The HDMI Standards Organisation has issued a clarification notice regarding the speed ratings being claimed by some cable manufacturers.

Under the heading What do Speed Ratings on HDMI Cables Measure?, it points out that there are only two official speed ratings - Standard and High Speed - and that these alone determine whether or not a cable can handle 1080p pictures, or just 1080i.

The full text reads as follows, with bold type as in the original statement:

'Regardless of what terms may be used in the marketplace to describe the capabilities of an HDMI cable, the HDMI specification only defines two cable types: “Standard” and “High Speed.” Both terms are based on specific performance criteria.

'A Standard HDMI cable is tested to support a throughput of 2.23 Gbps, and can reliably transmit an uncompressed 1080i signal at 60Hz.

More after the break

'A High Speed HDMI cable, by contrast, has been tested to the full 10.2 Gbps bandwidth of the most current HDMI standard, and is capable of transmitting uncompressed 1080p and beyond.

'While these are the only two “official” HDMI cable categories, with performance levels defined in the HDMI specification and measured by the compliance-testing process, some manufacturers have opted to go beyond these categories and provide their customers with additional information about cable performance capabilities. These efforts are often supported by third-party testing services such as Simplay Labs or the DPL program, which provide more specific speed ratings than those defined by HDMI Licensing.

'How valuable are these additional ratings? If a consumer is looking for a particular performance level so that they can buy exactly what they need, then speed ratings may be very helpful.

'One word of caution. Do check to make sure that the speed rating indicated on the package applies to the actual length of the cable. Cable performance deteriorates over length, so any speed rating should apply to the actual length of the cable in the package.'

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