core: update metadata during playback, allow streams to export metadata

STREAM_CTRL_GET_METADATA will be used to poll for streamcast metadata.
Also add DEMUXER_CTRL_UPDATE_INFO, which could in theory be used by
demux_lavf.c. (Unfortunately, libavformat is too crappy to read metadata
mid-stream for mp3 or ogg, so we don't implement it.)

core/mp_core.h

@@ -226,6 +226,7 @@ typedef struct MPContext {
     double audio_delay;
 
     double last_heartbeat;
+    double last_metadata_update;
 
     double mouse_timer;
     unsigned int mouse_event_ts;

core/mplayer.c

@@ -3643,6 +3643,11 @@ static void run_playloop(struct MPContext *mpctx)
             mp_input_get_cmd(mpctx->input, sleeptime * 1000, true);
     }
 
+    if (mp_time_sec() > mpctx->last_metadata_update + 2) {
+        demux_info_update(mpctx->demuxer);
+        mpctx->last_metadata_update = mp_time_sec();
+    }
+
     //================= Keyboard events, SEEKing ====================
 
     handle_pause_on_low_cache(mpctx);

demux/demux.c

@@ -976,6 +976,7 @@ static struct demuxer *open_given_type(struct MPOpts *opts,
         }
         add_stream_chapters(demuxer);
         demuxer_sort_chapters(demuxer);
+        demux_info_update(demuxer);
         return demuxer;
     } else {
         // demux_mov can return playlist instead of mov
@@ -1227,6 +1228,18 @@ char *demux_info_get(demuxer_t *demuxer, const char *opt)
     return NULL;
 }
 
+void demux_info_update(struct demuxer *demuxer)
+{
+    demux_control(demuxer, DEMUXER_CTRL_UPDATE_INFO, NULL);
+    // Take care of stream metadata as well
+    char **meta;
+    if (stream_control(demuxer->stream, STREAM_CTRL_GET_METADATA, &meta) > 0) {
+        for (int n = 0; meta[n + 0]; n += 2)
+            demux_info_add(demuxer, meta[n + 0], meta[n + 1]);
+        talloc_free(meta);
+    }
+}
+
 int demux_control(demuxer_t *demuxer, int cmd, void *arg)
 {
 

demux/demux.h

@@ -93,6 +93,7 @@ enum timestamp_type {
 #define DEMUXER_CTRL_OK 1
 #define DEMUXER_CTRL_GUESS 2
 
+#define DEMUXER_CTRL_UPDATE_INFO 8
 #define DEMUXER_CTRL_SWITCHED_TRACKS 9
 #define DEMUXER_CTRL_GET_TIME_LENGTH 10
 #define DEMUXER_CTRL_GET_START_TIME 11
@@ -385,6 +386,8 @@ int demux_info_add_bstr(struct demuxer *demuxer, struct bstr opt,
                         struct bstr param);
 char *demux_info_get(struct demuxer *demuxer, const char *opt);
 int demux_info_print(struct demuxer *demuxer);
+void demux_info_update(struct demuxer *demuxer);
+
 int demux_control(struct demuxer *demuxer, int cmd, void *arg);
 
 void demuxer_switch_track(struct demuxer *demuxer, enum stream_type type,

stream/cache.c

@@ -31,7 +31,7 @@
 // Time in seconds the cache updates "cached" controls. Note that idle mode
 // will block the cache from doing this, and this timeout is honored only if
 // the cache is active.
-#define CACHE_UPDATE_CONTROLS_TIME 0.1
+#define CACHE_UPDATE_CONTROLS_TIME 2.0
 
 
 #include <stdio.h>
@@ -102,6 +102,7 @@ struct priv {
     unsigned int stream_num_chapters;
     int stream_cache_idle;
     int stream_cache_fill;
+    char **stream_metadata;
 };
 
 // Store additional per-byte metadata. Since per-byte would be way too
@@ -306,6 +307,7 @@ static void update_cached_controls(struct priv *s)
 {
     unsigned int ui;
     double d;
+    char **m;
     s->stream_time_length = 0;
     if (stream_control(s->stream, STREAM_CTRL_GET_TIME_LENGTH, &d) == STREAM_OK)
         s->stream_time_length = d;
@@ -318,6 +320,10 @@ static void update_cached_controls(struct priv *s)
     s->stream_num_chapters = 0;
     if (stream_control(s->stream, STREAM_CTRL_GET_NUM_CHAPTERS, &ui) == STREAM_OK)
         s->stream_num_chapters = ui;
+    if (stream_control(s->stream, STREAM_CTRL_GET_METADATA, &m) == STREAM_OK) {
+        talloc_free(s->stream_metadata);
+        s->stream_metadata = talloc_steal(s, m);
+    }
     stream_update_size(s->stream);
     s->stream_size = s->stream->end_pos;
 }
@@ -368,6 +374,21 @@ static int cache_get_cached_control(stream_t *cache, int cmd, void *arg)
         }
         return STREAM_UNSUPPORTED;
     }
+    case STREAM_CTRL_GET_METADATA: {
+        if (s->stream_metadata && s->stream_metadata[0]) {
+            char **m = talloc_new(NULL);
+            int num_m = 0;
+            for (int n = 0; s->stream_metadata[n]; n++) {
+                char *t = talloc_strdup(m, s->stream_metadata[n]);
+                MP_TARRAY_APPEND(NULL, m, num_m, t);
+            }
+            MP_TARRAY_APPEND(NULL, m, num_m, NULL);
+            MP_TARRAY_APPEND(NULL, m, num_m, NULL);
+            *(char ***)arg = m;
+            return STREAM_OK;
+        }
+        return STREAM_UNSUPPORTED;
+    }
     }
     return STREAM_ERROR;
 }

stream/stream.h

@@ -103,6 +103,7 @@
 #define STREAM_CTRL_GET_CHAPTER_TIME 21
 #define STREAM_CTRL_GET_DVD_INFO 22
 #define STREAM_CTRL_SET_CONTENTS 23
+#define STREAM_CTRL_GET_METADATA 24
 
 struct stream_lang_req {
     int type;     // STREAM_AUDIO, STREAM_SUB