demux: export forced flag

At least Matroska files have a "forced" flag (in addition to the
"default" flag). Export this flag. Treat it almost like the default
flag, but with slightly higher priority.

DOCS/interface-changes.rst

@@ -20,6 +20,7 @@ Interface changes
 ::
 
  --- mpv 0.10.0 will be released ---
+    - add ``track-list/N/foced`` property
     - add audio-params/channel-count and ``audio-params-out/channel-count props.
     - add af volume replaygain-fallback suboption
     - add video-params/stereo-in property

DOCS/man/input.rst

@@ -1579,6 +1579,10 @@ Property list
         ``yes`` if the track has the default flag set in the file, ``no``
         otherwise.
 
+    ``track-list/N/foced``
+        ``yes`` if the track has the forced flag set in the file, ``no``
+        otherwise.
+
     ``track-list/N/codec``
         The codec name used by this track, for example ``h264``. Unavailable
         in some rare cases.
@@ -1616,6 +1620,7 @@ Property list
                 "lang"              MPV_FORMAT_STRING
                 "albumart"          MPV_FORMAT_FLAG
                 "default"           MPV_FORMAT_FLAG
+                "forced"            MPV_FORMAT_FLAG
                 "external"          MPV_FORMAT_FLAG
                 "external-filename" MPV_FORMAT_STRING
                 "codec"             MPV_FORMAT_STRING

demux/demux_lavf.c

@@ -636,7 +636,9 @@ static void handle_stream(demuxer_t *demuxer, int i)
         sh->lav_headers = codec;
 
         if (st->disposition & AV_DISPOSITION_DEFAULT)
-            sh->default_track = 1;
+            sh->default_track = true;
+        if (st->disposition & AV_DISPOSITION_FORCED)
+            sh->forced_track = true;
         if (priv->format_hack.use_stream_ids)
             sh->demuxer_id = st->id;
         AVDictionaryEntry *title = av_dict_get(st->metadata, "title", NULL, 0);

demux/demux_mkv.c

@@ -114,6 +114,7 @@ typedef struct mkv_track {
     double codec_delay;
 
     int default_track;
+    int forced_track;
 
     unsigned char *private_data;
     unsigned int private_size;
@@ -631,6 +632,11 @@ static void parse_trackentry(struct demuxer *demuxer,
         track->default_track = 1;
     }
 
+    if (entry->n_flag_forced) {
+        track->forced_track = entry->flag_forced;
+        MP_VERBOSE(demuxer, "|  + Forced flag: %u\n", track->forced_track);
+    }
+
     if (entry->n_default_duration) {
         track->default_duration = entry->default_duration / 1e9;
         if (entry->default_duration == 0) {
@@ -1171,6 +1177,7 @@ static void init_track(demuxer_t *demuxer, mkv_track_t *track,
     sh->demuxer_id = track->tnum;
     sh->title = track->name;
     sh->default_track = track->default_track;
+    sh->forced_track = track->forced_track;
 }
 
 static int demux_mkv_open_video(demuxer_t *demuxer, mkv_track_t *track);

demux/stheader.h

@@ -58,6 +58,7 @@ struct sh_stream {
     char *title;
     char *lang;                 // language code
     bool default_track;         // container default track flag
+    bool forced_track;          // container forced track flag
     int hls_bitrate;
 
     bool missing_timestamps;

player/command.c

@@ -1872,6 +1872,7 @@ static int get_track_entry(int item, int action, void *arg, void *ctx)
                         .unavailable = !track->lang},
         {"albumart",    SUB_PROP_FLAG(track->attached_picture)},
         {"default",     SUB_PROP_FLAG(track->default_track)},
+        {"forced",      SUB_PROP_FLAG(track->forced_track)},
         {"external",    SUB_PROP_FLAG(track->is_external)},
         {"selected",    SUB_PROP_FLAG(track->selected)},
         {"external-filename", SUB_PROP_STR(track->external_filename),

player/core.h

@@ -89,7 +89,7 @@ struct track {
     int ff_index; // same as stream->ff_index, or 0.
 
     char *title;
-    bool default_track;
+    bool default_track, forced_track;
     bool attached_picture;
     char *lang;
 

player/loadfile.c

@@ -132,6 +132,8 @@ static void print_stream(struct MPContext *mpctx, struct track *t)
         APPEND(b, " --%s=%s", langopt, t->lang);
     if (t->default_track)
         APPEND(b, " (*)");
+    if (t->forced_track)
+        APPEND(b, " (f)");
     if (t->attached_picture)
         APPEND(b, " [P]");
     if (t->title)
@@ -383,6 +385,7 @@ static struct track *add_stream_track(struct MPContext *mpctx,
         .ff_index = stream->ff_index,
         .title = stream->title,
         .default_track = stream->default_track,
+        .forced_track = stream->forced_track,
         .attached_picture = stream->attached_picture != NULL,
         .lang = stream->lang,
         .under_timeline = under_timeline,
@@ -424,7 +427,8 @@ 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
- * 3) track is marked default
+ * 3a) track is marked forced
+ * 3b) 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
@@ -444,6 +448,8 @@ static bool compare_track(struct track *t1, struct track *t2, char **langs,
     int l1 = match_lang(langs, t1->lang), l2 = match_lang(langs, t2->lang);
     if (l1 != l2)
         return l1 > l2;
+    if (t1->forced_track != t2->forced_track)
+        return t1->forced_track;
     if (t1->default_track != t2->default_track)
         return t1->default_track;
     if (t1->attached_picture != t2->attached_picture)
@@ -480,7 +486,8 @@ struct track *select_default_track(struct MPContext *mpctx, int order,
             pick = track;
     }
     if (pick && !select_fallback && !(pick->is_external && !pick->no_default)
-        && !match_lang(langs, pick->lang) && !pick->default_track)
+        && !match_lang(langs, pick->lang) && !pick->default_track
+        && !pick->forced_track)
         pick = NULL;
     if (pick && pick->attached_picture && !mpctx->opts->audio_display)
         pick = NULL;