[vlc-devel] Subtitle scaling fix and possible breakage

[R. Bernstein]

As best as I can tell setting the aspect ratio in a subtitle (or
subpicture) had no effect. I've just changed spu_RenderSubpictures of
src/video_output/vout_subpictures.c to address this. 

Basically we compare the aspect ratio of the underlying video with the
aspect of the subtitle and do an inverse scaling if they don't match.
(Now it looks like the scaling routine could stand a bit of
improvement.)

This change addresses bugs in SVCD and CVD subtitles which were
introduced when converting this to the newer subpicture renderer.
(Actually, the bug was technicially in the subpicture renderer.)

For DVD subtitles, it looks to me like the aspect ratio was set
incorrectly - what looks right is that the subtitle gets scaled the
same as the underlying video. To facilitate this notion of "keep make
the aspect ratio the same", I added a hack in spu_RenderSubpictures
that a zero aspect-ratio value means keep it the same as the
underlying video. This way one doesn't need to know what the aspect
ratio is in the subtitler which would open another set of issues.

NOTE: The image format dvbsub needs to be looked over to see if it is
correct.


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