Friday, June 15, 2012

The structure of each CD Optical tracks

Data CD

Data CD is the most frequently used format disc. Its Optical tracks have the following features: It has only one session, one Optical track; it can be used in many sessions and many Optical tracks. The CD has a directory structure.

The above picture is the Optical track structure of KILL98 software disc. From the picture, we can see the disc has one session; this session has only one Optical track set with directory structure that tally with ISO9660 standard. The software CDs published by software developers all have only one session and one Optical track. The computer fans, they would like to adopt multi-tracks and sessions while burning CDs. As the sessions would keep a 13 MB as intervals between each other, there would be a waste of space on CD-R. So it is not suitable for multi-session burning. 

Music CD

Music CD called CD gramophone record is belonged to CD-DA format. The feature of its Optical track is that it has one session with multiple Optical tracks; one song one track. It is set without directory structure. The above is the Optical track structure of the Music CD for the celebration of New Year festival. The picture shows the CD has one session set with 17 Optical tracks that correspondence to 17 songs. 

Video CD

Video CD is the frequently used VCD and SVCD. DVD is not belonged to the CD format. The feature of VCD Optical track: There is one session with multiple Optical tracks. It is set with directory structures, which is VCD file system. The file system is on the first Optical track. Then, each video will have one corresponding optical track. In the standard VCD, music material can be stored either by mixed with flash or static image or store as the VCD format.

The above diagram is the structure of a VCD. It has one session with three Optic tracks. The first track is the VCD file system. The second and third is the content of VCD program. This is a typical structure; the second picture shows the rights declaration, company logo and so on. The third track is the content of the whole story. Of course, the two parts can be edited to be one track. But there would be reputation of the logo, version rights. The two track style can make sure that the content of story shall be played once during the process of reviewing. VCD is set with directory structure that can be displayed on computer. As the picture shows the name of this VCD is "Video CD", and four file directory. One thing needs to pay attention to is that VCD composed by different software shall have different directory structure but they must be tally with the ISO9660 standard. 

Extended CD

Extended CD is the CD-Extra CD, sometimes called CD plus. Features of Optical tracks: There are two sessions, the first session is to store music, one track, one song, or piece of music, so there would be many tracks. The second session is to store data with the structure of data CD.

The above picture is the Optical track structure of CD-EX disc. As the picture shows it has two sessions. The first session has 7 Optical tracks. This indicates that 7 pieces of music has been stored on this disc. The second session is data session with only one optical track 08. The data session is set with directory, and the title of CD is "CDEX". In which, the "CD Plus" and "Pictures" is formed automatically during the burning of CE-EX. They are the structure data of CE-Extra CD.

The music can be played by CD player as the CD player can only read the first session while the computer usually read the last session. 

Mixed CD

The Optical track of Mixed Mode CD has following features: there is only one session with several optical tracks. Data is usually on the first track, the second track is to store music, a piece of music per track.

The above picture is the structure of optical tracks in mixed CD. This disc has only one session, the first session is to store data with a drive letter of "MIXCD", which is set with directory structure. The second to eighth track stores seven songs. 

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