Is Blu Ray really better than high definition cable?

30 Mar

March 30, 2009

By Geoff Meeker

In my last column, I reviewed the new Panasonic 46” plasma TV, with Viera Cast. While discussing the latest TV technology with the salesperson, I asked about Blu Ray DVD players.

I had assumed the high definition (hi def) programming I watched on cable was the same quality as the Blu Ray DVD player. Right?

Wrong.

According to Dave Budden of West End Electronics, there is a key difference. Hi def TV signals are distributed in 1080i format (and sometimes the inferior 720p), whereas Blue Ray DVD signals are 1080p.

And all this time, I had been watching hi def movies on cable, thinking I was seeing the ultimate in picture quality.

Budden gave me a document that explains the difference, but the language is pretty technical. Here is the nub of it:

“In 1080i each frame of video is sent or displayed in alternative fields. The fields in 1080i are composed of 540 rows of pixels or lines of pixels running from the top to the bottom of the screen, with the odd fields displayed first and the even fields displayed second. Together, both fields create a full frame, made up of all 1,080 pixel rows or lines, every 30th of a second.

“In 1080p, each frame of video is sent or displayed progressively. This means that both the odd and even fields that make up the full frame are displayed together. This results in a smoother looking image, with less motion artifacts and jagged edges.”

The big difference in the two, then, is not the number of pixels – it’s the image processing, which supposedly interlaces and overlaps each frame, creating a sharper and more seamless moving image.

Or so they say. The truth is in the viewing, and this was something I had to see for myself. Budden kindly lent me a Panasonic DMP-BD55 Blu Ray DVD player for a few days.

The verdict? There is a difference, but only barely discernible. Hi def TV images are already amazingly sharp; the Blu Ray DVD makes them just incrementally sharper. On a large screen TV, the discriminating eye can see the difference. But on a screen smaller than 40”, that difference will be negligible, if it’s noticeable at all (though it should be noted that Blu Ray offers superb audio quality, an important detail for surround sound purists).

There is one situation where Blu Ray is a must-have. If you are planning to install a projection TV theatre with a massive screen – as large as 12 feet – in your home, you really need a 1080p projector, and a Blu Ray DVD player. When projecting to a screen that large, you need to roll out the big guns to maintain image quality.

And Blue Ray does have one definite advantage over digital cable. Have you ever watched a hi def movie on TV, only to have the signal suddenly pixelate, or dissolve into a bunch of annoying little squares? This is the result of too much information coming down the pipe for the TV to render in real time, and usually happens when there is a lot of movement happening across the entire screen, such as a close-up of a waterfall. In my experience, this only happens on cable – the direct feed from Blu Ray is always perfect.

However, to summarize, Blu Ray is only marginally better in image quality than hi def cable.

As I’ve written before, the future of Blu Ray depends less on the quality of the format itself, than on the growing popularity of movies on digital cable.

Geoff Meeker is a communications consultant with a soft spot for technology. He also writes a blog about the local media scene, which is hosted at http://www.thetelegram.com.

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