The Miller Channel
By Kevin Miller
A new term in video is being bantered around a lot in home theater circles. Progressive-scan. What is it? How does it work? What makes it so special? These are all valid questions, especially considering there is a whole new crop of progressive-scan DVD players vying for your hard-earned dollar.
Your older analog TV uses the interlace method of drawing images on the screen where as the newer digital HDTVs use the progressive-scan method of drawing pictures all at once in the same time frame. During the transition period between analog TV and digital HDTV, line doublers were employed on sophisticated multi-scan front and rear-projection TVs to turn an interlaced NTSC picture into a progressively scanned image for big screen home theater applications. The line doubler effectively doubled the number of lines on the screen, making the scan lines that make up the picture less visible.
Progressive-scan pictures are drawn by a digital TV the same way your computer monitor delivers its images. That is it writes one full frame of video every 1/60th of a second from left to right across the screen. Traditional analog interlaced TVs write half a video frame every 1/60th of a second and the other half the second 1/60th of a second making that same video frame come together in two pieces every 30th of a second. Simply put a progressively scanned video image is better than an interlaced image, because there are no interlace artifacts or motion artifacts introduced into the picture if its done right.
Why are progressive-scan DVD players better than regular interlaced players? First off progressive-scan DVD players will only work with digital HDTVs, and are not compatible with older analog sets due to their higher horizontal scanning frequency of 31.5 kHz. All the progressive-scan DVD players worth their salt use 2:3 pull-down circuitry, which differentiates between film's 24 fps (frames per second) frame rate and video's 30 fps frame rate. I can't overemphasize the importance of this little circuit, which virtually eliminates what we in the industry call "jaggie" artifacts.
The best example on DVD comes in the very opening scene of "Star Trek: Insurrection". It opens with some children playing in haystacks. Then the camera pans to a village with a number of bridges and rooftops. If you watch this scene on an HDTV with a line doubler that lacks 2:3 pull-down (almost all of them do) and a regular interlaced DVD player you will see these nasty jaggy artifacts crawling along the bridge railings and all around the edges of the rooftops. Once you've seen this it will haunt you in all film based DVD material.
The other big reason why progressive-scan DVD players deliver much better pictures is that with an interlaced player fed to a digital HDTV, the TV's line doubler must convert an interlaced signal to a progressive (A/D) signal. With a progressive-scan player there is no analog to digital conversion process, making the output of the player direct digital to the TV. This results in sharper cleaner pictures. The good news is that progressive-scan DVD player prices will be plunging this summer to the $399 to $500 price points most of us can afford.
Advanced User Tip
When setting up your progressive-scan DVD player there are a couple of things you need to do to get the optimum performance from the player with your digital TV. First if you have independent input memories, meaning separate picture controls for each source, choose the Setup button or on some newer players like the Sony DVP-S9000ES hit the Display button. In the Setup menu of the player make sure you choose Enhanced Black or its equivalent. This will give the player a 0 IRE black level, which delivers deeper richer blacks when PLUGE is set properly with the TV's brightness control. Since HDTV is delivered at 0 IRE black, this will also ensure a closer match with your TV's HDTV black level, which would otherwise be significantly different. Remember also to choose the correct setting for your TV's shape whether it is 16:9 or 4:3.
6/5/01
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