subassconvert: do not escape likely ASS override tags

Usually SubRip files are not expected to contain ASS override tags,
but unfortunately these files seem to become more common. Example from
a real file:

1
00:00:00,800 --> 00:00:15,000
{\an8}本字幕由 {\c&H26F4FF&}ShinY {\c&HFFAE1A&}深影字幕组{\c&HFFFFFF&} 原创翻译制作

subassconvert.c escaped '{', so that libass displayed the above line
literally.

Try to apply a simple heuristic to detect whether '{' is likely to
start an ASS tag: if the string starts with '{\', and there is a
closing '}', assume it's an ASS tag, otherwise escape the '{' properly.
If it's a likely ASS tag, it's passed through to libass.

The end result is that the above script is displayed in color, while at
the same time legitimate uses of '{' and '}' should work fine. We assume
that nobody uses {...} for commenting text in SubRip files. (This kind
of comment is popular and legal in ASS files, though.)

0 files changed, 0 insertions, 0 deletions