Posted: Sat 11 Dec 2004, 1:04 Post subject: Which DVDs are interlaced?
Sorry if this isn't the right place to ask, but I just wanted to know which DVDs are interlaced. I'm buying a progressive scan TV and I don't want any interlaced signals — how do I know which DVDs are interlaced and which aren't? Or all they all interlaced?
And also, can anyone explain how an interlaced signal is encoded onto a DVD? I thought mpeg files were slightly blurry (for the sake of compression). If they are slightly blurry, then how can the crisp, sharp lines of the interlaced signal be preserved? And if the two fields bleed into each other then won't the motion look blurry?
Joined: 04 Feb 2003 Posts: 587 Location: Lisboa, Portugal
Posted: Sun 12 Dec 2004, 3:35 Post subject:
No, MPEG is not blurry unless you use a very low bitrate, but even if you do blur an interlaced image, it will still play correctly, because the two fields are likely to be very similar anyway (in fact, if an image is too sharp, like some computer-generated images, small details may "flash" when shown on an interlaced monitor). Blur them by about 0.4 pixels and they will look much better. It doesn't actually look blurry unless things are blurred by 1.5 pixels or more.
Regarding interlaced DVDs, there's no way to tell. If a DVD is made from video (ex., some TV series, some documentaries, etc.), it's likely to be interlaced.
If a DVD is made from film, it can be interlaced or not. PAL "film" DVDs are almost never interlaced (they simply play back at 25 fps instead of the film's 24 - that's why PAL versions are usually 4% shorter than NTSC versions). NTSC "film" DVDs can be interlaced or not. If they're not, it's up to the player to apply pulldown (convert each frame to 2 or 3 fields, alternately) when it's connected to an interlaced TV.
But you can get a progressive signal out of an interlaced DVD anyway (the player just needs to apply pullup to recover the original frames), so there's no need to worry about that. The only disadvantage of interlaced DVDs is the video files are a bit bigger (because they're 29.97 fps instead of 24) - the image itself is virtually identical.
One advantage of PAL DVDs is they have 20% better vertical resolution, but you need a TV that can handle the PAL signal.
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