Add explanation of the effect of changing frame rate.

2 files changed, 18 insertions, 1 deletions

diff --git a/src/lib/util.cc b/src/lib/util.cc
index 85a04ed17..d1450ccc2 100644
--- a/src/lib/util.cc
+++ b/src/lib/util.cc
@@ -960,4 +960,19 @@ FrameRateConversion::FrameRateConversion (float source, int dcp)
 	}
 
 	change_speed = !about_equal (source * factor(), dcp);
+
+	if (!skip && !repeat && !change_speed) {
+		explanation = _("DCP and source have the same rate.\n");
+	} else {
+		if (skip) {
+			explanation = _("DCP will use every other frame of the source.\n");
+		} else if (repeat) {
+			explanation = _("Each source frame will be doubled in the DCP.\n");
+		}
+
+		if (change_speed) {
+			float const pc = (source * factor()) * 100 / dcp;
+			explanation += String::compose (_("DCP will run at %1%% of the source speed."), pc);
+		}
+	}
 }
diff --git a/src/lib/util.h b/src/lib/util.h
index 103907151..b0f405890 100644
--- a/src/lib/util.h
+++ b/src/lib/util.h
@@ -78,7 +78,7 @@ struct FrameRateConversion
 
 		return 1;
 	}
-	
+
 	/** true to skip every other frame */
 	bool skip;
 	/** true to repeat every frame once */
@@ -93,6 +93,8 @@ struct FrameRateConversion
 	 *          source is 12.50fps, DCP is 25fps)
 	 */
 	bool change_speed;
+
+	std::string explanation;
 };
 
 int best_dcp_frame_rate (float);