demux_disc: hold BD jump boundaries for the player's resync seek

The resync seek that follows a disc-initiated jump must not reposition
the VM. On BD the jump is handled out-of-band by reopening the slave
demuxer on the packet-read path, and the VM already sits at the jump
destination. Repositioning it with the (stale) seek target time would
hop to the wrong place. Adopting the discontinuity counter here would
leave the old slave demuxer parsing the new playlist's data with the
wrong codec context. Flush our side only, and keep the counter stale so
the read path still performs the reopen.

stream/stream_bluray.c

@@ -151,6 +151,7 @@ struct bluray_priv_s {
     uint32_t discontinuity_id;       // bumped on actions that may hop (SELECT...)
     bool data_delivered;             // any byte returned from fill_buffer yet
     bool still_active;               // holding an indefinite still.
+    bool resync_owed;                // jump settled, resync seek not acked yet
 
     // Disc-driven audio/sub selection, mirrored from BD_EVENT_AUDIO_STREAM
     // and BD_EVENT_PG_TEXTST{,_STREAM}. The numbers are 1-based libbluray
@@ -493,8 +494,13 @@ static int bluray_stream_fill_buffer(stream_t *s, void *buf, int len)
 
     mp_mutex_lock(&b->overlay_lock);
     uint32_t disc_id = b->discontinuity_id;
+    bool resync_owed = b->resync_owed;
     mp_mutex_unlock(&b->overlay_lock);
 
+    // Resync pending, skip the read.
+    if (resync_owed)
+        return 0;
+
     int idle_reads = 0;
     bool hopped = false;
     while (!mp_cancel_test(s->cancel)) {
@@ -663,6 +669,9 @@ static int bluray_stream_fill_buffer(stream_t *s, void *buf, int len)
         if (hopped) {
             if (ev.event != BD_EVENT_NONE)
                 continue;
+            mp_mutex_lock(&b->overlay_lock);
+            b->resync_owed = true;
+            mp_mutex_unlock(&b->overlay_lock);
             MP_VERBOSE(s, "jump settled (id %u), EOF for demuxer resync\n",
                        b->discontinuity_id);
             return 0;
@@ -775,6 +784,11 @@ static int bluray_stream_control(stream_t *s, int cmd, void *arg)
         // API makes it hard to determine seeking success
         return STREAM_OK;
     }
+    case STREAM_CTRL_NAV_DRAIN_ACK:
+        mp_mutex_lock(&b->overlay_lock);
+        b->resync_owed = false;
+        mp_mutex_unlock(&b->overlay_lock);
+        return STREAM_OK;
     case STREAM_CTRL_GET_NUM_ANGLES: {
         mp_mutex_lock(&b->overlay_lock);
         const BLURAY_TITLE_INFO *ti = b->title_info;
@@ -964,6 +978,7 @@ static int bluray_stream_control(stream_t *s, int cmd, void *arg)
             .src_h = MPMAX(b->ig.disp_h, b->pg.disp_h),
             .change_id = b->nav_change_id,
             .discontinuity_id = b->discontinuity_id,
+            .drain_pending = b->resync_owed,
             .no_audio = no_audio,
             .active_audio_id = audio_pid,
             .active_sub_id = sub_pid,