DVD stands for Digital Versatile (or Video) Disc
DVD R stands for DVD Recordable and
DVD RW for DVD ReWriteable.
A recordable DVD can store up to 2 hours of good quality standard definition DVD-Video, including multiple audio tracks in various formats like stereo, Dolby Digital or DTS. It can also accommodate advanced menu systems, subtitles and still pictures that can be played by many standalone DVD Players and most computer DVD-ROMs.
It is possible to write more than two hours of video to a recordable DVD if you lower the video quality using low bitrates (the amount of data per second being used) or lower the resolution (the number of lines used on the screen to display the image) giving you quality more like VHS, SVHS, SVCD, CVD or VCD.
It is also possible to store up to 4.37Gbs of ordinary data on a recordable DVD disc that can be read by most computer DVD-ROMs.There are three DVD Recording standards or types:
DVD-R/DVD-RW and DVD+R/DVD+RW.
These two have very similar features and are compatible with most standalone DVD Players, computer DVD-ROMs and DVD camcorders.
DVD-RAM is an entirely different system and has less DVD Player, DVD-ROM and DVD camcorder compatibility. The main difference is that it offers the ability to do some minor editing of the DVD while still in the device.
DVD -R and DVD -RW
DVD-R was the first DVD recording format released and is a non-rewriteable format compatible with about 98% of all modern DVD Players, most DVD-ROMs and just about all DVD camcorders.
DVD-RW is a rewriteable format compatible with about 90% of all DVD Players, most DVD-ROMs and many DVD camcorders and DVD recorders.
DVD-R and DVD-RW single sided 4.37Gb DVDs are called DVD-R5 and double sided 8.75Gb DVDs are called DVD-R10.
DVD-R DL is called DVD-R9 and is a Dual Layer writeable DVD-R. The dual layered discs can hold 7.95Gb and dual layered double sided discs holding 15.9Gb are called DVD-R18. DVD +R and DVD +RWDVD+R is a non-rewritable format also compatible with about 98% of all DVD Players, most DVD-ROMs and most DVD camcorders and DVD recorders.
DVD+RW is a rewritable format compatible with about 90% of all DVD Players, most DVD-ROMs, many DVD camcorders and DVD recorders.
DVD+R and DVD+RW single sided 4.37Gb DVDs are called DVD+R5 and double side 8.75Gb DVDs are called DVD+R10.
DVD+R DL is called DVD+R9 and is a Dual Layer writeable DVD+R. The dual layered discs hold 7.95Gb and are called DVD+R9 and the dual layered double sided discs holding 15.9Gb are called DVD+R18.Note: In general, when you are reading about the capabilites of software or reference to DVD discs very often the reference will be to DVD-5 or DVD-9 discs without reference to whether it is + or – as it is assumed the the particular standard of the disc being referred is known.
DVD-RAM
DVD-RAM offers a wider range of recording features but is not compatible with many DVD-ROMs, DVD-Video players and DVD camcorders. It is used more in the field of DVD recorders due to the “onboard” editing features it offers and to some degree behaves more like a removable hard disk.
A sub-product of this standard is the DVD/VR mode of recording that some DVD recorders and DVD camcorders use when recording to +RW or -RW discs. This allows the user to immediately erase scenes from the disc while still in the device and to manipulate DVD menus also from within the device.
DVD File/Folder Structure
If you open up and take a look inside a data DVD you will see the normal file and folder structure you would see on any computer drive or storage medium and the disc should behave exactly like those.
On a video DVD you will at first see two folders.
The first of these is named AUDIO_TS written exactly as I have written it here.
Generally this folder is empty. Occasionally it is supposed to be used for extra features to the main movie or subtitle tracks however this seems to be rarely the case.
Because part of the DVD standard requires the presence of this folder many DVD devices will not recognize a disc as being compliant unless the AUDIO_TS folder is present even though it has nothing in it.
The other folder you will see will be named VIDEO_TS also written exactly as I have. Inside the VIDEO_TS folder you will see three types of files.
1. Files with the extension .IFO. The IFO files get their designation from the word information because they contain references and information relating to chapters, subtitle tracks and audio tracks.
2. Files with the extension .BUP. These are backup files of the IFO files.
3. Files with the extension .VOB. These are called video object files and are like a container that hold the actual video, audio, subtitles and menus. The video files of DVD are always MPEG2.
When you place a DVD into a DVD player or DVD ROM the software of the machine detects that a disc has been inserted.
The disc is then read and the first file looked for is VIDEO_TS.IFO. This begins the dialogue between the disc and the playback software identifying the disc as a DVD and directing the software to the position on the disc where the first item to be played is located.
It will tell the software to go to the VIDEO_TS.VOB at a certain point on the disc and play the contents of that .VOB file. This is usually the logo and intro then finishing with the menu.
This is the complete list of possible files and their basic functions:
VIDEO_TS.IFO
VIDEO_TS.VOB The first video play .VOB
VTS_01_0.BUP
VTS_01_0.IFO Title 01, IFO, usually the main movie.
VTS_01_0.VOB Title 01, VOB 0, the menu for this title
VTS_01_1.VOB Title 01, VOB 1, the video for this title
VTS_01_2.VOB Title 01, VOB 2, any .VOB larger than 1 GB will be split into multiple .VOBs.
VTS_01_3.VOB Title 01, VOB 3
VTS_01_4.VOB Title 01, VOB 4, up to 10(0-9) VOB files if needed.
VTS_02_0.BUP
VTS_02_0.IFO Title 02, IFO, usually movie extras.
VTS_02_0.VOB Title 02, VOB 0, the menu for this title.
VTS_02_1.VOB Title 02, VOB 1, the video for this title.
VTS_02_0.BUP
And so on up to 99 titles with a maximum of 10(0-9) VOB files each.
Just as an added note here, DVD video discs MUST be “closed” or “finalized” This means they cannot be written to, left open until a later date then written to again.
This is ok for data DVDs but not video DVDs.
The reason for this is that the whole .IFO, .BUP and VOB structure is written as part of the finalization process and is necessary to create all the reference points contained within those files.
DVD-Video
It is also important to note that the actual video files of any standard DVD are MPEG2 files.
MPEG2 does not denote a particular codec for the encoding or decoding of MPEG2 files although in common language this is how the term is used.
From the information below you can see that there are many different parameters that can be applied to an MPEG2 video files and still be compliant with the DVD standard.
MPEG2 is a set of guidelines of how the video files are created and what the parameters are. There can be wide variation in what denotes and MPEG2 and even wider variation in the codecs used to either encode to decode them.
PAL DVD Video Standards
Video portion:
Allowed bitrate: Up to 9800 kbps MPEG2 video.
Frame size:
720 x 576 pixels MPEG2 (the most common occurrence).
704 x 576 pixels MPEG2.(Common with DVD camcorders and DVD recorders.)
Uncommon but still within the defined specification:
352 x 576 pixels MPEG2 (Called Half-D1).
352 x 288 pixels MPEG2.
352 x 288 pixels MPEG1 (Same as the VCD Standard).
25 Frames per second. (fps).
16:9 aspect ratio only supported by 720×576.
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 data files that only can be read by computer DVD drives.
Total bitrate including video, audio and subtitles:
max. 10,080 kbps.
NTSC DVD Video Standards
Video portion:
Allowed bitrate up to 9800 kbps MPEG2 video
Frame size:
720 x 480 pixels MPEG2 (the most common occurrence).
704 x 480 pixels MPEG2 (common with DVD camcorders and DVD recorders).
Uncommon but still within the defined specification:
352 x 480 pixels MPEG2 (Called Half-D1).
352 x 240 pixels MPEG2.
352 x 240 pixels MPEG1 (Same as the VCD Standard).
29.97 Frames per second. (fps).
23.976 fps with 3:2 pulldown = 29.97 playback fps (NTSC Film, this is only supported by MPEG2 video)
16:9 aspect ration only supported by 720×480).
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 data files that only can be read by computer DVD drives.
Total bitrate including video, audio and subtitles:
max 10,080 kbps.
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