Fix missing subtitles when they start just after the start of a frame.

[dcpomatic.git] / src / lib / render_subtitles.cc

diff --git a/src/lib/render_subtitles.cc b/src/lib/render_subtitles.cc
index 56343cd507c9a25e6d202aee383a0e353e4eb430..5f587c3137504c759df8ba29306e4e0b99fb0926 100644 (file)
--- a/src/lib/render_subtitles.cc
+++ b/src/lib/render_subtitles.cc
@@ -85,7 +85,7 @@ set_source_rgba (Cairo::RefPtr<Cairo::Context> context, dcp::Colour colour, floa
  *  at the same time and with the same fade in/out.
  */
 static PositionImage
-render_line (list<SubtitleString> subtitles, list<shared_ptr<Font> > fonts, dcp::Size target, DCPTime time)
+render_line (list<SubtitleString> subtitles, list<shared_ptr<Font> > fonts, dcp::Size target, DCPTime time, int frame_rate)
 {
        /* XXX: this method can only handle italic / bold changes mid-line,
           nothing else yet.
@@ -242,9 +242,12 @@ render_line (list<SubtitleString> subtitles, list<shared_ptr<Font> > fonts, dcp:
        /* Compute fade factor */
        float fade_factor = 1;
 
-       DCPTime const fade_in_start = DCPTime::from_seconds (subtitles.front().in().as_seconds ());
+       /* Round the fade start/end to the nearest frame start.  Otherwise if a subtitle starts just after
+          the start of a frame it will be faded out.
+       */
+       DCPTime const fade_in_start = DCPTime::from_seconds(subtitles.front().in().as_seconds()).round(frame_rate);
        DCPTime const fade_in_end = fade_in_start + DCPTime::from_seconds (subtitles.front().fade_up_time().as_seconds ());
-       DCPTime const fade_out_end =  DCPTime::from_seconds (subtitles.front().out().as_seconds ());
+       DCPTime const fade_out_end =  DCPTime::from_seconds (subtitles.front().out().as_seconds()).round(frame_rate);
        DCPTime const fade_out_start = fade_out_end - DCPTime::from_seconds (subtitles.front().fade_down_time().as_seconds ());
 
        if (fade_in_start <= time && time <= fade_in_end && fade_in_start != fade_in_end) {
@@ -347,23 +350,25 @@ render_line (list<SubtitleString> subtitles, list<shared_ptr<Font> > fonts, dcp:
        return PositionImage (image, Position<int> (max (0, x), max (0, y)));
 }
 
-/** @param time Time of the frame that these subtitles are going on */
+/** @param time Time of the frame that these subtitles are going on.
+ *  @param frame_rate DCP frame rate.
+ */
 list<PositionImage>
-render_subtitles (list<SubtitleString> subtitles, list<shared_ptr<Font> > fonts, dcp::Size target, DCPTime time)
+render_subtitles (list<SubtitleString> subtitles, list<shared_ptr<Font> > fonts, dcp::Size target, DCPTime time, int frame_rate)
 {
        list<SubtitleString> pending;
        list<PositionImage> images;
 
        BOOST_FOREACH (SubtitleString const & i, subtitles) {
                if (!pending.empty() && fabs (i.v_position() - pending.back().v_position()) > 1e-4) {
-                       images.push_back (render_line (pending, fonts, target, time));
+                       images.push_back (render_line (pending, fonts, target, time, frame_rate));
                        pending.clear ();
                }
                pending.push_back (i);
        }
 
        if (!pending.empty ()) {
-               images.push_back (render_line (pending, fonts, target, time));
+               images.push_back (render_line (pending, fonts, target, time, frame_rate));
        }
 
        return images;