Flutter - FFmpeg Kit exit with code 1 when creating video but not converting video

Question

I'm working on simple flutter video converting app, its returning with 'Conversion Failed'. here is my code.

Directory tempDir = await getTemporaryDirectory();
    String timestamp = DateTime.now().millisecondsSinceEpoch.toString();
    String outputPath = "${tempDir.path}/$timestamp.mp4";

    String command =
        '-i $_videoPath -vf "scale=$vidWidth:$vidHeight" -c:v libx264 -crf 23 $outputPath';

    await FFmpegKit.executeAsync(command, (session) async {
      final returnCode = await session.getReturnCode();
      print('................... $returnCode');
      if (returnCode == 1) {
        ScaffoldMessenger.of(context)
            .showSnackBar(SnackBar(content: Text('Video Saved')));
        await GallerySaver.saveVideo(outputPath);
      } else {
        ScaffoldMessenger.of(context)
            .showSnackBar(SnackBar(content: Text('Conversion Failed')));
      }
    });

I use flutter_ffmpeg which was working fine. but its not working with FFmpegKit,