Welcome at the Zapping VBI library homepage

To quote Wikipedia: The vertical blanking interval (VBI) is an interval in a television signal that temporarily suspends transmission of the signal for the electron gun to move back up to the first line of the television screen to trace the next screen field.

The vertical blanking interval can be used to carry data, since anything sent during the VBI would naturally not be displayed; various test signals, closed captioning, and other digital data can be sent during this time period.

The Zapping VBI library, in short ZVBI, provides functions to capture and decode VBI data. It is written in plain ANSI C with few dependencies on other tools and libraries, and licensed under LGPL.

A Perl interface is also available, see the ZVBI page at CPAN.

Some features:

Functions to capture raw VBI data from Linux V4L and V4L2 devices (including bug work-arounds for some older drivers) and the FreeBSD BKTR driver, sliced VBI data from Linux DVB devices
A VBI Proxy to share one V4L or V4L2 device between multiple applications
Functions to demodulate raw into sliced VBI data, with support for a wide range of data services such as Closed Caption (NTSC and PAL), Teletext, VPS, WSS, XDS
Functions to multiplex and demultiplex DVB VBI PES and TS streams
A Level 3.5 Teletext decoder with support for all Teletext character sets, graphics, 4096 colors, TOP/FLOF navigation, a built-in page cache with search functions
A Closed Caption decoder which supports roll-up, pop-up and paint-on style caption, color, all character set, text attributes and free text placement
Functions to render Teletext and CC pages, export to HTML, PNG and other formats
Functions to determine network names from VBI data
Functions to find Teletext subtitle and program schedule pages
Functions to extract data transmissions in Teletext streams (currently Page Format Clear and Independent Data Line Format A)

Upcoming features include

Support for V4L2 sliced VBI devices
Multi-station Teletext page cache
Teletext and CC caption/subtitle recording in formats like MPSub, QuickTime Text, SAMI or SubViewer, with color, styles and position preserved as far as possible
Support for DTVCC (EIA 708-B)
Time of day from Teletext and XDS
VCR programming from Teletext
VPS/PDC decoder

The ZVBI source tarball contains example programs and various tools to visualize captured raw and sliced VBI data and to analyze the received VBI data, which are highly useful to debug drivers and applications. Command line tools to cut and filter Teletext streams for subtitle recording, to save Teletext pages, and to record legacy NTSC caption (EIA/CEA 608-B) and DTVCC (CEA 708-C) from analog and ATSC digital TV cards also included.