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Reader question: 720p on 1080i set

Kevin C. Tofel

In our "Truth in Advertising" post some time back, we discussed HD resolutions and our desire for mandatory labeling of display resolutions. HD Beat reader Mark recently commented with a question regarding 720p signals on a set that doesn't natively display 720p.

"I'm going to buy an hdtv and am considering the Panasonic CT-34WX15 TAU. (crt)It supports HDTV @ 1080i and EDTV @ 480p. My question is what happens when I view a resolution at 720p? Is this set going to display it properly? Also, the Panasonic DVD-S77 player puts out 1080i and 720p. Where is the 720p on the T.V.?"

I actually own the same basic Tau series CRT, but this question can be applied to any set that doesn't natively display a 720p signal.

Mark, the simple answer is that your set will display a 720p signal at 1080i due to upconversion. Like many other CRTs, your set (and mine) don't display 720p natively, so the set will automatically modify the incoming signal to make it display at 1080i. You may also have some settings for this conversion on a set-top box or ATSC tuner. This is both good and bad: theoretically, the picture is at a higher resolution because more pixels are displayed overall, but the set is only drawing half of the scan lines during each frame. Ultimately, it's a good thing because if the set wasn't capable of converting the 720p signal, you wouldn't get a picture at all with the signal!

For the DVD player that can output at 720p or 1080i, you might want to do some experimentation with both settings. The 720p setting will likely still work with your 1080i set as the set should modify the signal to a 1080i display. However, since your set natively displays at 1080i, consider "matching" that setting with your set by pumping out a 1080i signal from the DVD player. As a general rule of thumb, the less conversion the better and don't forget: to take full advantage of the upconversion from that Panasonic DVD player, you must use the HDMI connection.

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