No picture at all. The question I've often gotten is what if you're right on that digital precipice? That teetering space between "everything's good" and "I got nothin. Video As you've read, the ones and zeros of an HD image trot happily along, more or less, from your source to your TV.
Over short runs, there really isn't anything other than a faulty cable which itself isn't that likely that would cause any issue.
Over long runs, it's possible that interference of some kind, or a poorly made cable more on this later , can reduce the "quality" of the signal to the point where the TV can't make heads or tails of it. Heads or tails -- that's a digital joke. At this point, you're on the edge of the digital precipice. The most likely outcome is sparkles. Here's what they look like:. It looks a lot like snow, or static. The data received by the TV wasn't enough to figure out what those failed pixels are supposed to be.
Your TV likes you, though, and it really wants to show you an image. So it builds the rest of the video, minus the failed pixels. It's important to note that this artifact is pretty unlikely, even over long runs. You are way more likely to just not get anything at all. If it's so unlikely, why do I bring it up? Because it's important to understand that it is impossible for the pixel to be different. It's either exactly what it's supposed to be, or it fails and looks like one of the images above.
In order for one HDMI cable to have "better picture quality" than another, it would imply that the final result between the source and display could somehow be different. It's not possible. It's either everything that was sent, or full of very visible errors sparkles. The image cannot have more noise, or less resolution, worse color, or any other picture-quality difference. The pixels can't change. They can either be there perfect, yay!
All the claims about differences in picture quality are remnants of the analog days, which were barely valid then and not at all valid now. There is no way for different cables to create a different color temperature , change the contrast ratio , or anything else picture-quality-wise. At this point some of you are saying "but sparkles are noise. If you see sparkles, you need a different cable. Another potential "fail" is a failure of the HDCP copy protection, which shows up as a total snowy image, a blinking image, or something else hard to miss.
I have seen this in my testing, though, so it's worth mentioning. One in particular claims this is because there is no error correction on the audio and its cables are more likely to transmit all the data. First of all, this is untrue. Audio over HDMI actually has more error correction than the video signal. But even if this weren't the case, it's still utter nonsense. Dolby has extensive error correction built into its codecs. DTS presumably works in the same way, though the company ignored my repeated requests for info.
Cheap or expensive, the cable is irrelevant when it comes to transmitting Dolby or DTS. If the cable is faulty or if there is some cataclysm causing data to be lost between the player and the receiver, the decoders are designed to mute instead of blasting out compromised data.
There is no such thing as an audio version of "sparkles. So if you're getting audio dropouts, it's possible it's the HDMI cable. But if you're not getting video issues as well, the problem is likely elsewhere.
HDMI does have a dedicated compliance team that polices the industry. They even shut down some exhibitor booths at CES over licensing issues, and they work with big retailers to ensure all the products they offer are genuinely HDMI compliant. Longer cables are inevitably going to cost a little more, and they are becoming more common as more and more people wall-mount their TVs. These cables may require a USB port to draw power. The quality of the content is everything.
Realistically, it means that the occasional error will pop into the audio track. This means the receiving equipment can detect an error and correct it, as though it never happened. In other words, there is no longer an error.
In simpler terms, it's describing how a signal might not be properly in sync. This is because all digital data uses a clock to synchronise transmission, with each clock cycle a tick if you will used to send a bit of data. When plotted on a graph, you get a square graph with the values going up and down.
When the clock is accurate, each bit is sent at a perfect time interval, but the timing is often not as accurate as you may think. For example, rather than sending data every second, you may find that the first signal goes out at 0. With jitter distorting the transmission, two things can happen.
First, repeated errors can make the receiving device believe that is has a 0 instead of a 1 or vice versa , introducing an error. A bigger difference is made by the quality of the Digital-to-analog Converter DAC , which takes digital sounds and converts it back to the analog sounds we hear, but even this pales in comparison to the quality of your speakers and AV receiver.
Scientific explanations are all well and good, but it's practical testing where the talking stops and the evidence starts.
To prove the doubters wrong, we upped the ante and decided to test full-motion video to prove that changing cables makes no difference. Crucially, it performs no error correction, so we can accurately compare the output from different cables and spot any errors. For test footage, we used the open-source film Tears of Steel. In order to compare different cables, we needed to ensure that the captured footage was the same regardless of the cost of the cable.
To do this we used the TrueHD capture card to capture a few seconds of Tears of Steel for each cable, saving the results in an uncompressed video file. Once we got 50 frames from our range of test cables, we needed to compare them. In order to compare the files, we generated an MD5 hash of each image, which can be thought of like a digital fingerprint, as is represented as a digit hexadecimal number, such as 6add8f2f6edee97bfcbfe2f5e7.
In short, if the MD5 hash of two files is the same, the files are forensically identical. This tool is designed to mathematically and visually show the differences between two files.
This allows us to see where the error is. In our first set of tests, 49 of the 50 frames we captured from the expensive cable were completely identical to the 50 produced from the cheap cable.
With the one frame that was different, we got two completely different MD5 hashes. We needed to find out where the error was, so we used Compare to highlight the error and found that there was a one-pixel error. To see if you can spot where the error is, take a look at the images below and see if you can spot the difference: the top image is from the cheap cable, the middle image is from the expensive cable and the bottom image is from the expensive cable click any image to view it full-size.
Hard to tell, right? If we crop into the image see below to show the error, spotting a single-pixel error is incredibly hard. Look at the top-left of the right-hand image and look for the red pixel. This is the error, which is the difference between the cheap cable left and expensive cable right.
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