[Bug 668483] New: gstvideo: add support for global-alpha multiplicator for overlay rectangles

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=668483
  GStreamer | gst-plugins-base | git

           Summary: gstvideo: add support for global-alpha multiplicator
                    for overlay rectangles
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: hk at getslash.de
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=205855)
 View: https://bugzilla.gnome.org/attachment.cgi?id=205855
 Review: https://bugzilla.gnome.org/review?bug=668483&attachment=205855

Add support for global alpha multiplicator to video-blend and
gstoverlaycomposition interface

Hi,

the new Overlay Composition API
(http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-libs/html/gst-plugins-base-libs-gstvideooverlaycomposition.html)
can be used to overlay generic OSD elements over raw surfaces. An often used
feature of osd elements is fading them in and out. This is done bei adjusting
the alpha values of the overlayed pixels, which can be achieved on a per-pixel
basis or -- if supported by the API -- globally for a whole overlay
element/component/rectangle. The latter does not introduce performance overhead
if supported by the blending engine, whereas the former does.

This request asks to add support for a global-alpha multiplicator per
composition rectangle to allow for efficient fading support of the new Overlay
Composition API. 2 patches attached:

- add global_alpha flag to the GstVideoOverlayRectangle struct and the relvant
API calls and add support for global_alpha value in video_blend() func
- update textoverlay, which already makes use of the new API

We were not always sure whether the modification of the API calls where in line
with the API design principles. Please let us know if you prefer further
changes to the patches.

Thanks for your review and for the new API which is a great improvement for
OSD-elements,
  Holger

-- 
Configure bugmail: https://bugzilla.gnome.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.
You are the assignee for the bug.