Monday, July 2, 2012

DVD file system

DVD uses UDF/ISO9660 file system. UDF (Universal Disk Format), which was originally used to write and rewrite rewritable disc. It is the DVD standard file system.
ISO9660 is compatible with your computer's operating system.
The following diagram is published DVD disc of the directory structure, you can see there is a section of this DVD (Session), a light-rail (Optical track), using DVD discs UDF/ISO9660 default file system. In this way, it can be played both in DVD players and on the computer.

DVD-ROM is the basic format of DVD that is compatible with computer system. In the Windows Explorer, it is very easy for the computer to read the files in the DVD-ROM, it can be as easy as read local files on the hard disk. DVD-Audio and DVD-Video is the disc with a format based on DVD-ROM. Audio and Video disc has the same directory structure as the picture shows. The picture shows a typical directory structure of DVD. In the root of DVDVLUME or VOLUME, there are two contents, AUDIO_TS is to store audio data, VIDEO_TS is to store video data. Therefore, the disc has no files in the AUDIO_TS directory. Because of this, you can also customize the directory structure. The following diagram is a film disk named "Angel Will match".

In the picture, the home directory is defined as "Angle will match", there is only one content called VIDEO_TS that cancel the content AUDIO_TS. Now, let us look at the VIDEO_TS directory is what files? See the figure below.

There are three types of VOB, IFO, and BUP.
IFO is the information file, but is the backup files and vob is the Video Object files, for the DVD-Audio, which is the AOB, audio object files stored in AUDIO_TS.
IFO file is to control the play of VOB files. IFO files stores the information on how and when to play the data in the VOB files, such as the start and end time of paragraph, the position of audio data stream, position of subtitle stream and so on. DVD player and computer shall read IFO files to play the films with proper order. BUP is the backup of information files. As IFO files are very important for the proper play of film, so it needs a backup to ensure the related information can be read even if the IFO file errors. VOB file is to store the video data stream, audio data stream, multi-angle, multi-language and multi-subtitle data stream as well as the information on providing menu, button data, video standard, aspect ratio and so on. As a VOB file can store a primary video stream and several multi-angle video stream, 8 digital audio tracks, 32 data stream of subtitles, DVD has audio of 8 languages, 9 angles and subtitles of 32 languages.

Now let's look at the file name, there are two types of file names: VIDEO_TS and VTS_xx_y. TS is time stamp. VTS is short for video title set. xx is a double digit number, from 01 in sequence, the largest to 99. It stands for title number, a maximum of 99 title numbers. A disc has at least one title. y is a number, starting from 0 to 9. It is the sub-heading number, 10 sub-heading at most. One title has at least a subheading of "0" and "1" two sub-headings. The figure shows: This CD-ROM has "01" and "02" two headings. The head 01 has the sub-title of "0" and "1" two sub-titles, 02 has the sub-titles from "0" to "5" , in all 6 sub-headings. The number of the title is determined by the movie clip edited and synthesis settings. For example, we can set title sequence and the copyright notice, film, video shooting Snapshots as three headings. We can also join the first two letters or merge the last two titles and form two titles. Or even combine all the three titles into a head. IFO files with a sub-heading "0" is to store information on the scene, language, subtitles, and so the option menu information. Sub-title "1" Start is to store VOB video files. Under the heading, the size of each sub-VOB file should be less than 1GB (above chart). If the VOB file is larger than 1GB, it can not be played on a PC. The VOB file size is limited, so the video files is split into several sub-headings and played by sequence. Though these documents are divided in form, but the program chain (PGC) is seamlessly linked, making a coherent film, when played DVD player.

VIDEO_TS and VTS_xx_0 may contain files with the extended name of IFO, BUP, and VOB. Sometimes, there will be no VOB files, take the above picture for example, there are only IFO and BUP files. DVD discs have VMG in each disc and VMG is stored in the VIDEO_TS.IFO files, which stores the panorama information such as region code, selectable menu and so on. When the DVD disc is put into the DVD-ROM, the player shall first find the file VIDEO_TS.IFO. 

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1 comment:

  1. Hey Really Superb Spec. u've made definition of DVD much simpler...thanx

    Peter, developer of vob converter to mov on mac