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ZVBI library interface module for Perl

This repository contains the sources of the "Video::ZVBI" Perl module, which has its official home at https://metacpan.org/pod/Video::ZVBI. Please use the ticket interfaces at CPAN for reporting issues. This module is equivalent to the Zvbi module for Python.

This Perl extension module provides an object-oriented interface to the ZVBI library. The ZVBI library allows accessing television broadcast data services such as teletext or closed captions via analog or DVB video capture devices.

Official ZVBI library description:

The ZVBI library provides routines to access raw VBI sampling devices (currently the Linux DVB & V4L2 APIs and the FreeBSD, OpenBSD, NetBSD and BSDi bktr driver API are supported), a versatile raw VBI bit slicer, decoders for various data services and basic search, render and export functions for text pages. The library was written for the Zapping TV viewer and Zapzilla Teletext browser.

The ZVBI module for Perl covers all exported libzvbi functions.

The Perl interface is largely based on blessed references to binary pointers. Internally the module uses the native C structures of libzvbi as far as possible. Only in the last step, when a Perl script wants to manipulate captured data directly (i.e. not via library functions), the structures' data is converted into Perl data types. This approach allows for a pretty snappy performance.

Best starting point to get familiar with the module is having a look at the Class Hierarchy, description of the main classes in the API documentation, and the example scripts provided in the examples/ sub-directory, which demonstrate use of all the main classes. (The examples are a more or less direct C to Perl ports of the respective programs in the test/ sub-directory of the libzvbi source tree, plus a few additions, such as a teletext level 2.5 browser implemented in apx. 300 lines of Perl::Tk.) A description of all example scripts can be found in the API documentation in section Examples. Additionally you can look at the ZVBI home and the ZVBI library documentation (unfortunately not available online; built via doxygen when compiling the library).

Module information

Perl DLSIP-code: RcdOg

  • development stage: stable release
  • C compiler required for installation
  • support by developer
  • object oriented using blessed references
  • licensed under GPL (GNU General Public License)

Supported operating systems (as determined by ZVBI library):

  • Linux
  • FreeBSD
  • NetBSD
  • OpenBSD

Comparison with the "Video-Capture-VBI" Perl module

You may have noticed there already is a Perl module which provides similar functionality. The approach is completely different though: The older VBI module contains an actual implementation of a teletext and VPS slicers and databases, while ZVBI is an interface layer to an external C library.

Besides that, the reason for not just contributing code to the existing module was that libzvbi alone can almost entirely replace the older VBI module (i.e. it covers the same functionality, except currently for the high-level "nexTView" EPG decoding.) So there would not much to be gained by merging the code. On the other hand, libzvbi supports much more platforms, drivers (e.g. V4L2, DVB, BSD) and services, so that it seems warranted to make that available to the Perl universe.

Installation

Pre-requisite to the installation is a C compiler and the libzvbi library (oldest supported version is 0.2.16, or 0.2.4 when disabling USE_DL_SYM in Makefile.PL) which in turn requires the pthreads and PNG libraries. Once you have these, installation can be done in the usual steps:

    cd Video-ZVBI
    perl Makefile.PL
    make
    make install

However cleaner than installing directly is generating a package and installing that, as this will ensure dependencies are available and allow for easy removal of installed files. The repository contains a shell script that creates a Debian package (also works for all derived Linux distributions such as Ubuntu). Using that, the steps for installing are:

    (cd Video-ZVBI && perl Makefile.PL && make)
    bash create_deb.sh
    dpkg -i deb/libzvbi-perl_*_amd64.deb

Note there are no dependencies on other Perl modules by the module itself. Some of provided example scripts however depend on Perl::Tk

Trouble-shooting note: By default the module compiles against an internal copy of libzvbi.h and loads symbols added in recent library versions during module start from the shared library. If your compiled module doesn't load, try disabling compile switches USE_DL_SYM and USE_LIBZVBI_INT in Makefile.PL

Bug reports

Please submit bug reports relating to the interface module via CPAN.

If your bug report or request relates to libzvbi rather than the interface module, please contact the libzvbi authors, preferably via the Zapping mailing list. In case of capture problems, please make sure to specify which operating system and hardware you are using, and of course which version of libzvbi and which version of Perl and the ZVBI module respectively.

Documentation

For further information please refer to the following files:

Copyright

Copyright (C) 2006-2020 T. Zoerner.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License for more details.