Using videomixer and alpha channel

[Eric Trousset]

> -----Original Message-----
> From: Sebastian Dröge [mailto:sebastian at centricular.com]
> Sent: vendredi 22 novembre 2013 20:52
> To: Discussion of the development of and with GStreamer
> Subject: Re: Using videomixer and alpha channel
> 
> On Mi, 2013-11-20 at 12:10 +0100, Eric Trousset wrote:
> > Hi,
> >
> > I am using, videomixer to mixer to streams, but it seems the alpha channel
> is not used for the mixing, eg, part of the image with a 0 alpha aren't
> transparent...
> >
> > Is there a way to enable alpha transparency in the video mixer?

> 
> Are you making sure that the video input to videomixer is still having the
> alpha channel, i.e. there's no videoconvert element in front of it that
> converts it to something without alpha channel?
> 
> The blending code in videomixer should use the alpha channel already.

Yes I had a videoconvert element. So I removed it but still, it seems the pixel alpha is not taken into account. I can see the checker background only if I set the pad's "alpha" property to some value.

> 
> > Also, I am using imagefreeze to display a still image. Is there a way to make
> this element to ask the source for a new image at some point?
> 
> There isn't, but it could be implemented with some custom event. Or maybe
> all this should just handle the request-keyunit event. Nothing is
> implemented yet for that.


That would be a great feature :)


> 
> --
> Sebastian Dröge <sebastian at centricular.com> Centricular Ltd -
> http://www.centricular.com Expertise, Straight from the Source