Progressive Scan Questions
Dear Gary: I have some very basic questions. If you have an HDTV and a progressive-scan DVD player, will it improve the picture of all disc formats or only anamorphic widescreen? If you buy a standalone scaler/deinterlacer, do you need a progressive-scan DVD player? Will it improve the picture from a VHS tape player, cable TV feed or LaserDisc player? I’m just getting started in higher end home theatre, and although I subscribe to several magazines, including Widescreen Review, most of the articles presuppose a certain level of knowledge. Thank you for any help you might be able to give.
BravesNoles845@aol.com
Video Technical Editor Greg Rogers Comments:
You have asked some basic, but important questions. They are interrelated, but I’ll try to answer them in the order you asked. Any display (not just HDTVs) with a 16:9 (1.78:1) screen should improve the picture quality of DVDs that have the 16:9 (anamorphic) format. Both 16:9 and 4:3 (1.33:1) DVD formats have 480 scan lines in a video frame. When you display a 16:9 format DVD on a 16:9 screen you get to see all 480 scan lines on the screen. But when you display a 16:9 DVD on a 4:3 screen, the DVD player must scale the 480 scan lines into only 360 lines so the frame will occupy a 16:9 area on the 4:3 screen. Consequently, a 16:9 screen allows you to have 33 percent more vertical resolution with 16:9 DVDs, but not with 4:3 letterboxed or 4:3 full-frame DVDs. There are also some TVs with 4:3 screens that have a special mode to produce a 16:9 picture by reducing the height of the raster scan area (the visible picture). These TVs can also take advantage of the increased vertical resolution of 16:9 DVDs. Many HDTVs have CRTs or optics with better resolution than standard-definition TVs. That can make all DVD pictures look sharper than they would on most standard-definition TVs. Of course, higher resolution also reveals problems in noisy or ghosted sources. Most HDTVs also include built-in line doublers or scalers and upconvert all standard-definition sources to 480p or 540p. This can have mixed results. Upconverters generally follow the rule, “some garbage in, more garbage out.” Sources with a lot of video noise and jitter, in the case of some VCRs, may look worse on an HDTV when upconverted to 480p or 540p. A progressive-scan DVD player produces progressive signals for all DVD picture formats. But a progressive-scan DVD player may or may not be a significant benefit with an HDTV. Almost all progressive-scan DVD players include inverse-telecine deinterlacing, which detects 3:2 pulldown in movie sources to convert interlaced video to progressive video. This is the optimum way to deinterlace film sources. Most new HDTVs also have inverse-telecine deinterlacing. But some HDTVs still use older deinterlacing techniques that leave artifacts in the picture. So, in those cases, a progressive DVD player or an external line doubler or scaler will be a very significant benefit. Even when an HDTV has inverse-telecine processing, there may still be some benefit from using a higher-end progressive-scan DVD player. The best progressive players take full advantage of digitally coupling their deinterlacing circuits to their MPEG decoder. They may also include additional features and use higher performance circuits in their progressive outputs than their interlaced outputs. This may result in better signal accuracy, better resolution, less noise, and fewer artifacts. The visibility of these improvements will depend on the resolution and performance of the HDTV. The advantage of an external line doubler or scaler over a progressive-scan DVD player is that it will process all standard-definition video sources, which includes VCRs, cable and broadcast TV, satellite TV, DVD players and LaserDisc players. Some scalers/line doublers do have problems syncing to the output of some VCRs when running in the fast forward or reverse modes. If you intend to use it for this application, you should test the product with your VCR before buying. Most scalers do not accept progressive video signals from progressive-scan DVD players. You can still use a DVD player’s interlaced video outputs with the scaler, but you won’t benefit from any special features or circuits associated with the DVD player’s progressive output. Some scalers that do accept progressive video have had problems with the progressive Macrovision copy-protection signals that a DVD player adds when playing most DVDs. Since this is subject to change, you should check with the scaler manufacturer to get their latest information concerning compatibility with progressive-scan Macrovision copy protection.
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