Hacker Guide/Demux

Description

The modules of 'demux' capability are designed to handle the different "file" formats. They usually come after the access in the modules chain.

Examples of demuxers are WMV/ASF, Ogg or Mkv.

Write an demuxer module

To write an demuxer module, read the introduction to module writing.

Then, you should specify your module of being of demux type:

set_capability( "demux", 60 )  
set_category( CAT_INPUT )                                                                                                                                                                                  
set_subcategory( SUBCAT_INPUT_DEMUX )

Functions to implement

After implementing Open() and Close() functions, you will need to implement a few majors features that will be implemented by your functions.

As you can see include/vlc_demux.h, you should define:

• Demux, as in pf_demux
• Control, as in pf_control

After implementing those functions, you should assign them to the corresponding pf_ function.

Control

Prototype:

int         (*pf_control)( access_t *, int i_query, va_list args);

Control function is quite easy, the input core will query the module using this function with:

• A pointer to the module structure.
• An i_query parameter that can be of several type. We will cover afterward the most important on.
• A list of arguments, that depends on the i_query type.

Return:

If the query has succeeded, it should return VLC_SUCCESS. Else it should return VLC_EGENERIC (fail).

Control Query types

See include/vlc_demux.h

Demux

Prototype:

 int (*pf_demux)  ( demux_t * ); 

Demux function is quite easy, it pulls data from s* the pointer to the stream_t.

Return:

It should return 0 for EOF, something positive when success and something negative when fail to demux.

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