[Matroska-users] Video as Overlay with Alpha Blending

John Anthony Kazos Jr. johnkazos at blacksburg.ntc-com.net
Sat Nov 13 01:39:31 CET 2004


I want to have one primary video stream, one or more (selectable, one at a 
time) primary audio streams, and a second video stream overlaid (or hidden, 
selectably) upon the primary video stream with transparency by alpha 
blending. My second choice would be to have it overlaid with simple binary 
transparency. Preferably, in either case, it would be compressed with a 
DivX/XviD codec; raw video (even with RLE or somesuch) would probably be 
too big.

 From the tidbits I have gleaned off the 'Net, somehow using a subtitle 
track with video content would allow it to be overlaid and to be toggled, 
but I can't find a clue as to how. I need to know if Matroska supports it 
at all, and how to get it into the container, assuming I have all video and 
audio streams ready with gaps and chapters determined.

Then again, if this isn't possible at all, is there any way I could somehow 
have multiple angles that are automatically switched? For example, I have 
one master video stream without the overlaid video, and then a secondary 
video stream (either with gaps or in pieces) that, if the user enables it, 
will display /instead/ of the primary stream whenever there would have been 
video overlay? (So the secondary stream wouldn't be a second full stream 
with the overlaid video, but would be just those pieces of the video that 
had overlay.)





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