[Matroska-users] Re: Video as Overlay with Alpha Blending

Mike Matsnev mike at po.cs.msu.su
Mon Nov 15 09:27:49 CET 2004

John Anthony Kazos Jr. wrote:
> 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.
The only method that is currently available and is widely supported is
using vobsub subtitles as on dvd (4-color bitmaps with binary transparency).
I have some experimental code that does alpha blending via vmr9, but vmr
sometimes lockups and hangs hard, so I didnt release it. If you want to
have some better overlays than vobsubs, I think it wouldnt be too hard
to add such support to vsfilter.


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