Fix FCPXML import failing DTD validation in Final Cut Pro

[wassgha]

The bug

Jack reported that importing an exported FCPXML timeline into Final Cut Pro always fails:

The XML document sent from application "(null)" could not be imported.
DTD validation failed. (The data couldn't be read because it isn't in the correct format.)

His hunch about a 12-hour vs 24-hour date format was the right thread to pull.

Cause

Two problems in the FCPXML we emit. Before:

<project name="interview" modDate="2026-08-29 12:35:09 America/Los_Angeles">
  <sequence ...>
    <spine>
      <asset-clip name="interview.mp4 1" ref="ra24740a9b9ee" offset="0s" duration="1/1s" start="0s">
        <asset-clip name="interview.mp4 1" ref="ra24740a9b9ee" offset="0s" duration="1/1s" start="0s" lane="1"/>
      </asset-clip>

1. modDate is unparseable. FCP wants a numeric UTC offset (2026-08-29 12:35:09 -0700); the upstream writer stamps an IANA zone name instead. A modDate FCP can't parse takes down the whole document with the generic DTD error. FCP 10.6.x is stricter still — it only accepts the clock format matching the user's system 12/24-hour setting, so even a well-formed value is a coin flip. The attribute is optional and we have nothing meaningful to put there, so we drop it.

2. Duplicate connected clips. We hand the writer parallel V1/A1 tracks, which XMEML and AAF both need. But a single FCP asset-clip already carries the video and audio of its asset, so the writer turned A1 into connected clips in lane 1 — that imports as a duplicate video overlay with doubled audio. We now collapse to one track for the FCPXML path only.

After

<project name="interview">
  <sequence duration="5/2s" format="r1" tcStart="0s" tcFormat="NDF" audioLayout="stereo" audioRate="48k">
    <spine>
      <asset-clip name="interview.mp4 1" ref="ra24740a9b9ee" offset="0s" duration="1/1s" start="0s"/>
      <asset-clip name="interview.mp4 2" ref="ra24740a9b9ee" offset="1/1s" duration="3/2s" start="2/1s"/>
    </spine>

Premiere/Resolve XMEML and AAF output are unchanged.

Testing

npm run test:timeline passes, with new coverage for: no modDate in the output, one asset-clip per keep range with no lane= attributes, audio-only FCPXML projects still landing on the spine, stripFcpxmlModDate not touching non-project tags, and XMEML keeping both its tracks. tsc --noEmit and eslint are clean.

I could not verify the import in Final Cut Pro itself — it isn't installed here — so that check is still worth doing before release. The output is well-formed per xmllint, and both defects are independently confirmed against how real FCP-authored files look.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
app.rescript	Ready	Preview	Aug 29, 2026 7:40pm