[gstreamer-bugs] [Bug 639763] [dvbsuboverlay] Green borders around subtitles

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=639763
  GStreamer | gst-plugins-bad | git

Mart Raudsepp <leio> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
                 CC|                            |leio at gentoo.org
     Ever Confirmed|0                           |1

--- Comment #1 from Mart Raudsepp <leio at gentoo.org> 2011-02-01 00:04:19 UTC ---
Interestingly commit 994156c1b - "dvbsuboverlay: remove unnecessary RGB -> YUV
conversion by using YUV palettes" seemingly made the green borders even thicker
than before in initial code and also changed the tones of the white fill.

The sample media does not seem to use alpha values other than 0 or 255.
When observing the look of it before commit 994156c1b, it seems as if it has a
green tint next to subtitle overlayed pixels at places where no transparency
changes to full transparency in the middle of a 2x2 subsampled block. E.g, the
top side of both lines are nicely aligned to the 2x2 blocks, and I can't
observe any green tinting above, while it doesn't align with the bottom of a
2x2 block at the bottom of the text, and there's one pixel of green shade. Same
with various places on the right and left edges. Looked at it in magnification
of a screenshot in gimp.
So there it smells like there's some issue with alpha change handling in the
I420 blending code, but the shading seemingly being strengthened to go across
the 2x2 blocks after change to YUV CLUT palette is weird.

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