Differences between version 22 and predecessor to the previous major change of DVDVideo.
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| Newer page: | version 22 | Last edited on Tuesday, December 30, 2008 6:56:26 pm | by LawrenceDoliveiro | Revert |
| Older page: | version 21 | Last edited on Sunday, May 13, 2007 3:01:34 pm | by LawrenceDoliveiro | Revert |
@@ -11,15 +11,15 @@
While an audio stream may have different numbers of channels (e.g. 2-channel stereo, 5.1 surround) and use a couple of different codecs, the sample rate must always be 48kHz.
!Subpictures
-A ''subpicture'' is a generalization of the concept of a subtitle. On a DVD-Video disc, subtitles are not kept in text form: instead, they are stored as a picture
, allowing for use of arbitrary fonts, language scripts, writing directions etc. Definition of transparent pixels allows the creation of graphics that overlay any part of the screen, and since the subpicture is stored in a stream just like the video and audio streams, it can animate as the title is playing.
+A ''subpicture'' is a generalization of the concept of a subtitle. On a DVD-Video disc, subtitles are not kept in text form: instead, they are stored as a bitmap
, allowing for use of arbitrary fonts, language scripts, writing directions etc. Definition of transparent pixels allows the creation of graphics that overlay any part of the screen, and since the subpicture is stored in a stream just like the video and audio streams, it can animate as the title is playing.
-In fact, menu buttons are implemented as subpictures superimposed on top of a video background. There is one subpicture showing all the menu buttons in their default (non-selected) state; another showing them all in their selected state; and a third showing them highlighted (when the user presses the "OK" or "Enter" button on the remote with a menu button selected). The actual area of each button is defined as a rectangle in a field in the .VOB file; this is what selects what portion of the appropriate subpicture to show when a button is in a particular state.
-
-which is defined as part of the menu or title
. It is also possible to specify a 4-bit alpha (transparency) value for each of the four chosen colours.
+A subpicture holds two bits per pixel, allowing the use of four different colours from a palette of 16. It is also possible to specify a 4-bit alpha (transparency) value for each of the four chosen colours.
!Menus & Titles
+Menus are implemented as subpictures superimposed on top of a video background, together with additional information about button position and highlighting information.
+
Each titleset can have its own set of menus. The files comprising a titleset are named VTS_''nn''_''m''.IFO/BUP/VOB, where ''nn'' is the titleset number and ''m'' is incremented if the .VOB file needs to be broken up into multiple pieces because each file is not allowed to exceed 1GiB in size.
There is also another titleset-like grouping called the "Video Manager" (VMG), of which there can only be one on the disc. This is kept in the files VIDEO_TS.IFO/BUP/VOB. This is only allowed to contain menus, no titles. It is intended to act as a top-level set of menus for accessing the various titles, though how things are actually linked together is very much up to the people authoring the DVD. There are several ways to achieve the same effect, except that one titleset cannot jump to another, only to menus and titles within the same titleset or in the VMG.
