{"id":13099,"library":"ebml-block","title":"EBML Block Parser","description":"ebml-block is a specialized JavaScript library designed to parse the raw binary data of an EBML Block or SimpleBlock structure. These blocks typically contain actual media frames (video, audio) and their associated metadata, such as timecodes and keyframe indicators, commonly found within Matroska (MKV) and WebM container formats. The package's current stable version is 1.1.2, released in March 2017. While functional, its development has been dormant since then, suggesting a maintenance-only status rather than active feature development. It is crucial to note that ebml-block does not parse entire EBML documents; instead, it expects a pre-extracted Buffer representing a single Block element. This differentiates it from broader EBML parsers, making it a low-level utility for processing specific data chunks within a larger EBML stream, often used in conjunction with a full EBML stream decoder.","status":"maintenance","version":"1.1.2","language":"javascript","source_language":"en","source_url":"https://github.com/mathiasvr/ebml-block","tags":["javascript","ebml","matroska","mkv","block","simpleblock","lacing"],"install":[{"cmd":"npm install ebml-block","lang":"bash","label":"npm"},{"cmd":"yarn add ebml-block","lang":"bash","label":"yarn"},{"cmd":"pnpm add ebml-block","lang":"bash","label":"pnpm"}],"dependencies":[{"reason":"Required to decode the overall EBML stream and extract individual Block or SimpleBlock elements, whose raw data is then processed by ebml-block.","package":"ebml","optional":false}],"imports":[{"note":"The package is primarily designed for CommonJS environments as indicated by its last update in 2017. While ESM import might work with tooling, 'require' is the canonical usage.","wrong":"import ebmlBlock from 'ebml-block'","symbol":"ebmlBlock","correct":"const ebmlBlock = require('ebml-block')"},{"note":"Assuming ESM compatibility and that the package exports a default function. It does not appear to have named exports based on its CJS usage pattern.","wrong":"import { ebmlBlock } from 'ebml-block'","symbol":"ebmlBlock","correct":"import ebmlBlock from 'ebml-block'"}],"quickstart":{"code":"const fs = require('fs');\nconst ebml = require('ebml'); // Required for decoding the overall EBML stream\nconst ebmlBlock = require('ebml-block'); // The library: parses the raw Block data\n\n// Initialize an EBML Decoder from the 'ebml' package.\n// This decoder processes the high-level EBML structure of a file like .mkv or .webm.\nconst decoder = new ebml.Decoder();\n\n// Listen for 'data' events. Each 'chunk' represents an EBML element found.\ndecoder.on('data', function (chunk) {\n  // We're interested in 'Block' or 'SimpleBlock' elements, which contain\n  // the actual video/audio frame data along with metadata like timecodes.\n  if (chunk[1].name === 'Block' || chunk[1].name === 'SimpleBlock') {\n    // The 'data' property of the element is a Buffer containing the raw block.\n    // Pass this Buffer to ebmlBlock for detailed parsing.\n    const block = ebmlBlock(chunk[1].data);\n    console.log('Parsed EBML Block:', block);\n    console.log(`  Track Number: ${block.trackNumber}`);\n    console.log(`  Timecode (ms): ${block.timecode}`);\n    console.log(`  Keyframe: ${block.keyframe}`);\n    console.log(`  Number of frames in block: ${block.frames.length}`);\n  }\n});\n\ndecoder.on('error', (err) => {\n  console.error('EBML Decoder encountered an error:', err.message);\n});\n\ndecoder.on('end', () => {\n  console.log('Finished processing EBML stream.');\n});\n\n// To run this, ensure 'media.mkv' exists in the current directory or provide a valid path.\n// This pipes an MKV file stream through the EBML decoder.\n// The decoder then emits 'data' events for ebml-block to process.\nfs.createReadStream('media.mkv').pipe(decoder);","lang":"javascript","description":"Demonstrates how to use `ebml-block` in conjunction with the `ebml` package to parse individual EBML Block or SimpleBlock elements from a Matroska (MKV) file stream, extracting their structured data like timecodes and frames."},"warnings":[{"fix":"Use a higher-level EBML parser (e.g., `ebml` package) to extract `Block` or `SimpleBlock` element data, then pass that data to `ebml-block`.","message":"`ebml-block` is a low-level parser for individual EBML `Block` or `SimpleBlock` data buffers, not a full EBML document parser. It will not process an entire `.mkv` or `.webm` file; it expects only the data payload of a block element.","severity":"gotcha","affected_versions":">=1.0.0"},{"fix":"Evaluate its suitability for critical applications or consider alternatives if active maintenance is a requirement. Thoroughly test in your target environment.","message":"The library has not seen active development since March 2017 (v1.1.2). While it remains functional for its specific purpose, it may not be actively maintained, potentially lacking updates for newer Node.js features, performance optimizations, or security patches.","severity":"gotcha","affected_versions":">=1.0.0"},{"fix":"Ensure `npm install ebml` is run and the `ebml.Decoder` is used to preprocess the stream before feeding block data to `ebml-block`.","message":"`ebml-block` relies on the `ebml` package (or a similar EBML stream parser) to correctly identify and extract the `Block` or `SimpleBlock` elements from an EBML stream. Installing and using `ebml` is a prerequisite for typical usage.","severity":"gotcha","affected_versions":">=1.0.0"}],"env_vars":null,"last_verified":"2026-04-19T00:00:00.000Z","next_check":"2026-07-18T00:00:00.000Z","problems":[{"fix":"Install `ebml` (`npm install ebml`) and ensure it's imported in your code (`const ebml = require('ebml');`).","cause":"The `ebml` peer dependency, essential for extracting EBML block data from a stream, was not imported or installed.","error":"ReferenceError: ebml is not defined"},{"fix":"For CommonJS, use `const ebmlBlock = require('ebml-block');`. For ESM, use `import ebmlBlock from 'ebml-block;'` (assuming it provides a default export, though the package is CJS).","cause":"The `ebml-block` package was not correctly imported or required, or the imported object does not expose the expected parsing function directly.","error":"TypeError: ebmlBlock is not a function"},{"fix":"Ensure 'media.mkv' exists in the current working directory, or update the path to point to a valid Matroska/WebM file.","cause":"The `fs.createReadStream()` call in the quickstart example cannot find the specified media file.","error":"Error: No such file or directory, open 'media.mkv'"}],"ecosystem":"npm","meta_description":null,"install_score":null,"install_tag":null,"quickstart_score":null,"quickstart_tag":null,"pypi_latest":null,"cli_name":""}