OpenTimelineIO is an open source library for the interchange of editorial information. This document describes the structure of the python library.

To import the library into python: import opentimelineio as otio

Canonical Structure

Although you can compose your OTIO files differently if you wish, the canonical OTIO structure is as follows:

  • root: otio.schema.Timeline. This file contains information about the root of a timeline, including a global start offset, and a top level container, .tracks
  • timeline.tracks: This member is a otio.schema.Stack which contains otio.schema.Track objects
  • timeline.tracks[i]: The otio.schema.Track contained by a timeline.tracks contain the clips, transitions and subcontainers that compose the rest of the editorial data.


The most interesting pieces of OTIO to a developer integrating OTIO into another application or workflow are:

  • otio.schema: the classes that describe the in-memory OTIO representation
  • otio.opentime Classes and utility functions for representing time, time ranges and time transforms.
  • otio.adapters: modules that can read and or write to or from an on-disk format and the in-memory OTIO representation.

Additionally, for developers integrating OTIO into a studio pipeline:

  • otio.media_linker: plugin system for writing studio or workflow specific media linkers that run after adapters read files


The in-memory OTIO representation data model is rooted at an otio.schema.Timeline which has a member .tracks which is a otio.schema.Stack of otio.schema.Sequences, which contain either otio.schema.Clip or otio.schema.Gap. The otio.schema.Clip objects can reference media through a otio.media_reference.External or indicate that they are missing a reference to real media with a otio.media_reference.MissingReference. All objects have a metadata dictionary for blind data.

Schema composition objects (otio.schema.Stack and otio.schema.Sequence) implement the python mutable sequence API. A simple script that prints out each shot might look like:

import opentimelineio as otio

# read the timeline into memory
tl = otio.adapters.read_from_file("my_file.otio")

for each_seq in tl.tracks:
  for each_item in each_seq:
   if isinstance(each_item, otio.schema.Clip):
    print each_item.media_reference

or, in the case of any nested composition, like this:

import opentimelineio as otio

# read the timeline into memory
tl = otio.adapters.read_from_file("my_file.otio")

for clip in tl.each_clip():
  print clip.media_reference

Time on otio.schema.Clip

A clip may set its timing information (which is used to compute its duration() or its trimmed_range()) by configuring either its:

  • .media_reference.available_range This is the range of the available media that can be cut in. So for example, frames 10-100 have been rendered and prepared for editorial.
  • .source_range The range of media that is cut into the sequence, in the space of the available range (if it is set). In other words, it further truncates the available_range.

A clip must have at least one set or else its duration is not computable.

CannotComputeAvailableRangeError: No available_range set on media reference on clip: Clip("example", External("file:///"), None, {})

You may query the available_range and trimmed_range via accessors on the Clip() itself, for example:

cl.available_range() # == cl.media_reference.available_range

Generally, if you want to know the range of a clip, we recommend using the .trimmed_range() method, since this takes both the media_reference.available_range and the .source_range into consideration.

Time On Clips in Containers

Additionally, if you want to know the time of a clip in the context of a container, you can use the local: .trimmed_range_in_parent() method, or a parent’s .trimmed_range_of_child(). These will additionally take into consideration the .source_range of the parent container, if it is set. They return a range in the space of the specified parent container.


Opentime encodes timing related information.


A point in time at rt.value*(1/rt.rate) seconds. Can be rescaled into another RationalTime’s rate.


A range in time. Encodes the start time and the duration, meaning that end_time_inclusive (last portion of a sample in the time range) and end_time_exclusive can be computed.


OpenTimelineIO includes several adapters for reading and writing from other file formats. The otio.adapters module has convenience functions that will auto-detect which adapter to use, or you can specify the one you want.

Adapters can be added to the system (outside of the distribution) via JSON files that can be placed on the OTIO_PLUGIN_MANIFEST_PATH environment variable to be made available to OTIO.

Most common usage only cares about:

  • timeline = otio.adapters.read_from_file(filepath)
  • timeline = otio.adapters.read_from_string(rawtext, adapter_name)
  • otio.adapters.write_to_file(timeline, filepath)
  • rawtext = otio.adapters.write_to_string(timeline, adapter_name)

The native format serialization (.otio files) is handled via the “otio_json” adapter, otio.adapters.otio_json.

In most cases you don’t need to worry about adapter names, just use otio.adapters.read_from_file and otio.adapters.write_to_file and it will figure out which one to use based on the filename extension.

For more information, see How To Write An OpenTimelineIO Adapter


Media linkers run on the otio file after an adapter calls .read_from_file or .read_from_string. They are intended to replace media references that exist after the adapter runs (which depending on the adapter are likely to be MissingReference) with ones that point to valid files in the local system. Since media linkers are plugins, they can use proprietary knowledge or context and do not need to be part of OTIO itself.

You may also specify a media linker to be run after the adapter, either via the media_linker_name argument to .read_from_file or .read_from_string or via the OTIO_DEFAULT_MEDIA_LINKER environment variable. You can also turn the media linker off completely by setting the media_linker_name argument to otio.media_linker.MediaLinkingPolicy.DoNotLinkMedia.

For more information about writing media linkers, see How To Write An OpenTimelineIO Media Linker

Example Scripts

Example scripts are located in the examples subdirectory.