SubtitleEdit/subtitleedit · error · InvalidOperationException

No image handler for format '{options.Format}'

Error message

No image handler for format '{options.Format}'

What it means

Thrown by WritePreservedBitmaps when LibSEIntegration.NormalizeFormatName(options.Format) does not match any image-output handler. The bitmap-passthrough path can only re-emit into the image formats ImageOutputWriter.TryCreateHandler knows (Blu-ray sup, VobSub, BDN-XML, DOST, FCP, D-Cinema, images-with-time-codes, WebVTT thumbnail). A text-only format here is a CLI/usage error.

Source

Thrown at src/seconv/Core/SubtitleConverter.cs:569

            {
                foreach (var item in items)
                {
                    item.Dispose();
                }
            }
        }

        await Task.CompletedTask;
        return true;
    }

    private static void WritePreservedBitmaps(
        IReadOnlyList<BitmapSubtitleLoader.BitmapSubtitleItem> items,
        string outputFile,
        ConversionOptions options)
    {
        var handler = ImageOutputWriter.TryCreateHandler(LibSEIntegration.NormalizeFormatName(options.Format))
            ?? throw new InvalidOperationException($"No image handler for format '{options.Format}'");
        var outputDir = Path.GetDirectoryName(outputFile);
        if (!string.IsNullOrEmpty(outputDir) && !Directory.Exists(outputDir))
        {
            Directory.CreateDirectory(outputDir);
        }
        ImageOutputWriter.WritePreservedBitmaps(items, outputFile, handler, options);
    }

    private List<string> GetInputFiles(ConversionOptions options)
    {
        var files = new List<string>();

        var baseFolder = string.IsNullOrEmpty(options.InputFolder)
            ? Directory.GetCurrentDirectory()
            : options.InputFolder;

        foreach (var entry in options.Patterns)
        {

View on GitHub (pinned to 17a9f07487)

Solutions

1. Use a supported image target: bluraysup, vobsub, bdnxml, dost, fcpimage, dcineterop, imageswithtimecodes, or webvttthumbnail.
2. If you actually want text, configure an OCR engine (--ocr-engine tesseract, etc.) so the text path runs instead of bitmap passthrough.
3. Check the format spelling against seconv's --help format list; NormalizeFormatName only accepts known aliases.

Example fix

// before
seconv movie.mkv srt            // bitmap track + text target with no OCR
// after (image target)
seconv movie.mkv bluraysup
// or enable OCR
seconv movie.mkv srt --ocr-engine tesseract

var handler = ImageOutputWriter.TryCreateHandler(LibSEIntegration.NormalizeFormatName(options.Format));
if (handler is null && !HasOcrEngine(options))
    throw new ArgException($"'{options.Format}' is not a valid image target and no OCR engine is set.");

static readonly HashSet<string> ImageTargets = new(StringComparer.OrdinalIgnoreCase)
{ "bluraysup","vobsub","bdnxml","bdnxml8bit","dost","fcpimage","dcineterop","dcineteroppng","dcismpte2014","imageswithtimecodes","webvttthumbnail" };
static bool IsImageTarget(string fmt) => ImageTargets.Contains(LibSEIntegration.NormalizeFormatName(fmt).Trim());

null

When it happens

Trigger: A bitmap source (MKV PGS/VobSub or TS DVB-sub) is being preserved as-is, but options.Format normalizes to something TryCreateHandler returns null for (e.g. 'srt', 'ass', a typo, or an unsupported image format).

Common situations: Asking seconv to convert PGS bitmaps into 'srt' without OCR (no OCR engine configured), or passing an unrecognised format string. The passthrough path has no renderer for text.

Related errors

• --output-filename can only target a single DVB-sub PID. Foun
• Tesseract not found on PATH. Install it from https://tessera
• Failed to start tesseract process.
• Tesseract exited with code {proc.ExitCode}: {err}
• No VOB files supplied.

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/112026d99a07923e. Report an issue: GitHub.