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DVD Technical Details

With the advent of DVD there is a whole new set of terms and technology to handle. The purpose of this section is to help with that task.

DVD Specs

Item

CD

DVD

Diameter 120mm 120mm
Thickness 1.2mm 0.6mm
Track Pitch 1.6 microns 0.74 microns
Minimum Pit Length 0.834 microns 0.40 microns
Laser Wavelength 780 nm (infra red light) 640 nm (red light)
Data Capacity (per layer) .68 GB 4.7 GB
Layers 1 1,2,4
CD DVD

disc[1].gif (36230 bytes)

DVD Features

bulletOver two hours of play time, 8 on a 'flippy' or two sided disc or a dual-layer disc
bulletOften features pan and scan and letterbox on the same DVD
bulletOften supports regular TV aspect ratio of 4,3 and widescreen TVs with 16,9
bulletUp to eight tracks of digital audio permitting alternate languages and/or commentary tracks from actors or directors.
bulletUp to 32 subtitle tracks.
bulletUp to nine camera angles.
bulletAutomatic 'seamless branching' permitting multiple storylines or ratings. For example, the DVD Kalifornia permits the selection of the 'R' rated or unrated versions via a menu selection.
bulletMenu and other interactive features including some simple interactive quizzes or games.
bulletRandom access and programmability  permitting selection of any track, random track play, repeat of tracks or portions of tracks and/or  'bookmarking', i.e. user control return points.
bulletForward and reverse single frame stepping.
bulletNot susceptible to magnetic fields. Resistant to heat.
bulletSix-channel analog output from internal audio decoder.
bulletRecognition and output of DTS Digital Surround audio tracks
bulletParental lock which refuses playback of objectionable tracks or the whole disc.
bulletAbility to read dual layer discs.

Most DVD players have the following output connections

bulletVideo: Composite video (CVBS), RCA (NTSC or PAL Y/C (s-video) (NTSC or PAL), Component Video
bulletAudio: Dual RCA stereo analog audio (with Dolby Surround encoding) Digital audioIEC-958 Type II RCA coax [S/P DIF] EIAJ CP-340 optical Toslink]. Raw digital audio Dolby 5.1 (AC-3) MPEG-2 PCM (Pulse Code Modulation) DTS or SDDS (optional, DTS growing in popularity not SDDS) 

Video Resolution

Currently, a DVD offers about 480 lines of resolution. This is double the 240 lines of the VHS format. Once HDTV gets going the DVD specs permit an upgrade (with newer players) to 720 lines of resolution. The 480 lines is best seen on a progressing DVD player which can convert the 480 interlaced video (480I) into 480 line progressive format (480p). The advantage of this is the progressive display has a 31.5 kHz or higher scans rate which eliminates all traces of scan delay and provides a more film like picture. Some of the more advanced progressive scan sets now offer 1080 lines of resolution designated as 1080p sets.

Compatibility with Standard CDs

Most DVD players are fully compatible with standard audio CDs (CD-DA) as long as the CD was produced in accordance with the 'Red Book' standards. There are problems with some CD-Rs created under the 'Orange Book' part II standards. If you are buying a DVD for your computer be sure that it is a type 2 DVD ROM.  This is especially important if you own a CD burner or often use CDs created on such a burner. (Look for a gold or greenish color instead of the normal CD silver.) Although all current DVD manufacturers permit the reading of CDs it is not part of the DVD specifications.    Normal CD-ROMs  created under the 'Yellow Book' standards are readable in DVD ROMS. CD-Rewritable created in accordance with the  'Orange Book' Part III has a lower reflectivity difference, requiring new automatic-gain-control (AGC) circuitry. CD-RW discs can't be read by most existing CD-ROM drives and CD players. The new "MultiRead"  standard addresses this, and some DVD manufacturers have suggested they will support it. The optical circuitry in even first-generation DVD-ROM drives and DVD players is usually able to read CD-RW discs, since CD-RW does not have the "invisibility" problem of CD-R

Please be aware that DVDs cannot be played in CD-ROMs or audio CD players. The pits are too small to be read, the track distances differ etc.

 

                                   

 

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