FFmpeg Helper

This skill guides you through using FFmpeg in .NET applications, specifically focusing on the FFMpegCore wrapper and Xabe.FFmpeg.Downloader for binary management, based on the patterns established in MediaTranscriptKnowledgeRAG.

Core Components

•FFMpegCore: A .NET wrapper for FFmpeg. Used for executing commands.
•Xabe.FFmpeg.Downloader: A utility to download the latest FFmpeg binaries. Used for bootstrapping.

1. Bootstrapping FFmpeg

Ensure FFmpeg binaries are available before execution. Use a Bootstrapper or Startup service.

Pattern: Check and Download

csharp

using Xabe.FFmpeg.Downloader;
using FFMpegCore;

public async Task InitializeAsync(CancellationToken cancellationToken)
{
    // 1. Determine target directory
    var ffmpegDir = Path.Combine(AppContext.BaseDirectory, "ffmpeg");
    if (!Directory.Exists(ffmpegDir))
    {
        Directory.CreateDirectory(ffmpegDir);
    }

    // 2. Check if executable exists
    var ffmpegExe = Path.Combine(ffmpegDir, "ffmpeg.exe");
    if (!File.Exists(ffmpegExe))
    {
        // 3. Download if missing
        await FFmpegDownloader.GetLatestVersion(FFmpegVersion.Official, ffmpegDir);
    }

    // 4. Configure FFMpegCore to use this directory
    GlobalFFOptions.Configure(new FFOptions { BinaryFolder = ffmpegDir });
}

2. Audio Extraction (for Whisper)

Whisper typically requires 16kHz, Mono, WAV audio.

Pattern: Extract Audio

csharp

using FFMpegCore;

public async Task<string> ExtractAudioAsync(string videoPath, string outputPath)
{
    // Ensure output directory exists
    // ...

    await FFMpegArguments
        .FromFileInput(videoPath)
        .OutputToFile(outputPath, true, options => options
            .WithAudioSamplingRate(16000)
            .WithAudioCodec("pcm_s16le")
            .ForceFormat("wav")
            .WithCustomArgument("-ac 1")) // Mono
        .ProcessAsynchronously();

    return outputPath;
}

3. Configuration

Avoid hardcoding paths. Use appsettings.json or environment variables.

appsettings.json:

json

{
  "FFmpeg": {
    "ExecutablePath": "ffmpeg" // Relative folder name or absolute path
  }
}

Loading Configuration:

csharp

var executablePath = configuration["FFmpeg:ExecutablePath"] ?? "ffmpeg";
// Logic to resolve full path...

4. Dependencies

Add these packages to your project:

xml

<PackageReference Include="FFMpegCore" Version="5.4.0" />
<PackageReference Include="Xabe.FFmpeg.Downloader" Version="6.0.2" />

Common Issues

•Path Resolution: Ensure GlobalFFOptions.Configure is called before any FFMpegArguments usage.
•Permissions: Ensure the process has write permissions to the ffmpeg directory for downloading.
•Platform: Xabe.FFmpeg.Downloader detects the OS and downloads the appropriate binaries (Windows/Linux/MacOS).