SubtitleEdit/subtitleedit · error · InvalidOperationException

Error in paragraph {p.StartTime} after '{sb}': {ex.Message}

Error message

Error in paragraph {p.StartTime} after '{sb}': {ex.Message}

What it means

Thrown by Pac when decoding a PAC subtitle paragraph and an InvalidOperationException bubbles up from the inner decoding logic (alignment computation, margin calculation, or text processing). The wrapper enriches the message with the paragraph's StartTime and a prefix buffer 'sb' so the binary region that triggered the failure can be located.

Source

Thrown at src/libse/SubtitleFormats/Pac.cs:2010

                    }

                    var linesAfter = 12 - verticalAlignment - Math.Max(1, Utilities.GetNumberOfLines(p.Text));
                    p.MarginV = linesAfter <= 0 ? null : (linesAfter * 100 / 12.0).ToString(CultureInfo.InvariantCulture) + "%";
                }

                // Remove position tags
                var indexOfPositioningCodes = p.Text.IndexOf("\u002e\u001f", StringComparison.Ordinal);
                if (indexOfPositioningCodes > 0)
                {
                    p.Text = p.Text.Substring(0, indexOfPositioningCodes + 1);
                }

                p.Text = p.Text.RemoveControlCharactersButWhiteSpace().TrimEnd();
                return p;
            }
            catch (InvalidOperationException ex)
            {
                throw new InvalidOperationException($"Error in paragraph {p.StartTime} after '{sb}': {ex.Message}", ex);
            }
        }

        /// <summary>
        /// Fix italic tags, lines starting with ">" - whole line is italic, words between &lt;&gt; is italic
        /// </summary>
        private static string FixItalics(string input)
        {
            var pre = string.Empty;
            var text = input;
            if (text.StartsWith("{\\", StringComparison.Ordinal))
            {
                var endIdx = text.IndexOf('}', 2);
                if (endIdx > 2)
                {
                    pre = text.Substring(0, endIdx + 1);
                    text = text.Remove(0, endIdx + 1);
                }

View on GitHub (pinned to 17a9f07487)

Solutions

1. Note the StartTime and 'sb' prefix in the message to locate the byte region in the file.
2. Try the file in SubtitleEdit's GUI with the correct codepage/language selection.
3. Re-acquire the PAC file from the original source — corruption is the most common cause.
4. If decoding programmatically, catch the exception and skip the paragraph to salvage the rest.

// Pac decoding is binary; best pre-check is file integrity
var fi = new FileInfo(fileName);
if (!fi.Exists || fi.Length < MinimumPacSize)
{
    // reject obviously corrupt/empty files
    return;
}

try
{
    new Pac().LoadSubtitle(sub, lines, fileName);
}
catch (InvalidOperationException ex) when (ex.Message.StartsWith("Error in paragraph"))
{
    // ex.Message includes StartTime and a byte prefix to locate the region
    logger.Error(ex, "PAC decode failed");
}

When it happens

Trigger: Decoding a PAC (.pac) file where the binary glyph/alignment data leads to an unexpected state during paragraph reconstruction — e.g. an out-of-range vertical alignment value, a missing encoding mapping, or malformed control codes that cause a substring or index operation to throw.

Common situations: Corrupt or non-standard PAC files; PAC files in a language/encoding the decoder does not fully map; files truncated before the paragraph terminator.

Related errors

• Unknown byte ({buffer[index]}) in subtitle file @ binary off
• Unknown byte ({b}) in subtitle file @ binary offset {index}.
• Unknown byte (0x{b:X2}) in subtitle file @ binary offset {in
• Parse error in event #{i + 1} style: {ex.Message}
• Invalid ASSA time code: {time}

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/946ba4cdd006da37. Report an issue: GitHub.