[gstreamer-bugs] [Bug 617512] [alpha] should work in passthrough in all formats if alpha == 1.0

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=617512
  GStreamer | gst-plugins-good | git

--- Comment #2 from Edward Hervey <bilboed at gmail.com> 2010-05-03 11:41:20 UTC ---
(In reply to comment #1)
> Wouldn't that mean the caps are dependant on when the alpha value was last set
> - i.e. if you started with alpha=0.9 and while the pipeline ran set it to 1.0
> you'd get AYUV

  It will start with AYUV, but the moment you set it to 1.0 it should attempt
to renegotiate caps (which might or might not end up in pushing out AYUV,
depending on what downstream can accept).

, but if you started with alpha=1.0 and didn't set it you'd end
> up with I420?

  yes

> 
> Or would that mean that for a controlled channel with a tween from 1.0 to 0.0
> you'd get I420 in the beginning and AYUV when the tween starts changing the
> alpha value?

  yes

 Would that mean pipelines that miss a colorspace element could
> error out half-way through?

  yes, no big problem there imho.

> 
> So in short I think it's a bad idea to make the negotiated caps depend on a
> controllable (i.e. settable while the pipeline runs) property.

 You do realize you don't need a GstController to change that property ?
Changing caps at runtime isn't a problem with other elements (videoscale does
that fine), why should it be a problem now ?

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