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Crave * Why all HDMI cables are the same Why all HDMI cables are the same Expensive HDMI cables are a rip-off and offer no difference in picture quality over cheap ones. So when a salesman tries to up-sell, politely tell him he's wrong and move on with the sale.
Salespeople, retailers, and especially cable manufacturers want you to believe that you'll get better picture and sound quality with a more expensive HDMI cable. Dozens of reputable and disreputable companies market HDMI cables, and many outright lie to consumers about the "advantages" of their product. Worse, the profit potential of cables is so great, every retailer pushes high-end HDMI cables in the hopes of duping the buyer into spending tens, if not hundreds, of dollars more than necessary. Here's the deal: expensive HDMI cables offer no difference in picture quality over cheap HDMI cables.
Transition Minimized Differential Signaling, or TMDS TMDS has two basic aspects. The first is that the ones and zeros at the source (a Blu-ray player or HD cable/satellite box) are not exactly the ones and zeros your TV uses to create a picture -- at least, not in exactly the same order. Before sending the signal out via the HDMI output, the ones and zeros are rearranged to minimize how many transitions there are. So instead of 10101010, the transmission may look like 11110000.
how it does this is cool, but it's not really important to understanding the concept as a whole. HDMI plug end (Credit: HDMIorg ) Even though this conversion is weird, it makes it much more likely that the data transmitted can be rebuilt on the other end (as in, at the display). The second part of TMDS (the DS part) is the HDMI cable itself. Each HDMI cable is actually multiple small, copper wires.
The TV receives all the data, puts the out-of-phase signal back in phase, then compares it to the "real" signal. Any noise picked up along the way will now be out of phase, and as such it is effectively negated and ignored.
TMDS works really well, allowing for short cables and fairly long cables to carry what is a pretty intense amount of data. It also means you can have inexpensive cables that work just as well as expensive ones. More important to our discussion, it means that when something goes wrong, it goes really wrong. It's often said that with an HDMI signal, you either get everything and it's perfect, or it isn't perfect and you get nothing. If you're getting an image that looks correct, and there are no dropouts in the audio or video, then you're getting everything that's being sent. If the cable is faulty, or it's a really long run with an under-built cable, most of the time you'll just get nothing. The question I've often gotten is what if you're right on that digital precipice? 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. At this point, you're on the edge of the digital precipice. Here's what they look like: HDMI sparkles An HDMI cable "fail" leads to sparkles (the white pixels). Image taken on a 50-inch flat-panel TV attempting to show a 1080p Blu-ray concert video. Image taken from a projected image, 1080p source and display. Note these are still artifacts, indicating that the cable is not able to pass the intended signal. Same Blu-ray disc as above, different Blu-ray player on the same projector. The different colors in the sparkles here are due to the camera. 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. 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 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. 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.
HDCP copy protection, which shows up as a total snowy image, a blinking image, or something else hard to miss. This is actually even less likely, as the TMDS is more likely to fail than the channel HDCP requires for its handshake. I have seen this in my testing, though, so it's worth mentioning.
Audio Several companies claim that their HDMI cables sound better than other HDMI cables. 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. 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. In other words, if you are sending the Dolby Digital Plus, TrueHD, or whatever bitstream over HDMI from your Blu-ray player, the data going into the DAC in your receiver is bit-for-bit the same as what's on the disc. 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. If the audio isn't muting, then as long as you're outputting an audio codec, you're getting exactly what's on the disc. If you're playing a CD on a Blu-ray player, the output is PCM to the receiver. This data is packetized, just like the rest of the audio and video signal.
DAC in the receiver is going to have a far greater effect on the sound than the jitter in the transmission. Before you leap on that, keep in mind that the DAC has a smaller effect on the sound than the amp, the speakers, and definitely less than the room itself. Oh, and in case that wasn't clear, the jitter is inherent in the HDMI transmission itself. Likely transmission The big "if" that I've been repeating is "if the signal gets there." Over short runs -- a few meters, say -- it is incredibly unlikely that even the cheapest HDMI cable won't work perfectly. The variables of the transmitter and receiver combo in the source and display, plus any repeaters you have in the mix (like a receiver), mean that not every long HDMI cable can handle all the data. If you need to run long HDMI cables, it's a safe bet you're going to run it through a wall. If so, it is vital you test the cable with all your equipment before you install it. Plus, as tempting as it is to get the cheapest cable that will work in this case, just because a cable works with all your current gear, doesn't necessarily mean it will work with your future gear.
I tried out several brands of 50-foot-plus HDMI cables, including Monoprice, Monster, and Straight Wire, and got some interesting results. The cable lies In the home, there are only four basic types of HDMI cables: * High-speed (also called Category 2) * High-speed (also called Category 2) with Ethernet * Standard-speed (Category 1) * Standard-speed (Category 1) with Ethernet That's it. Many standard-speed cables can probabl...
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