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 discs.

Can DVD-ROM drives play/read standard CD-ROM discs?
Yes, DVD-ROM drives are backward compatible with standard CD-ROM and CD audio discs.

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 layer).

Why is an MPEG-2 card required to use a DVD-ROM drive?
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.

DVD FAQ

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 Format
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
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.

Presentations
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 track.

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 provides.

1. Capability of adapting widescreen movies on standard or wildscreen TVs (4:3 and 16:9 picture format)
   
   
2. Menus
   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.
   
   
3. 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.
   
   
4. 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.
   
   
5. Storage
   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.
   

DVD AUTHORING PROCESS

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.