[vlc-devel] Chroma-key plugin for VLC as class broadcast client

Rémi Denis-Courmont remi at remlab.net
Mon May 4 12:17:08 CEST 2009

On Mon, 4 May 2009 10:30:26 +0200 (CEST), jpd at m2x.nl wrote:
> Another way could be to use the shape extention, requiring vlc to provide
> its own mask and telling the system to only paint what isn't masked out,
> provided updating can be done fast enough (also on the server side).
> The thing is more or less that it's not something the application does,
> but the windowing system (in X11's case, the window- or compositing
> manager), though of course a vlc plugin could be made to specifically
> support steering the component that actually does it.

Err, it *is* mostly a VLC limitation at this point. Sure, you need a modern
X server or Windows/OSX equivalent, but that's already written, available
and widely deployed. We would need to extend the video output to handle
RGBA. At least 1-bit alpha channel is needed, though it is probably simpler
at this point in time to go to full 32-bits RGBA. I guess some small tweaks
to the video output core might be needed, but mostly changes to each and
every video outputs...

It gets trickier if you consider that certain outputs simply cannot do
that. I guess GLX and X11 can, but XVideo cannot?

> This then leaves the problem of taking the picture output and re-forming
> it into some form that can be encoded and broadcast. A vlc screen capture
> plugin and an accompanying masking/chroma keying plugin might be worth
> investigating.

Rémi Denis-Courmont

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