| DVD-ROM FAQ
What is DVD-ROM?
DVD-ROM stands for DVD - Read Only Memory. Like CD-ROM discs, DVD-ROM
discs are intended for computer use, and are molded with the information
pressed right into the disc. However, unlike CD-ROM with its 650 MB capacity,
DVD-ROM discs can hold up to 4.7 GB of information. Even higher capacities
are possible with additional information layers and double sided DVD-ROM
Can DVD-ROM drives play/read standard CD-ROM discs?
Yes, DVD-ROM drives are backward compatible with standard CD-ROM and CD
Can DVD-Video discs be played on a DVD-ROM drive?
Yes, with an MPEG-2 card installed in the PC and appropriate audio playback
hardware (sound card & speakers), DVD-Video movies can be enjoyed
on the PC.
Why should I purchase a DVD-ROM drive instead of
a CD-ROM drive?
DVD-ROM drives, being backward compatible with CD-ROM, protect your investment
in those discs while opening up the exciting world of DVD to your PC.
What is the capacity of DVD-ROM discs?
Basic capacity is 4.7 GB (single sided, single layer), however 8.5 GB
is possible (Double sided, single layer), as is 17 GB (Double sided, double
Why is an MPEG-2 card required to use a DVD-ROM
Any DVD-ROM title that contains MPEG-2 video sequences, or a DVD-Video
movie, requires a MPEG-2 decoder to decompress the video stream and pass
the data to the PC's display so the video can be viewed.
What is DVD?
DVD stands for Digital Versatile Disc. It is the next generation in technology,
the optical disk for data storage. Basically it is bigger and faster than
CD, althow it is a CD sized disc. DVD offers 4.7 gigabytes of storage
(4700 Megabytes, or more than 7 times what a CD-ROM can hold).
And what about those DVD Formats?
DVD-ROM is a basic format that carries data.
DVD-Video (or just DVD)
DVD-Video uses text menus, MPEG-2 video - video compressed into NTSC-North
American or PAL format - European TV broadcast standards and a variety
of different audio formats.
DVD-Audio uses the enormous storage capacity of DVD to store high quality,
multi-channel recorded music.
What DVD offers?
DVD is a new medium with it's own features, capabilities and limitations.
Because of it's enormous capacity and capabilities it revolutionalized
the entertainment software industry, making VHS tape and CD obsolete.
DVD offers high video and audio quality combined with many extra features,
like extra scenes, alternate angles, and multiple audio tracks. Many films
are now being produced with DVD extras in mind.
Unlike traditional tape based formats, head and tape wear is no longer
an issue - for example, you can watch over and over your favorite scene
without a fear of damaging that part of movie.
DVD is an ideal format for various kinds of video presentations. DVD's
inherent skip track settings allow random access to information without
fast forwarding or rewinding through minutes of irrelevant tape.
What DVD has that traditional VHS tape has not?
One of the most obvious difference between DVD and traditional VHS tape
is in video and audio quality. The DVD specification allows for Dolby
Digital© sound. This is a discrete 5.1 channel audio format, allowing
the users to expiriance sound of studio quality. But, users must be set
up with a six speaker system, otherwise they will receive the normal stereo
Video quality provided by digital MPEG-2 stream allows near digital beta
video quality.This means that the video signal is heads above VHS and
even Betacam SP quality, on condition that the master is in good shape.
DVD's greatest advantage over VHS is in all of the extra features that
DVD AUTHORING PROCESS
- Capability of adapting widescreen movies on standard or wildscreen
TVs (4:3 and 16:9 picture format)
Usually a DVD is broken into scenes and the menu system allows the navigation
to each individual scene. The menu system can also determine audio tracks,
subtitles, multiple angles and be used to navigate through extra scenes.
- DVD has capability of multiple angles
Users may seemlessly change camera angles while the audio channel stays
the same during selected scenes.
This way , DVD puts each user in the director's chair.
- Audio and Subtitles
DVD has many multiple language capabilities. In addition to 8 separate
audio tracks, each DVD is also allowed 32 different subtitle streams.
This means that you can choose the language you want to listen to, or
choose subtitle language.
A single layer, single-sided DVD has enough room for 4.7 gigabytes of
storage. This is DVD-5 standard. But, there is more: DVD-9 standard
( single-sided, dual-layer) with about 9 gigabytes; DVD-10 which is
dual-sided, single layer has about 10 gigabytes; and dual layer, dual-sided
DVD-18 has incredible 18 gigabytes.
How is a DVD made, or authored?
DVD Authoring is a complex process of preparing content, encoding video
and audio, and creating the final DVD image. It involves the laying out
of multiple audio tracks and a video track, generation of sub-titles,
manu pages, parental lock-out features, interactive functions such as
program search, time search, seamless play, and pause, and finaly editing
of video and audio. Since authoring is always performed along with encoding
and disc formating it is the entire DVD pre-mastering process.
The first step in authoring is the collection of materials. These materials
include video, audio, still images and sub-pictures. DVD's video source
format is the CCIR-601 studio format compresed to MPEG-2 format. The frame
rate is 29.97 f/s for NTSC sources and 25 f/s for PAL/SECAM sources. The
maximum allowable bit rate is 9.8 Mbps. Audio includes the surround track
and up to 8 different language tracks for each title. Still images are
used to provide break points in the title, so that search functions and
other interactive functions can be implemented. Sub-pictures are bitmaps
that are overlaid on the top of the video. They include menus, sub-titles,
graphics and simple animation. Up to a maximum of 32 sub-picture bit-streams
are allowed in a title ( 32 subtitles ).
The next step is determination of basic parameters for each DVD title.
Those parameters are:
- the number of audio channels
- the number of language versions
- the number of sub-picture elements
- the number of breakpoints in the video
- the number and the levels of rated versions of te title
- the number of still images used at each breakpoint
- the type of parental lock outs
- the type of direktors cuts
- the audio encoding techniques
- the format used for still images
After preparing the different "segments" of a DVD title, a
multiplexing process should link everything together and define the program
flow of the DVD title. This final step should specify how each of the
media elements will be presented to the user and how the user can interact
with the program.
After all the media elements and control information are multiplexed
into one stream, simulation testing is to be performed. The stream must
quarantee that audio, video, and sub-pictures are synchronized; otherwise,
the content must be re-edited or re-encoded. Besides synchronization,
interactive functions may also be simulated and verified.
When everything is simulated and verified, next process is DVD mastering
and DVD replication in factory.