options: disable vsfilter blur compat by default

See #7435 and related for context.

Basically, it seems that while the original vsfilter processed subtitles
like with this option set to "yes", many current players (mpc-hc
default, vlc, probably most libass users) treat them like with "no". In
the linked issue, this makes rendering severely slower, and can consume
a lot of memory (or just overflow libass memory calculations). It seems
that changing this to "no" will lead to more good than bad, especially
because newer subtitles may be authored for the "no" behavior.

Most libass users seem to use "no" exactly because they do not call
ass_set_storage_size() at all. This API was needed because the scaling
of the subtitles depends on the video size (vsfilter bugs, or
something). In addition, it's my personal opinion that rendering should
not depend on the video at all, so I like setting the default of this to
"no".

DOCS/man/options.rst

@@ -2200,7 +2200,7 @@ Subtitles
 
 ``--sub-ass-vsfilter-blur-compat=<yes|no>``
     Scale ``\blur`` tags by video resolution instead of script resolution
-    (enabled by default). This is bug in VSFilter, which according to some,
+    (disabled by default). This is bug in VSFilter, which according to some,
     can't be fixed anymore in the name of compatibility.
 
     Note that this uses the actual video resolution for calculating the

options/options.c

@@ -255,7 +255,7 @@ const struct m_sub_options mp_subtitle_sub_opts = {
         .sub_scale = 1,
         .ass_vsfilter_aspect_compat = 1,
         .ass_vsfilter_color_compat = 1,
-        .ass_vsfilter_blur_compat = 1,
+        .ass_vsfilter_blur_compat = 0,
         .ass_style_override = 1,
         .ass_shaper = 1,
         .use_embedded_fonts = 1,