Difference between revisions of "Hacker Guide/How To Write a Module"

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The module descriptor begins with:
The module descriptor begins with:

Revision as of 21:21, 15 July 2007

  • This guide is being written by a VLC media player novice. Please check all statements below.
  • Using dvdread.c as the template.

Module Descriptor

A VLC media player Module must include a description of itself, and the parameters it accepts.

The module descriptor begins with:


You should set some category information on your module:

    set_shortname( _("DVD without menus") );
    set_description( _("DVDRead Input (DVD without menu support)") );
    set_category( CAT_INPUT );

Note the use of _("") to create a string that needs to be translated.

Predefined Categories include:

    set_subcategory( SUBCAT_INPUT_ACCESS );

See include/vlc_configuration.h for definition of all categories and sub-categories.

Adding Parameters

All macros take the following argument list:

 add_integer(name, value, p_callback, text, longtext, advc) 
  • name is the string that identifies this parameter in the configuration. This name may be used at the command prompt to set the configuration value.
  • value is the default value for this parameter,
  • p_callback is a function pointer that will be called when the value of this parameter is changed.
    • p_callback is called with the following arguments:
      ( p_this, psz_name, oldval, val, p_config->p_callback_data )
      • p_this is a pointer to a vlc_object_t struct,
      • psz_name is the name of your parameter that is being changed,
      • oldval is the old value of the parameter,
      • val is the new value of the parameter,
      • p_call_back_data is void* data that you can assign for each parameter. Usually NULL.
  • text A short description of the parameter,
  • longtext A complete description of the parameter,
  • advc Boolean, ADVanced Configuration. If TRUE, this parameter will only be displayed when using the --advanced flag. e.g.
vlc -p dvdread --advanced


 add_integer("dvdread-angle", 1, NULL, "DVD Angle", "Default DVD Angle", NULL") 

You may add the following parameters to your module:

  • add_integer,
  • add_string,
  • add_float,
  • add_bool,
  • add_key,
  • add_file,
  • add_directory,

For complete definitions, see include/vlc_configuration.h

Open(vlc_object_t *)

Close(vlc_object_t *)