VBI
Vertical Blanking Interval - the part of a TV transmission that is blanked, or left clear of viewable content, to allow time for the TV’s electron gun to move from the bottom to the top of the screen as it scans images. This blank area is now being used to broadcast closed captioned and text formatted information.



VBR
Variable Bit Rate - the bitrate can vary at any part of a single video or audio stream. VBR can is used to increase bitrate during high motion scenes in a video or to reduce overall file size. DVD MPEG-2 video is often variable bit rate. Also see CBR (constant bit rate).



VCD
VCD stands for 'Video Compact Disc' and basically it is a CD that contains moving pictures and sound. If you're familiar with regular audio/music CDs, then you will know what a VCD looks like. A VCD has the capacity to hold up to 74/80 minutes on 650MB/700MB CDs respectively of full-motion video along with quality stereo sound. VCDs use an encoding standard called MPEG-1 to store the video and audio. A VCD can be played on almost all standalone DVD Players and of course on all computers with a DVD-ROM or CD-ROM drive with the help of a software based decoder / player.


VCD Header trick
Some DVD players just can't play SVCD... but in this case and if you are lucky your DVD player may be able to play VCDs that use the "VCD-Header Trick". By changing the "Header" of a SVCD MPEG-2 video file into the one of a VCD2.0 MPEG-1 file and by using it as standard VCD2.0 file, you may be able to play MPEG-2 files with your home DVD player.




VHS
VHS an analog format capable of delivering 240 lines of video resolution, along with stereo sound that's nearly as good as CD (in dynamic range and frequency response). Blank tapes usually feature either 120 minutes or 160 minutes of recording time at the highest recording speed (6 hours or 8 hours at the slowest speed). VHS and VCR's are slowly being phased out in favor of DVD players and other digital tape media.



Video Encoding
The process for changing a video from one format to another by altering the resolution and/or the bitrate. Normally the result of this process is a movie with a different compression. For a proper encoding you need a piece of software and/or hardware, which is called codec.



VIDEO_TS
The UDF file name used for DVD-Video directory on a DVD disc volume. Files under this directory name contain pointers to the sectors on the disc which hold the program streams.

VLC
A program used to view VCDs and SVCDs on a variety of operating systems.

VOB
All DVD movies are stored in on a DVD video disc in so-called VOB files. VOB files usually contain multiplexed Dolby Digital audio and MPEG-2 video. VOB files on a DVD are numbered as follows: vts_XX_y.vob where XX represents the title and Y the part of the title. There can be 99 titles and 10 parts, although vts_XX_0.vob does not contain any video, usually just menu or navigational information. You can find them on a DVD video disc in a subdirectory labelled VIDEO_TS (all upper case).

All VOB files are essentially MPEG2 Program streams with audio, video, sub-picture and navigation data multiplexed. A VOB file is organized as a set of cells; a cell is a basic unit of play data. Each cell consists of a sequence of units called VOBUs. Each VOBU is a sequence of
packs. The first pack in a VOBU is a navigation pack and contains Program Control Information (PCI) packet and Data Search Information (DSI) packet. The remaining packs contain audio,
video and sub-picture data multiplexed together. Each pack has a fixed size of 2048 bytes. A pack typically contains only one data packet and may be stuffed with dummy bytes or a packet
called ‘padding’ bytes/packet to make it a fixed size.

DVD allows easy navigation in its audio and video data. Information for navigation across different VTS is contained in the VMGM. Within a title, the play order of different cells (from one or more VOBs in the title) is described in a Program Chain (PGC). A PGC is a logical unit to present a part of or the entire Title or Menu. A PGC is further divided into programs. Each program contains integral number of cells. A Title may have one or more PGCs. However, a Title that has parental guidance levels, will have more than one PGC. Depending on the parental level selected by the DVD disk viewer, the PGCs are selected for being played. PGC contains PGCI which gives the order of presentation of cells within that PGC. The information for presentation of a cell, such as the angle information for seamless and nonseamless play and highlight information is contained in the Navigation packs occurring within the cell. When playing non-seamlessly, the cells within a logical block are placed contiguously. Therefore, during cell presentation, intermittent blocks may have to be skipped depending on the angle information selected by the DVD disk viewer.

An angle block is a logical block containing cells for different angle presentations. During presentation, not all the cells within the block are played. The different angle cells are of almost the same play time and since they are placed adjacent to each other, the DVD disk viewer can seamlessly change from one angle to another. When playing a parental level seamlessly, cells from different VOBs may be interleaved in a logical block. Such a block is called an interleaved block. Each unit of VOB that lies in an interleaved block is called an ILVU of that VOB. This means that the cells in a VOB may not be placed contiguously over the physical address space and may be interleaved with ILVUs from other VOBs.

back to the top