@chatoctopus/timeline

Import and export video editing timelines for Final Cut Pro, Adobe Premiere Pro, DaVinci Resolve, and OpenTimelineIO.

Generates well-formed FCPXML 1.8 (Final Cut Pro), FCP7 XML / xmeml v5 (Premiere, Resolve), and OTIO (OpenTimelineIO) with frame-accurate rational time math -- no floating-point drift.

Installation

npm install @chatoctopus/timeline

Requires Node.js >= 18. For buildTimelineFromFiles() or probeMediaReference(), FFmpeg/FFprobe must be installed and on your PATH. Converting between formats does not require FFmpeg/FFprobe.

CLI

The package ships with a timeline CLI focused on format conversion and validation:

npx @chatoctopus/timeline convert ./edit.fcpxml --to otio --out ./edit.otio
npx @chatoctopus/timeline validate ./edit.xml
npx @chatoctopus/timeline validate ./edit.otio --json

Commands

| Command | Description | | ------- | ----------- | | convert <input> --to <fcpx\|premiere\|resolve\|otio> [--out <path>] | Auto-detect input format, convert to target editor format, and write to file (--out) or stdout. Import and lossy-export warnings are written to stderr. | | validate <input> [--json] | Validate timeline integrity and frame alignment; exits with non-zero on hard errors |

Quick Start

Import from an existing project file

Auto-detects FCPXML, xmeml, or OTIO format.

import { importTimeline, exportTimeline } from "@chatoctopus/timeline"
import { readFileSync, writeFileSync } from "fs"

// Read a Final Cut Pro project
const fcpxml = readFileSync("project.fcpxml", "utf-8")
const { timeline, warnings } = importTimeline(fcpxml)

console.log(`Imported "${timeline.name}" with ${timeline.tracks.length} tracks`)
if (warnings.length > 0) console.warn("Warnings:", warnings)

// Convert to Premiere Pro format
writeFileSync("project.xml", exportTimeline(timeline, "premiere"))

Convert between formats

import { importTimeline, exportTimeline } from "@chatoctopus/timeline"
import { readFileSync, writeFileSync } from "fs"

// Premiere XML -> Final Cut Pro
const premiereXml = readFileSync("edit.xml", "utf-8")
const { timeline } = importTimeline(premiereXml)
writeFileSync("edit.fcpxml", exportTimeline(timeline, "fcpx"))

// Final Cut Pro -> DaVinci Resolve
const fcpxml = readFileSync("edit.fcpxml", "utf-8")
const { timeline: tl } = importTimeline(fcpxml)
writeFileSync("edit-resolve.xml", exportTimeline(tl, "resolve"))

// OTIO -> Final Cut Pro
const otio = readFileSync("project.otio", "utf-8")
const { timeline: tl2 } = importTimeline(otio)
writeFileSync("project.fcpxml", exportTimeline(tl2, "fcpx"))

// Any format -> OTIO
const anyFile = readFileSync("timeline.fcpxml", "utf-8")
const { timeline: tl3 } = importTimeline(anyFile)
writeFileSync("timeline.otio", exportTimeline(tl3, "otio"))

Build a timeline from media files

The simplest path: provide file paths and optional trim points. Metadata is extracted automatically via FFprobe into inline ExternalReference objects.

buildTimelineFromFiles() validates trim inputs strictly: startAt and duration must be finite, non-negative numbers, 0 is treated as an explicit value, still images require an explicit duration, and mixed-frame-rate trims may be rejected when they cannot be represented consistently.

import { buildTimelineFromFiles, exportTimeline } from "@chatoctopus/timeline"
import { writeFileSync } from "fs"

const timeline = await buildTimelineFromFiles("Wedding Highlights", [
  { path: "/footage/ceremony.mp4", startAt: 30, duration: 10 },
  { path: "/footage/reception.mp4", duration: 15 },
  { path: "/footage/speeches.mp4", startAt: 120, duration: 20 },
  { path: "/slides/title-card.png", duration: 3 },
])

// Final Cut Pro
writeFileSync("wedding.fcpxml", exportTimeline(timeline, "fcpx"))

// Adobe Premiere Pro
writeFileSync("wedding.xml", exportTimeline(timeline, "premiere"))

// DaVinci Resolve
writeFileSync("wedding.xml", exportTimeline(timeline, "resolve"))

// OpenTimelineIO (universal interchange)
writeFileSync("wedding.otio", exportTimeline(timeline, "otio"))

Construct a timeline manually

For full control, build the OTIO-first Timeline model directly. All timing uses Rational numbers ({ num, den }) to stay frame-aligned.

import {
  exportTimeline,
  rational,
  ZERO,
  FRAME_RATES,
} from "@chatoctopus/timeline"
import type { Timeline } from "@chatoctopus/timeline"
import { writeFileSync } from "fs"

const timeline: Timeline = {
  name: "My Edit",
  format: {
    width: 1920,
    height: 1080,
    frameRate: FRAME_RATES["29.97"], // { num: 30000, den: 1001 }
    audioRate: 48000,
    colorSpace: "1-1-1 (Rec. 709)",
  },
  tracks: [
    {
      kind: "video",
      name: "V1",
      items: [
        {
          kind: "clip",
          name: "interview",
          mediaReference: {
            type: "external",
            name: "interview.mp4",
            targetUrl: "file:///footage/interview.mp4",
            mediaKind: "video",
            availableRange: {
              startTime: ZERO,
              duration: rational(9000 * 1001, 30000), // 9000 frames at 29.97fps
            },
          },
          sourceRange: {
            startTime: rational(300 * 1001, 30000), // start from frame 300 in source
            duration: rational(150 * 1001, 30000), // 150 frames = ~5 seconds
          },
          metadata: {
            role: "dialogue",
          },
        },
      ],
    },
  ],
}

writeFileSync("output.otio", exportTimeline(timeline, "otio"))
writeFileSync("output.fcpxml", exportTimeline(timeline, "fcpx"))

Timeline is the API for OTIO, FCPXML, and xmeml workflows.

API Reference

High-Level Functions

| Function | Description | | -------------------------------------------- | -------------------------------------------------------------------------------------- | | exportTimeline(timeline, editor, options?) | Export a Timeline. editor is "fcpx", "premiere", "resolve", or "otio". | | importTimeline(content) | Parse FCPXML, xmeml, or OTIO into Timeline. | | buildTimelineFromFiles(name, files) | Probe files with FFprobe and build a linear Timeline with inline media references. | | createTimeline(options) | Create a Timeline with default format values for synthetic or programmatic edits. |

Format-Specific Functions

| Function | Description | | --------------------------------- | ---------------------------------- | | writeFCPXML(timeline, options?) | Generate FCPXML 1.8 string from Timeline | | readFCPXML(xmlString) | Parse FCPXML into Timeline | | writeXMEML(timeline, options?) | Generate xmeml v5 string from Timeline | | readXMEML(xmlString) | Parse xmeml into Timeline | | writeOTIO(timeline) | Generate OTIO JSON from Timeline | | readOTIO(jsonString) | Parse OTIO JSON into Timeline |

Lossy export note:

exportTimeline(timeline, "fcpx", {
  onWarning(message) {
    console.warn(message)
  },
})

Use onWarning when exporting to FCPXML or xmeml if you want to be notified when transitions, markers, metadata, missing references, or other core-only fields are dropped.

Transitions are overlap items in the core model. computeTimelineDuration() accounts for that overlap, while current FCPXML and xmeml exports flatten transitions into butt cuts and warn because those adapters do not yet emit native transition elements.

Time Utilities

All timing uses Rational ({ num: number, den: number }) to avoid floating-point drift.

| Function | Description | | ---------------------------------------- | -------------------------------------------------------------------------------- | | rational(num, den) | Create a simplified rational number | | add(a, b) | Add two rationals | | subtract(a, b) | Subtract (clamps to zero) | | toSeconds(r) | Convert rational to float seconds | | toFCPString(r) | Format as FCP time string ("1001/24000s") | | parseFCPString(s) | Parse FCP time string back to rational | | secondsToFrameAligned(secs, frameRate) | Convert seconds, snapped to nearest frame boundary | | toFrames(duration, frameDuration) | Convert rational to frame count | | parseTimecode(tc, frameRate) | Parse SMPTE timecode ("01:00:00;00") with drop-frame support | | FRAME_RATES | Common presets: "23.976", "24", "25", "29.97", "30", "59.94", "60" |

Validation

| Function | Description | | ----------------------------------- | ----------------------------------------------------------------------------------- | | validateTimeline(timeline) | Returns array of ValidationError (checks media refs, source ranges, frame alignment, dimensions) | | hasErrors(results) | true if any hard errors (not just warnings) | | computeTimelineDuration(timeline) | Compute total duration from all track items |

Probing

| Function | Description | | ---------------------- | ------------------------------------------------------------- | | probeMediaReference(filePath) | Run FFprobe on a file and return a populated ExternalReference for video, audio, or image media |

Types

interface Timeline {
  name: string
  format: NLEFormat
  tracks: Track[]
  metadata?: Record<string, unknown>
  markers?: Marker[]
  globalStartTime?: Rational
}

interface NLEFormat {
  width: number
  height: number
  frameRate: Rational // e.g. { num: 30000, den: 1001 } for 29.97fps
  audioRate: number // e.g. 48000
  audioChannels?: number
  audioLayout?: string
  colorSpace?: string
}

type TrackItem = Clip | Gap | Transition

interface Track {
  kind: "video" | "audio"
  name?: string
  items: TrackItem[]
  metadata?: Record<string, unknown>
  markers?: Marker[]
  enabled?: boolean
}

interface Clip {
  kind: "clip"
  name: string
  mediaReference: MediaReference
  sourceRange?: TimeRange
  metadata?: Record<string, unknown>
  markers?: Marker[]
  enabled?: boolean
}

interface Gap {
  kind: "gap"
  sourceRange: TimeRange
  metadata?: Record<string, unknown>
  enabled?: boolean
}

interface Transition {
  kind: "transition"
  name?: string
  transitionType?: string
  inOffset: Rational
  outOffset: Rational
  metadata?: Record<string, unknown>
}

interface TimeRange {
  startTime: Rational
  duration: Rational
}

type MediaReference = ExternalReference | MissingReference

interface ExternalReference {
  type: "external"
  targetUrl: string
  name?: string
  mediaKind?: "video" | "audio" | "image" | "unknown"
  availableRange?: TimeRange
  metadata?: Record<string, unknown>
  streamInfo?: StreamInfo
}

interface MissingReference {
  type: "missing"
  name?: string
  metadata?: Record<string, unknown>
}

interface StreamInfo {
  hasVideo?: boolean
  hasAudio?: boolean
  width?: number
  height?: number
  frameRate?: Rational
  audioRate?: number
  audioChannels?: number
  colorSpace?: string
}

type NLEEditor = "fcpx" | "premiere" | "resolve" | "otio"

Still images are modeled as ExternalReference objects with mediaKind: "image" on normal video tracks. The clip carries the display duration via sourceRange, and buildTimelineFromFiles() will populate an availableRange for stills when you provide an explicit duration.

Builder inputs:

interface TimelineFileInput {
  path: string
  startAt?: number
  duration?: number
  track?: number
  kind?: "video" | "audio"
}

interface CreateTimelineOptions {
  name: string
  format?: Partial<NLEFormat>
  tracks?: Track[]
  metadata?: Record<string, unknown>
  markers?: Marker[]
  globalStartTime?: Rational
}

Supported Formats

| Format | Extension | Editors / Tools | Read | Write | | -------------- | --------- | ------------------------------------------ | ---- | ----- | | FCPXML 1.8 | .fcpxml | Final Cut Pro | Yes | Yes | | xmeml v5 | .xml | Adobe Premiere Pro, DaVinci Resolve | Yes | Yes | | OpenTimelineIO | .otio | Resolve 18+, Hiero, rv, and OTIO ecosystem | Yes | Yes |

Verification

Run the test suite:

npm test

Run tests with coverage:

npm run test:coverage

Type-check without emitting:

npm run lint

Build:

npm run build

Quick smoke test

node --input-type=module -e "
import { exportTimeline, rational, ZERO, FRAME_RATES } from './dist/index.js';

const timeline = {
  name: 'Smoke Test',
  format: {
    width: 1920, height: 1080,
    frameRate: FRAME_RATES['29.97'],
    audioRate: 48000,
  },
  tracks: [{
    kind: 'video',
    items: [{
      kind: 'clip',
      name: 'clip',
      mediaReference: {
        type: 'external',
        name: 'clip.mp4',
        targetUrl: 'file:///tmp/clip.mp4',
        mediaKind: 'video',
        availableRange: {
          startTime: ZERO,
          duration: rational(300 * 1001, 30000),
        },
      },
      sourceRange: {
        startTime: ZERO,
        duration: rational(150 * 1001, 30000),
      },
    }],
  }],
};

const fcpxml = exportTimeline(timeline, 'fcpx');
const xmeml = exportTimeline(timeline, 'premiere');
const otio = exportTimeline(timeline, 'otio');

console.log('FCPXML:', fcpxml.includes('<fcpxml') ? 'OK' : 'FAIL');
console.log('xmeml:', xmeml.includes('<xmeml') ? 'OK' : 'FAIL');
console.log('OTIO:', otio.includes('Timeline.1') ? 'OK' : 'FAIL');
console.log('Done.');
"

Architecture

src/
├── index.ts           Public API: exportTimeline, importTimeline, createTimeline, buildTimelineFromFiles
├── types.ts           OTIO-first core types
├── time.ts            Rational arithmetic, frame alignment, SMPTE timecode parsing
├── probe.ts           FFprobe -> ExternalReference probing
├── media-kind.ts      Shared file-extension media kind inference
├── builders.ts        Core-native timeline construction helpers
├── validate.ts        Core validation and duration computation
├── fcpxml/
│   ├── writer.ts      FCPXML 1.8 generation
│   └── reader.ts      FCPXML parsing
├── xmeml/
│   ├── writer.ts      xmeml v5 generation (Premiere / Resolve)
│   └── reader.ts      xmeml parsing
└── otio/
    ├── writer.ts      OpenTimelineIO JSON generation
    └── reader.ts      OpenTimelineIO JSON parsing

How It Works

Rational time math is the core of the library. All NLE software uses frame-aligned timing internally -- expressing durations as rational fractions like 1001/30000s (one frame at 29.97fps). Using floating-point seconds causes frame drift and "not on edit frame boundary" errors in Final Cut Pro.

Every clip duration and offset goes through secondsToFrameAligned() which snaps to the nearest frame boundary, matching the behavior of both buttercut (Ruby) and cutlass (Go) which this library draws from.

Three interchange formats cover all major editors and tools:

• FCPXML 1.8 for Final Cut Pro -- trackless magnetic timeline with <asset-clip> elements inside a <spine>
• xmeml v5 for Premiere and Resolve -- track-based with linked <clipitem> elements for video and audio
• OpenTimelineIO (.otio) -- the industry-standard JSON interchange format backed by the Academy Software Foundation. OTIO acts as a universal hub: any tool that speaks OTIO gets instant access to timelines from any other format. In this package, OTIO now maps directly to the core model, including explicit gaps, transitions, markers, metadata, and inline media references.

Acknowledgments

This project draws on ideas and timing behavior from buttercut and cutlass, and we gratefully acknowledge those projects as upstream inspiration.

Trademarks

Final Cut Pro is a trademark of Apple Inc. Adobe Premiere Pro is a trademark of Adobe. DaVinci Resolve is a trademark of Blackmagic Design Pty Ltd. All other product names, logos, and brands are the property of their respective owners.

License

MIT