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Here's why DVD is so goodMar 01 '00 (Updated Mar 29 '00) Write an essay on this topic.By now almost everyone has heard about DVD if not actually seen one in action. There is a lot of hype about this format and most of it is justified. For those still considering this issue of whether or not to buy in, here is my epinion about this format. VHS or DVD? Some say they already have a movie delivery system in their homes, VHS tape, so why would they want yet another incompatible format, DVD? OK, here’s some info about both; VHS is an analog videotape format developed by a consortium of Japanese electronics manufacturers in the early 1980’s. To make it affordable to the consumer the standards for NTSC standard broadcast quality video were greatly compromised. The luminance bandwidth was cut in half so detail resolution is a mere 220 lines per horizontal line. Broadcast quality recorders at the time could record up to 450 lines of resolution (Over the air broadcast delivery gets only around 330 lines of resolution to the home). To fit the color information on the VHS tape it was cut down to a mere 20% of the original detail so there are approximately only 40 lines of color information per horizontal line! That means that anything with color in it is going to become a rather fat and blurry blob instead of finely grained color detail. In two words Primitive! Compromised! What DVD does for the consumer is finally create a delivery system that gets all the information to the consumer created in the master digital component tape during the film transfer. With DVD, image data is recorded as microscopic pits on a reflective surface, similar to CD’s, only the pits are far smaller and more densely packed than CD’s. Information is recorded as an MPEG2 highly compressed component digital video signal. Compression rates are roughly 40 to 1 but careful quality control during the mastering process can usually preserve a great deal of the original picture quality in the MPEG2 data. There are over 450 lines of luminance detail and over 220 lines of color information per line. Try reading the credits on a VHS tape and you’ll see right away what I mean here. On VHS words smear together making them practically illegible. Skin textures dissolve into blobby areas with no detail at all. Compare this to the same images on a DVD. The credits are sharp enough to read on even the smallest disclaimers and copyrights. Skin comes alive with visible fine detail, pores, wrinkles, and all the color nuances of small areas such as freckles and blemishes. You could draw an analogy by comparing VHS to AM radio and DVD's to CD. The quality differences are that pronounced! In a few words Near D-1 Quality! Sharp, clean, quiet! What about noise? Noise in a video signal shows up as a snowy texture superimposed over the image. VHS, with its marginal bandwidth also creates wiggly and fat enhancement artifacts on edges. VHS will make a person’s face appear to have a line drawn around it and this is not a subtle thing at all. This was not in the original film and not in the original high quality video master. DVD lets you see the film, not the artifacts of a low quality copy of the film. DVD is inherently noise free. If you see grain or noise in the image from the DVD it’s most likely not your playback machine doing it, but an artifact of the original film grain or noise in the original scanning of the film. So here’s what you can look forward to with DVD compared to VHS; 1. Much more realistic and detailed images. 2. Much better color detail. 3. Cleaner, quieter images (noise free). 4. No rewind. It’s like a CD not a tape. 5. Lots of extras. DVD’s are often produced with additional chapters that give info on the actors, "The Making of.." type info, trailers, alternative languages, and director's comment tracks. The formatting of the DVD really depends on the imagination and budget of the manufacturer. The digital format allows the data to be organized in chapters and easily accessible via the remote control through a graphical interface menu which is part of each DVD. The graphical interface is very flexible and the actual graphics are unique for each DVD. Each chapter can be almost instantly accessed via the remote. Hop to your favorite scene or special feature in a flash! 6. Wide Screen capable. Movies are recorded in both Wide Screen (16/9) format and Standard (4/3 Pan and Scan) on many discs. Make sure to read the box before you rent or buy to make sure the disc has the version you want. Some discs have both version’s on them, some have only one or the other. 7. Superior Audio Bear in mind that I have not yet even touched on the audio aspects of DVD. Because of my background in television post production I tend to value the picture quality highest but the audio is a big part of any home theater experience. DVD will not let you down here. Basically, Audio on DVD's is digital, like on CD's, and usually (but not always) will include a Dolby Digital 5.1 discrete channel soundtrack. Some DVD players will have built in Dolby Digital decoders, some won't. VHS may have a Hi-Fi Stereo audio track but can only be about as good as an FM Stereo broadcast in quality. Try reading some of Sir Montego's posts on these topics for a lot more in depth info on DVD audio. Convinced? Shop around Some DVD players are better than others in reconstructing the image from the highly compressed MPEG2 data. This is where comparative shopping will tell you a thing or too. Look for blocky compression artifacts in dark areas of the picture and compare different models to see which ones give you the best performance. No blockiness at all is ideal but not completely possible to achieve with MPEG2. Always use the same scene from the same DVD to evaluate this critical parameter if this is an issue for you. I hope this is not too long winded and that you get something useful out of this. There is a lot more to DVD than this brief intro. For the technically curious try visiting the url below for a list of a couple of DVD FAQ's and even more in depth info about DVD's; http://www.unik.no/~robert/hifi/dvd/ Hope all this helps. Major revisons done March 27, 2000 Please leave a comment. Thanks Dave  |
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