[gst-devel] Some basic video plugins

[Edward Hervey]

Hi,

On 9/9/07, Paul Jack <poetbeware at gmail.com> wrote:
> So looking through the plug-ins list, I'm not seeing some basic video
> plugins that would be useful in practically any video editing
> application. So I'm thinking of writing them, and wanted to be sure I
> didn't miss anything.
>
> The plugins I plan to write are:
>
> composite: Take two video streams and overlay one on top of the other,
> supporting blending modes like the GIMP's (eg, Addition, Multiply,
> Screen, Overlay...)

  This can be done to some extent by the 'videomixer' plugin.
Currently it only supports standard overlay using AYUV streams.(if the
top stream is completely transparent you'll see the other stream, if
the top stream is completely opaque you'll only see that one, ...).
BUT there is some commented out code in the plugin to allow for other
blending modes, including the ones you mention. Trying to re-activate
those would be the best course of action.

>
> affine: Apply an arbitrary affine transform to an image. Can be used
> to translate/scale/rotate in one pass.

  There is no 'generic' affine transformation element. But we do have
some plugins that do:
  'scaling' : videoscale
  'croping' : videocrop/videobox (can't remember which one is the best)
  Using a combination of the above you can do translations.

>
> blur_channel: Blur just one channel of an image (particularly useful
> for blurring just the alpha channel).

  no

>
> copy_channel: Copy one channel of an image to another (particularly
> useful for copying any color channel of a grayscale matte to the alpha
> channel).

 no

>
> maximum/minimum: Replace a channel value of each pixel with the
> maximum/minimum value of its neighboring pixels.

  no

>
> bezier: Use cairo to draw bezier curves onto one or more channels (can
> be used to create masks if applied to the apha channel).

  no, although there are two elements already using cairo for other
effects (cairotextoverlay and cairotimeoverlay), so maybe that element
could be added to that plugin.

>
> chroma_key: Replace a color with alpha, for greenscreen/bluescreen work.

  no.

>
> Do any of these already exist?
>
> Thanks,
>
> -Paul

  don't hesitate to ask for help, these are really needed plugins for
video editing.

    Edward

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-- 
Edward Hervey
Multimedia editing developer
http://www.pitivi.org/