DASH XSD to JSON Schema Converter

This project provides tools for working with MPEG-DASH manifests in JSON format:

1. XSD to JSON Schema Converter - Converts MPEG-DASH XSD schemas to JSON Schema format
2. MPD to JSON Converter - Converts MPD XML manifests to validated JSON
3. JSON to MPD Converter - Converts JSON back to MPD XML (round-trip support)

JSON Schema Version

This project generates schemas compliant with JSON Schema 2020-12, the latest stable version of the JSON Schema specification:

• Core: https://json-schema.org/draft/2020-12/json-schema-core
• Validation: https://json-schema.org/draft/2020-12/json-schema-validation
• Relative JSON Pointer: https://datatracker.ietf.org/doc/html/draft-bhutton-relative-json-pointer-00

Installation

npm install

Usage

Convert MPD to JSON

Convert a DASH MPD XML manifest to JSON format with validation:

npm run mpd2json -- <input.mpd> [options]

# Example: Convert with full validation
npm run mpd2json -- manifest.mpd -o manifest.json

# Example: Skip XSD validation (faster)
npm run mpd2json -- manifest.mpd --skip-xsd -o manifest.json

# Example: Verbose mode
npm run mpd2json -- manifest.mpd -v -o manifest.json

MPD to JSON CLI Options

mpd2json <input.mpd> [options]

Options:
  -o, --output <file>       Output JSON file (default: stdout)
  --xsd <path>              Path to XSD schema (default: xml-schemas/DASH-MPD.xsd)
  --json-schema <path>      Path to JSON Schema (default: output/dash-mpd.schema.json)
  --skip-xsd                Skip XSD validation
  --skip-json-schema        Skip JSON Schema validation
  --no-pretty               Output minified JSON
  -v, --verbose             Show detailed validation messages
  -h, --help                Show help

The converter performs the following steps:

1. XSD Validation - Validates the input MPD against the DASH-MPD XSD schema (using xmllint)
2. XML to JSON Conversion - Converts XML to JSON matching our schema structure
3. JSON Schema Validation - Validates the output JSON against the generated JSON Schema

Convert XSD to JSON Schema

Convert an XSD file to JSON Schema:

npm run convert <input.xsd> -o <output.json>

# Example
npm run convert xml-schemas/DASH-MPD.xsd -o output/dash-mpd.schema.json

XSD to JSON Schema CLI Options

xsd2jsonschema <input.xsd> [options]

Options:
  -o, --output <file>      Output file (default: stdout)
  --base-uri <uri>         Base URI for $id in the schema
  --attr-prefix <prefix>   Prefix for XML attributes (e.g., '@')
  --no-pretty              Output minified JSON
  -h, --help               Show help

XSD to JSON Schema Mapping

XSD Construct	JSON Schema Equivalent
xs:string	"type": "string"
xs:integer	"type": "integer"
xs:boolean	"type": "boolean"
xs:double	"type": "number"
xs:dateTime	"type": "string", "format": "date-time"
xs:duration	"type": "string" with ISO 8601 pattern
xs:anyURI	"type": "string", "format": "uri-reference"
xs:enumeration	"enum": [...]
xs:pattern	"pattern": "..."
xs:minInclusive/maxInclusive	"minimum"/"maximum"
xs:complexType	"type": "object" with "properties"
xs:sequence	"properties" + "required"
xs:choice	"oneOf"
xs:extension	"allOf" with "$ref"
xs:list	"type": "array"

Source Schemas

The xml-schemas/ directory contains the MPEG-DASH XSD schemas:

• DASH-MPD.xsd - Main Media Presentation Description schema
• CENC.xsd - Common Encryption schema
• xlink.xsd - XLink attributes
• DASH-MPD-UP.xsd - URL parameters extension
• DASH-MPD-PATCH.xsd - MPD patch operations

Output

Generated JSON Schemas are written to the output/ directory:

• dash-mpd.schema.json - Complete DASH MPD schema (~70KB, 98 type definitions)
• cenc.schema.json - CENC types
• xlink.schema.json - XLink types
• dash-mpd-up.schema.json - URL parameter types

XML to JSON Mapping

When converting MPD XML to JSON, the following conventions are used:

XML Construct	JSON Representation
Element with text content only (no attributes in schema)	"Element": "text value"
Element with text + possible attributes (defined in schema)	"Element": { "$value": "text", "attr": "value" }
Repeated elements	"Element": [...] (array)
Attributes	Direct properties on the object
Namespace declarations	Root-level $ns object mapping URIs to prefixes
Namespaced attributes (e.g., xlink:href)	Grouped under prefix key (e.g., "xlink": { "href": "..." })
Extension elements	Grouped under prefix key (e.g., "ext": { "CustomElement": ... })

Note: Elements use $value for text content when the XSD schema defines possible attributes for that element type, even if no attributes are present in a particular instance. This ensures consistent JSON structure.

Example

XML:

<BaseURL availabilityTimeOffset="5.0">https://example.com/video/</BaseURL>

JSON:

{
  "BaseURL": [{
    "$value": "https://example.com/video/",
    "availabilityTimeOffset": 5.0
  }]
}

Namespace Example

XML:

<MPD xmlns="urn:mpeg:dash:schema:mpd:2011"
     xmlns:xlink="http://www.w3.org/1999/xlink">
  <Period id="p0" xlink:href="http://example.com/period.xml" xlink:actuate="onLoad"/>
</MPD>

JSON:

{
  "$ns": {
    "http://www.w3.org/1999/xlink": {
      "prefix": "xlink",
      "attributes": ["href", "actuate"]
    }
  },
  "Period": [{
    "id": "p0",
    "xlink": {
      "href": "http://example.com/period.xml",
      "actuate": "onLoad"
    }
  }]
}

Namespace declarations are collected at the root $ns object only. Each prefix maps to exactly one URI and vice versa. See docs/dash-json-representation.md Section 9 for the full specification.

Prerequisites

• Node.js 18+
• xmllint (for XSD validation) - typically pre-installed on macOS/Linux

Development

# Build TypeScript
npm run build

# Run tests
npm test

License

MIT