For many home cinema enthusiasts, deciding on which HDMI cable to get can be as tedious as picking out the actual set box they intend connecting. Just like set top box reviews, there are AV websites and home cinema magazines that praise the advantages of high price HDMI cables claiming remarkable things they achieve over the average budget cable, such as better colour reproduction of skin tones. Expert Reviews has now carried out their own HDMI cable tests, but rather than reviewing an individual cable, they went to prove that expensive cables do not make any difference over much cheaper cables.
While high quality component, coaxial, S-Video and Scart cables can deliver considerably improved analogue picture quality than basic cables, cables for digital connections just merely need to be able to deliver the digital bits (1’s and 0’s) from one end to the other without any bits flipping. So in theory, as long as the cable can transfer the digital bits accurately, the picture quality the TV gets is identical to what the source put out. A HDMI connection is a digital connection.
When trying to compare one digital cable against another using a blind test with TVs set up side-by-side, there are several problems. Even with identical TVs, Blu-ray players and discs, it is not possible to create a level playing field, as every TV and Blu-ray has minor differences that results in slight differences in the colour, brightness and so on. Another problem with a blind test is that people tend to pick one side or the other even when both pictures are identical.
Expert Reviews has come up with their own testing method that overcomes these issues – They used a PC to play the open source film Sintel and used a Digital Foundry TrueHD capture card to capture a RAW uncompressed 24-bit RGB format without error correction. By using a PC, they could grab a frame at the source as well as from the capture card. By capturing the same frames at both ends, they could then do a comparison using ImageMagick as well as generate an MD5 hash. If the MD5 hash of both frames matches, then they are physically identical without any doubt. If the hash codes mismatch, the ImageMagick tool highlights which pixels are different.
After comparing 24 different frames (one second of video, about a billion pixel’s worth), every single cable they tested gave identical MD5 hash results between the source PC and capture card frames. These HDMI cables ranged from £5 to a hefty £150, including lengths between 1 metre (3.3 feet) and 10 metres (33 feet.) What they were able to prove is that expensive HDMI cables do not deliver any improvement over considerably cheaper HDMI cables.
As long as the cable is HDMI certified to the spec you need (many cheap cables are even v1.4 compliant), the only main risk with buying cheap cables is poor workmanship, where pins may become loose or the wires are not crimped properly, in which case an affected cable would deliver an intermittent picture or no picture at all. In the worst case scenario where a bad cable does cause bits to flip, these will show up as different colour pixels randomly flickering about the screen. It would not affect the colour-cast, brightness or cause ghosting like a low quality analogue cable would.
The expensive HDMI cable testing article can be read at Expert Reviews.