sub: merge vsfilter-aspect and vsfilter-blur-compat options

The naming for "blur-compat" was misleading since the setting
actually affects more than just blur affects. Additionally
forwarding storage resolution but forcing an aspect ratio
of 1.0 for the video is likely to result in odd rendering
and there’s no known usecase for it.

Both options control which video properties are exposed to libass
so to fix the aforementioned issues merge these settings into one
tri-state sub-ass-use-video-data.

The default V keybind now cycles through all states of
use-video-data instead of toggling vsfilter-aspect-compat.

Resolves: https://github.com/mpv-player/mpv/issues/10680

DOCS/interface-changes/sub-ass-use-video-data.txt

@@ -0,0 +1,5 @@
+Remove sub-ass-vsfilter-aspect-compat.
+Remove sub-ass-vsfilter-blur-compat.
+Add sub-ass-use-video-data.
+Change default V keybind to cycle sub-ass-use-video-data
+instead of toggling the now removed sub-ass-vsfilter-aspect-compat.

DOCS/man/mpv.rst

@@ -181,8 +181,8 @@ u
     style. See ``--sub-ass-override`` for more info.
 
 V
-    Toggle subtitle VSFilter aspect compatibility mode. See
-    ``--sub-ass-vsfilter-aspect-compat`` for more info.
+    Cycle through which video data gets used for ASS rendering.
+    See ``--sub-ass-use-video-data`` for more info.
 
 r and R
     Move subtitles up/down. The ``t`` key does the same as ``R`` currently, but

DOCS/man/options.rst

@@ -2568,31 +2568,22 @@ Subtitles
 
     Default: yes.
 
-``--sub-ass-vsfilter-aspect-compat=<yes|no>``
-    Stretch SSA/ASS subtitles when playing anamorphic videos for compatibility
-    with traditional VSFilter behavior. This switch has no effect when the
-    video is stored with square pixels.
+``--sub-ass-use-video-data=<none|aspect-ratio|all>``
+    Controls which information about the video stream is passed to libass.
+    Any option but ``all`` is incompatible with standard ASS and VSFilters.
 
-    The renderer historically most commonly used for the SSA/ASS subtitle
-    formats, VSFilter, had questionable behavior that resulted in subtitles
-    being stretched too if the video was stored in anamorphic format that
-    required scaling for display.  This behavior is usually undesirable and
-    newer VSFilter versions may behave differently. However, many existing
-    scripts compensate for the stretching by modifying things in the opposite
-    direction.  Thus, if such scripts are displayed "correctly", they will not
-    appear as intended.  This switch enables emulation of the old VSFilter
-    behavior (undesirable but expected by many existing scripts).
+    For certain kinds of broken ASS files which got repurposed across
+    several video resolutions without either setting ``LayoutRes`` headers
+    or adjusting affected effects, it may be desirable to withhold storage resolution
+    information from libass to ensure consistent rendering across resolutions.
+    Among others this affects 3D rotations and blurs.
+    When encountering such files, try setting ``aspect-ratio``.
 
-    Enabled by default.
+    Even more broken files on anamorphic video might also exhibit stretching
+    unless aspect ratio information is also faked, in this case you can try
+    using ``none``. This has never an effect on non-anamorphic video.
 
-``--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,
-    can't be fixed anymore in the name of compatibility.
-
-    Note that this uses the actual video resolution for calculating the
-    offset scale factor, not what the video filter chain or the video output
-    use.
+    Default: ``all``
 
 ``--sub-vsfilter-bidi-compat=<yes|no>``
     Set implicit bidi detection to ``ltr`` instead of ``auto`` to match ASS'