Dvd
DvdResearch on DVD
A Brief Summary
DVD is a new technology very similar to compact discs. A DVD looks just like an ordinary compact disc, however a DVD can hold up too 6 times as much as a CD! That's 4.7 gigabytes! This gives enough room to hold an entire movie at twice the quality of VHS with theatre quality sound (better than CD-quality). Since it is on a disc, you can jump to any scene instantly, and you never need to rewind.
The Different types of DVD include:
DVD-ROM
DVD-ROM stands for Digital Versatile Disc - Read Only Memory. It is an optical disk the same diameter as a CD, but unlike the CD�s capacity of 650 megabytes, it can hold up to 4.7 gigabytes of storage. Its capacity is over six times that of a CD and the reason for this is that data is written to DVD with a smaller laser than a CD, which makes it possible to store data more efficiently. The storage capacity of DVD is so great that over 95% of all feature length films can be stored with room to spare, and also fast data access enables you to read from DVD the same as a hard-disk drive. The best thing of all about the DVD-ROM drive is the fact that it is backward compatible with standard CD-ROM and CD audio discs.
DVD-RAM
DVD-RAM stands for Digital Versatile Disc - Random Access Memory, and is the approved format by the Official DVD Forum. DVD-RAM are dual sided and can hold up to 2.6 gigabytes per side. They use phase-change as a recording material, �wobbled land and groove� recording method, embossed pits for header information, Zoned Constant Linear Velocity (ZCLV) rotational control, and is a random-access, non-sequential medium. DVD-RAM-Compatible readers will require servos to handle switching between the lands and grooves. DVD-RAM drives will also need a decoder to handle scattered 32K ECC Blocks, something not needed for DVD-ROM and DVD+RW, since their blocks are contiguous.
DVD-RW
DVD-RW stands for Digital Versatile Disc - Rewriteable. It uses a phase-change-recording layer, a lot like the CD-RW. It allows a disc to be recorded, erased, and rewritten that is readable only in DVD read-only drives and players.
DVD-R
DVD-R stands for Digital Versatile Disc - Recordable, and it is the DVD version of the CD-R, in that it uses the same wavelength -specific organic dye-based media to record once on a disc that is readable in DVD read-only drives and players.
DVD-Video
Up to the application level DVD-Video is identical to DVD-ROM, the only thing at all that is different between these two is the application layer. The application layer for DVD-Video is clearly defined as the type of video codec, audio compression, navigational commands, auxiliary files, and other data types that it may contain. Only DVD discs that abide by these definitions will work on a DVD-Video-Player.
The DVD-Video-Disc is not an MPEG 2 digital video stream, but a stream of all these elements put together. What goes out of a DVD-Video-Player and into the television is not actually digital-video, but one of three types of standard television signals: component, composite, or S-Video.