🎬 MLT Virtual DOM (mlt-vdom)

A strictly-typed, Namespace-driven Virtual DOM for generating MLT Framework XML files.
Designed for 2026 automation workflows, it ensures structural integrity through proactive hierarchy validation, automatic reference syncing, and professional formatting.

🚀 Installation

Install via npm:

npm install mlt-vdom

📖 Core Concepts

1. Unified Constructor Convention

Every element in the library follows a consistent constructor signature:

new Mlt.ElementName(attributes, content)

• attributes: An object { key: 'value' } representing XML attributes.
• content: Can be a string, a number, a single MltNode, or an Array<MltNode>.

2. Node Behaviors

To prevent "Broken XML," the library separates nodes into two distinct functional classes:

• ContainerNode (Type 0): Structural elements like Producer, Playlist, or Tractor. They use .add() to manage multiple children.
• ReferenceNode (Type 1): Pointer elements like Entry or Track. They use .bind() to point to a source and automatically sync the producer attribute.

💻 Usage Example

import { Mlt } from 'mlt-vdom';

// 1. Create the root project
const mlt = new Mlt({ id: 'main_project' });

// 2. Define a Video Source (Producer)
const producer = new Mlt.Producer({ id: 'vid_01' }, [
    new Mlt.Property({ name: 'resource' }, 'clip.mp4'),
    new Mlt.Property({ name: 'mlt_service' }, 'avformat')
]);

// 3. Define the Timeline (Playlist)
const playlist = new Mlt.Playlist({ id: 'main_bin' });

// 4. Create an Entry (Links to the Producer)
const entry = new Mlt.Entry({ in: 0, out: 150 });
entry.bind(producer); // Correct semantic linking

// 5. Assemble the Tree
playlist.add(entry);
mlt.add(producer);
mlt.add(playlist);

// 6. Build the XML String
console.log(mlt.dump(true, 'optional/save/path/file.mlt'));

📝 Expected Output

Running the code above produces this perfectly formatted MLT XML:

<?xml version="1.0" encoding="utf-8"?>
<mlt LC_NUMERIC="C" version="7.37.0" xmlns="http://www.mltframework.org/bin/view/MLT/" id="main_project">
  <producer id="vid_01">
    <property name="resource">clip.mp4</property>
    <property name="mlt_service">avformat</property>
  </producer>
  <playlist id="main_bin">
    <entry in="0" out="150" producer="vid_01"/>
  </playlist>
</mlt>

🏗️ API Reference

Mlt.build(indent)

Generates the final XML string. Called only on the root Mlt instance.

• false (default): Minified XML.
• true: Pretty-printed XML (2 spaces).
• number: Pretty-printed XML with N spaces.

Methods by Node Type

| Method | Applicable To | Description | | :--- | :--- | :--- | | .add(node) | Containers | Adds a child to the internal stack. Throws if hierarchy is invalid. | | .remove(node) | Containers | Removes a specific child node. | | .bind(node) | References | Binds a Producer/Playlist. Auto-sets the producer ID. | | .unbind() | References | Clears the binding and removes the producer attribute. | | .setAttribute(k, v) | All | Manually sets an XML attribute. | | .getAttribute(k) | All | Retrieves an attribute value. |

🛡️ Validation Logic

The library enforces the MLT schema at assignment time. If you try to add a node where it doesn't belong, it throws a Hierarchy Error immediately rather than generating invalid XML.

const playlist = new Mlt.Playlist();
const tractor = new Mlt.Tractor();

playlist.add(tractor); 
// ❌ Error: Hierarchy Error: <tractor> is not a valid child for <playlist>

⚖️ License

MIT