Linqpad 7 script to create vp9 webms using ffmpeg 2

// Creates a webm in the directory `$Path` named "`$OutputFile`.webm".
// Requires ffmpeg be installed and accessible in PATH.
// Could take a while to encode!
// =====================
var config = new EncodeWebmConfig
{
    Path = @"G:\Movies\Anime\Genocyber (1994) [DVD] [kuchikirukia]",
    SourceFile = "01. Genocyber [DVD 540p Hi10P AC-3 dual-audio][kuchikirukia].mkv",
    TempFile = "input.mkv",
    OutputFile = "genocyber-cockblocked",
    StartTime = DateTime.Parse("00:19:05.324"),
    EndTime = DateTime.Parse("00:19:21.296"),
    Resolution = new Vector2(720, 540),
    ResolutionDivisor = 2, // Divide the resolution by this number to get the output resolution
    WithSubtitles = false,
    WithAudio = false,
    AudioCodec = "vorbis",
    TargetBitrate = 1.8m,
    TwoPassMethod = true,
    UseCrfTwoPass = true,
    Crf = 20, // 0-51, 0 best, 30 default
    NativeAac = false,
    Framerate = 0,
    FastMode = false,
};


// Run
// =====================
var arguments = CreateVp9FfmpegArgs(config);
EncodeWebm(config, arguments);


// Argument generation
// =====================
string CreateVp9FfmpegArgs(EncodeWebmConfig config)
{
    // https://trac.ffmpeg.org/wiki/Encode/VP9
    var sb = new StringBuilder();
    sb.Append(GetBaseVp9Args(config));

    if (config.TwoPassMethod)
    {
        sb.Append($" -pass 1 -an -f null NUL");

        sb.Append($" && ffmpeg");
        sb.Append(GetBaseVp9Args(config));
        sb.Append($" -pass 2");
    }

    if (config.WithAudio)
    {
        // https://trac.ffmpeg.org/wiki/Encode/HighQualityAudio
        if (config.NativeAac)
        {
            sb.Append($" -c:a copy");
        }
        else
        {
            sb.Append($" -c:a {config.AudioCodec} -strict -2");
        }
    }
    else
    {
        sb.Append($" -an");
    }

    sb.Append($" -movflags +faststart \"{config.OutputFile}.webm\"");
    return sb.ToString();

    string GetBaseVp9Args(EncodeWebmConfig config)
    {
        var sb = new StringBuilder();
        sb.Append($" -y -i {config.TempFile}");
        sb.Append($" -c:v libvpx-vp9");

        if (config.TwoPassMethod && config.UseCrfTwoPass)
        {
            sb.Append($" -b:v 0 -crf {config.Crf}");
        }
        else
        {
            // Target bitrate
            sb.Append($" -b:v {config.TargetBitrate:0}M");
        }

        // Framerate
        if (config.Framerate > 0)
        {
            sb.Append($" -r {config.Framerate}");
        }

        sb.Append($" -nostats"); // -loglevel 2");

        // Go fast
        if (config.FastMode)
        {
            sb.Append($" -row-mt 1 -tile-columns 5 -threads 10 -speed 2");
        }

        if (!config.WithSubtitles)
        {
            sb.Append($" -sn");
        }
        else
        {
            // https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo
            // -sn to not include built-in
            sb.Append($" -sn -vf subtitles={config.TempFile}");
        }

        sb.Append($" -ss {config.StartTime.ToString("HH:mm:ss.fff")} -t {config.Duration.ToString(@"hh\:mm\:ss\.fff")}");
        sb.Append($" -s {config.ScaledResolution.X}x{config.ScaledResolution.Y}");

        return sb.ToString();
    }
}

void EncodeWebm(EncodeWebmConfig config, string arguments)
{
    $"ffmpeg {arguments}".Dump();

    var start = DateTime.Now;

    Directory.SetCurrentDirectory(config.Path);
    Util.Cmd($"del {config.TempFile}");
    Util.Cmd($"mklink {config.TempFile} \"{config.SourceFile}\"");
    Util.Cmd($"ffmpeg {arguments}");
    Util.Cmd($"del {config.TempFile}");

    var end = DateTime.Now;
    var duration = end - start;
    $"Job took {duration.ToString()}".Dump();
}

class EncodeWebmConfig
{
    // Root directory we start in. Output will be published here.
    public string Path { get; set; }

    // The video file you want to clip a webm from. Include extension.
    public string SourceFile { get; set; }

    // If you want subtitles, specify it here. If it's an MKV with embedded subtitles, set this to the same as the source file.
    // Commented out - using MKV built-in subs using the TempFile alias
    //public string SubtitlesFile { get; set; }

    // Name of temp file created when processing. Is deleted afterwards. (Actually a symbolic link).
    public string TempFile { get; set; }

    // The name of the output file. Don't include .webm
    public string OutputFile { get; set; }

    // Start time in the video to clip from
    public DateTime StartTime { get; set; }

    // End time in the video to clip to
    public DateTime EndTime { get; set; }

    // Include audio in output
    public bool WithAudio { get; set; } = true;

    // Include subtitles in output
    public bool WithSubtitles { get; set; } = false;

    // Target bitrate. Doesn't apply in two-pass CRF mode.
    public decimal TargetBitrate { get; set; } = 3.0m;

    // Target output video resolution
    public Vector2 Resolution { get; set; }

    // Use the two-pass method (takes longer; better quality).
    // See: https://trac.ffmpeg.org/wiki/Encode/VP9
    public bool TwoPassMethod { get; set; } = false;

    // Is the video using AAC encoding already? Then copy the audio directly into the output.
    public bool NativeAac { get; set; }

    // Target output framerate. Set to zero to be auto.
    public int Framerate { get; set; }

    // Use the CRF method when using the two-pass method.
    public bool UseCrfTwoPass { get; set; }

    // A witch doctor on the internet told me you can unlock secret speed techniques by setting "-row-mt 1 -tile-columns 5 -threads 10 -speed 2"
    // Not sure I believe it, but here's the setting for it.
    public bool FastMode { get; set; }

    // CRF value, 0-51. 0 is lossless.
    public int Crf { get; set; } = 30;

    // If > 0, divide the output resolution by this much.
    public int ResolutionDivisor { get; set; } = 0;

    public string AudioCodec { get; set; } = "vorbis";

    public TimeSpan Duration => (EndTime - StartTime);

    public Vector2 ScaledResolution => (ResolutionDivisor > 0 ? Resolution / ResolutionDivisor : Resolution);
}