player: add --subs-with-matching-audio option

This allows users to control whether full dialogue subtitles are displayed
with an audio track already in their preferred subtitle language.

Additionally, this improves handling for the forced flag, automatically
selecting between forced and unforced subtitle streams based on the user's
settings and the selected audio.

6 files changed, 40 insertions, 9 deletions

diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index 5245e18cae..30ea5d7ce1 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -135,6 +135,11 @@ Track Selection
     Note that if ``--lavfi-complex`` is set before playback is started, the
     referenced tracks are always selected.
 
+``--subs-with-matching-audio=<yes|no>``
+    When autoselecting a subtitle track, select a non-forced one even if the selected
+    audio stream matches your preferred subtitle language (default: yes). Disable this
+    if you'd like to only show subtitles for foreign audio or onscreen text.
+
 
 Playback Control
 ----------------
@@ -2487,9 +2492,12 @@ Subtitles
     subtitles (if the difference is smaller than 210 ms, the gap or overlap
     is removed).
 
-``--sub-forced-only``
+``--sub-forced-only=<auto|yes|no>``
     Display only forced subtitles for the DVD subtitle stream selected by e.g.
-    ``--slang``.
+    ``--slang`` (default: ``auto``). When set to ``auto``, enabled when the
+    ``--subs-with-matching-audio`` option is on and a non-forced stream is selected.
+    Enabling this will hide all subtitles in streams that don't make a distinction
+    between forced and unforced events within a stream.
 
 ``--sub-fps=<rate>``
     Specify the framerate of the subtitle file (default: video fps). Affects
diff --git a/options/options.c b/options/options.c
index 6e22de0a07..35b23abce3 100644
--- a/options/options.c
+++ b/options/options.c
@@ -228,7 +228,8 @@ const struct m_sub_options mp_subtitle_sub_opts = {
         {"sub-fps", OPT_FLOAT(sub_fps)},
         {"sub-speed", OPT_FLOAT(sub_speed)},
         {"sub-visibility", OPT_FLAG(sub_visibility)},
-        {"sub-forced-only", OPT_FLAG(forced_subs_only)},
+        {"sub-forced-only", OPT_CHOICE(forced_subs_only,
+            {"auto", -1}, {"no", 0}, {"yes", 1})},
         {"stretch-dvd-subs", OPT_FLAG(stretch_dvd_subs)},
         {"stretch-image-subs-to-screen", OPT_FLAG(stretch_image_subs)},
         {"image-subs-video-resolution", OPT_FLAG(image_subs_video_res)},
@@ -269,6 +270,7 @@ const struct m_sub_options mp_subtitle_sub_opts = {
     .size = sizeof(OPT_BASE_STRUCT),
     .defaults = &(OPT_BASE_STRUCT){
         .sub_visibility = 1,
+        .forced_subs_only = -1,
         .sub_pos = 100,
         .sub_speed = 1.0,
         .ass_enabled = 1,
@@ -489,6 +491,7 @@ static const m_option_t mp_opts[] = {
     {"slang", OPT_STRINGLIST(stream_lang[STREAM_SUB])},
     {"vlang", OPT_STRINGLIST(stream_lang[STREAM_VIDEO])},
     {"track-auto-selection", OPT_FLAG(stream_auto_sel)},
+    {"subs-with-matching-audio", OPT_FLAG(subs_with_matching_audio)},
 
     {"lavfi-complex", OPT_STRING(lavfi_complex), .flags = UPDATE_LAVFI_COMPLEX},
 
@@ -992,6 +995,7 @@ static const struct MPOpts mp_default_opts = {
                      [STREAM_VIDEO] = -2,
                      [STREAM_SUB] = -2, }, },
     .stream_auto_sel = 1,
+    .subs_with_matching_audio = 1,
     .audio_display = 1,
     .audio_output_format = 0,  // AF_FORMAT_UNKNOWN
     .playback_speed = 1.,
diff --git a/options/options.h b/options/options.h
index 00b58dfbff..62eef010d7 100644
--- a/options/options.h
+++ b/options/options.h
@@ -73,6 +73,7 @@ struct mp_subtitle_opts {
     float sub_fps;
     float sub_speed;
     int forced_subs_only;
+    int forced_subs_only_current;
     int stretch_dvd_subs;
     int stretch_image_subs;
     int image_subs_video_res;
@@ -252,6 +253,7 @@ typedef struct MPOpts {
     int stream_id[2][STREAM_TYPE_COUNT];
     char **stream_lang[STREAM_TYPE_COUNT];
     int stream_auto_sel;
+    int subs_with_matching_audio;
     int audio_display;
     char **display_tags;
 
diff --git a/player/loadfile.c b/player/loadfile.c
index 97ae9328f1..f8d5327acf 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -453,17 +453,19 @@ static int match_lang(char **langs, char *lang)
  * 1) track is external (no_default cancels this)
  * 1b) track was passed explicitly (is not an auto-loaded subtitle)
  * 2) earlier match in lang list
- * 3a) track is marked forced
- * 3b) track is marked default
+ * 3a) track is marked forced and we're preferring forced tracks
+ * 3b) track is marked non-forced and we're preferring non-forced tracks
+ * 3c) track is marked default
  * 4) attached picture, HLS bitrate
  * 5) lower track number
  * If select_fallback is not set, 5) is only used to determine whether a
  * matching track is preferred over another track. Otherwise, always pick a
  * track (if nothing else matches, return the track with lowest ID).
+ * Forced tracks are preferred when the user prefers not to display subtitles
  */
 // Return whether t1 is preferred over t2
 static bool compare_track(struct track *t1, struct track *t2, char **langs,
-                          struct MPOpts *opts)
+                          int prefer_forced, struct MPOpts *opts)
 {
     if (!opts->autoload_files && t1->is_external != t2->is_external)
         return !t1->is_external;
@@ -477,7 +479,7 @@ static bool compare_track(struct track *t1, struct track *t2, char **langs,
     if (l1 != l2)
         return l1 > l2;
     if (t1->forced_track != t2->forced_track)
-        return t1->forced_track;
+        return prefer_forced ? t1->forced_track : !t1->forced_track;
     if (t1->default_track != t2->default_track)
         return t1->default_track;
     if (t1->attached_picture != t2->attached_picture)
@@ -512,6 +514,10 @@ struct track *select_default_track(struct MPContext *mpctx, int order,
     struct MPOpts *opts = mpctx->opts;
     int tid = opts->stream_id[order][type];
     char **langs = opts->stream_lang[type];
+    int prefer_forced = type != STREAM_SUB ||
+                        (!opts->subs_with_matching_audio &&
+                         mpctx->current_track[0][STREAM_AUDIO] &&
+                         match_lang(langs, mpctx->current_track[0][STREAM_AUDIO]->lang));
     if (tid == -2)
         return NULL;
     bool select_fallback = type == STREAM_VIDEO || type == STREAM_AUDIO;
@@ -528,7 +534,7 @@ struct track *select_default_track(struct MPContext *mpctx, int order,
             continue;
         if (duplicate_track(mpctx, order, type, track))
             continue;
-        if (!pick || compare_track(track, pick, langs, mpctx->opts))
+        if (!pick || compare_track(track, pick, langs, prefer_forced, mpctx->opts))
             pick = track;
     }
     if (pick && !select_fallback && !(pick->is_external && !pick->no_default)
@@ -539,6 +545,9 @@ struct track *select_default_track(struct MPContext *mpctx, int order,
         pick = NULL;
     if (pick && !opts->autoload_files && pick->is_external)
         pick = NULL;
+    if (pick && type == STREAM_SUB && prefer_forced && !pick->forced_track &&
+        opts->subs_rend->forced_subs_only == -1)
+        opts->subs_rend->forced_subs_only_current = 1;
     return pick;
 }
 
@@ -1522,6 +1531,8 @@ static void play_current_file(struct MPContext *mpctx)
     if (reinit_complex_filters(mpctx, false) < 0)
         goto terminate_playback;
 
+    opts->subs_rend->forced_subs_only_current = (opts->subs_rend->forced_subs_only == 1) ? 1 : 0;
+
     for (int t = 0; t < STREAM_TYPE_COUNT; t++) {
         for (int i = 0; i < num_ptracks[t]; i++) {
             struct track *sel = NULL;
diff --git a/sub/sd_ass.c b/sub/sd_ass.c
index 7c40a01faf..eae1536df8 100644
--- a/sub/sd_ass.c
+++ b/sub/sd_ass.c
@@ -533,6 +533,12 @@ static struct sub_bitmaps *get_bitmaps(struct sd *sd, struct mp_osd_res dim,
     if (pts == MP_NOPTS_VALUE || !renderer)
         goto done;
 
+    // Currently no supported text sub formats support a distinction between forced
+    // and unforced lines, so we just assume everything's unforced and discard everything.
+    // If we ever see a format that makes this distinction, we can add support here.
+    if (opts->forced_subs_only_current)
+        goto done;
+
     double scale = dim.display_par;
     if (!converted && (!opts->ass_style_override ||
                        opts->ass_vsfilter_aspect_compat))
diff --git a/sub/sd_lavc.c b/sub/sd_lavc.c
index 81906ceb23..77877fdbd1 100644
--- a/sub/sd_lavc.c
+++ b/sub/sd_lavc.c
@@ -191,7 +191,7 @@ static void read_sub_bitmaps(struct sd *sd, struct sub *sub)
             MP_ERR(sd, "unsupported subtitle type from libavcodec\n");
             continue;
         }
-        if (!(r->flags & AV_SUBTITLE_FLAG_FORCED) && opts->forced_subs_only)
+        if (!(r->flags & AV_SUBTITLE_FLAG_FORCED) && opts->forced_subs_only_current)
             continue;
         if (r->w <= 0 || r->h <= 0)
             continue;