AlistGo/alist · warning

ffmpeg-go produced empty buffer for %s

Error message

ffmpeg-go produced empty buffer for %s

What it means

ffmpeg exited with status 0 but wrote zero bytes to the stdout pipe while resizing an image. This means ffmpeg considered the run successful yet produced no output frames — typically because the demuxer opened the file but the decoder yielded no video stream, or output arguments (e.g. an image2pipe muxer with no frames flushed) silently produced nothing.

Source

Thrown at drivers/local/util.go:111

		outputArgs["vcodec"] = vcodec
	}
	if outputFormat == "mjpeg" {
		outputArgs["q:v"] = "3"
	}

	err = ffmpeg.Input(inputFile).
		Output("pipe:", outputArgs). // Output to pipe (stdout)
		GlobalArgs("-loglevel", "error").
		Silent(true).                     // Suppress ffmpeg's own console output
		WithOutput(outBuffer, os.Stderr). // Capture stdout to outBuffer, stderr to os.Stderr
		// ErrorToStdOut(). // Alternative: send ffmpeg's stderr to Go's stdout
		Run()

	if err != nil {
		return nil, fmt.Errorf("ffmpeg-go failed to resize image %s to buffer: %w", inputFile, err)
	}
	if outBuffer == nil || outBuffer.Len() == 0 {
		return nil, fmt.Errorf("ffmpeg-go produced empty buffer for %s", inputFile)
	}

	return outBuffer, nil
}

func generateThumbnailWithImagingOptimized(imagePath string, targetWidth int, quality int) (*bytes.Buffer, error) {

	file, err := os.Open(imagePath)
	if err != nil {
		return nil, fmt.Errorf("failed to open image: %w", err)
	}
	defer file.Close()

	img, err := imaging.Decode(file, imaging.AutoOrientation(true))
	if err != nil {
		return nil, fmt.Errorf("failed to decode image: %w", err)
	}

View on GitHub (pinned to 843d9dc814)

Solutions

1. Verify the file is a real, complete image: 'file <path>' and open it locally
2. Re-run ffmpeg manually with '-loglevel debug' to see why no frames are emitted
3. Return this error to the caller so the driver can skip thumbnail caching for this file instead of retrying

// reject obviously non-media inputs before invoking ffmpeg
if info, err := os.Stat(path); err != nil || info.Size() < 100 {
    // not a plausible image; skip thumbnail
    return nil, nil, nil
}

Wrap the call; on 'empty buffer' treat the file as un-thumbnail-able and record a negative cache entry so it is skipped on subsequent listings instead of retrying every time.

When it happens

Trigger: Passing a file that is not actually a still image or video (e.g. a .png extension on a text file, an audio file), a zero-byte image, or a format where ffmpeg's decoder fails lazily without setting a non-zero exit code.

Common situations: Misnamed media files, files still being written (upload in progress) when the thumbnail request arrives, or encrypted/truncated downloads that keep a valid container header but no frames.

Related errors

• invalid input file path: %w
• ffmpeg-go failed to resize image %s to buffer: %w
• failed to open image: %w
• failed to decode image: %w
• failed to encode thumbnail: %w

AI-assisted analysis of AlistGo/alist@843d9dc814 (2026-08-15). Data as JSON: /api/errors/39b9ec25bf25051e. Report an issue: GitHub.