The DVD and Blu-ray disc, both are the type of optical disk format which can store video, audio, software, games, e.t.c. They are the commonly used as a medium for the digital representation.

DVD stands for Digital Versatile/Video Disc, which have a capacity of holding data from 4.7GB to 17 GB. Blu-ray Disc (BD), is a next-generation optical disc format developed by the Blu-ray Disc Association (BDA), a group of the world's leading consumer electronics, personal computer and media manufacturers (including Apple, Dell, Hitachi, HP, JVC, LG, Mitsubishi, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, TDK and Thomson). The format was developed to recording, rewriting and playback of high-definition video (HD), as well as storing large amounts of data. The Blu-ray disc is capable of holding 25GB in single layer disc and 50 GB of content in dual layer disc. This extra capacity combined with the use of advanced video and audio codecs will offer an unprecedented HD experience.

The Blu-ray Disc derived its name from the blue laser (violet-colored, which is used to read and write Blu-ray disc. The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision.

A two-layer Blu-ray Disc has a capacity of storing, almost six times the capacity of a two-layer DVD, or ten and a half times that of a single-layer DVD.

DVD uses MPEG-2 for encoding (compress video data, etc.), whereas Blu-ray uses MPEG-2, H.264/MPEG-4 AVC, and VC-1

Types of DVDs:

Based on format:

1. DVD-R and DVD-RW
DVD-R was the first DVD recording format which has compatible with standalone DVD Players.
DVD-R is a non-rewriteable format and compatible with about 93% of all DVD Players and most DVD-ROMs.
DVD-RW is a rewriteable format compatible with about 80% of all DVD Players and most DVD-ROMs.
DVD-R and DVD-RW supports single side 4.37 computer GB DVDs(called DVD-5) and double sided 8.75 computer GB DVDs(called DVD-10).

2. DVD+R and DVD+RW
DVD+R is a non-rewritable format, compatible with about 89% of all DVD Players and most DVD-ROMs.
DVD+RW is a rewritable format, compatible with about 79% of all DVD Players and most DVD-ROMs.
DVD+R and DVD+RW supports single side 4.37 computer GB DVDs(called DVD-5) and double side 8.75 computer GB DVDs(called DVD-10).

3. DVD+R DL
DVD+R DL or called DVD+R9 is a Dual Layer writeable DVD+R. The dual layered discs can hold 7.95 computer GB (called DVD-9) and dual layered double sides 15.9 computer GB (called DVD-18).

4. DVD-R DL
DVD-R DL or called DVD-R9 is a Dual Layer writeable DVD-R. The dual layered discs can hold 7.95 computer GB and dual layered double sides 15.9 computer GB.

5. DVD-RAM
DVD-RAM has the best recording features but it is not compatible with most DVD-ROM drives and DVD-Video players. Think more of it as a removable hard disk.

Based on 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.

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.

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.

Type of Blu-Ray Disc:

Mini Blu-ray Disc, is a compact 8cm diameter variant of the Blu-ray Disc that can store 7.5 GB of data. Recordable (BD-R) and rewritable (BD-RE) versions of Mini Blu-ray Disc have been developed specifically for compact camcorders and other compact recording devices.

BD9/BD5 Blu-ray Disc

BD9 and BD5 are lower capacity variants of the Blu-ray Disc that contain Blu-ray compatible video and audio streams contained on a conventional DVD. BD9 uses a standard 8152MB DVD9 dual-layer disc while BD5 uses a standard 4482MB DVD5 single-layer disc..

AVCREC

AVCREC is an official lower capacity variant of the Blu-ray Disc used for storing Blu-ray Disc compatible content on conventional DVD discs. It is being promoted for use in camcorders, distribution of short HD broadcast content and other cost-sensitive distribution needs.

Blu-ray Disc recordable

Blu-ray Disc recordable refers to two optical disc formats that can be recorded with an optical disc recorder. BD-R discs can be written to once, whereas BD-RE can be erased and re-recorded multiple times. The theoretical maximum speed for Blu-ray Discs is about 12x

Recording Speed of Blu-ray:

Drive    Data rate           Write time for Blu-ray Disc (minutes)      

Speed  Mbit/s   MB/s    Single Layer      Dual Layer

1×        36         4.5        90                     180

2×        72         9          45                     90

4×        144       18         23                     45

6×        216       27         15                     30

8×*       288       36         12                     23

12×**    432       54         8                      15

Recording Speed of DVD:

Drive                Data rate           Write time for DVD (min)

speed   (Mibit/s)            (MB/s) Single Layer      Double Layer

1×        10.55                1.35      61                     107

2×        21.09                2.70      30                     54

2.6×      27.43                3.51      24                     42

4×        42.19                5.40      15                     27

6×        63.30                8.10      11                     18

8×        84.38                10.80    8                      14

12×       126.60              16.20    6                      11

16×       168.75              21.60    4                      7

18×       189.90              24.30    3                      5

20×       211.00              27.00    3                      4