Pre-roll subtitles when accurate seeking in DCPs to avoid disappearing subs on frame...

diff --git a/src/lib/dcp_decoder.cc b/src/lib/dcp_decoder.cc
index 59a85e05145aef96010e6d65dcb5d2216e7f33b9..44053c5dff791b43747d7c2c0dabd6a66d82413b 100644 (file)
--- a/src/lib/dcp_decoder.cc
+++ b/src/lib/dcp_decoder.cc
@@ -158,6 +158,27 @@ DCPDecoder::pass ()
                audio->emit (_dcp_content->audio->stream(), data, ContentTime::from_frames (_offset, vfr) + _next);
        }
 
+       pass_subtitles (_next);
+
+       _next += ContentTime::from_frames (1, vfr);
+
+       if ((*_reel)->main_picture ()) {
+               if (_next.frames_round (vfr) >= (*_reel)->main_picture()->duration()) {
+                       next_reel ();
+                       _next = ContentTime ();
+               }
+       }
+
+       return false;
+}
+
+void
+DCPDecoder::pass_subtitles (ContentTime next)
+{
+       double const vfr = _dcp_content->active_video_frame_rate ();
+       /* Frame within the (played part of the) reel that is coming up next */
+       int64_t const frame = next.frames_round (vfr);
+
        if ((*_reel)->main_subtitle() && (_decode_referenced || !_dcp_content->reference_subtitle())) {
                int64_t const entry_point = (*_reel)->main_subtitle()->entry_point ();
                list<dcp::SubtitleString> subs = (*_reel)->main_subtitle()->asset()->subtitles_during (
@@ -177,17 +198,6 @@ DCPDecoder::pass ()
                                );
                }
        }
-
-       _next += ContentTime::from_frames (1, vfr);
-
-       if ((*_reel)->main_picture ()) {
-               if (_next.frames_round (vfr) >= (*_reel)->main_picture()->duration()) {
-                       next_reel ();
-                       _next = ContentTime ();
-               }
-       }
-
-       return false;
 }
 
 void
@@ -241,6 +251,34 @@ DCPDecoder::seek (ContentTime t, bool accurate)
        _offset = 0;
        get_readers ();
 
+       if (accurate) {
+               int const pre_roll_seconds = 2;
+
+               /* Pre-roll for subs */
+
+               ContentTime pre = t - ContentTime::from_seconds (pre_roll_seconds);
+               if (pre < ContentTime()) {
+                       pre = ContentTime ();
+               }
+
+               /* Seek to pre-roll position */
+
+               while (_reel != _reels.end() && pre >= ContentTime::from_frames ((*_reel)->main_picture()->duration(), _dcp_content->active_video_frame_rate ())) {
+                       pre -= ContentTime::from_frames ((*_reel)->main_picture()->duration(), _dcp_content->active_video_frame_rate ());
+                       next_reel ();
+               }
+
+               /* Pass subtitles in the pre-roll */
+
+               double const vfr = _dcp_content->active_video_frame_rate ();
+               for (int i = 0; i < pre_roll_seconds * vfr; ++i) {
+                       pass_subtitles (pre);
+                       pre += ContentTime::from_frames (1, vfr);
+               }
+       }
+
+       /* Seek to correct position */
+
        while (_reel != _reels.end() && t >= ContentTime::from_frames ((*_reel)->main_picture()->duration(), _dcp_content->active_video_frame_rate ())) {
                t -= ContentTime::from_frames ((*_reel)->main_picture()->duration(), _dcp_content->active_video_frame_rate ());
                next_reel ();

diff --git a/src/lib/dcp_decoder.h b/src/lib/dcp_decoder.h
index 6ec9de684d74da53abb204b578e91ee1f314c2c5..7238f3bb200224af81da71dba1a3dbead5998212 100644 (file)
--- a/src/lib/dcp_decoder.h
+++ b/src/lib/dcp_decoder.h
@@ -56,6 +56,7 @@ private:
 
        void next_reel ();
        void get_readers ();
+       void pass_subtitles (ContentTime next);
 
        /** Time of next thing to return from pass relative to the start of _reel */
        ContentTime _next;