DVD

DVD (sometimes known as the "Digital Video Disc" or "Digital Versatile Disc") is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. DVDs resemble compact discs as their physical dimensions are the same (12 cm (4.72 inches) or occasionally 8 cm (3.15 inches) in diameter) but they are encoded in a different format and at a much higher density.

DVDs are made from a 0.6 mm thick disc of polycarbonate plastic coated with a much thinner reflective layer of aluminium or gold. Two such discs are glued together to form a 1.2 mm disc that can be designed to be read from one side (single sided) or both sides (double sided). The substrates are half as thick as a CD to make it possible to use a lens with a higher numerical aperture and therefore use smaller pits and narrower tracks. Discs commonly come in 8 cm or 12 cm diameters.

A single-layer DVD can store 4.7 GB (4.38 GiB, or 4,707,000,000 Bytes), which is around seven times as much as a standard CD-ROM. By employing a red laser at 650 nm wavelength (compared to 780 nm for CD) and a numerical aperture of 0.6 (compared to 0.45 for CD), the read-out resolution is increased by a factor 1.65. This holds for two dimensions, so that the actual physical data density increases by a factor of 3.5. DVD uses a more efficient coding method in the physical layer. CD's error correction, CIRC, is replaced by a powerful Reed-Solomon product code, RS-PC; Eight-to-Fourteen Modulation (EFM) is replaced by a more efficient version, EFMPlus, which uses eight-to-sixteen modulation. There is no subcode as in CD. As a result, the DVD format is 47% more efficient with respect to CD-ROM, which uses a "third" error correction layer.

There are a variety of application types for DVD:

DVD-Video (containing movies (video & sound))
DVD-Audio (containing high-definition sound)
VR Mode (containing recorded video and sound, usually from TV or camcorder)
DVD-ROM (computer data: operating systems, applications, encyclopedias; Games)

Different Media

The disc medium can be:

DVD-ROM: read only, manufactured by a press
DVD-R: recordable once
DVD-RW: rewritable
DVD-RAM: random-access rewritable
DVD+R: recordable once
DVD+RW: rewritable
DVD-R DL: dual-layer record once
DVD+R DL: double-layer record once
DVD-RW DL: dual-layer rewritable
DVD+RW DL: double-layer rewritable (note: contrary to established usage, the DVD+RW Alliance chose to use "double" instead of "dual" to refer to layers instead of sides)

DVD Write and Read Speed

Single Layer(4.7GB) write speeds
1x (CLV) = about 58 minutes
2x (CLV) = about 29 minutes
2.4x (CLV) = about 24 minutes
4x (CLV) = about 14.5 minutes
6x (CLV/ZCLV) = about 10-12 minutes
8x (PCAV/ZCLV) = about 8-10 minutes
12x (PCAV/ZCLV) = about 6.5-7.5 minutes
16x (CAV/ZCLV) = about 6-7 minutes

Dual/Double Layer(8.5GB) write speeds
1x CLV = about 105 minutes
2.4x CLV = about 44 minutes
4x CLV = about 27 minutes

Single Layer (4.7GB) read speeds
1x read speed is 1.321MB/s = ~56 minutes
6x CAV (avg. ~4x) read speed is max 7.93MB/s = ~14 minutes
8x CAV (avg. ~6x) read speed is max 10.57MB/s = ~10 minutes
12x CAV (avg. ~8x) read speed is max 15.85MB/s = ~7 minutes
16x CAV (avg. ~12x) read speed is max 21.13MB/s = ~5 minutes

* write speed time and read speed time is not the same because writing requires some extra steps and also does the faster writing above 6x usually use lower write speeds for some parts of the dvd. 4x DVD speed = 36x CD speed.

PAL
Video:
Up to 9.8 Mbps* (9800 kbps*) MPEG2 video
Up to 1.856 Mbps (1856 kbps) MPEG1 video
720 x 576 pixels MPEG2 (Called Full-D1)
704 x 576 pixels MPEG2
352 x 576 pixels MPEG2 (Called Half-D1, same as the CVD Standard)
352 x 288 pixels MPEG2
352 x 288 pixels MPEG1 (Same as the VCD Standard)
25 fps*
16:9 Anamorphic (only supported by 720x576)

Audio:
48000 Hz
32 - 1536 kbps
Up to 8 audio tracks containing Dolby Digital, DTS, PCM(uncompressed audio), MPEG-1 Layer2. One audio track must have MPEG-1, DD or PCM Audio.

Extras:
Motion menus, still pictures, up to 32 selectable subtitles, seamless branching for multiple storylines, 9 camera angles. And also additional DVD-ROM / data files that only can be read by computer DVD drives.

Total:
Total bitrate including video, audio and subs can be max 10.08 Mbps (10080 kbps)

* Mbps = million bits per second
* kbps = thousand bits per second
* fps = frames per second

For more technical DVD-Video details read the DVDDemystified DVD FAQ section 3.4 or the mpeg.org DVD Technical Notes.

NTSC(NTSC Film)
Video:
Up to 9.8 Mbps* (9800 kbps*) MPEG2 video
Up to 1.856 Mbps (1856 kbps) MPEG1 video
720 x 480 pixels MPEG2 (Called Full-D1)
704 x 480 pixels MPEG2
352 x 480 pixels MPEG2 (Called Half-D1, same as the CVD Standard)
352 x 240 pixels MPEG2
352 x 240 pixels MPEG1 (Same as the VCD Standard)
29,97 fps*
23,976 fps with 3:2 pulldown = 29,97 playback fps (NTSC Film, this is only supported by MPEG2 video)
16:9 Anamorphic (only supported by 720x480)

Audio:
48000 Hz
32 - 1536 kbps
Up to 8 audio tracks containing DD (Dolby Digital/AC3), DTS, PCM(uncompressed audio), MPEG-1 Layer2. One audio track must have DD or PCM Audio.

Extras:
Motion menus, still pictures, up to 32 selectable subtitles, seamless branching for multiple storylines, 9 camera angles. And also additional DVD-ROM / data files that only can be read by computer DVD drives.

Total:
Total bitrate including video, audio and subs can be max 10.08 Mbps (10080 kbps)

The DVD sizes can be a bit confusing. There are basicly 4 different DVD Sizes,

DVD-5, holds around 4 700 000 000 bytes and that is 4.37 computer GB where 1 kbyte is 1024 bytes* . DVD+R/DVD+RW and DVD-R/DVD-RW supports this format. Also called Single Sided Single Layered. This is the most common DVD Media, often called 4.7 GB Media.

DVD-10, holds around 9 400 000 000 bytes and that is 8.75 computer GB. DVD+R/DVD+RW and DVD-R/DVD-RW supports this format. Also called Double Sided Single Layered.

DVD-9, holds around 8 540 000 000 bytes and that is 7.95 computer GB. DVD+R supports this format. Also called Single Sided Dual Layered. This media is called DVD-R9, DVD-R DL, DVD+R9, DVD+R DL or 8.5 GB Media.

DVD-18, holds around 17 080 000 000 bytes and that is 15.9 computer GB. DVD+R supports this format. Also called Double Sided Dual Layered.

* In the computer world is 1 KB data = 1024 bytes so 4 700 000 000 bytes / 1024 = 4 589 843KB / 1024 = 4482MB / 1024 = 4.37GB.

DVD+R/DVD+RW/DVD+R DL and DVD-R/DVD-RW exact sizes
DVD-R/DVD-RW = 4 706 074 624 bytes ( 4488 MB )
DVD+R/DVD+RW = 4 700 372 992 bytes ( 4482 MB )
DVD+R DL = 8 547 993 600 bytes ( 8152 MB )