Convert From MP3 in C# | https://docs.conholdate.com/net/convert-from-mp3/

AudioConnector.cs

public class AudioConnector : IAudioConnector
{
    private readonly Dictionary<AudioFileType, Action<FFMpegArgumentOptions>> _optionsMap = new Dictionary<AudioFileType, Action<FFMpegArgumentOptions>>();

    public AudioConnector()
    {
        _optionsMap.Add(AudioFileType.Mp3, SetMp3ConvertOptions);
        _optionsMap.Add(AudioFileType.Ogg, SetOggConvertOptions);
        _optionsMap.Add(AudioFileType.Aac, SetAacConvertOptions);
        _optionsMap.Add(AudioFileType.Ac3, SetAc3ConvertOptions);
        _optionsMap.Add(AudioFileType.Flac, SetFlacConvertOptions);
        _optionsMap.Add(AudioFileType.Wma, SetWmaConvertOptions);
        _optionsMap.Add(AudioFileType.Wav, SetWavConvertOptions);
        _optionsMap.Add(AudioFileType.M4a, SetM4aConvertOptions);
        _optionsMap.Add(AudioFileType.Aiff, SetAiffConvertOptions);
    }

    public Stream ConvertAudio(Stream sourceStream, AudioConvertOptions convertOptions)
    { 
        var resultStream = new MemoryStream();


        var arguments = FFMpegArguments
            .FromPipeInput(new StreamPipeSource(sourceStream))
            .OutputToPipe(new StreamPipeSink(resultStream), options =>
            {
                if (_optionsMap.ContainsKey(convertOptions.Format))
                {
                    _optionsMap[convertOptions.Format].Invoke(options);
                }
                else
                {
                    throw new InvalidOperationException(
                        $"Conversion to {convertOptions.Format.Extension} is not supported at the moment");
                }
            });
        arguments.ProcessSynchronously();
            
        return resultStream;
    }

    private void SetMp3ConvertOptions(FFMpegArgumentOptions options)
    {
        options.WithAudioCodec(AudioCodec.LibMp3Lame);
        options.ForceFormat("mp3");
    }

    private void SetOggConvertOptions(FFMpegArgumentOptions options)
    {
        options.WithAudioCodec(AudioCodec.LibVorbis);
        options.ForceFormat("ogg");
    }

    private void SetAacConvertOptions(FFMpegArgumentOptions options)
    {
        options.WithAudioCodec(AudioCodec.Aac);
        options.ForceFormat("adts");
    }

    private void SetAc3ConvertOptions(FFMpegArgumentOptions options)
    {
        options.WithAudioCodec(AudioCodec.Ac3);
        options.ForceFormat("ac3");
    }

    private void SetFlacConvertOptions(FFMpegArgumentOptions options)
    {
        options.ForceFormat("flac");
    }

    private void SetWmaConvertOptions(FFMpegArgumentOptions options)
    {
        options.ForceFormat("asf");
    }

    private void SetWavConvertOptions(FFMpegArgumentOptions options)
    {
        options.ForceFormat("wav");
    }

    private void SetM4aConvertOptions(FFMpegArgumentOptions options)
    {
        options.WithAudioCodec(AudioCodec.Aac);
        options.ForceFormat("adts");
    }

    private void SetAiffConvertOptions(FFMpegArgumentOptions options)
    {
        options.ForceFormat("aiff");
    }
}

mp3-to-flac.cs

// Load the source MP3 file
AudioLoadOptions loadOptions = new AudioLoadOptions();
loadOptions.SetAudioConnector(new AudioConnector());
using (Converter converter = new Converter("sample.mp3", () => loadOptions))
{
    // Set the convert options for FLAC format
    AudioConvertOptions options = new AudioConvertOptions {
        Format = AudioFileType.Flac
    };
    // Convert to FLAC format
    converter.Convert("converted.flac", options);
}