and common-mode signals have different propagation rates and different loss factors, therefore, depending on the shape and spectrum of the transmitted signals, the resulting error leads to an additional component of jitter (jitter) correlated with the signals. Note that the common-mode components themselves do not introduce jitter into the signal. Problems start with conversion. Imperfect differential transformation of the components significantly spoils the signal, and not the identity of the twisted pairs in the cable further exacerbates the situation. In systems for image transmission via DVI and HDMI, the restoration of clock frequencies in the display device (monitor, panel) is performed using PLL systems, the malfunction of which can be caused not only by a high level of noise induced on the connecting cables, but also by the difference in delays transmission clock frequencies and information signals. That is, such systems are sensitive to both the noise immunity of the cable and the magnitude of its delay and dispersion. According to Silicon Image's experience, DVI cables with a length of 2 meters work fine, but the quality can deteriorate noticeably as the length increases to 5 meters (and even more so to 10 meters). (“Digital connection of LCD monitors: DVI quality tests at ATi and nVidia” D. Chekanov, Lars Veinand). Many problems of digital signal transmission have been investigated and described for a long time, and for everyone who wants to study this issue in more detail, I recommend the article: "Digital connection of LCD monitors: DVI quality tests from ATi and nVidia".

The increase in the jitter level caused by the phenomena discussed above leads to the appearance of visually noticeable image defects. Jitter caused by a mismatch in the initial phase of the sampling rate in adjacent lines results in additional noise on the edges of the video signal. The largest errors are observed for signals of higher frequency and amplitude. How does all this visually appear on the screen? When transmitting image signals, a greater noise level is observed at the signal edges (many times higher than the noise present on a flat background). This is especially pronounced when reproducing contrasting frame transitions (edges of objects, lattices, etc.), as well as images containing a large number of small details (backgrounds, leaves, ripples of glare from the sun, etc.). There is a subjective feeling of decreasing image depth and decreasing contrast. Black becomes less black. If you look closely at the dark areas of the frame, you can notice the noise in the form of small dots. This is the reason for the decrease in image contrast. The image may look less stable, this is manifested in "wiggling pixels", especially noticeable on leaves or complex backgrounds with a lot of elements, especially when the camera moves (a kind of "ghosting" occurs). In addition, color rendering also suffers, which is especially noticeable on projection systems and plasma panels with a large diagonal. Color distortions are observed primarily in complex subjects. Colors are visually faded and less clear. In some cases, a decrease in the brightness and sharpness of the image is noticeable. Sharpness is reduced as a result of blurring the boundaries of the contours of objects, although some perceive such a picture as more "film" and "analog". At the last stages of signal degradation, the so-called. Flies and stripes. Then there is a loss of synchronization and the image disappears.

Fig. 19

But before this "happy" moment, there is a gradual degradation of the signal associated with the above processes (Fig. 19). Thus, the data transmission channel, in our case it is an HDMI cable, has a significant impact on the quality of image signal transmission even at short lengths, and its influence cannot be ignored. In conclusion, I want to say that for the last three years I had the most direct relation to testing an HDMI cable and came to the following conclusions:

1. The difference in cable quality is visually noticeable even on 26-inch TVs.

2. It is difficult to say in advance at what length full or partial signal degradation will occur.

This is highly dependent on the cable itself and the source / receiver combination of the signal. The same cable can work fine on one source / receiver combination, give worse picture problems on another, and not work at all on a third. When testing 20 m HDMI, in addition to laboratory studies, several dozen source / receiver options were tested to test the operability, as a result, a construct was chosen that provided 100% operability (today, about 150 variants of equipment combinations have been tested for a 1080p signal). Anticipating possible questions about instrumental control (which was carried out outside of Russia) and the additional need for "field" tests, I will immediately answer that the end user will not be pleased if the laboratory test is passed, but on his system, nevertheless, there will be a problem.

I would like to sincerely thank Dmitry Andronnikov for his editing assistance and valuable comments.

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It is not enough just to purchase an HDMI cable, it is important to know the model, length and many other little things that directly affect the quality of the information transmitted through it. Next, we will consider all the nuances of purchasing a high-quality HDMI cable, thoroughly studying all the available information regarding this issue.

Which HDMI cable is better?

The quality of the cable, and therefore the quality of the information passing through it, depends on many nuances. Let's analyze the most important of them:

1. Price. A certain part of interested people advises not to judge the price of the HDMI cable itself, since they believe that digital transmission is strictly regulated. That is, there is no difference between a $ 5 cable and a $ 100 cable - it will either transmit information or not. If you take a screenshot from the screen when using cables of different price categories, then their checksums will completely coincide (they will turn out to be completely identical).
   On the other hand, more expensive HDMI cables are made a little denser, thicker, which increases isolation, protects against interference, which directly affects the picture quality. In the presence of a serious source of interference, it is better to choose a more expensive cable, and if not, then a lower quality will do.

1. VersionHDMI. Depending on the version of the cable, its main purpose changes, therefore, the appropriate version should be chosen, which is supported by the devices that it connects.

It is almost impossible to find out the HDMI version by the cable itself (sometimes the cable itself is marked, but often not), so you should save the packaging after purchase to know the version.

Today, the problem of connecting sound from a computer to a TV is becoming relevant, which is exactly what the HDMI cable will help.

At the moment, the following versions of HDMI cables are most common:

• 4 - support for HD resolution 4K, 3D video and Internet connections up to 100 Mbps;
• 4a - even more functions for 3D images;
• 4b - 3D now works in 1080p @ 120Hz; throughput per wire increased to 15 Gbps;
• 0 - Many improvements in 4K @ 60Hz video transmission, support for the highest audio quality, dynamic sync video / audio streams, etc .;
• 1 (from 04/01/2017) - increasing the bandwidth of the video stream up to a resolution of 10K at 120 Hz.

HDMI cable version 2.1 can afford to produce a video stream with 10240 x 4320 resolution at a stable 120 frames per second. Even VGA and DVI combined cannot afford such a thing. For a picture of this quality, you need the best and quite expensive HDMI cable. And this is not taking into account the characteristics of the outgoing device.

It is necessary to select a cable of a specific version according to the existing equipment. If, for example, your computer cannot play video at least in 2K resolution, then there is no point in purchasing HDMI 2.0. On the other hand, version 2.0 cable is backward compatible. If the TV only supports HDMI 1.4, then the 2.0 cable will be able to transmit the picture, but with a quality level equivalent to 1.4, and not exceeding it.

From the change of places of the terms, the sum does not change: the same state of affairs will be if the HDMI cable has version 1.4, and the TV supports 2.0 - the image quality will be equal to 1.4.

However, for an ordinary user, an inexpensive ($ 5) HDMI cable version 1.4 will be quite enough, because it fully justifies the hopes placed on it and meets the necessary requirements. But this rule applies to cables no longer than 10 meters.

1. LengthHDMIcable. There are some specific indicators of cable length:

• 0.75 / 0.8 m;
• 1.5 m;
• 2.5 m;
• 3.5 m;
• 10 m (cables longer than 10 meters are not standardized, so you can find and buy cables of both 15 m and 55 m - it all depends on the wishes of the buyer and his needs).

Everyone chooses the length of the HDMI cable individually depending on the needs, but the longer the cable, the thicker it should be in order to avoid the influence of various interference and the like.

The longer the cable, the more interference it will have. This is directly proportional to the quality of the resulting image. Expensive cables are made from special materials, so they are less prone to distortion.

1. Cable quality. At the moment, there are many companies supplying HDMI cables of various versions, types and sizes. The best quality cables are from the following manufacturers:

• ProLink
• Belkin

They treat their products with enviable attention, so you can safely trust and purchase an HDMI cable from any of these companies. However, you should carefully inspect the technical documentation of the equipment in order to know which HDMI cable is best suited for your particular specific case.

Which is better: HDMI, DVI or VGA?

Now let's figure out the differences between HDMI and VGA and DVI cables:

1. Unlike HDMI, VGA performs unnecessary information conversion according to the “digital-to-analog” scheme, less often - “digital-analog-to-digital” (meaning digital and analog signals). HDMI allows you to avoid this due to direct output immediately in the digital version, increasing the overall quality of the transmitted information (in this context, the quality of the picture on the TV). Often, the difference is practically invisible, but it happens quite the opposite. Such cases are not at all uncommon, so it is much more preferable to use an HDMI cable.
2. HDMI supports a much wider range of resolution standards, the screen image will be much more stable. VGA cannot boast of this.
3. The very fact of the absence of various transformations allows the picture to look much sharper in comparison with VGA. HDMI initially produces a pure digital signal, and the presence of a post-error correction mechanism puts it at once a dozen steps higher than any other analogs. Although the post-correction directly depends on the cable length.
4. VGA (like DVI) does not output audio (requires an appropriate, separate cable). HDMI, in principle, does not have identical situations (in addition to the picture, it also outputs sound).
5. If we compare HDMI and DVI separately, then it should be noted that the DVI interface is much more cumbersome. It requires additional mounts, and HDMI is used even in mobile electronics due to its compactness.
6. The throughput of an HDMI cable is already 3 times higher than that of DVI (VGA is not compared due to the analog signal, which by default is worse than digital).

Summing up, the especially big difference between VGA and HDMI outputs is difficult to notice "by eye" (although sometimes it is quite obvious). But through careful study, it becomes clear why HDMI is far from the last position in the whole world: a much better picture, the absence of "artifacts" on the screen and many other advantages.

The VGI interface is much closer in quality to HDMI, but given its dimensions and the impossibility of transmitting sound, a reasonable question arises - is it really necessary if there is HDMI?

Taking into account the considered features and nuances, an HDMI cable for a TV should be selected depending on the needs: the version suitable for the characteristics of the device, the correct type of connector, the length is the minimum possible. HDMI - the best solution thanks to the highest quality, simplicity and undeniable versatility.

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