options, subs: add --ass-vsfilter-aspect-compat

Add option --ass-vsfilter-aspect-compat and corresponding property
ass_vsfilter_aspect_compat. The setting controls whether to enable the
emulation of traditional VSFilter behavior where subtitles are
stretched if the video is anamorphic (previously always enabled for
native SSA/ASS subtitles). Enabled by default. Add 'V' as a new
default keybinding to toggle the property.

DOCS/man/en/mplayer.1

@@ -251,6 +251,9 @@ Toggle displaying "forced subtitles".
 Toggle subtitle alignment: top / middle / bottom.
 .IPs "x and z"
 Adjust subtitle delay by +/\- 0.1 seconds.
+.IPs "V\ \ \ \ "
+Toggle subtitle VSFilter aspect compatibility mode.
+See -ass\-vsfilter\-aspect\-compat for more info.
 .IPs "C (\-capture only)"
 Start/stop capturing the primary stream.
 .IPs "r and t"
@@ -2226,6 +2229,25 @@ Enables placing toptitles and subtitles in black borders when they
 are available.
 .
 .TP
+.B \-ass\-vsfilter\-aspect\-compat
+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.
+.sp 1
+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).
+Enabled by default.
+.
+.TP
 .B \-dumpjacosub
 Convert the given subtitle (specified with the \-sub option) to the time-based
 JACOsub subtitle format.

DOCS/tech/slave.txt

@@ -585,6 +585,7 @@ sub_alignment      int       0       2       X   X   X    subtitle alignment
 sub_visibility     flag      0       1       X   X   X    show/hide subtitles
 sub_forced_only    flag      0       1       X   X   X
 sub_scale          float     0       100     X   X   X    subtitles font size
+ass_vsfilter_aspect_compat flag 0    1       X   X   X    SSA/ASS aspect ratio correction
 tv_brightness      int       -100    100     X   X   X
 tv_contrast        int       -100    100     X   X   X
 tv_saturation      int       -100    100     X   X   X

cfg-mplayer.h

@@ -699,6 +699,7 @@ const m_option_t common_opts[] = {
     {"ass-bottom-margin", &ass_bottom_margin, CONF_TYPE_INT, CONF_RANGE, 0, 2000, NULL},
     {"ass-use-margins", &ass_use_margins, CONF_TYPE_FLAG, 0, 0, 1, NULL},
     {"noass-use-margins", &ass_use_margins, CONF_TYPE_FLAG, 0, 1, 0, NULL},
+    OPT_MAKE_FLAGS("ass-vsfilter-aspect-compat", ass_vsfilter_aspect_compat, 0),
     {"embeddedfonts", &use_embedded_fonts, CONF_TYPE_FLAG, 0, 0, 1, NULL},
     {"noembeddedfonts", &use_embedded_fonts, CONF_TYPE_FLAG, 0, 1, 0, NULL},
     OPT_STRINGLIST("ass-force-style", ass_force_style_list, 0),

command.c

@@ -1973,6 +1973,27 @@ static int mp_property_ass_use_margins(m_option_t *prop, int action,
         return m_property_flag(prop, action, arg, &ass_use_margins);
     }
 }
+
+static int mp_property_ass_vsfilter_aspect_compat(m_option_t *prop, int action,
+                                                  void *arg, MPContext *mpctx)
+{
+    if (!mpctx->sh_video)
+        return M_PROPERTY_UNAVAILABLE;
+
+    switch (action) {
+    case M_PROPERTY_SET:
+        if (!arg)
+            return M_PROPERTY_ERROR;
+    case M_PROPERTY_STEP_UP:
+    case M_PROPERTY_STEP_DOWN:
+        //has to re-render subs with new aspect ratio
+        mpctx->osd->ass_force_reload = 1;
+    default:
+        return m_property_flag(prop, action, arg,
+                               &mpctx->opts.ass_vsfilter_aspect_compat);
+    }
+}
+
 #endif
 
 /// Show only forced subtitles (RW)
@@ -2316,6 +2337,8 @@ static const m_option_t mp_properties[] = {
 #ifdef CONFIG_ASS
     { "ass_use_margins", mp_property_ass_use_margins, CONF_TYPE_FLAG,
       M_OPT_RANGE, 0, 1, NULL },
+    { "ass_vsfilter_aspect_compat", mp_property_ass_vsfilter_aspect_compat,
+      CONF_TYPE_FLAG, M_OPT_RANGE, 0, 1, NULL },
 #endif
 
 #ifdef CONFIG_TV
@@ -2427,6 +2450,8 @@ static struct property_osd_display {
 #ifdef CONFIG_FREETYPE
     { "sub_scale", 0, -1, _("Sub Scale: %s")},
 #endif
+    { "ass_vsfilter_aspect_compat", 0, -1,
+      _("Subtitle VSFilter aspect compat: %s")},
 #ifdef CONFIG_TV
     { "tv_brightness", OSD_BRIGHTNESS, -1, _("Brightness") },
     { "tv_hue", OSD_HUE, -1, _("Hue") },

defaultopts.c

@@ -49,6 +49,7 @@ void set_default_mplayer_options(struct MPOpts *opts)
 #ifdef CONFIG_ASS
         .ass_enabled = 1,
 #endif
+        .ass_vsfilter_aspect_compat = 1,
 
         .lavc_param = {
             .workaround_bugs = 1, // autodetect

etc/input.conf

@@ -75,6 +75,7 @@ t sub_pos +1            #                down
 #? sub_step -1		#                     previous
 #? sub_scale +0.1	# increase subtitle font size
 #? sub_scale -0.1	# decrease subtitle font size
+V step_property_osd ass_vsfilter_aspect_compat  # stretch SSA/ASS subtitles with anamorphic videos to match historical VSFilter behavior
 f vo_fullscreen
 T vo_ontop              # toggle video window ontop of other windows
 w panscan -0.1          # zoom out with -panscan 0 -fs

input/input.c

@@ -472,6 +472,7 @@ static const struct cmd_bind def_cmd_binds[] = {
   { { 't', 0 }, "sub_pos +1" },
   { { 'a', 0 }, "sub_alignment" },
   { { 'v', 0 }, "sub_visibility" },
+  { { 'V', 0 }, "step_property_osd ass_vsfilter_aspect_compat" },
   { { 'j', 0 }, "sub_select" },
   { { 'J', 0 }, "sub_select -3" },
   { { 'F', 0 }, "forced_subs_only" },

libmpcodecs/vf_ass.c

@@ -358,8 +358,9 @@ static int put_image(struct vf_instance *vf, mp_image_t *mpi, double pts)
 {
     struct osd_state *osd = vf->priv->osd;
     ASS_Image *images = 0;
-    ASS_Renderer *renderer = osd->vsfilter_aspect ?
-        vf->priv->renderer_vsfilter : vf->priv->renderer_realaspect;
+    ASS_Renderer *renderer = osd->vsfilter_aspect
+            && vf->opts->ass_vsfilter_aspect_compat
+            ? vf->priv->renderer_vsfilter : vf->priv->renderer_realaspect;
     if (sub_visibility && renderer && osd->ass_track
             && (pts != MP_NOPTS_VALUE)) {
         if (osd->ass_force_reload) {

libmpcodecs/vf_vo.c

@@ -23,6 +23,7 @@
 
 #include "config.h"
 #include "mp_msg.h"
+#include "options.h"
 
 #include "mp_image.h"
 #include "vf.h"
@@ -155,7 +156,7 @@ static int control(struct vf_instance *vf, int request, void* data)
         double pts = video_out->next_pts;
         ASS_Renderer *renderer;
         double scale;
-        if (osd->vsfilter_aspect) {
+        if (osd->vsfilter_aspect && vf->opts->ass_vsfilter_aspect_compat) {
             renderer = vf->priv->renderer_vsfilter;
             scale = vf->priv->scale_ratio;
         } else {

options.h

@@ -92,6 +92,7 @@ typedef struct MPOpts {
     char **sub_paths;
     int sub_auto;
     int ass_enabled;
+    int ass_vsfilter_aspect_compat;
     char **ass_force_style_list;
     struct lavc_param {
         int workaround_bugs;