What causes "PAC code page is empty." in SubtitleEdit/subtitleedit?

Pass a named code page, e.g. `--pac-codepage=Latin`.

SubtitleEdit/subtitleedit · error · FormatException

PAC code page is empty.

Error message

PAC code page is empty.

What it means

Thrown by PacCodepageParser.Parse when the `--pac-codepage` value is null/empty/whitespace. PAC (Philips SVCD caption) files are encoded using a code page; the parser needs a name (Latin, Greek, ...) or a numeric code to decode bytes, and an empty string cannot resolve to either.

Source

Thrown at src/seconv/Core/PacCodepageParser.cs:36

        ["Arabic"] = Pac.CodePageArabic,
        ["Hebrew"] = Pac.CodePageHebrew,
        ["Thai"] = Pac.CodePageThai,
        ["Cyrillic"] = Pac.CodePageCyrillic,
        ["ChineseTraditional"] = Pac.CodePageChineseTraditional,
        ["ChineseSimplified"] = Pac.CodePageChineseSimplified,
        ["Korean"] = Pac.CodePageKorean,
        ["Japanese"] = Pac.CodePageJapanese,
        ["LatinTurkish"] = Pac.CodePageLatinTurkish,
        ["Turkish"] = Pac.CodePageLatinTurkish,
        ["LatinPortuguese"] = Pac.CodePageLatinPortuguese,
        ["Portuguese"] = Pac.CodePageLatinPortuguese,
    };

    public static int Parse(string input)
    {
        if (string.IsNullOrWhiteSpace(input))
        {
            throw new FormatException("PAC code page is empty.");
        }

        var s = input.Trim();
        if (Named.TryGetValue(s, out var named))
        {
            return named;
        }

        if (int.TryParse(s, NumberStyles.None, CultureInfo.InvariantCulture, out var num) &&
            num >= Pac.CodePageLatin && num <= Pac.CodePageLatinPortuguese)
        {
            return num;
        }

        throw new FormatException(
            $"PAC code page '{input}' is invalid. Expected a name (Latin, Greek, ...) or a number 0-12.");
    }
}

View on GitHub (pinned to 17a9f07487)

Solutions

Pass a named code page, e.g. `--pac-codepage=Latin`.
Or pass a numeric code in the valid range, e.g. `--pac-codepage=0`.
Omit the flag if your workflow does not read PAC files.
Guard scripts to only emit the flag when the variable is non-empty.

Example fix

# before
seconv in.pac out.srt --pac-codepage=
# after
seconv in.pac out.srt --pac-codepage=Latin

Defensive patterns

Strategy: validation

Validate before calling

if (string.IsNullOrWhiteSpace(rawPac))
    throw new ArgumentException("--pac-codepage requires a value");
var cp = PacCodepageParser.Parse(rawPac);

Type guard

static bool IsPacCodepageParsable(string? s)
{
    if (string.IsNullOrWhiteSpace(s)) return false;
    try { PacCodepageParser.Parse(s); return true; } catch { return false; }
}

Try / catch

try { var cp = PacCodepageParser.Parse(input); }
catch (FormatException ex) when (ex.Message == "PAC code page is empty.")
{
    // default to Latin or abort
}

Prevention

Default to a sensible code page (e.g. Latin) when none is supplied.
Length-check the input before parsing.
Validate at arg-parse time for PAC inputs only.

When it happens

Trigger: Calling `PacCodepageParser.Parse(input)` with an empty string, typically because `--pac-codepage=` was passed without a value.

Common situations: Shell expansion blanking the value; wrapper script defaulting to empty; user assumes there is a default code page but PAC requires an explicit one for non-Latin content.

Related errors

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/bec6fe07f6610698. Report an issue: GitHub.