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Originally Posted by Fozzie Bear
What's a VCD? Is it like a DVD? Can it be viewed on a DVD player or only in a computer?
What is it and how does it work? (The quick answer).
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VCD (VideoCD) was an early attempt to put digital video into the consumer marketplace. It flopped. The playing time of a VCD is the same as that of a CD - 74 or 80 minutes. Most DVD players (probably all of them by now) will play VCDs without problems.
However, the compression scheme used for VCD is pretty elderly now. It was good for its day, but technology has moved on quite a bit since the late 80s when it was designed! A VCD picture is significantly poorer quality than VHS. There are two basic problems: resolution and compression problems.
To give you a direct comparison, these are the picture resolutions of various systems:
PAL DVD: 720x576 pixels
NTSC DVD: 720x480 pixels
PAL VCD: 352x288 pixels
NTSC VCD: 352x240 pixels
If VHS were represented in the above terms, it would be roughly 352x576 for PAL and 352x480 for NTSC. Literally "by definition", VCD has half the resolution of VHS...
Compression problems are what lead to the picture looking 'blocky'. You may also see this on poorly-encoded DVD pictures; the cause is the same. The effect tends to be more pronounced on VCD, as there is less space available to store the data, and so a lot of fine details in the image have to be thrown away. Transferring something from VHS won't help much, since the picture is unbelievably 'noisy', and this translates into lots and lots of fine detail. Inevitably, in order to compress this, a lot of pertinent picture gets lost along the way :-(
The other significant problem is that VCDs do not support interlaced video. Anything that originated on interlaced video, which includes *all* videotape-produced Henson shows except VMC, will have juddery motion when transferred to a VCD, much like a great many bootleg DVDs do. How bad this problem is depends on whether the person who created the VCD actually knows the first thing about video, but there will always be a problem: it's a limitation of the format. To see a good example of the *type* of thing I mean, watch "The Muppets at Walt Disney World". In the shots where Kermit shares the picture with Mickey, the motion suddenly becomes very jerky when compared to the surrounding shots. This is basically what a VCD taken from interlaced video would look like.
As an aside, this type of question gets asked a fair bit around here. I am thinking of maybe posting a FAQ or starting a sticky thread where people can ask the questions (and look up the answers before asking :-). What do people think?
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