How to extract audio from video with ffmpegKit in flutter

Question

I want to extract audio from video with this method:

 Future<Audio> extractAudio(Video video, String formatAudioByUser) async {
   
    final pathAudio = video.pathIn;

    FFmpegKit.execute(
            '-i ${video.pathIn} -q:a 0 -map a audio_${video.title}.mp3')
        .then((session) async {
      final returnCode = await session.getReturnCode();

      if (ReturnCode.isSuccess(returnCode)) {
        Fluttertoast.showToast(msg: 'Extraccion exitosa');
      } else if (ReturnCode.isCancel(returnCode)) {
        Fluttertoast.showToast(msg: 'Extraccion cancelada');
      } else {
        final error = await session.getFailStackTrace();
        Fluttertoast.showToast(msg: 'Fallo al extraer audio: $error');
      }
    });

//creates object
  final audio = Audio(
      id: 'audio_${video.id}',
      title: 'audio_${video.title}',
      duration: video.duration,
      pathIn: video.pathIn, 
      pathOut:pathAudio,
      format: formatAudioByUser,
    );
    
    return audio;
  }

which i use in my datasource_impl.

But when choosing the media (video) and running the method, it doesn't work from the ffmpegkit script, and it shows this error: "Fallo al extraer audio: null"

I've reviewed the debugging mode, and created brakpoints, but all the video data looks good.