sub: add auto option to --sub-fix-timing

Third try is the charm? I stupidly missed that this option already
existed in my previous commits. Instead, add an auto value to it and
enable it by default for sd_lavc but not sd_ass. On my limited samples,
it seems to fix the gaps issue that can occur but without regressing
some duration timings for sub_lavc subtitles. Well hopefully anyway.
Fixes #12327.

DOCS/interface-changes.rst

@@ -56,6 +56,7 @@ Interface changes
     - add `--video-crop`
     - add `video-params/crop-[w,h,x,y]`
     - remove `--tone-mapping-mode`
+    - add `auto` to `--sub-fix-timing` and make it the default
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

DOCS/man/options.rst

@@ -2627,10 +2627,11 @@ Subtitles
         particular subtitles in mkv files) are always assumed to be UTF-8.
 
 
-``--sub-fix-timing=<yes|no>``
+``--sub-fix-timing=<auto|yes|no>``
     Adjust subtitle timing is to remove minor gaps or overlaps between
     subtitles (if the difference is smaller than 210 ms, the gap or overlap
-    is removed).
+    is removed). The ``auto`` value enables this for non-text subtitles such
+    as PGS or DVD (default: ``auto``).
 
 ``--sub-forced-events-only=<yes|no>``
     Enabling this displays only forced events within subtitle streams. Only

options/options.c

@@ -267,7 +267,8 @@ const struct m_sub_options mp_subtitle_sub_opts = {
         {"stretch-dvd-subs", OPT_BOOL(stretch_dvd_subs)},
         {"stretch-image-subs-to-screen", OPT_BOOL(stretch_image_subs)},
         {"image-subs-video-resolution", OPT_BOOL(image_subs_video_res)},
-        {"sub-fix-timing", OPT_BOOL(sub_fix_timing)},
+        {"sub-fix-timing", OPT_CHOICE(sub_fix_timing,
+                {"auto", -1}, {"no", 0}, {"yes", 1})},
         {"sub-pos", OPT_FLOAT(sub_pos), M_RANGE(0.0, 150.0)},
         {"sub-gauss", OPT_FLOAT(sub_gauss), M_RANGE(0.0, 3.0)},
         {"sub-gray", OPT_BOOL(sub_gray)},
@@ -306,6 +307,7 @@ const struct m_sub_options mp_subtitle_sub_opts = {
     .defaults = &(OPT_BASE_STRUCT){
         .sub_visibility = true,
         .sec_sub_visibility = true,
+        .sub_fix_timing = -1,
         .sub_pos = 100,
         .sub_speed = 1.0,
         .ass_enabled = true,

options/options.h

@@ -89,7 +89,7 @@ struct mp_subtitle_opts {
     bool stretch_dvd_subs;
     bool stretch_image_subs;
     bool image_subs_video_res;
-    bool sub_fix_timing;
+    int sub_fix_timing;
     bool sub_scale_by_window;
     bool sub_scale_with_window;
     bool ass_scale_with_window;

sub/sd_ass.c

@@ -498,7 +498,7 @@ static long long find_timestamp(struct sd *sd, double pts)
 
     long long ts = llrint(pts * 1000);
 
-    if (!sd->opts->sub_fix_timing || sd->opts->ass_style_override == 0)
+    if (sd->opts->sub_fix_timing != 1 || sd->opts->ass_style_override == 0)
         return ts;
 
     // Try to fix small gaps and overlaps.