clipwright-transition 0.2.0

MCP tool for adding transition directives (fade, dissolve, fadeblack, fadewhite) to an OTIO timeline for realisation by clipwright-render.

clipwright-transition

MCP tool that adds transition directives (fade, dissolve, fadeblack, fadewhite) to an OTIO timeline for realisation by clipwright-render.

Overview

clipwright-transition accepts an OTIO timeline (typically produced by clipwright-sequence) and annotates it with transition directives at clip boundaries. The directives are stored in metadata["clipwright"]["transition"] and consumed by clipwright-render, which materialises them as xfade/acrossfade filter chains during the final encoding pass.

Design principle (separation of annotation and realisation): clipwright-transition writes only the OTIO directive; it does not transcode or touch media files. All media processing is deferred to clipwright-render.

No FFmpeg or FFprobe is needed at transition-annotation time.

Prerequisites

• Python 3.11 or later
• clipwright core package (shared types, envelope, OTIO utils)
• An OTIO timeline with two or more video clips on a single V1 track (e.g. produced by clipwright-sequence)

MCP Tool: clipwright_add_transition

Parameters

Name	Type	Default	Description
timeline	string	required	Path to the input OTIO timeline file (.otio extension required).
output	string	required	Output OTIO timeline file path (.otio extension required, must differ from timeline). The parent directory must exist.
options	AddTransitionOptions	required	Transition mode: either uniform (apply the same transition to all internal boundaries) or per_boundary (specify per-boundary transitions). Exactly one must be provided.
options.uniform	TransitionSpec | null	null	Apply a single transition spec to every internal clip boundary.
options.uniform.type	string	required	Transition type: "fade", "dissolve", "fadeblack", or "fadewhite".
options.uniform.duration_sec	float	required	Transition duration in seconds (0 < duration ≤ 5.0).
options.per_boundary	list[BoundaryTransition] | null	null	Per-boundary transition list (max 1000 entries). All internal boundaries must be covered (no partial/gapped specification in v1).
options.per_boundary[].after_clip_index	int	required	Zero-based index of the clip before the boundary (≥ 0).
options.per_boundary[].type	string	required	Transition type (same allowlist as uniform.type).
options.per_boundary[].duration_sec	float	required	Transition duration in seconds (same constraint as uniform.duration_sec).

Return value

{
  "ok": true,
  "summary": "Applied dissolve transition (0.5s) to 2 boundary(ies) [uniform mode]. Generated output.otio. Pass it to clipwright-render to materialise the transitions.",
  "data": {
    "boundary_count": 2,
    "mode": "uniform"
  },
  "artifacts": [{"role": "timeline", "path": "output.otio", "format": "otio"}],
  "warnings": []
}

Error codes

Code	Cause
INVALID_INPUT	output has a non-.otio extension
INVALID_INPUT	output parent directory does not exist
INVALID_INPUT	output resolves to the same path as timeline
INVALID_INPUT	The timeline has fewer than two video clips
INVALID_INPUT	The timeline has no video track or two or more video tracks
INVALID_INPUT	The timeline already contains an OTIO Transition object
INVALID_INPUT	A per_boundary index is out of range [0, n_clips-2]
INVALID_INPUT	per_boundary contains duplicate after_clip_index values
UNSUPPORTED_OPERATION	per_boundary does not cover all internal boundaries (partial/gapped specification is unsupported in v1; use uniform or specify all n_clips-1 boundaries)
FILE_NOT_FOUND	The timeline path does not exist

Three-Phase Workflow

clipwright_build_sequence(clips, output)          # Phase 1 — build multi-clip OTIO
        │
        ▼  OTIO timeline with ordered V1 clips
clipwright_add_transition(timeline, output, opts)  # Phase 2 — annotate transitions
        │
        ▼  OTIO timeline with transition directives
clipwright_render(timeline, output_media)          # Phase 3 — encode with transitions
        │
        ▼  single output video with crossfades

MCP Client Registration

Register clipwright-transition as a standalone MCP server in your client configuration (.mcp.json / claude_desktop_config.json). No environment variables are required at annotation time.

{
  "mcpServers": {
    "clipwright-transition": {
      "command": "clipwright-transition"
    }
  }
}

clipwright-render (which materialises the transitions into a video) requires CLIPWRIGHT_FFMPEG.

Usage Examples

Apply a uniform dissolve between all clips

# Via MCP call_tool
result = await session.call_tool("clipwright_add_transition", {
    "timeline": "/project/sequence.otio",
    "output": "/project/with_transitions.otio",
    "options": {
        "uniform": {"type": "dissolve", "duration_sec": 0.5}
    }
})
# Then render
render_result = await session.call_tool("clipwright_render", {
    "timeline": "/project/with_transitions.otio",
    "output": "/project/final.mp4"
})

Apply per-boundary transitions

result = await session.call_tool("clipwright_add_transition", {
    "timeline": "/project/sequence.otio",
    "output": "/project/with_transitions.otio",
    "options": {
        "per_boundary": [
            {"after_clip_index": 0, "type": "fade", "duration_sec": 1.0},
            {"after_clip_index": 1, "type": "fadeblack", "duration_sec": 0.5}
        ]
    }
})

Note: All internal boundaries must be covered in v1. For a 3-clip timeline (after_clip_index values 0 and 1 are the two internal boundaries), both must be specified. Partial/gapped specification will return UNSUPPORTED_OPERATION.

Non-Destructive Guarantee

clipwright-transition never modifies the input timeline file. It always writes a new OTIO file to output. Existing metadata["clipwright"] keys (from other tools) are preserved; only the "transition" key is added.

Installation

Within a uv workspace:

uv run --package clipwright-transition clipwright-transition

Or install from PyPI:

pip install clipwright-transition
clipwright-transition

License

MIT — See LICENSE for details.