BabylonJS/Babylon.js · error · Error

Unexpected end of file before frame time

Error message

Unexpected end of file before frame time

What it means

ReadBvh parses a BVH motion-capture file line by line. After the MOTION header it expects a 'Frame Time:' line, and this error is thrown when the lines array is exhausted before that line is found, meaning the file ends prematurely in the MOTION section.

Source

Thrown at packages/dev/loaders/src/BVH/bvhLoader.ts:375

    if (!framesLine) {
        throw new Error("Unexpected end of file before frame count");
    }
    const framesTokens = framesLine.trim().split(/[\s]+/);
    if (framesTokens.length < 2) {
        throw new Error("Invalid frame count line");
    }

    // number of frames
    const numFrames = parseInt(framesTokens[1]);
    if (isNaN(numFrames)) {
        throw new Error("Failed to read number of frames.");
    }
    context.numFrames = numFrames;

    // frame time
    const frameTimeLine = lines.shift();
    if (!frameTimeLine) {
        throw new Error("Unexpected end of file before frame time");
    }
    const frameTimeTokens = frameTimeLine.trim().split(/[\s]+/);
    if (frameTimeTokens.length < 3) {
        throw new Error("Invalid frame time line");
    }
    const frameTime = parseFloat(frameTimeTokens[2]);
    if (isNaN(frameTime)) {
        throw new Error("Failed to read frame time.");
    }
    if (frameTime <= 0) {
        throw new Error("Failed to read frame time. Invalid value " + frameTime);
    }

    context.frameRate = 1 / frameTime;

    // read frame data line by line
    for (let i = 0; i < numFrames; ++i) {
        const frameLine = lines.shift();

View on GitHub (pinned to 0592b347b8)

Solutions

  1. Open the BVH file and verify it contains the full MOTION section ending with 'Frame Time: <seconds>' followed by frame data lines
  2. Re-download or re-export the BVH from the source application to get an untruncated file
  3. Check the file size against the expected size from the exporter; if smaller, the transfer was interrupted
  4. If generating BVH programmatically, ensure Frame Time line is emitted after the Frames: line

Example fix

// before (truncated file)
MOTION
Frames: 100
// after (complete MOTION header)
MOTION
Frames: 100
Frame Time: 0.033333
Defensive patterns

Strategy: validation

Validate before calling

function validateBvhMotionHeader(text) {
  const lines = text.split(/\r?\n/);
  const motionIdx = lines.findIndex(l => /^MOTION/i.test(l.trim()));
  if (motionIdx === -1) throw new Error('No MOTION section');
  const rest = lines.slice(motionIdx + 1).map(l => l.trim()).filter(Boolean);
  if (!/^Frames?:\s+\d+/i.test(rest[0] ?? '')) throw new Error('Missing Frames: line');
  if (!/^Frame Time:\s+\d/i.test(rest[1] ?? '')) throw new Error('Missing/truncated Frame Time line');
}

Type guard

function hasFrameTimeLine(text: string): boolean {
  const m = text.slice(text.toUpperCase().indexOf('MOTION'));
  return /^Frame Time:\s+\S+/im.test(m);
}

Try / catch

try {
  skeleton.readBvh(text);
} catch (e) {
  if (e instanceof Error && e.message === 'Unexpected end of file before frame time') {
    console.error('BVH file truncated in MOTION section; re-export the file');
  } else throw e;
}

Prevention

When it happens

Trigger: Calling ReadBvh (via skeleton) with a BVH file whose MOTION section is truncated: the Frame:, Frames:, or Frame Time: lines are missing because the file was cut off, saved incompletely, or the hierarchy consumed all lines.

Common situations: Partially downloaded or interrupted BVH transfers, files truncated by editors or version control, hand-edited BVH files where the frame-time line was deleted, or feeding a plain skeleton definition HIERARCHY-only file with no MOTION block.

Related errors

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/0a3f9eaae8cc3c91. Report an issue: GitHub.