[Bug 731791] New: videometa: add GstVideoAffineTransformationMeta

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=731791
  GStreamer | gst-plugins-base | git

           Summary: videometa: add GstVideoAffineTransformationMeta
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: matthieu.bouron at collabora.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Hello,

Here is a proposal for a new buffer metadata responsible for carrying a 4x4
transformation matrix.

This implementation let user specify a custom transformation matrix as well as
a custom get_matrix function, see
get_buffer_add_video_affine_transformation_meta() function.

The custom get_matrix function can be helpful when the transformation matrix
have to be retrieved from the buffer to which the meta is attached to. I'm
thinking about the android media buffers here where a transformation matrix has
to be retrieved from the android surface texture after updateTexImage() has
been called and be used to sample the texture. In this case the get_matrix
function will retrieved the transformation matrix from the surface texture
stored in the buffer and then multiply it with the matrix stored in the meta.

The user can also apply transformations using the
gst_video_affine_transformation_apply_matrix() function.

The resulting matrix is retrieved by the
gst_video_affine_transformation_get_matrix() function.

Comments welcome.

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