remotion-dev/remotion · error

Invalid block size

Error message

Invalid block size

What it means

Thrown by getBlockSize() when the 4-bit block-size field in a FLAC frame header does not match any of the defined patterns. Per RFC 9639, the 4 bits cover: 0b0000 (reserved/get from streaminfo), 0b0001 (192 samples), 0b0010-0b0101 (scaled from 144*2^n), 0b0110 (u8 uncommon), 0b0111 (u16 uncommon), and 0b1000-0b1111 (2^n). Since every 4-bit value maps to one of these branches, this throw is effectively unreachable defensive code — it would only fire if the bit-reading logic itself were broken.

Source

Thrown at packages/media-parser/src/containers/flac/get-block-size.ts:34

	}

	if (bits >= 0b0010 && bits <= 0b0101) {
		return 144 * 2 ** bits;
	}

	if (bits === 0b0110) {
		return 'uncommon-u8';
	}

	if (bits === 0b0111) {
		return 'uncommon-u16';
	}

	if (bits >= 0b1000 && bits <= 0b1111) {
		return 2 ** bits;
	}

	throw new Error('Invalid block size');
};

View on GitHub (pinned to 78fe4bb3fd)

Solutions

1. If you encounter this, it is likely a bug in @remotion/media-parser — report it with the exact FLAC file and the parsed bits value.
2. Verify you are on the latest version of @remotion/media-parser; the branch logic may have been fixed.
3. Switch to Mediabunny (https://www.remotion.dev/docs/mediabunny/metadata).

try {
  const result = await parseMedia({src, fields: {durationInSeconds: true}});
} catch (e) {
  if (e instanceof Error && e.message === 'Invalid block size') {
    // This is effectively unreachable; if hit, report as internal bug
    console.error('Internal parser error in FLAC block size. Report this file to Remotion.');
  } else {
    throw e;
  }
}

When it happens

Trigger: Logically unreachable: all 16 possible 4-bit values (0b0000 through 0b1111) are handled by prior branches. Would only trigger in case of an internal logic error in the iterator's getBits() returning an out-of-range value, or if the function's branch logic were edited to introduce a gap.

Common situations: Should never occur in normal operation. If observed, it indicates either a bug in the BufferIterator bit-reading implementation or a modification to getBlockSize that removed a branch without removing the fallthrough throw.

Related errors

• Invalid channel count: ${bits.toString(2)}
• Invalid sample rate mode: ${mode.toString(2)}
• Blocking bit should be set
• Cannot determine timestamp
• Streaminfo not found

AI-assisted analysis of remotion-dev/remotion@78fe4bb3fd (2026-08-12). Data as JSON: /api/errors/57d200ab2d966eb9. Report an issue: GitHub.