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High Definition: The Basics

As I’ve already mentioned, the subject of high definition TV is not a simple one, so I’ll start by covering the requirements laid down by EICTA in order for a TV to carry the “HD Ready” logo.

1) The minimum resolution of the display must be 720 lines in a widescreen aspect ratio.
2) The display must accept an HD signal via an analogue YPbPr (component video) connection and either DVI or HDMI digital connections.
3) The HD inputs must accept both the standard high definition formats:
• 1,280 x 720 @ 50 & 60Hz Progressive (720p)
• 1,920 x 1,080 @ 50 & 60Hz Interlaced (1080i)
4) The DVI or HDMI digital input must be HDCP compliant.



Starting with point one of the HD Ready specification it’s clear that the minimum number of lines in high definition video is 720. Obviously that’s a significant increase in resolution over SD PAL’s 576 lines, but a massive increase over SD NTSC’s 480 lines. Another important point is that a television MUST conform to a widescreen aspect ratio in order to sport the HD Ready logo, which could be the final death knell for 4:3 TVs – no bad thing in my opinion.

It’s worth pointing out though, that the HD Ready logo requires a widescreen aspect ratio and NOT a widescreen resolution. This is why certain plasma TVs carry the HD Ready logo, but bizarrely sport what looks like a 4:3 resolution like 1,024 x 768. Despite the physical resolution, these TVs still produce a widescreen aspect ratio due to the way the pixels are constructed or laid out on the glass.

Number two is pretty self explanatory. The stipulation for component video and a digital input is a good decision, giving the consumer the option of connecting pretty much any high definition source to the TV. I was very happy to see that component video was a prerequisite, since I have spent many years arguing with people who believed that SCART RGB was better quality than component video, and the fact that it is part of the high definition standard kind of proves my point.



DVI (Digital Visual Interface) and HDMI (High Definition Multimedia Interface) are pretty similar digital video interfaces, but HDMI has the advantage of carrying sound as well as video. Also HDMI is a smaller connector, making it more friendly for consumer electronics devices. Although DVI is more common on computer monitors, there are several HDTVs with this connection. Don’t worry about a mismatch though since DVI to HDMI (and vice versa) converters are easy to come by.

Number three is interesting because, as mentioned before, the devil is in the detail. The thing to remember here is that an HD Ready television only has to accept both 720p and 1080i signals, but it doesn’t have to be able to display the 1080 lines of information for the latter format. This means that if your HDTV has a resolution of 1,366 x 768, it will downscale the 1080 signal to 720 lines and display it, since it physically doesn’t have enough lines. I’ll come back to resolutions and standards in a minute, but for the moment let me finish explaining the HD Ready requirements.

Number four stipulates that the digital interface must be HDCP (High-Bandwidth Digital Content Protection) compliant. Again I’ll go into more detail about HDCP a bit later, but ensuring that a TV has this feature means that any copy protected source material can be displayed without issue.

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