AAF Writer: Improves support of nesting (AcademySoftwareFoundation#493)

When writing AAF Sequences, make sure each one is nested inside a Submaster OperationGroup.

Author: freesonluxo

contrib/opentimelineio_contrib/adapters/aaf_adapter/aaf_writer.py

@@ -32,6 +32,7 @@
 import uuid
 import opentimelineio as otio
 import os
+import copy
 
 
 AAF_PARAMETERDEF_PAN = aaf2.auid.AUID("e4962322-2267-11d3-8a4c-0050040ef7d2")
@@ -256,6 +257,25 @@ def _generate_empty_mobid(clip):
     return clip_mob_ids
 
 
+def _stackify_nested_groups(timeline):
+    """
+    Ensure that all nesting in a given timeline is in a stack container.
+    This conforms with how AAF thinks about nesting, there needs
+    to be an outer container, even if it's just one object.
+    """
+    copied = copy.deepcopy(timeline)
+    for track in copied.tracks:
+        for i, child in enumerate(track.each_child()):
+            is_nested = isinstance(child, otio.schema.Track)
+            is_parent_in_stack = isinstance(child.parent(), otio.schema.Stack)
+            if is_nested and not is_parent_in_stack:
+                stack = otio.schema.Stack()
+                track.remove(child)
+                stack.append(child)
+                track.insert(i, stack)
+    return copied
+
+
 class _TrackTranscriber(object):
     """
     _TrackTranscriber is the base class for the conversion of a given otio track.
@@ -294,20 +314,11 @@ def transcribe(self, otio_child):
             source_clip = self.aaf_sourceclip(otio_child)
             return source_clip
         elif isinstance(otio_child, otio.schema.Track):
-            operation_group = self.nesting_operation_group()
-            sequence = operation_group.segments[0]
-            length = 0
-            for nested_otio_child in otio_child:
-                result = self.transcribe(nested_otio_child)
-                sequence.components.append(result)
-                length += result.length
-
-            sequence.length = int(length)
-            operation_group.length = length
-            return operation_group
+            sequence = self.aaf_sequence(otio_child)
+            return sequence
         elif isinstance(otio_child, otio.schema.Stack):
-            raise otio.exceptions.NotSupportedError(
-                "Unsupported otio child type: otio.schema.Stack")
+            operation_group = self.aaf_operation_group(otio_child)
+            return operation_group
         else:
             raise otio.exceptions.NotSupportedError(
                 "Unsupported otio child type: {}".format(type(otio_child)))
@@ -369,7 +380,8 @@ def aaf_sourceclip(self, otio_clip):
         # We need both `start_time` and `duration`
         # Here `start` is the offset between `first` and `in` values.
 
-        offset = otio_clip.visible_range().start_time - otio_clip.available_range().start_time
+        offset = (otio_clip.visible_range().start_time -
+                  otio_clip.available_range().start_time)
         start = offset.value
         length = otio_clip.visible_range().duration.value
 
@@ -453,6 +465,49 @@ def aaf_transition(self, otio_transition):
         transition["DataDefinition"].value = datadef
         return transition
 
+    def aaf_sequence(self, otio_track):
+        """Convert an otio Track into an aaf Sequence"""
+        sequence = self.aaf_file.create.Sequence(media_kind=self.media_kind)
+        length = 0
+        for nested_otio_child in otio_track:
+            result = self.transcribe(nested_otio_child)
+            length += result.length
+            sequence.components.append(result)
+        sequence.length = length
+        return sequence
+
+    def aaf_operation_group(self, otio_stack):
+        """
+        Create and return an OperationGroup which will contain other AAF objects
+        to support OTIO nesting
+        """
+        # Create OperationDefinition
+        op_def = self.aaf_file.create.OperationDef(AAF_OPERATIONDEF_SUBMASTER,
+                                                   "Submaster")
+        self.aaf_file.dictionary.register_def(op_def)
+        op_def.media_kind = self.media_kind
+        datadef = self.aaf_file.dictionary.lookup_datadef(self.media_kind)
+
+        # These values are necessary for pyaaf2 OperationDefinitions
+        op_def["IsTimeWarp"].value = False
+        op_def["Bypass"].value = 0
+        op_def["NumberInputs"].value = -1
+        op_def["OperationCategory"].value = "OperationCategory_Effect"
+        op_def["DataDefinition"].value = datadef
+
+        # Create OperationGroup
+        operation_group = self.aaf_file.create.OperationGroup(op_def)
+        operation_group.media_kind = self.media_kind
+        operation_group["DataDefinition"].value = datadef
+
+        length = 0
+        for nested_otio_child in otio_stack:
+            result = self.transcribe(nested_otio_child)
+            length += result.length
+            operation_group.segments.append(result)
+        operation_group.length = length
+        return operation_group
+
     def _create_tapemob(self, otio_clip):
         """
         Return a physical sourcemob for an otio Clip based on the MobID.
@@ -514,35 +569,6 @@ def _create_mastermob(self, otio_clip, filemob, filemob_slot):
         mastermob_slot.segment = mastermob_clip
         return mastermob, mastermob_slot
 
-    def nesting_operation_group(self):
-        '''
-        Create and return an OperationGroup which will contain other AAF objects
-        to support OTIO nesting
-        '''
-        # Create OperationDefinition
-        op_def = self.aaf_file.create.OperationDef(AAF_OPERATIONDEF_SUBMASTER,
-                                                   "Submaster")
-        self.aaf_file.dictionary.register_def(op_def)
-        op_def.media_kind = self.media_kind
-        datadef = self.aaf_file.dictionary.lookup_datadef(self.media_kind)
-
-        # These values are necessary for pyaaf2 OperationDefinitions
-        op_def["IsTimeWarp"].value = False
-        op_def["Bypass"].value = 0
-        op_def["NumberInputs"].value = -1
-        op_def["OperationCategory"].value = "OperationCategory_Effect"
-        op_def["DataDefinition"].value = datadef
-
-        # Create OperationGroup
-        operation_group = self.aaf_file.create.OperationGroup(op_def)
-        operation_group.media_kind = self.media_kind
-        operation_group["DataDefinition"].value = datadef
-
-        # Sequence
-        sequence = self.aaf_file.create.Sequence(media_kind=self.media_kind)
-        operation_group.segments.append(sequence)
-        return operation_group
-
 
 class VideoTrackTranscriber(_TrackTranscriber):
     """Video track kind specialization of TrackTranscriber."""

contrib/opentimelineio_contrib/adapters/advanced_authoring_format.py

@@ -943,21 +943,19 @@ def read_from_file(filepath, simplify=True):
 
 def write_to_file(input_otio, filepath, **kwargs):
 
-    if not isinstance(input_otio, otio.schema.Timeline):
-        raise otio.exceptions.NotSupportedError(
-            "Currently only supporting top level Timeline"
-        )
+    with aaf2.open(filepath, "w") as f:
 
-    # in order to write a valid AAF file, OTIO may require either metadata
-    # or access to the files at the ends of media references. This 
-    # preflight check makes sure that the conditions are correct for
-    # authoring a valid AAF file.
-    aaf_writer.validate_metadata(input_otio)
+        timeline = aaf_writer._stackify_nested_groups(input_otio)
 
-    with aaf2.open(filepath, "w") as f:
-        otio2aaf = aaf_writer.AAFFileTranscriber(input_otio, f, **kwargs)
+        aaf_writer.validate_metadata(timeline)
+
+        otio2aaf = aaf_writer.AAFFileTranscriber(timeline, f, **kwargs)
+
+        if not isinstance(timeline, otio.schema.Timeline):
+            raise otio.exceptions.NotSupportedError(
+                "Currently only supporting top level Timeline")
 
-        for otio_track in input_otio.tracks:
+        for otio_track in timeline.tracks:
             # Ensure track must have clip to get the edit_rate
             if len(otio_track) == 0:
                 continue

contrib/opentimelineio_contrib/adapters/tests/sample_data/nested_stack.aaf

@@ -59,6 +59,10 @@
     SAMPLE_DATA_DIR,
     "nesting_test.aaf"
 )
+NESTED_STACK_EXAMPLE_PATH = os.path.join(
+    SAMPLE_DATA_DIR,
+    "nested_stack.aaf"
+)
 NESTING_PREFLATTENED_EXAMPLE_PATH = os.path.join(
     SAMPLE_DATA_DIR,
     "nesting_test_preflattened.aaf"
@@ -885,6 +889,9 @@ def _verify_first_clip(self, original_timeline, aaf_path):
     def test_aaf_writer_nesting(self):
         self._verify_aaf(NESTING_EXAMPLE_PATH)
 
+    def test_aaf_writer_nested_stack(self):
+        self._verify_aaf(NESTED_STACK_EXAMPLE_PATH)
+
     def _verify_aaf(self, aaf_path):
         otio_timeline = otio.adapters.read_from_file(aaf_path, simplify=True)
         fd, tmp_aaf_path = tempfile.mkstemp(suffix='.aaf')
@@ -931,23 +938,24 @@ def _verify_aaf(self, aaf_path):
                         otio_track.each_child(shallow_search=True),
                         sequence.components):
                     type_mapping = {
-                        aaf2.components.SourceClip: otio.schema.Clip,
-                        aaf2.components.Transition: otio.schema.Transition,
-                        aaf2.components.Filler: otio.schema.Gap,
-                        aaf2.components.OperationGroup: otio.schema.Track,
+                        otio.schema.Clip: aaf2.components.SourceClip,
+                        otio.schema.Transition: aaf2.components.Transition,
+                        otio.schema.Gap: aaf2.components.Filler,
+                        otio.schema.Stack: aaf2.components.OperationGroup,
+                        otio.schema.Track: aaf2.components.OperationGroup
                     }
-                    self.assertEqual(type(otio_child),
-                                     type_mapping[type(aaf_component)])
+                    self.assertEqual(type(aaf_component),
+                                     type_mapping[type(otio_child)])
 
                     if isinstance(aaf_component, SourceClip):
                         self._verify_compositionmob_sourceclip_structure(aaf_component)
 
                     if isinstance(aaf_component, aaf2.components.OperationGroup):
-                        aaf_nested_components = aaf_component.segments[0].components
-                        for nested_otio_child, aaf_nested_component in zip(
-                                otio_child.each_child(), aaf_nested_components):
+                        nested_aaf_segments = aaf_component.segments
+                        for nested_otio_child, nested_aaf_segment in zip(
+                                otio_child.each_child(), nested_aaf_segments):
                             self._is_otio_aaf_same(nested_otio_child,
-                                                   aaf_nested_component)
+                                                   nested_aaf_segment)
                     else:
                         self._is_otio_aaf_same(otio_child, aaf_component)