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DVD and computers

SO far we have focussed on the media representation and standard DVD players. DVD and DVD-ROM in particular is beginning to have a huge impact on computers.

For a computer to employ DVD it must have the following features:

In addition to a DVD-ROM drive, you must have extra hardware to decode MPEG-2 video and Dolby Digital/MPEG-2/PCM audio. The computer operating system or playback system must support regional codes and be licensed to decrypt copy-protected movies. You may also need software that can read the MicroUDF format used to store DVD data files and interpret the DVD control codes. It's estimated that 10-30% of new computers with DVD-ROM drives will include decoder hardware, and that most of the remaining DVD-ROM computers will include movie playback software.

Some DVD-Videos and many DVD-ROMs will use video encoded using MPEG-1 instead of MPEG-2. Many existing computers have MPEG-1 hardware built in or are able to decode MPEG-1 with software.

CompCore Multimedia and Mediamatics make software to play DVD-Video movies (SoftDVD, DVD Express). Both require at least a 233 MHz Pentium MMX with AGP and an IDE/SCSI DVD-ROM drive with bus mastering DMA support to achieve about 20 frame/sec film rates (or better than 300 MHz for 30 frame/sec video), and can decrypt copy-protected movies. Oak's software requires hardware support. The software navigators support most DVD-Video features (menus, subpictures, etc.) and can emulate a DVD-Video remote control.

CompCore, Mediamatics, and Oak Technology have defined standards to allow certain MPEG decoding tasks to be performed by hardware on a video card and the remainder by software. Video graphics controllers with this feature are being called DVD MPEG-2 accelerated. (The Mediamatics standard is called MVCCA.)

If you have at least a 433 MHz Alpha workstation you'll be able to play DVD movies at full 30 fps in software.

DVD-ROM Drives:

Most DVD-ROM drives have a seek time of 150-200 ms, access time of 200-250 ms, and data transfer rate of 1.3 MB/s (11.08*106/8/220) with burst transfer rates of up to 12 MB/s or higher. The data transfer rate from DVD-ROM discs is roughly equivalent to a 9x CD-ROM drive. DVD spin rate is about 3 times faster than CD, so when reading CD-ROMs, some DVD-ROM drives transfer data at 3x speed while others are faster. 2x and 3x DVD-ROM drives are already in the works. Hitachi is shipping samples of a 2x DVD-ROM drive which also reads CDs at 20x.

Connectivity is similar to that of CD-ROM drives: EIDE (ATAPI), SCSI-2, etc. All DVD-ROM drives have audio connections for playing audio CDs. No DVD-ROM drives have been announced with DVD audio or video outputs (which would require internal audio/video decoding hardware).

DVD-ROMs use a MicroUDF/ISO 9660 bridge file system. The OSTA UDF file system will eventually replace the ISO 9660 system of CD-ROMs, but the bridge format provides backwards compatibility until operating systems support UDF.

Recordable DVD-ROM: DVD-R and DVD-RAM:

There are two recordable versions of DVD-ROM: DVD-R (record once) and DVD-RAM (erase and record many times), with capacities of 3.95 and 2.58 G bytes. Both specifications have been published. DVD-R and DVD-RAM are not currently usable for home video recording.

DVD-R uses organic dye polymer technology like CD-R and is compatible with almost all DVD drives. The technology will improve to support 4.7 G bytes in 1 to 2 years, which is crucial for desktop DVD-ROM and DVD-Video production.

next up previous
Next: Further Information Up: Storage Media Previous: Interactive DVD features
Dave Marshall