Writer: added support for mob attribute list

src/otio_aaf_adapter/adapters/aaf_adapter/aaf_writer.py

@@ -114,6 +114,7 @@ def __init__(self, input_otio, aaf_file, **kwargs):
 
         # transcribe timeline comments onto composition mob
         self._transcribe_user_comments(input_otio, self.compositionmob)
+        self._transcribe_mob_attributes(input_otio, self.compositionmob)
 
     def _unique_mastermob(self, otio_clip):
         """Get a unique mastermob, identified by clip metadata mob id."""
@@ -126,12 +127,14 @@ def _unique_mastermob(self, otio_clip):
             self.aaf_file.content.mobs.append(mastermob)
             self._unique_mastermobs[mob_id] = mastermob
 
-            # transcribe clip comments onto master mob
+            # transcribe clip comments / mob attributes onto master mob
             self._transcribe_user_comments(otio_clip, mastermob)
+            self._transcribe_mob_attributes(otio_clip, mastermob)
 
-            # transcribe media reference comments onto master mob.
-            # this might overwrite clip comments.
+            # transcribe media reference comments / mob attributes onto master mob.
+            # this might overwrite clip comments / attributes.
             self._transcribe_user_comments(otio_clip.media_reference, mastermob)
+            self._transcribe_mob_attributes(otio_clip.media_reference, mastermob)
 
         return mastermob
 
@@ -226,6 +229,22 @@ def _transcribe_user_comments(self, otio_item, target_mob):
                     f"'{type(val)}' for key '{key}'."
                 )
 
+    def _transcribe_mob_attributes(self, otio_item, target_mob):
+        """Transcribes mob attribute list onto the `target_mob`.
+        This can be used to roundtrip specific mob config values, like audio channel
+        settings.
+        """
+        mob_attr_map = otio_item.metadata.get("AAF", {}).get("MobAttributeList", {})
+        mob_attr_list = aaf2.misc.TaggedValueHelper(target_mob['MobAttributeList'])
+        for key, val in mob_attr_map.items():
+            if isinstance(val, (int, str)):
+                mob_attr_list[key] = val
+            elif isinstance(val, (float, Rational)):
+                mob_attr_list[key] = aaf2.rational.AAFRational(val)
+            else:
+                raise ValueError(f"Unsupported mob attribute type '{type(val)}' for "
+                                 f"key '{key}'.")
+
 
 def validate_metadata(timeline):
     """Print a check of necessary metadata requirements for an otio timeline."""

tests/test_aaf_adapter.py

@@ -1906,6 +1906,30 @@ def test_aaf_writer_user_comments(self):
             self.assertEqual(dict(master_mob.comments.items()), expected_comments)
             self.assertEqual(dict(comp_mob.comments.items()), expected_comments)
 
+    def test_aaf_writer_metadata_roundtrip(self):
+        """Tries to roundtrip metadata through AAF and `MobAttributeList`."""
+        og_aaf_tl = otio.adapters.read_from_file(ONE_AUDIO_CLIP_PATH)
+        clip = og_aaf_tl.find_clips()[0]
+
+        # change a value to test roundtrip
+        clip.media_reference.metadata["AAF"]["MobAttributeList"]["_USER_POS"] = 2
+        _, tmp_aaf_path = tempfile.mkstemp(suffix='.aaf')
+        otio.adapters.write_to_file(og_aaf_tl, tmp_aaf_path)
+
+        roundtripped_tl = otio.adapters.read_from_file(tmp_aaf_path)
+
+        clip = roundtripped_tl.find_clips()[0]
+        expected = {
+            "_IMPORTSETTING": "__AttributeList",
+            "_SAVED_AAF_AUDIO_LENGTH": 0,
+            "_SAVED_AAF_AUDIO_RATE_DEN": 1,
+            "_SAVED_AAF_AUDIO_RATE_NUM": 24,
+            "_USER_POS": 2,
+            "_VERSION": 2
+        }
+        self.assertEqual(clip.media_reference.metadata["AAF"]["MobAttributeList"],
+                         expected)
+
     def test_aaf_writer_global_start_time(self):
         for tc, rate in [("01:00:00:00", 23.97),
                          ("01:00:00:00", 24),