sub: make --sub-fix-timing configurable

Instead of hardcoding the threshold and keep duration in a header,
expose them as options for users to configure and set old hardcoded
values as the new defaults for those options.

DOCS/interface-changes/configurable-sub-fix-timing.txt

@@ -0,0 +1,2 @@
+add `--sub-fix-timing-threshold`
+add `--sub-fix-timing-keep`

DOCS/man/options.rst

@@ -2885,8 +2885,19 @@ Subtitles
 
 ``--sub-fix-timing=<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).
+    subtitles.
+
+    See also: ``--sub-fix-timing-threshold`` and ``--sub-fix-timing-keep``.
+
+``--sub-fix-timing-threshold=<amount>``
+    Set the threshold in milliseconds for fixing subtitle timing (default: 210).
+    If the gap between two subtitle events is smaller than this, the gap is
+    removed.
+
+``--sub-fix-timing-keep=<amount>``
+    Set the minimum duration in milliseconds for subtitle events to be
+    considered for timing fixes (default: 400). If a subtitle event has a
+    duration smaller than this, its timing is not changed.
 
 ``--sub-forced-events-only=<yes|no>``
     Enabling this displays only forced events within subtitle streams. Only

options/options.c

@@ -304,6 +304,8 @@ const struct m_sub_options mp_subtitle_sub_opts = {
         {"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-threshold", OPT_INT(sub_fix_timing_threshold)},
+        {"sub-fix-timing-keep", OPT_INT(sub_fix_timing_keep)},
         {"sub-stretch-durations", OPT_BOOL(sub_stretch_durations)},
         {"sub-gauss", OPT_FLOAT(sub_gauss), M_RANGE(0.0, 3.0)},
         {"sub-gray", OPT_BOOL(sub_gray)},
@@ -351,6 +353,8 @@ const struct m_sub_options mp_subtitle_sub_opts = {
     .defaults = &(OPT_BASE_STRUCT){
         .sub_speed = 1.0,
         .ass_enabled = true,
+        .sub_fix_timing_threshold = 210,
+        .sub_fix_timing_keep = 400,
         .sub_scale_by_window = true,
         .sub_use_margins = true,
         .sub_scale_with_window = true,

options/options.h

@@ -102,6 +102,8 @@ struct mp_subtitle_opts {
     bool stretch_image_subs;
     bool image_subs_video_res;
     bool sub_fix_timing;
+    int sub_fix_timing_threshold;
+    int sub_fix_timing_keep;
     bool sub_stretch_durations;
     bool sub_scale_by_window;
     bool sub_scale_with_window;

sub/sd.h

@@ -5,10 +5,6 @@
 #include "demux/packet.h"
 #include "misc/bstr.h"
 
-// up to 210 ms overlaps or gaps are removed
-#define SUB_GAP_THRESHOLD 0.210
-// don't change timings if durations are smaller
-#define SUB_GAP_KEEP 0.4
 // slight offset when sub seeking or sub stepping
 #define SUB_SEEK_OFFSET 0.01
 #define SUB_SEEK_WITHOUT_VIDEO_OFFSET 0.1

sub/sd_ass.c

@@ -670,8 +670,8 @@ static long long find_timestamp(struct sd *sd, double pts)
 
     // Try to fix small gaps and overlaps.
     ASS_Track *track = priv->ass_track;
-    int threshold = SUB_GAP_THRESHOLD * 1000;
-    int keep = SUB_GAP_KEEP * 1000;
+    int threshold = sd->opts->sub_fix_timing_threshold;
+    int keep = sd->opts->sub_fix_timing_keep;
 
     // Find the "current" event.
     ASS_Event *ev[2] = {0};

sub/sd_lavc.c

@@ -374,7 +374,7 @@ static void decode(struct sd *sd, struct demux_packet *packet)
             if (prev->endpts == MP_NOPTS_VALUE || prev->endpts > pts)
                 prev->endpts = pts;
 
-            if (opts->sub_fix_timing && pts - prev->endpts <= SUB_GAP_THRESHOLD)
+            if (opts->sub_fix_timing && pts - prev->endpts <= opts->sub_fix_timing_threshold / 1000.0)
                 prev->endpts = pts;
 
             for (int n = 0; n < priv->num_seekpoints; n++) {