When is HDTV not HDTV?

We've covered the definition of HDTV pretty comprehensively on the The HDTV Tuner, in particular here and we've also dealt with the differences between EDTV and HDTV, but a question from a reader the other day prompted me to think that it's worth covering again.

In order to receive and watch an HDTV signal you need a number of things. Firstly, you need to be in a country and area where HDTV is broadcast, either over the air, by cable or by satellite. If you live in the US, you can almost certainly receive HDTV by one, if not all of these media. In Europe, you will be more limited. For example, in the UK you need to either sign-up to Telewest (cable) or Sky (satellite) to get HDTV (although you could invest in a Freesat box and receive satellite HDTV without a subscription).

Secondly you need a tuner that can receive HDTV. This will typically either be a cable, satellite, or off-air set-top box, but could also be an integrated HDTV, CableCard or Mac/PC HDTV tuner (usually either a PCI card or USB 2 peripheral).

Thirdly, you need a display which is capable of reproducing HDTV signals. To do this, it must have a vertical resolution of at least 720 pixels, be able to display progressive scan signals, and have a minimum width to height aspect ratio of 16:9. EDTVs have a vertical resolution of only 480 lines and so can't display HDTV signals at HDTV quality.

Finally, you need to be able to hook the three elements together. The key part here is that the TV must be connected to the tuner, if it's not built-in, by a medium capable of transferring high definition signals. For a TV or projector this means DVI, HDMI, or component connections — although if you choose component, you may run into trouble later on when watching signals encoded using particular HDCP. For a computer tuner, a PCI slot, USB 2 or FireWire interface will do the job.