Convert GIF to MP4 with Nodejs and ffmpeg with buffer as input

Question

When using ffmpeg with buffer as input, the output video is incomplete, but if i use the same input file as file the video is ok, some help to find the problem?

let inStream = streamifier.createReadStream(file.Body);

ffmpeg(inStream).inputFormat('gif')
 .outputOptions(['-pix_fmt yuv420p', '-movflags frag_keyframe+empty_moov', '-movflags +faststart'])
 .toFormat('mp4').save('test.mp4')
 .on('error', function(err, stdout, stderr) {
      console.log('Cannot process video: ' + err.message);
 })
 .on('end', function() {
      console.log('Finished processing');
 });

https://github.com/fluent-ffmpeg/node-fluent-ffmpeg/issues/892