[vlc-devel] [GCI] libvlc: An API for listing audio & video filters

[Olivier Aubert]

Hello

I am also in favor of a generic API, for enumerating available modules
and setting config values, which does not prevent from designing
specialised APIs for specific features. Regrettably, such proposals have
generally been met with reluctance on this list (see
http://mailman.videolan.org/pipermail/vlc-devel/2009-July/062333.html
for instance).

IMHO, it is rather hypocritical, since many libvlc-based solutions have
to specify command line parameters either when instanciating the vlc
instance, or by setting parameters on input items. And in this case, you
cannot even dynamically check for the presence of a plugin, you just
have to hope that it will work.

That is why I think a generic API would be a very useful addition to
libvlc (and once again, it would not prevent the design of specialised
APIs).

Regards,
Olivier


On Fri, 2010-12-03 at 20:55 +0100, Jakub Wieczorek wrote:
> Hi,
> 
> I'm working on adding an API to libvlc [1] that can give the client a
> list of available audio/video filters. One of the use cases is my
> webcam application [2], that basically needs the list of video filters
> to let the user choose which ones to apply on the video stream.
> 
> My idea was to do something like:
> const char** libvlc_get_available_plugins(libvlc_instance_t* instance,
> const char* type);
> where type would be one of the { "audio_filter", "video_filter",
> "codec", "audio_output", "video_output", "stream_out", ... }.
> 
> i.e. libvlc_get_available_plugins(instance, "video_filter") would give
> you an array ( "invert", "mosaic", "wave", "gaussianblur", ..., 0 ).
> 
> I thought that a generic solution like this would be best and could
> work with all the different types of modules. Yet, I was told that
> it's a bad idea and that it's better to create separate APIs for all
> the different module types, e.g.
> libvlc_get_available_video_filters(libvlc_instance_t*),
> libvlc_get_available_audio_filters(libvlc_instance_t*), and that not
> all module groups should be covered, but only those that really make
> sense, like, in my case, video filters. I don't quite agree with that
> and I'd love to hear some feedback on this before I do this task. What
> do you think?
> 
> Best regards,
> Jakub Wieczorek
> 
> [1] http://socghop.appspot.com/gci/task/show/google/gci2010/videolan/t129139732694
> [2] http://socghop.appspot.com/gci/task/show/google/gci2010/videolan/t128984225208
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