Fix rounding of timecodes in at least some cases (#323).

Reported-by: Gérald Maruccia

4 files changed, 16 insertions, 5 deletions

diff --git a/src/lib/film.cc b/src/lib/film.cc
index 1d07ec77f..134810452 100644
--- a/src/lib/film.cc
+++ b/src/lib/film.cc
@@ -900,25 +900,25 @@ Film::playlist_changed ()
 OutputAudioFrame
 Film::time_to_audio_frames (Time t) const
 {
-	return t * audio_frame_rate () / TIME_HZ;
+	return divide_with_round (t * audio_frame_rate (), TIME_HZ);
 }
 
 OutputVideoFrame
 Film::time_to_video_frames (Time t) const
 {
-	return t * video_frame_rate () / TIME_HZ;
+	return divide_with_round (t * video_frame_rate (), TIME_HZ);
 }
 
 Time
 Film::audio_frames_to_time (OutputAudioFrame f) const
 {
-	return f * TIME_HZ / audio_frame_rate ();
+	return divide_with_round (f * TIME_HZ, audio_frame_rate ());
 }
 
 Time
 Film::video_frames_to_time (OutputVideoFrame f) const
 {
-	return f * TIME_HZ / video_frame_rate ();
+	return divide_with_round (f * TIME_HZ, video_frame_rate ());
 }
 
 OutputAudioFrame
diff --git a/src/lib/sndfile_content.cc b/src/lib/sndfile_content.cc
index 796229777..98171a843 100644
--- a/src/lib/sndfile_content.cc
+++ b/src/lib/sndfile_content.cc
@@ -147,7 +147,7 @@ SndfileContent::full_length () const
 	shared_ptr<const Film> film = _film.lock ();
 	assert (film);
 
-	OutputAudioFrame const len = audio_length() * output_audio_frame_rate() / content_audio_frame_rate ();
+	OutputAudioFrame const len = divide_with_round (audio_length() * output_audio_frame_rate(), content_audio_frame_rate ());
 	
 	/* XXX: this depends on whether, alongside this audio, we are running video slower or faster than
 	   it should be.  The calculation above works out the output audio frames assuming that we are just
diff --git a/src/lib/util.cc b/src/lib/util.cc
index 25fbc130b..f604cd10a 100644
--- a/src/lib/util.cc
+++ b/src/lib/util.cc
@@ -1016,3 +1016,13 @@ entities_to_text (string e)
 	boost::algorithm::replace_all (e, "%2F", "/");
 	return e;
 }
+
+int64_t
+divide_with_round (int64_t a, int64_t b)
+{
+	if (a % b >= (b / 2)) {
+		return (a + b - 1) / b;
+	} else {
+		return a / b;
+	}
+}
diff --git a/src/lib/util.h b/src/lib/util.h
index ef29cc08f..fc17dc944 100644
--- a/src/lib/util.h
+++ b/src/lib/util.h
@@ -123,6 +123,7 @@ extern std::string get_required_string (std::multimap<std::string, std::string>
 extern int get_optional_int (std::multimap<std::string, std::string> const & kv, std::string k);
 extern std::string get_optional_string (std::multimap<std::string, std::string> const & kv, std::string k);
 extern void* wrapped_av_malloc (size_t);
+extern int64_t divide_with_round (int64_t a, int64_t b);
 
 /** @class Socket
  *  @brief A class to wrap a boost::asio::ip::tcp::socket with some things