Digital AV cables rip-off

No. Our testing found no statistically significant variations in score either for picture or sound. Although the results were slightly in favour of the more expensive brand for longer lengths, the differences were not enough to conclude any brand delivers a significantly better result.

Results for the digital audio cable were even more conclusive, with no advantage to be gained through the use of more expensive cables for better performance. See the table for prices.

HDMI

The High Definition Multimedia Interface (HDMI), a recent introduction to the home entertainment landscape, is a trademarked standard that combines audio and video in a digital format.

Aside from vision and audio, an HDMI cable can also identify other connected devices making it easier to integrate your home theatre system. Unlike analog cables such as SCART, component, composite and so on, HDMI cables can recognise copy protection information as well.

The price variation for HDMI cable is astonishing, with short-run cables of up to three metres selling for anything from $30 to more than $300. In an effort to justify such exorbitant prices, performance claims on the packaging attempt to make the purchaser feel better about the investment.

One company claims its product "eliminates digital-to-analog conversion between your video source and display for the most accurate high definition picture" – in other words, it’s an HDMI cable that does what it’s designed to do.

Toslink

Toslink (TOShiba LINK) is a much older technology than HDMI, introduced as a computer connection in the early 1980s.

The optical cable allows for digital audio (both left and right channels or multi-channel sound) to be transported between components using light as the carrier.

In contrast to the more robust construction of an HDMI cable, a Toslink cable is arguably more easily damaged.

However, based on our test results, you should still be able to get a good quality, short-length Toslink cable for about $30, even though you can spend $200 or more on a cable that performs the same task.

CHOICE verdict

If you require a short HDMI cable of anything less than four metres, you should be able to find many good cable options between $40 and $60. Spending $300 on a short length of cable is pointless; the money could be put to better use on a better set of speakers or upgraded DVD or Blu-ray player.

For longer cables over 10 metres, differences in performance may possibly be an issue if there is significant interference between the video source and display, but we did not find any difference until lengths were combined to form lengths more than 33 metres.

How we test

Four panellists compare a range of HDMI and Toslink digital audio cables at various price points to determine the amount of difference in audio/video quality that can be detected. The panellists are unaware of the cable designators, the brand and cable lengths. Each cable is compared twice unless an obvious impairment makes further checking necessary. The second run follows a different randomised order.

Picture and sound quality The panellists score the picture quality and/or sound quality on a scale of 1-10, where 10 means no impairment can be seen and/or heard. They are asked to describe any impairment which causes a score of less than 10. Short sequences from a Blu-ray movie are shown for the HDMI test and from a CD for the optical cable test, including male vocal, female vocal, rock, classical and Celtic music styles.

Performance To extract a performance difference, our testers combine a number of cables using female/female joiners, however we do not recommend this setup as it could lead to some degradation in video quality. Various combinations of up to four of the supplied cables are tried, using three joiners. No effects on the picture were seen. The maximum length tried from the supplied cables was 26m. Finally, by adding two generic 5m cables to cables used in the test, making the cable length 33m, we could discern “sparklies” (small white pixels not in the original footage) on close inspection of a 1080p video source. When the video was reduced to 720p the errant pixels disappeared.

Further testing

CHOICE conducts more tests with a different four-person panel, including male and female participants covering a broad age range.

Video quality To evaluate video quality, a copy of a Blu-ray movie sequence is shown using a Sony PS3 with the latest firmware applied and viewed on a Panasonic 50-inch plasma TV (TH-50PZ800A). Cables are swapped manually and the panel does not know which cable is in use at any given time.

Length discrepancies For our long (10-metre) test we use a Jaycar Concord brand ($100) and a Monster brand cable ($600). Toslink Reference tracks are played on a Pioneer DVD player that is connected to the Denon AV receiver to Aaron stereo loudspeakers. Cables are swapped manually, and the panel does not know which cable is in use at any given time.

High definition for TV sets refers to the number of lines on the screen; anything above 720p or 1080i is generally considered HD. Technically, high-definition sources can be anything from 576p at the low end of HD TV broadcasting, up to 1080p with Blu-ray.

The “p” stands for “progressive”, which gives a more stable picture than an interlaced picture which usually has an “i” after the number, while numbers such as 1080 or 720 represent the number of lines the TV uses to display the picture, and is regarded as high definition. The “i” and “p” denote different ways of displaying those lines. HDMI version 1.3 allows for WQXGA resolution (2560 x 1600) and up to 16 bits per pixel, which is a much higher resolution than 1080p.

Our test is limited to 1080p and the Blu-ray standard of 8 bits per pixel, since there is no commonly available source material or player beyond 1080p (8-bit) or any commercially available display higher than 1080p. What this means is that the current HDMI standard supports technologies beyond even the latest Blu-ray equipment, and even if and when these higher quality resolutions become available, the effect for the average user of current HDMI cables will be minimal.

Creating a better home theatre experience

• Look at reducing the ambient light in your room with blinds or choose a room where direct sunlight is least intrusive.
• Take the time to properly calibrate your home theatre system for the best quality sound.
• Don’t spend your entire budget on the display and ignore your audio system; good sound is just as important as video.
• Don’t expect those amazingly cheap DVDs you may have purchased while overseas to provide fantastic quality video and audio. No matter how much you spend on cables, the maxim of "garbage in, garbage out" applies to all video and audio.
• If your TV does not support HDMI, check to see if you can use component video instead of composite or S-video. The results could still give you HD quality video, with up to 1080i resolutions achievable.

Jargonbuster

• DVI (Digital Visual Interface) supports video only, with an identical signal to HDMI. It was introduced by the PC industry and can be found on many PC monitors as well as some flat panel TVs. DVI provides complete support for HDMI video through the use of an HDMI/DVI converter.
• HDMI 1.3a is the latest HDMI standard that incorporates faster data transfer speed support for future video technologies and support for more colours.
• DVD upscaling allows you to view your current DVD titles in an “enhanced video” mode, where the picture is interpolated to either 1080i or 1080p so your DVD movie appears almost HD. However, you need an HDMI connection and TV that can display HD to enjoy the benefits of DVD upscaling.
• Toslink provides a digital audio connection and is a good option if you’re unable to use HDMI to connect your Blu-ray player to your home theatre system. However, while Toslink supports most digital audio formats, it doesn’t support audio formats such as Dolby TrueHD and DTS HD Master audio signals.
• Component is the only analog cable solution to provide up to HD (1080i) quality if the TV can display the resolution. Three video cables are required to show the video, and you need a separate cable for sound.
• WQXGA (Wide Quad eXtended Graphics Array) is a resolution quality allowing pictures to be displayed at up to 2560 x 1600 pixels. Bits per pixel is a way to define the ability to resolve various degrees of colour resolution.