EBML

Extensible Binary Meta Language (EBML) is a binary, extensible container format designed to store structured data in a self-describing, hierarchical form. It serves as a general-purpose schema for organizing information, with the actual meaning of each piece defined by an accompanying EBML schema rather than by human-readable tags.

An EBML document is composed of elements. Each element has an ID that identifies its type, a size field that specifies the length of the element's data, and the data itself. Both the ID and the size are encoded as variable-length integers (VINTs). The data portion may contain raw binary values or nested child elements, forming a tree structure.

The standard defines a core schema that assigns IDs and data types to elements. The root element is EBML, and its children include an EBML header containing versioning information and a docType that names the schema in use (for example, Matroska). The design is intentionally extensible, allowing new element IDs to be introduced without breaking existing parsers.

EBML is widely used as the container format for Matroska multimedia files (MKV, MKA, MKS) and the WebM project. It is also used by other applications that require a compact, binary, self-describing data format. The binary nature enables efficient parsing, streaming, and indexing, while the schema-driven approach provides forward and backward compatibility.

Implementation-wise, EBML libraries (notably libebml) provide parsing and writing facilities used by Matroska tools and other software. As with any binary format, interoperability depends on using the same schema version and docType; documents without a known schema may be ambiguous to interpret.