diff --git a/src/otio_aaf_adapter/adapters/aaf_adapter/aaf_writer.py b/src/otio_aaf_adapter/adapters/aaf_adapter/aaf_writer.py
index 65343a6..b1e0549 100644
--- a/src/otio_aaf_adapter/adapters/aaf_adapter/aaf_writer.py
+++ b/src/otio_aaf_adapter/adapters/aaf_adapter/aaf_writer.py
@@ -693,18 +693,35 @@ def _create_timeline_mobslot(self):
         return timeline_mobslot, sequence
 
     def default_descriptor(self, otio_clip):
-        # TODO: Determine if these values are the correct, and if so,
-        # maybe they should be in the AAF metadata
         descriptor = self.aaf_file.create.CDCIDescriptor()
-        descriptor["ComponentWidth"].value = 8
-        descriptor["HorizontalSubsampling"].value = 2
-        descriptor["ImageAspectRatio"].value = "16/9"
-        descriptor["StoredWidth"].value = 1920
-        descriptor["StoredHeight"].value = 1080
-        descriptor["FrameLayout"].value = "FullFrame"
-        descriptor["VideoLineMap"].value = [42, 0]
-        descriptor["SampleRate"].value = 24
-        descriptor["Length"].value = 1
+        descriptor_dict = otio_clip.media_reference.metadata.get("AAF", {}).get(
+            "EssenceDescription", {})
+
+        video_linemap = descriptor_dict.get("VideoLineMap", [42, 0])
+        video_linemap = [int(x) for x in video_linemap]
+
+        descriptor["ComponentWidth"].value = int(
+            descriptor_dict.get("ComponentWidth", 8)
+        )
+        descriptor["HorizontalSubsampling"].value = int(
+            descriptor_dict.get("HorizontalSubsampling", 2)
+        )
+        descriptor["ImageAspectRatio"].value = descriptor_dict.get(
+            "ImageAspectRatio", "16/9"
+        )
+        descriptor["StoredWidth"].value = int(
+            descriptor_dict.get("StoredWidth", 1920)
+        )
+        descriptor["StoredHeight"].value = int(
+            descriptor_dict.get("StoredHeight", 1080)
+        )
+        descriptor["FrameLayout"].value = descriptor_dict.get(
+            "FrameLayout", "FullFrame"
+        )
+        descriptor["VideoLineMap"].value = video_linemap
+
+        descriptor["SampleRate"].value = int(descriptor_dict.get("SampleRate", 24))
+        descriptor["Length"].value = int(descriptor_dict.get("Length", 1))
 
         media = otio_clip.media_reference
         if isinstance(media, otio.schema.ExternalReference):
@@ -715,6 +732,9 @@ def default_descriptor(self, otio_clip):
                 descriptor['SampleRate'].value = media.available_range.duration.rate
                 descriptor["Length"].value = int(media.available_range.duration.value)
 
+        for key, value in descriptor_dict.items():
+            descriptor[key].value = value
+
         return descriptor
 
     def _transition_parameters(self):
@@ -848,20 +868,33 @@ def _create_timeline_mobslot(self):
 
     def default_descriptor(self, otio_clip):
         descriptor = self.aaf_file.create.PCMDescriptor()
-        descriptor["AverageBPS"].value = 96000
-        descriptor["BlockAlign"].value = 2
-        descriptor["QuantizationBits"].value = 16
-        descriptor["AudioSamplingRate"].value = 48000
-        descriptor["Channels"].value = 1
-        descriptor["SampleRate"].value = 48000
-        descriptor["Length"].value = int(
-            otio_clip.media_reference.available_range.duration.value
+        descriptor_dict = otio_clip.media_reference.metadata.get("AAF", {}).get(
+            "EssenceDescription", {})
+
+        sample_rate = int(descriptor_dict.get("SampleRate", 48000))
+        descriptor_dict["AverageBPS"] = int(descriptor_dict.get("AverageBPS", 96000))
+        descriptor_dict["BlockAlign"] = int(descriptor_dict.get("BlockAlign", 2))
+        descriptor_dict["QuantizationBits"] = int(
+            descriptor_dict.get("QuantizationBits", 16)
         )
 
         if isinstance(otio_clip.media_reference, otio.schema.ExternalReference):
             locator = self.aaf_network_locator(otio_clip.media_reference)
             descriptor["Locator"].append(locator)
 
+        descriptor_dict["AudioSamplingRate"] = int(
+            descriptor_dict.get("AudioSamplingRate", 48000)
+        )
+        descriptor_dict["Channels"] = int(descriptor_dict.get("Channels", 1))
+        descriptor_dict["SampleRate"] = sample_rate
+        descriptor_dict["Length"] = int(descriptor_dict.get("Length", int(
+            otio_clip.media_reference.available_range.duration.rescaled_to(
+                sample_rate).value
+        )))
+
+        for key, value in descriptor_dict.items():
+            descriptor[key].value = value
+
         return descriptor
 
     def _transition_parameters(self):
diff --git a/tests/test_aaf_adapter.py b/tests/test_aaf_adapter.py
index 19a5bef..d8b1127 100644
--- a/tests/test_aaf_adapter.py
+++ b/tests/test_aaf_adapter.py
@@ -2031,6 +2031,38 @@ def test_aaf_writer_audio_pan(self):
 
             self.assertEqual(param_dicts, expected)
 
+    def test_essence_descriptor(self):
+        """Tests custom values for essence descriptor
+        """
+        tl = otio.schema.Timeline()
+        range = otio.opentime.TimeRange(
+            start_time=otio.opentime.RationalTime(0, 24),
+            duration=otio.opentime.RationalTime(100, 24),
+        )
+        clip = otio.schema.Clip(source_range=range)
+        clip.media_reference = otio.schema.MissingReference(available_range=range)
+        tl.tracks.append(otio.schema.Track())
+        tl.tracks[0].append(clip)
+
+        # set custom essence descriptor values
+        clip.media_reference.metadata["AAF"] = {
+            "SourceID": str(MobID(int=13)),
+            "EssenceDescription": {
+                "SampleRate": 48,
+                "Length": 100
+            }
+        }
+
+        # write to temp AAf file
+        _, tmp_aaf_path = tempfile.mkstemp(suffix='.aaf')
+        otio.adapters.write_to_file(tl, tmp_aaf_path)
+
+        # check if essence descriptor parameters in AAF file match
+        with aaf2.open(tmp_aaf_path) as aaf_file:
+            source_mob = list(aaf_file.content.sourcemobs())[1]
+            self.assertEqual(source_mob.descriptor['Length'].value, 100)
+            self.assertEqual(source_mob.descriptor['SampleRate'].value, 48)
+
     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')