nilaoda/N_m3u8DL-RE · error · FileNotFoundException

ResString.ffmpegNotFound

Error message

ResString.ffmpegNotFound

What it means

DoWorkAsync pre-checks that an ffmpeg binary is available before doing work: it tries option.FFmpegBinaryPath, then GlobalUtil.FindExecutable("ffmpeg") on PATH. If none resolves to an existing file it throws FileNotFoundException with the localized 'ffmpeg not found' resource string. Merging/muxing and some decryption paths require ffmpeg.

Solutions

1. Install ffmpeg or place ffmpeg(.exe) on PATH
2. Pass the explicit binary location via --ffmpeg-binary-path (e.g. C:\tools\ffmpeg\bin\ffmpeg.exe)
3. Verify the path with: ffmpeg -version in a terminal
4. In Docker, use an image that includes ffmpeg or add it in the Dockerfile

Example fix

// before
N_m3u8DL-RE "URL" -M
// after (custom path)
N_m3u8DL-RE "URL" -M --ffmpeg-binary-path "/usr/local/bin/ffmpeg"

var ffmpeg = GlobalUtil.FindExecutable("ffmpeg");
if (ffmpeg == null || !File.Exists(ffmpeg))
    throw new FileNotFoundException("install ffmpeg or pass --ffmpeg-binary-path");

static bool FfmpegAvailable(CLIOptions o) => (o.FFmpegBinaryPath != null && File.Exists(o.FFmpegBinaryPath)) || GlobalUtil.FindExecutable("ffmpeg") != null;

try { await DoWorkAsync(option); }
catch (FileNotFoundException ex) when (ex.FileName == null && ex.Message.Contains("ffmpeg"))
{
    Console.Error.WriteLine("ffmpeg not found: install it or set --ffmpeg-binary-path");
}

When it happens

Trigger: ffmpeg is not installed, not on PATH, the custom --ffmpeg-binary-path points to a nonexistent file, or FFmpegBinaryPath was set to a bad value programmatically.

Common situations: Fresh systems/dockers without ffmpeg; Windows users who never added ffmpeg to PATH; typo'd custom binary path; renamed binaries.

Related errors

• ResString.mkvmergeNotFound
• MuxAfterDone disabled, MuxImports not allowed!
• ResString.shakaPackagerNotFound
• Key must be 12 or 8 bytes!
• Download init file failed!

AI-assisted analysis of nilaoda/N_m3u8DL-RE@e113dee70c (2026-09-13). Data as JSON: /api/errors/3622b0e2a9fb2818. Report an issue: GitHub.

Appendix: source

Thrown at src/N_m3u8DL-RE/Program.cs:135

        if (option.UseShakaPackager) 
        {
            option.DecryptionEngine = DecryptEngine.SHAKA_PACKAGER;
        }

        // LivePipeMux开启时 LiveRealTimeMerge必须开启
        if (option is { LivePipeMux: true, LiveRealTimeMerge: false })
        {
            Logger.WarnMarkUp("LivePipeMux detected, forced enable LiveRealTimeMerge");
            option.LiveRealTimeMerge = true;
        }

        // 预先检查ffmpeg
        option.FFmpegBinaryPath ??= GlobalUtil.FindExecutable("ffmpeg");

        if (string.IsNullOrEmpty(option.FFmpegBinaryPath) || !File.Exists(option.FFmpegBinaryPath))
        {
            throw new FileNotFoundException(ResString.ffmpegNotFound);
        }

        Logger.Extra($"ffmpeg => {option.FFmpegBinaryPath}");

        // 预先检查mkvmerge
        if (option is { MuxOptions.UseMkvmerge: true, MuxAfterDone: true })
        {
            option.MkvmergeBinaryPath ??= GlobalUtil.FindExecutable("mkvmerge");
            if (string.IsNullOrEmpty(option.MkvmergeBinaryPath) || !File.Exists(option.MkvmergeBinaryPath))
            {
                throw new FileNotFoundException(ResString.mkvmergeNotFound);
            }
            Logger.Extra($"mkvmerge => {option.MkvmergeBinaryPath}");
        }

        // 预先检查
        if (option.Keys is { Length: > 0 } || option.KeyTextFile != null)
        {

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