diff --git a/scenedetect/_cli/commands.py b/scenedetect/_cli/commands.py
index 2940a11c..478ff1dc 100644
--- a/scenedetect/_cli/commands.py
+++ b/scenedetect/_cli/commands.py
@@ -387,4 +387,5 @@ def save_otio(
         frame_rate=video_stream.frame_rate,
         name=Template(name).safe_substitute(VIDEO_NAME=video_name),
         audio=audio,
+        source_duration=video_stream.duration,
     )
diff --git a/scenedetect/output/__init__.py b/scenedetect/output/__init__.py
index 69495cfe..02f109cd 100644
--- a/scenedetect/output/__init__.py
+++ b/scenedetect/output/__init__.py
@@ -656,6 +656,7 @@ def write_scene_list_otio(
     frame_rate: Fraction,
     name: str | None = None,
     audio: bool = True,
+    source_duration: FrameTimecode | None = None,
 ):
     """Writes the given list of scenes to `output_path` as an OTIO Timeline.1 JSON document.
 
@@ -670,6 +671,9 @@ def write_scene_list_otio(
             current OTIO format does not support rational timings.
         name: Timeline name. Defaults to the stem of `video_path`.
         audio: If True (default), include an audio track alongside the video track.
+        source_duration: Total duration of the source media. Written as the media reference's
+            available range so NLEs can seek into the source. If None, the available range is
+            left unspecified rather than inferred from the selected scenes.
     """
     # `_open_output_file` replaces filesystem paths with writable text streams.
     assert isinstance(output_path, _SupportsWrite)
@@ -681,6 +685,21 @@ def write_scene_list_otio(
     video_base_name = video_path.name
     video_abs_path = str(video_path.absolute())
     fps = float(frame_rate)
+    available_range = None
+    if source_duration is not None:
+        available_range = {
+            "OTIO_SCHEMA": "TimeRange.1",
+            "duration": {
+                "OTIO_SCHEMA": "RationalTime.1",
+                "rate": fps,
+                "value": round(source_duration.seconds * fps, 6),
+            },
+            "start_time": {
+                "OTIO_SCHEMA": "RationalTime.1",
+                "rate": fps,
+                "value": 0.0,
+            },
+        }
 
     # List of track mapping to resource type.
     # TODO(https://scenedetect.com/issues/497): Allow OTIO export without an audio track.
@@ -726,19 +745,7 @@ def write_scene_list_otio(
                                 "DEFAULT_MEDIA": {
                                     "OTIO_SCHEMA": "ExternalReference.1",
                                     "name": video_base_name,
-                                    "available_range": {
-                                        "OTIO_SCHEMA": "TimeRange.1",
-                                        "duration": {
-                                            "OTIO_SCHEMA": "RationalTime.1",
-                                            "rate": fps,
-                                            "value": 1980.0,
-                                        },
-                                        "start_time": {
-                                            "OTIO_SCHEMA": "RationalTime.1",
-                                            "rate": fps,
-                                            "value": 0.0,
-                                        },
-                                    },
+                                    "available_range": available_range,
                                     "available_image_bounds": None,
                                     "target_url": video_abs_path,
                                 }
diff --git a/tests/test_output.py b/tests/test_output.py
index 13d1c738..da7a23d2 100644
--- a/tests/test_output.py
+++ b/tests/test_output.py
@@ -654,3 +654,73 @@ def test_write_scene_list_otio_output_target(tmp_path: Path, target_kind: str):
     assert "\r\n" not in text
     doc = json.loads(text)
     assert doc["OTIO_SCHEMA"] == "Timeline.1"
+
+
+@pytest.mark.parametrize("frame_rate", [_FPS_CFR, _FPS_NTSC])
+@pytest.mark.parametrize("audio", [False, True])
+@pytest.mark.parametrize("ranges", [[], [(0, 24)], [(2400, 4800)], [(24, 72), (3000, 3600)]])
+def test_write_scene_list_otio_unknown_available_range(tmp_path, frame_rate, audio, ranges):
+    """Scene ranges do not reveal the source video's full available duration."""
+    output_path = tmp_path / "scenes.otio"
+    write_scene_list_otio(
+        output_path,
+        scene_list=_fake_scenes(frame_rate, ranges),
+        video_path=tmp_path / "source.mp4",
+        frame_rate=frame_rate,
+        audio=audio,
+    )
+
+    doc = json.loads(output_path.read_text())
+    tracks = doc["tracks"]["children"]
+    assert len(tracks) == (2 if audio else 1)
+    for track in tracks:
+        assert len(track["children"]) == len(ranges)
+        for clip, (start, end) in zip(track["children"], ranges, strict=True):
+            ref = clip["media_references"]["DEFAULT_MEDIA"]
+            assert ref["available_range"] is None
+            assert clip["source_range"]["start_time"]["value"] == pytest.approx(start)
+            assert clip["source_range"]["duration"]["value"] == pytest.approx(end - start)
+
+
+@pytest.mark.parametrize("frame_rate", [_FPS_CFR, _FPS_NTSC])
+@pytest.mark.parametrize("source_frame_rate", [_FPS_CFR, _FPS_NTSC])
+@pytest.mark.parametrize("source_frames", [0, 6000])
+@pytest.mark.parametrize("audio", [False, True])
+def test_write_scene_list_otio_source_duration(
+    tmp_path, frame_rate, source_frame_rate, source_frames, audio
+):
+    """Available media duration uses the full source, not the selected scenes."""
+    source_duration = FrameTimecode(source_frames, fps=source_frame_rate)
+    ranges = [(24, 72), (120, 180)] if source_frames else [(0, 0)]
+    output_path = tmp_path / "scenes.otio"
+    write_scene_list_otio(
+        output_path,
+        scene_list=_fake_scenes(frame_rate, ranges),
+        video_path=tmp_path / "source.mp4",
+        frame_rate=frame_rate,
+        audio=audio,
+        source_duration=source_duration,
+    )
+
+    doc = json.loads(output_path.read_text())
+    fps = float(frame_rate)
+    expected_duration = round(source_duration.seconds * fps, 6)
+    tracks = doc["tracks"]["children"]
+    assert len(tracks) == (2 if audio else 1)
+    for track in tracks:
+        assert len(track["children"]) == len(ranges)
+        for clip, (start, end) in zip(track["children"], ranges, strict=True):
+            available = clip["media_references"]["DEFAULT_MEDIA"]["available_range"]
+            assert available["OTIO_SCHEMA"] == "TimeRange.1"
+            assert available["start_time"] == {
+                "OTIO_SCHEMA": "RationalTime.1",
+                "rate": fps,
+                "value": 0.0,
+            }
+            assert available["duration"] == {
+                "OTIO_SCHEMA": "RationalTime.1",
+                "rate": fps,
+                "value": expected_duration,
+            }
+            assert clip["source_range"]["start_time"]["value"] == pytest.approx(start)
+            assert clip["source_range"]["duration"]["value"] == pytest.approx(end - start)
diff --git a/website/pages/changelog.md b/website/pages/changelog.md
index 1610808e..a1c6fbbe 100644
--- a/website/pages/changelog.md
+++ b/website/pages/changelog.md
@@ -3,6 +3,10 @@
 
 ## PySceneDetect 0.7
 
+### Unreleased
+
+ - [bugfix] OTIO exports use the full source duration when provided, including from the CLI, instead of declaring a fixed 1,980-frame duration. The available range remains unspecified when the duration is unknown. Scene source ranges are unchanged. [#580](https://github.com/Breakthrough/PySceneDetect/pull/580)
+
 ### PySceneDetect 0.7.2 (October 11, 2026)
 
 PySceneDetect 0.7.2 ships improved defaults for the histogram and perceptual hash detectors, adds PyAV 19 support, and fixes several timing and output bugs. **Default output of `detect-hist` and `detect-hash` will change in this release due to improved default values**.