[12] About CD & DVD

CD-ROM

CD-ROM stands for Compact Disc - Read-Only Memory. It is a type of CD made to hold data, as opposed to audio, which the CD was originally developed for. CD-ROM is used to distribution millions of dollars worth of software and games around the world every year. CD-ROM is made to be readable using a computer equipped with a CD-ROM drive. The most common size for a CD-ROM disc is 120mm in diameter, though smaller Mini-CDs with an 80mm diameter are available.

ISO 9660 defines the standard file system used by a CD-ROM, though ISO 13490 is expected to replace it. A CD-ROM sector contains 2352 bytes, divided into 98 24-byte frames. To protect against errors, the Reed-Solomon error correction is included on a CD-ROM disc. A standard 120mm CD-ROM disc typically stores about 640MB or 700MB.

CD-ROM compilations can be produced at home with the help or recordable CD-R or CD-RW blank media.

CD-R

CD-R stands for Compact Disc - Recordable. It is a write-once recordable CD media that is suitable for creating audio or data CD compilations (CD-ROM). Though a CD-RW disc can be erased and written again, many CD players and other equipment generally perform better with CD-R media (always check if a CD player supports CD-RW before you buy it). A standard CD-R is 120 mm in diameter and usually comes with a capacity of either 640MB or 700MB. A CD-R will store 74 or 80 minutes of CD audio.

CD-R's are particularly inexpensive, but in some countries, a levy has been placed on the price of blank CD media. This levy aims to compensate copyright holders and artists if blank media is used to copy retail audio CDs or to burn MP3 files. While many consumers cite fair use rights to oppose the levies, the record industry itself distances itself from acknowledging the legitimacy of "fair use".

Using software solutions such as Nero Burning Rom, at-home users can create audio CD or CD-ROM data CD compilations. While a CD-R is not re-writable, several sessions of data can be burned to the disc at separate times. This type of disc is known as a multisession disc.

CD-RW

CD-R stands for Compact Disc - Rewritable. It is re-writable CD media that is suitable for data CD compilations (CD-ROM). Though a CD-RW disc can be erased and written again, many CD players and other equipment generally perform better with CD-R media (always check if a CD player supports CD-RW before you buy it). A standard CD-RW is 120 mm in diameter and usually comes with a capacity of either 640MB or 700MB. A CD-RW will store 74 or 80 minutes of CD audio, but as mentioned, is much less compatible with CD players than CD-R.

Using software solutions such as Nero Burning Rom, at-home users can create audio CD or CD-ROM data CD compilations.

DVD-R

A DVD Forum (the industry body that controls the development of DVD formats) approved recordable DVD format. Format allows single-layer data to be stored on each side of the disc -- in other words, one side of the disc can hold upto 4.38 gigabytes of information (NOT 4.7GB what the disc labels claim -- 4.7GB is achieved by tweaking the numbers and using 1,000 in calculations between megabyte and gigabyte, when the correct number to be used should be 1,024). This poses a problem when backing up pressed DVD-Video discs that can hold dual-layer worth of data per side, 8.5GB. Those discs need to be split to two DVD-R discs if all the information has to be preserved from the original disc.

Dual-layer DVD recordables entered the markets in Q2/2004.

DVD-R is technically slightly less advanced than its competitor, DVD+R. But the year 2002's projections of blank media sales show that sales of DVD-R media will exceed 90,000,000 discs during 2002 while sales of DVD+R media will be only 13,000,000.

Both, DVD-R and DVD+R, formats are write-once formats. DVD-R's "sister format" is called DVD-RW which is essentially a re-writable version of DVD-R. DVD+R's sister format is called DVD+RW.

DVD-R discs can be read with virtually any PC DVD-ROM drive and with most of the regular, stand-alone DVD players.

DVD-RW

A DVD Forum (the industry body that controls the development of DVD formats) approved re-writable DVD format. Format allows single-layer data to be stored on each side of the disc -- in other words, one side of the disc can hold upto 4.38 gigabytes of information (NOT 4.7GB what the disc labels claim -- 4.7GB is achieved by tweaking the numbers and using 1,000 in calculations between megabyte and gigabyte, when the correct number to be used should be 1,024). Dual-layer discs that could hold 8.5GB don't exist and most likely never will due technical limitations. This poses a problem when backing up pressed DVD-Video discs that can hold dual-layer worth of data per side, 8.5GB. Those discs need to be split to two DVD-RW discs if all the information has to be preserved from the original disc.

DVD-RW is technically slightly less advanced than its competitor, DVD+RW. But the year 2002's projections of blank media sales show that sales of DVD-RW media will dominate the markets with appx. 75 percent re-writable market share.

Both, DVD-RW and DVD+RW, formats are re-writable formats. DVD-RW's "sister format" is called DVD-R which is essentially a record-once version of DVD-RW. DVD+RW's sister format is called DVD+R.

DVD-RW discs can be read with virtually any PC DVD-ROM drive and with most of the regular, stand-alone DVD players.

DVD+R

A propietary recordable DVD format, developed by DVD+RW Alliance. Format currently (10/2003) allows single-layer data to be stored on each side of the disc -- in other words, one side of the disc can hold upto 4.38 gigabytes of information (NOT 4.7GB what the disc labels claim -- 4.7GB is achieved by tweaking the numbers and using 1,000 in calculations between megabyte and gigabyte, when the correct number to be used should be 1,024).

Dual-layer discs that can hold 8.5GB entered the market in Q2/2004. However, dual-layer discs can't be burned using the old DVD+R writers that support only single-layer burning (==all DVD+R capable burners made before 2004 or so).

Single layer discs pose a problem when backing up pressed DVD-Video discs that can hold dual-layer worth of data per side, 8.5GB. Those discs need to be split to two DVD+R discs if all the information has to be preserved from the original disc.

DVD+R is technically slightly more advanced than its competitor, DVD-R, but DVD-R still leads DVD+R by rather wide margin in terms of blank media sales.

Both, DVD+R and DVD-R, formats are write-once formats. DVD+R's "sister format" is called DVD+RW which is essentially a re-writable version of DVD+R. DVD-R's sister format is called DVD-RW.

All most common recordable DVD formats, DVD+R, DVD+RW, DVD-R and DVD-RW can be read with most stand-alone DVD players and with virtually all DVD-ROM drives.

DVD+RW

A propietary re-writable DVD format, developed by DVD+RW Alliance. Format allows single-layer data to be stored on each side of the disc -- in other words, one side of the disc can hold upto 4.38 gigabytes of information (NOT 4.7GB what the disc labels claim -- 4.7GB is achieved by tweaking the numbers and using 1,000 in calculations between megabyte and gigabyte, when the correct number to be used should be 1,024). Dual-layer discs that could hold 8.5GB don't exist and most likely never will due technical limitations. This poses a problem when backing up pressed DVD-Video discs that can hold dual-layer worth of data per side, 8.5GB. Those discs need to be split to two DVD+RW discs if all the information has to be preserved from the original disc.

DVD+RW is technically slightly more advanced than its competitor, DVD-RW. But the year 2002's projections of blank media sales show that sales of DVD-RW dominate the rewritable market by ratio of 75-to-25 when compared to DVD+RW.

Both, DVD+RW and DVD-RW, formats are re-writable formats. DVD+RW's "sister format" is called DVD+R which is essentially a record-only-once version of DVD+R. DVD-RW's sister format is called DVD-R.

DVD-RAM

DVD-RAM is a competing DVD Re-Writable format with many advantages over its rivals. DVD-RAM stands for DVD-Random Access Memory, a name given to the format that is widely debated. The problem some people find with the "RAM" part of the name, is that DVD-RAM is not really "Random Access Memory" - the name really gives a comparison between DVD-RAM and other format such as DVD-RW because of its "Random Access" capabilities (that we will look at a little later). Beyond the name, DVD-RAM surpasses other recordable DVD media in many ways whether its a question of reliability, quality, speed or ease of use. In this glossary item we will take a look at this excellent format and what it has to offer for you.

DVD-ROM

DVD-ROM is the term used to describe any digital versatile disc (DVD) that is read-only. The use of the term in general is often reserved for retail DVD "pressed" discs or specifically, DVD Data discs (excluding those with DVD-Video compilations stored). This usage is actually incorrect as DVD-ROM can be used to describe literally "any" DVD disc that cannot be written to. This also applies to a burned DVD-R and so is not only reserved for pressed media.