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Contrary to popular belief (and misinformation), HDMI cables do not actually make much difference in overall image quality. Sadly, people are still buying high-priced HDMI cables in bulk, and they spend too much unnecessary money thinking they will get better quality videos. Of course, there are less and less meaningless HDMI cable reviews online, but this long struggle is still underway, and this is a struggle we are willing to win.
Despite our rigorous testing, we still often read about the advantages of expensive HDMI cables in technical and Hi-Fi publications and the ways in which the author claims they are very different. You may have guessed it, and we think this is incorrect. Many readers agree with us, including a magazine that filed a formal complaint with the Press Complaints Committee, which stubbornly declared its love for expensive HDMI equipment.
We have pushed this topic forward for some time, hoping to provide some much-needed information for the debate. For your benefit, we have divided this article into two parts. First, we have a theory to explain why HDMI cables are largely similar to each other, including a lot of scientific explanations. The second part at the bottom of this article is an in-depth analysis and explanation of why you don't need to spend too much money on HDMI cables. However, the main point you need to understand is that you can always spend a lot of money on Amazon cables with a limited budget and save a lot of cash in the process.
This is impossible, which shows that the HDMI cable has built-in smart functions. Therefore, the reviewer is delusional at best, and lying to you at worst. Inside, the HDMI cable has 19 separate wires connected to 19 pins, each of which is designed for a specific job, but in reality, these wires are just metal designed to conduct electrical signals. It is important to note that there is absolutely no processing in the cables, and as far as the wires are concerned, they may carry images, audio or anything else.
For example, to make the HDMI cable have a better skin tone, you must first decode the video signal, process the location of the personnel, and then adjust all the images, and then re-encode. Consider a cable that can significantly improve branches and leaves-how to deal with Kermit, a frog standing in a green field? Will it make his green tone better, or can it distinguish the grass and make it better? Of course, the answer is neither, because the cable does not have a processor.
Think about it another way, if HDMI cables can improve image quality, can more expensive SATA cables make text documents easier to read? Imagine that Dan Brown bought a SATA cable worth £2,000, opened his latest novel, and found that it has changed from his usual skill to Dickensian beauty. Of course, this is nonsense, and we are troubled by Dan Brown's prose and HDMI cables that cannot touch the image quality.
The active cable draws power from the HDMI port to power the signal booster. This helps to extend the cable length (for example, more than 5m), or enables you to use a thinner HDMI cable. Some of these movable cables must be inserted in a certain way to work properly, because inserting them in a "wrong" way introduces some errors. Please note that an effective cable will not improve image quality, but can reduce errors.
The difference can be seen in the test, but it depends on the kit used. Each TV will interpret the signal slightly differently and display different colors. Each Blu-ray player will also output slightly different images. This is why calibration is recommended. However, it is definitely not the cable that causes these problems.
It's not. The problem we face is the word "better". This means that one HDMI cable can improve another HDMI cable, but not. Through the digital signal, all content is sent in the form of 0 and 1. If you receive 1 as 0 or 0 as 1, an error will occur. In this way, the HDMI cable can transmit everything correctly, or it can introduce errors. Technically speaking, poor HDMI cables may transmit more errors than expensive cables.
of course not. We freely admit that digital signals sometimes cause transmission errors, but this must be considered. The HDMI standard allows one error per billion bits, which is the so-called bit error rate (BER). Assuming that 24-bit color (RGB is 8 bits) is used to transmit pictures at a resolution of 1920 x 1,080 (2,073,600 pixels), each frame totals 49,766,400 bits. The movie standard is 24fps, which is 1,194,393,600 bits (1.1 billion bits). In other words, the HDMI standard allows the worst cable to have a single error in one pixel at one frame per second. You must have incredible vision to discover this error. In addition, a bit error may occur in HDCP copy protection or audio tracks, which means you can't even see it. Finally, the video image has an error detection function to find such situations.
Suppose your one-bit error causes a problem with the image, and one pixel is incorrect, the error detection on the TV will let it know where the problem is. The TV can analyze the surrounding pixels and make an educated guess as to which color the wrong pixel should be. Therefore, you may get one pixel per second, and the color of that pixel is even slightly wrong. If you can discover this, then you will have the best vision ever. Well done.
Although there are different HDMI standards, HDMI 2.0 is the latest, but there are only two HDMI cable standards: standard and high-speed. Standard is now obsolete and supports lower resolutions; high-speed support for all content, including the HDMI 2.0 standard, can provide you with a 4K TV (Ultra HD) at 60fps.
Likewise, one of the billions enters here. In practice, this means that occasional errors will suddenly appear in the audio track. If not corrected, such errors may cause noticeable pops or spots. Fortunately, audio has error detection and correction functions. This means that the receiving device can detect the error and correct it as if it never happened. In other words, there are no more errors. If there are too many errors, you will not hear any sound at all, because the receiver kit is programmed to turn off the audio instead of outputting sounds that can be disruptive and offensive.
Jitter is described as the deviation from the true periodicity of an assumed periodic signal, which may not be important to most people. In simple terms, it describes how the signal may not be synchronized properly. This is because all digital data uses a clock to synchronize transmission, and each clock cycle (if necessary, will be ticked) is used to send a little data. The way the data is sent varies from system to system, but a simple view is that when there is data, the voltage will rise to the maximum. When it is zero, the voltage drop is zero. When you draw on the chart, you will get a square chart whose values will continue to rise and fall.
When the clock is accurate, each bit will be sent in the ideal time interval, but the timing is usually not as accurate as you think. For example, you may find that the first signal is not output at the speed of sending data per second, but at 0.99s, 1.12s, and 1.05s. We exaggerated the example to illustrate the problem. Digital transmission happens faster and with fewer errors, but it shows how timing affects the signal.
As jitter distorts the transmission, two things can happen. First, repeated errors can cause the receiving device to think that the device has 0 instead of 1 (and vice versa), thus introducing errors. As we discussed, these errors have been corrected to the point where you can't see them on audio or video.
Second, if you want to output in real time (or near real time), blurring may mean that there is a problem with the audio, because the sound may occur too early or too late, which will distort the analog waveform from digital conversion. However, the receiving device will buffer some audio to help eliminate these problems, and the subtle differences in time cannot be heard.
More importantly, for the purposes of this article, the cause of jitter is not the HDMI cable, but the HDMI standard. In other words, HDMI cables cannot and will not have any effect on jitter. The quality of the digital-to-analog converter (DAC) makes a bigger difference. It can absorb digital sound and convert it back to the analog sound we hear, but compared with the quality of speakers and AV receivers, this is still pale .
The scientific explanation is good, but where the conversation stops and the evidence starts are actual tests. To prove that the skeptics were wrong, we raised the stakes and decided to test full-motion video to prove that changing the cable would not cause any impact. For scientific testing, we turned to the Digital Foundry TrueHD card, which can capture RAW and uncompressed HDMI signals. Crucially, it does not perform error correction, so we can accurately compare the output of different cables and spot any errors.
As an input, we connected the laptop to the TrueHD card via HDMI. We set Windows to use a resolution of 1,920 x 1,080 with 24-bit RGB color and a refresh rate of 50 Hz (PAL). Please note that there is no difference in the playback device, because the HDMI signal is the same regardless of whether it is a Blu-ray player, game console or PC. For the test shots, we used open source movies
. When our PC is set to 50Hz, the video is played at 25fps (25p), which is the standard of PAL.
In order to compare different cables, we need to ensure that the captured material is the same regardless of the cost of the cable. To this end, we use a TrueHD capture card to capture a few seconds of "tears of steel" for each cable, and save the results in an uncompressed video file. Then, we use the frame grabber tool to get the same 50 frames (worth 2 seconds) from each captured video file and save it as an uncompressed BMP file. To ensure that the same frame is captured, we start from the first frame of the spacecraft's take-off; it is easy to find because before this frame is completely black.
Once we get 50 frames from the test cable series, we need to compare them. Our reasoning is that if the first frame from HDMI cable 1 is the same as the first frame from HDMI cable 2 (and so on), there is no difference in the cable. In order to compare files, we have generated an MD5 hash of each image, which can be regarded as a digital fingerprint, expressed as a 32-digit hexadecimal number, for example
. In short, if the MD5 hashes of two files are the same, these files are the same in court.
If any captured frames are found to be different, we can use the second method to check for differences, which is ImageMagick's "Compare" tool. This tool is designed to show the differences between two files mathematically and visually. It creates a new image with red pixels to indicate that there is a difference between the two images. This allows us to see where the error is.
Our first comparison is between an expensive 1m HDMI cable that costs £70 and a 1m cable that costs £4.99. In our first set of tests, 49 of the 50 frames captured from an expensive cable were exactly the same as the 50 frames captured from a cheap cable. Through a different frame, we got two completely different MD5 hash values.
We need to find the source of the error, so we use "compare" to highlight the error and find that there is a pixel error. To see if you can find the source of the error, check the image below and see if there is a difference: the top image is from a cheap cable, the middle image is from an expensive cable, and the bottom image is from an expensive cable (click any The image can be viewed in full size).
It's hard to tell, right? If we crop the image (see below) to show the error, it is very difficult to find a single pixel error. Look at the upper left corner of the image on the right, and look for the red pixels. This is the error, this is the difference between a cheap cable (left) and an expensive cable (right). As if to prove that our views on cable quality have not changed, the single pixel error we found did not come from the output of a cheap cable; it was a dark gray spot on the single frame of the expensive cable output.
Remember, this is one of the 2 million other pixels, and the display time is 1/25 second. In the extreme cases we set in our tests, this hardly attracted attention, so the probability that you will find it on a TV with built-in error correction is close to zero. More importantly, one frame in every 50 frames happens to be within the error range of the HDMI standard.
Next, we decided to compare the cheap 5m cable (£5.99) with the expensive 5m cable (£130) because the length of the cheap cable would be affected. This time, we found no errors on both cables. In all our mathematical and scientific tests, excluding a bit error, we can't see any difference between expensive cables and cheap cables, proving that price does not affect quality.
After more testing, we found that the only reason you might want to pay more for the HDMI cable is to get a better build quality. This is not because you won't see any difference out of the box, but because more expensive cables may be stronger and have better connectors. To prove this, we tested some cables that had been suspended for several years. These cables were subjected to considerable abuse and poor storage. These cables showed signs of physical wear and when we plugged them into the capture card without error correction, there were a lot of errors in every frame. Therefore, the cable will no longer be HDMI certified, so it has actually been disconnected.
Dozens of sparkling, colored and white dots are beating on the screen to show the degree of damage to the cable. However, even if the cable is poorly maintained, it is difficult to find on the TV, because error correction will make these pixels impossible to find even if they are technically wrong.
Even so, this still provides us with two important pieces of information. First of all, please handle the HDMI cable carefully and make sure that the connector is firmly inserted and there is no pressure. Second, if you want to buy a set of HDMI cables that you carry with you, such as a projector or laptop, and often unplug and replug, you need to buy a stronger cable and a cable. The connection between the cable connector and the wire itself is stronger and less flexible.
We were told that we had not tested the motion the last time we ran the test, but since then we have still proven that there is no difference in quality between an expensive HDMI cable and a cheap HDMI cable. One of our concessions on this issue is that more expensive cables have better manufacturing quality and stronger durability, so if you keep pulling out the wires, it is a better choice. Even so, there is no need to go crazy and make a fortune. We are also happy to blindly test anyone who still believes they can see the difference, even though we don't think anyone dared to do so.
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