[MPlayer-dev-eng] [BUG] various weirdness in vf_expand when expanded width > frame width

[Jason Tackaberry]

The expand filter does some peculiar things when expanding to a width
greater than the frame width.  For example, take some 4:3 content, and
do -vf expand=:::::16/9.

     1. The bars added to either side of the video are gray.  When
        displaying and hiding OSD, there is cruft remaining from the OSD
        in the gray parts.  (I think this bug is probably known.)
     2. When using the osd feature in expand, -vf expand=::::1:16/9, the
        OSD is not visible at all.
     3. If I put a filter (one that implements a put_image, so not
        dsize, for example) in front of expand, e.g. -vf
        eq,expand=::::1:16/9, the bars on each side are properly black,
        and in this case, OSD works again.  However when the OSD is
        hidden, cruft is still left behind (unsurprisingly).
     4. Putting scale after expand is a recipe for corruption.  For
        example, -vf expand=::::1:16/9,scale=640:-2 produces an image
        where the original frame is left-aligned (not centered) and the
        right portion of the frame (whose width is the combined width of
        what the bars would be) has a portion of the frame with some
        slight corruption.  In this case, expand OSD support no longer
        works (as in #2 above).
     5. Putting a parameterless scale before expand works as expected
        (side bars are black, no OSD cruft when OSD hidden), but only if
        expand OSD option not enabled.  e.g. -vf scale,expand=:::::16/9.
        If I do -vf scale,expand=::::1:16/9, OSD behaves again as in #2.


Given that 16:9 televisions are getting more and more popular and there
is still a fair bit of 4:3 content out there, I'm sure there's some
growing desire to see this bug fixed.  Unfortunately vf_expand does some
get_image voodoo that I don't entirely grok; does anyone have any idea
what the proper solution to this bug would be?

Thanks,
Jason.