The DVD Video Disk
The DVD video disk is the most well-known DVD format. It is a 4.7 GB disk, which can hold up to135 minutes top quality video with 8 digital soundtracks (AC3, Digital Dolby) and sub-titles in 32 languages. Plus special features like interviews and trailers, alternate versions.
The Dolby AC-3 is a sound system with five full range speakers to surround you with sound, plus a supplementary low frequency special effect channel. To get the full use of the movie sound tracks, you need a AC-3 compatible stereo set up.
MPEG-2 decodingThe video format on DVD disks is in MPEG-2 coding. That is a compression technology, which requires lots of processor power. When you buy or rent a DVD video disk, the digital video stream of the movie has been heavily compressed. Hence, the data stream from the disk has to be decoded when you watch the film. This has to be done in real-time during the replay (real time decoding).
Soft or hard decoding?MPEG-2 decoding can be done in two ways:
The software-based decoding is done by the PCs CPU using special software. This is not always very good since it drains the PC. Also the CPU seldom is powerful enogh to perform a perfect decoding. Some graphics chips include DVD decoding features, but have to work together with a software decoder as well.
. The software based decoding does not require any new hardware, but it requires a very powerful CPU and/or graphics adapter. If there is not sufficient processor power, you will see a loss of some individual images. The movie gets "choppy."
The hardware-based decoding is to prefer. Here the PC is equipped with a special chip (on an adapter) which only has to decode the MPEG data stream. The most well-known products are based on the called Real Magic Hollywood+ chipset.
The advantage of the hardware based decoding is that the result does not depend on the CPU in your PC. The disadvantage is that you need to install an extra card in the PC to enable seeing DVD films. It often comes with the DVD drive as here:
However, MPEG cards are not always powerful enough either, according to the reviews and to what I so far have seen. All in all, I might wait for further DVD and MPEG developments. In a couple of years the MPEG decoding will surely become a standard task (included in graphics chip sets), which all PC’s can perform without problems.
The playersYou can view DVD video several ways:
If you use your PC to replay videos, you should have a hardware-based MPEG-2 decoder in the PC. But the best replay comes from a DVD-Video home player:
These units only play DVD video disk and do not interface with the PC.
MultiplayersIn 1999 we suddenly saw a series of new products, namely integrated CD, MP3 and DVD players from Taiwan. The devices are designed to fit into the HIFI stereo set:
I have one of those new players myself, and it works fine. It plays so to say any type of optic disc, be it music CD, CD-R with (12 hours of) MP3, DVD or small laserdiscs.
The device is based on a standard PC DVD drive, so it can be pretty noisy. The Video DVD replay is comparable to the one from a PC with DVD drive and MPEG-2 adapter.
The regional codesDVD movies are made in several "codes." Region one is USA and Canada, while Europe and Asia is region two:
When you play movies, your hardware (MPEG decoder) must match the DVD region. The movies are made in separate formats, each with their own coding. The DVD drives has to be set to one of the codes, and this setting can be changed perhaps five times.
Most players can be altered so the become code-free. The operation is quite simple, but it is a violation against the one year guarantee.
Many European users dislike the coding system: The companies sell the same movie at higher prices for region 2 than for region 1. This region thing is a typical example of industrial stupidity. From the consumers view, there is absolutely no need for this division of markets. It only makes things more difficult and expensive.
Incidentially Sony PlayStation2 machine are cabable of playing both region 1 and 2! This was not intended. It only goes for some region 1 DVDs, though.
A typical reaction from PC nerds and hacker types have been to crack the DVD encryption. In 1999 a 14 years old Norwegian boy was succesfull in this. The industry tried to prosecute him ...
To understand their worry, we have to look ahead. Today it is hard to imagine many copys from DVD video disks made on DWD-recorders. But maybe in 5 to 10 years we will have digital copies of all the Hitchcock movies circulating in Napster-like networks as the situation is with music and MP3s today.
Module 4d about MO drives.
Please read Module 4e about tape streamers (they are not drives).
Please read Module 5c about SCSI.
Please read Module 6a about file
Copyright (c) 1996-2005 by Michael B. Karbo. www.karbosguide.com.