Michael Niedermayer wrote:
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 ...)
I thought about this idea, but what I don't like is doing calls to
swscale instead of just having the vf_overlay inserting an scaler
filter. Having a filter needing to force the insertion of others will be
possible in several other cases (padding, deinterlacing, resizing, etc).
That's why I thought that having at a first time a simpler solution is
better (instead of delaying too much the svn inclusion).
-Vitor
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