Change cmx_3600 adapter to use transition duration frames (Issue #895)

src/py-opentimelineio/opentimelineio/adapters/cmx_3600.py

@@ -268,6 +268,7 @@ def add_transition(self, clip_handler, transition, data):
         if transition not in ['C']:
             md = clip_handler.clip.metadata.setdefault("cmx_3600", {})
             md["transition"] = transition
+            md["transition_duration"] = float(data)
 
     def parse_edl(self, edl_string, rate=24):
         # edl 'events' can be comprised of an indeterminate amount of lines
@@ -665,7 +666,18 @@ def _expand_transitions(timeline):
                     "currently.".format(transition_type)
                 )
 
-            transition_duration = clip.duration()
+            # Using transition data for duration (with clip duration as backup.)
+            # Link: https://ieeexplore.ieee.org/document/7291839
+            # Citation: "ST 258:2004 - SMPTE Standard - For Television — Transfer
+            #   of Edit Decision Lists," in ST 258:2004 , vol., no., pp.1-37,
+            #   6 April 2004, doi: 10.5594/SMPTE.ST258.2004.
+            if clip.metadata.get("cmx_3600", {}).get("transition_duration"):
+                transition_duration = opentime.RationalTime(
+                    clip.metadata["cmx_3600"]["transition_duration"],
+                    clip.duration().rate
+                )
+            else:
+                transition_duration = clip.duration()
 
             # EDL doesn't have enough data to know where the cut point was, so
             # this arbitrarily puts it in the middle of the transition

tests/sample_data/transition_duration.edl

@@ -0,0 +1,8 @@
+TITLE:   TRANSITION_DURATION_TEST
+FCM: NON-DROP FRAME
+001  ABC0100. V     C        01:00:12:15 01:00:17:01 01:00:48:20 01:00:53:06 
+002  ABC0200. V     C        01:00:11:07 01:00:14:09 01:00:53:06 01:00:56:08 
+003  ABC0200. V     C        01:00:14:09 01:00:14:09 01:00:56:08 01:00:56:08 
+003  ABC0300. V     D    026 01:00:10:08 01:00:13:09 01:00:56:08 01:00:59:09 
+* BLEND, DISSOLVE 
+004  ABC0400. V     C        01:00:11:09 01:00:17:20 01:00:59:09 01:01:05:20 

tests/test_cmx_3600_adapter.py

@@ -59,6 +59,7 @@
     "speed_effects_small.edl"
 )
 MULTIPLE_TARGET_AUDIO_PATH = os.path.join(SAMPLE_DATA_DIR, "multi_audio.edl")
+TRANSITION_DURATION_TEST = os.path.join(SAMPLE_DATA_DIR, "transition_duration.edl")
 
 
 class EDLAdapterTest(unittest.TestCase, otio_test_utils.OTIOAssertions):
@@ -1038,6 +1039,14 @@ def test_speed_effects(self):
             )
         )
 
+    def test_transition_duration(self):
+        tl = otio.adapters.read_from_file(TRANSITION_DURATION_TEST)
+        self.assertEqual(len(tl.tracks[0]), 5)
+
+        self.assertIsInstance(tl.tracks[0][2], otio.schema.Transition)
+
+        self.assertEqual(tl.tracks[0][2].duration().value, 26.0)
+
 
 if __name__ == "__main__":
     unittest.main()