[vlc-devel] Missing features in libvlc

Chris Lahey clahey at clahey.net
Wed Mar 28 21:16:12 CEST 2007

I'm going to start by talking about what I'm doing with vlc and what
functionality I need.  Then I will talk about how I want to implement
it and get your input.

I work on Democracy Player, a video podcast client.  On the windows
platform, we use the vlc mozilla plugin to view videos.  I can change
the plugin code as well as the libvlc code.  We ship a patched copy of
the plugin and the library so as to not require an installed vlc and
to make sure we're always using the same version of vlc.

Currently, I'm trying to implement a new feature that we have on the
other platforms.  Specifically, I need to fetch the duration and a
frame for use as a thumbnail for each video, without playing the

I'd like to continue using the mozilla plugin to implement this
behavior, but there's a couple of missing features.  The plugin can
only have one video loaded at a time, but to work around this, I plan
to simply embed a second plugin with the different features and
without it being displayed.

There are still a number of things that I need to change.  Firstly, I
need to code the plugin to allow you to specify the output mode.  This
shouldn't be too much of a problem.  I need to be able to specify the
image video output.  I think for this I just need to specify the
output plguin in the argv.

The next problem, and the one I don't know how exactly I'm going to
fix is that the plugin provides no way to load a video and get
metadata like duration and to set the input plugin to a certain time.
In this case, I'd like to set the time to half of the duration to
match the behavior on the other platforms.  I'd be fine setting the
time to 30 seconds in, if the duration isn't set for a video, but as
it is, there's no way to set the offset until after the video starts

I got on irc to ask about this and they suggested preparse, but libvlc
doesn't have such a function.  Can anyone suggest how I would go about
adding this functionality to libvlc and the mozilla plugin?  (I'm not
nearly as concerned about the plugin.  It's a very thin wrapper around
libvlc.)  Preparse would also be useful for the main app, but we work
around it there by repeatedly trying to set the offset until it

The final thing I'm concerned about is how I will get the image plugin
to play a single frame and then stop.  Or at the very least, how I'll
be able to tell that it's finished that first frame.

Any suggestions you can offer on these problems are appreciated.  I
would appreciate any answers to my specific questions, things I'm
doing wrong in general, or suggestions of approaches.

Feel free to ask any questions about what I'm up to also.


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