{"record":{"id":"7186e8e5ac244df6","repo":"remotion-dev/remotion","slug":"not-enough-bytes-left-to-parse-ebml-this-should","errorCode":null,"errorMessage":"Not enough bytes left to parse EBML - this should not happen","messagePattern":"Not enough bytes left to parse EBML - this should not happen","errorType":"exception","errorClass":"Error","httpStatus":null,"severity":"error","filePath":"packages/media-parser/src/containers/webm/parse-ebml.ts","lineNumber":26,"sourceCode":"\tgetTrack,\n\tNO_CODEC_PRIVATE_SHOULD_BE_DERIVED_FROM_SPS,\n} from './make-track';\nimport type {PossibleEbml} from './segments/all-segments';\nimport {ebmlMap} from './segments/all-segments';\nimport type {WebmRequiredStatesForProcessing} from './state-for-processing';\n\nexport type Prettify<T> = {\n\t[K in keyof T]: T[K];\n} & {};\n\nexport const parseEbml = async (\n\titerator: BufferIterator,\n\tstatesForProcessing: WebmRequiredStatesForProcessing | null,\n\tlogLevel: MediaParserLogLevel,\n): Promise<Prettify<PossibleEbml> | null> => {\n\tconst hex = iterator.getMatroskaSegmentId();\n\tif (hex === null) {\n\t\tthrow new Error(\n\t\t\t'Not enough bytes left to parse EBML - this should not happen',\n\t\t);\n\t}\n\n\tconst off = iterator.counter.getOffset();\n\tconst size = iterator.getVint();\n\tconst minVintWidth = iterator.counter.getOffset() - off;\n\n\tif (size === null) {\n\t\tthrow new Error(\n\t\t\t'Not enough bytes left to parse EBML - this should not happen',\n\t\t);\n\t}\n\n\tconst hasInMap = ebmlMap[hex as keyof typeof ebmlMap];\n\n\tif (!hasInMap) {\n\t\tLog.verbose(logLevel, `Unknown EBML hex ID ${JSON.stringify(hex)}`);","sourceCodeStart":8,"sourceCodeEnd":44,"githubUrl":"https://github.com/remotion-dev/remotion/blob/78fe4bb3fdb5a2cd68724393d63cb223db333fa7/packages/media-parser/src/containers/webm/parse-ebml.ts#L8-L44","documentation":"parseEbml reads the next EBML element ID via iterator.getMatroskaSegmentId(); if that returns null there were not enough bytes for even the element-id octets. The 'this should not happen' comment means the contract is that callers (expectSegment) verify bytes remain before recursing into parseEbml. Reaching this throw means the byte stream ended mid-element.","triggerScenarios":"A truncated WebM/MKV stream (download cut off, partial fetch, aborted reader), or an internal caller that recurses into parseEbml after the iterator has been consumed past the declared container size. Also reachable via a corrupted size VInt that points beyond EOF.","commonSituations":"Network reader returning a short body, range requests that stop early, file served with wrong Content-Length, interrupted Blob/ReadableStream, or a seek into a region the reader cannot supply.","solutions":["Verify the source URL/blob is fully downloadable and that Content-Length matches the actual bytes.","If using a custom reader, ensure it does not resolve read() before yielding all requested bytes unless truly at EOF, and that EOF is reached cleanly after the Segment closes.","Re-fetch or re-encode the file from a known-good source.","Migrate to Mediabunny, which has a different, more tolerant streaming implementation."],"exampleFix":"// before\nawait parseMedia({src: partiallyDownloadedUrl, fields: {durationInSeconds: true}});\n\n// after - ensure the reader sees the complete file\nconst buf = await fetch(url).then(r => r.arrayBuffer());\nawait parseMedia({src: new Blob([buf]), fields: {durationInSeconds: true}});","handlingStrategy":"try-catch","validationCode":"// Ensure the full byte range is available before parsing.\nconst res = await fetch(url);\nif (!res.ok || Number(res.headers.get('content-length')) !== realExpectedLength) {\n  throw new Error('source not fully available');\n}\nconst buf = new Uint8Array(await res.arrayBuffer());\n// only parse once the whole file is buffered\nawait parseMedia({src: buf});","typeGuard":null,"tryCatchPattern":"try {\n  await parseMedia({src, fields: {durationInSeconds: true}});\n} catch (err) {\n  if (err instanceof Error && /Not enough bytes left to parse EBML/.test(err.message)) {\n    throw new Error('Truncated media stream; re-download or verify Content-Length.', {cause: err});\n  }\n  throw err;\n}","preventionTips":["Buffer the entire file into memory before parsing when feasible.","Verify Content-Length and byte counts on custom readers.","Do not resolve reader.read() early; signal EOF only at true end."],"tags":["webm","matroska","ebml","media-parser","truncation","reader"],"backgroundTag":null,"analyzedSha":"78fe4bb3fdb5a2cd68724393d63cb223db333fa7","analyzedAt":"2026-08-12T17:18:50.444Z","schemaVersion":2},"datasetVersion":"2026-08-12T18:17:37.767Z"}