{"record":{"id":"cacb2b96cda31bb5","repo":"remotion-dev/remotion","slug":"expected-block-segment","errorCode":null,"errorMessage":"Expected block segment","messagePattern":"Expected block segment","errorType":"exception","errorClass":"Error","httpStatus":null,"severity":"error","filePath":"packages/media-parser/src/containers/webm/parse-ebml.ts","lineNumber":278,"sourceCode":"\t\t\treturn {\n\t\t\t\ttype: 'Block',\n\t\t\t\tvalue: new Uint8Array([]),\n\t\t\t\tminVintWidth: ebml.minVintWidth,\n\t\t\t};\n\t\t}\n\t}\n\n\tif (ebml.type === 'BlockGroup') {\n\t\t// Blocks don't have information about keyframes.\n\t\t// https://ffmpeg.org/pipermail/ffmpeg-devel/2015-June/173825.html\n\t\t// \"For Blocks, keyframes is\n\t\t// inferred by the absence of ReferenceBlock element (as done by matroskadec).\"\"\n\n\t\tconst block = ebml.value.find(\n\t\t\t(c) => c.type === 'SimpleBlock' || c.type === 'Block',\n\t\t);\n\t\tif (!block || (block.type !== 'SimpleBlock' && block.type !== 'Block')) {\n\t\t\tthrow new Error('Expected block segment');\n\t\t}\n\n\t\tconst hasReferenceBlock = ebml.value.find(\n\t\t\t(c) => c.type === 'ReferenceBlock',\n\t\t);\n\n\t\tconst sample =\n\t\t\tblock.value.length === 0\n\t\t\t\t? null\n\t\t\t\t: await getSampleFromBlock({\n\t\t\t\t\t\tebml: block,\n\t\t\t\t\t\twebmState,\n\t\t\t\t\t\toffset,\n\t\t\t\t\t\tstructureState,\n\t\t\t\t\t\tcallbacks,\n\t\t\t\t\t\tlogLevel,\n\t\t\t\t\t\tonVideoTrack,\n\t\t\t\t\t\tavcState,","sourceCodeStart":260,"sourceCodeEnd":296,"githubUrl":"https://github.com/remotion-dev/remotion/blob/78fe4bb3fdb5a2cd68724393d63cb223db333fa7/packages/media-parser/src/containers/webm/parse-ebml.ts#L260-L296","documentation":"While post-processing a BlockGroup, the parser looks for a SimpleBlock or Block child and throws if none (or a non-block child matched) is found. Per the Matroska spec a BlockGroup must contain a Block, so this indicates a malformed BlockGroup element.","triggerScenarios":"A BlockGroup element whose children are only ReferenceBlock/BlockAdditions/etc. with no actual Block/SimpleBlock; a partial BlockGroup cut by truncation; corruption that renamed the child element ID.","commonSituations":"Damaged MKV files, files produced by non-conformant muxers, or streams truncated inside a BlockGroup.","solutions":["Re-mux the file ('ffmpeg -i in.mkv -c copy out.mkv') to reconstruct valid BlockGroups.","Validate with ffprobe; if it errors on the same region, the file is damaged.","Use a different source file.","Try Mediabunny as an alternate parser."],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"try {\n  await parseMedia({src: 'in.mkv', fields: {samples: true}});\n} catch (err) {\n  if (err instanceof Error && /Expected block segment/.test(err.message)) {\n    throw new Error('Malformed BlockGroup in source; re-mux with ffmpeg.', {cause: err});\n  }\n  throw err;\n}","preventionTips":["Re-mux user uploads with ffmpeg before parsing.","Validate files with ffprobe/MediaInfo first.","Keep a fallback source URL for re-fetch on parse failure."],"tags":["webm","matroska","ebml","media-parser","block","malformed-file"],"backgroundTag":null,"analyzedSha":"78fe4bb3fdb5a2cd68724393d63cb223db333fa7","analyzedAt":"2026-08-12T17:18:50.444Z","schemaVersion":2},"datasetVersion":"2026-08-12T18:17:37.767Z"}