On Sun, Dec 06, 2009 at 05:12:37PM +0100, Vitor Sessak wrote: > Hi and sorry for the delay. > > Artur Bodera wrote: >> On Tue, Dec 1, 2009 at 12:50 AM, Vitor Sessak <vitor1...@gmail.com> wrote: >>> While I normally oppose making non-committed code more complex, I think >>> this feature is so often requested that it is worth the extra work in the >>> future. Stefano, Michael, any strong opinion about this? >>> >> I think the vf_overlay should be modified altogether. Although >> mathematically alpha-blending is more expensive than opaque pixel >> replacement, I think that it should be automatically decided by analyzing >> the overlay format. >> So the alpha-blending should be a "built-in" functionality (not a >> switchable >> parameter) and should be implicitly functional with any overlay >> stream/image >> that has alpha channel (i.e. rgba). If there is no alpha channel, then >> pixel >> overriding would be used. This makes much more sense. > > I agree that this would be nice, but there is no way to make it work with > the current format negotiation in libavfilter. For example, there is no way > to have a filter that accepts either "input: rgb, output rgba" or "input: > yuv, output: yuva", so I suggest you just do as your present patch for the > time been.
an overlay filter that supports rgb -> rgb yuv -> yuv ^ OR ^ rgba yuva cant be done, but you can do: rgb -> rgb yuv -> yuv ^ OR ^ yuva||rgba yuva||rgba this might end up requireing rgb<->yuv converting the thing to be overlaid in the overlay filter (its just a call to the swscaler ...) and about the current format negotiation, if you have better ideas which i doubt ;) they are welcome. The issue is just that with arbitrary graphs its not so easy to negotiate the format in a way that is scaleable and doesnt break down to O(2^n) time [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In fact, the RIAA has been known to suggest that students drop out of college or go to community college in order to be able to afford settlements. -- The RIAA
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