Hi Gerwin, It's a bit of a tricky situation. The actual content of the alpha channel mainly depends on FFmpeg implementation (and not osg). If I remember correctly, the obsolete colour conversion routines set the alpha value to 1 when the video was only RGB, while the libswscale routines set it to 0. As both paths are still used, you cannot know for sure the content of the alpha channel.
Note that most movies do not feature transparency. In fact, only FLV files with transparency are supported. To know if a movie supports transparency, you can call osg::ImageStream::isImageTranslucent(). The FFmpeg osg plugin will return true if the movie features a meaningful alpha channel. If it returns false, I suggest you treat the content of the alpha channel as undefined. I do not suggest modifying the plugin to enforce the alpha value, as this would impact performance. Cheers, Tanguy -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Gerwin de Haan Sent: 04 August 2009 09:23 To: [email protected] Subject: [osg-users] [osgPlugins] ffmpeg plugin and transparency Hi all, I've been toying with the ffmpeg plugin and osg 2.9.5. As I was hoping, this is definitely a great improvement over the buggy xine plugin. I'm currently adding more playback controls, such as seek and pausing support. I did notice a surprising effect when using a regular (non-transparent) movie with a transparent StateSet. Apparently, the alpha value in the rgba texture remain at 0 by default, resulting in a fully transparent texture. It took me a while to figure this one out, but when I used a fragmentshader to override the alpha value, the movie becomes visible again. This behavior is not the case with regular images or when using xine. Is this behavior by design, am I missing something or should we add code to correctly set the alpha value for non-transparent movies? Cheers, Gerwin ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=15759#15759 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
