fluent-ffmpeg thumbnail creation error

i try to create a video thumbnail with fluent-ffmpeg here is my code

var ffmpeg = require('fluent-ffmpeg');

exports.thumbnail = function(){
    var proc = new ffmpeg({ source: 'Video/express2.mp4',nolog: true })
    .withSize('150x100')
    .takeScreenshots({ count: 1, timemarks: [ '00:00:02.000' ] }, 'Video/', function(err, filenames) {
    console.log(filenames);
    console.log('screenshots were saved');
  });
}

but i keep getting this error

  "mate data contains no duration, aborting screenshot creation"

any idea why,

by the way am on windows, and i put the ffmpeg folder in c/ffmpeg ,and i added the ffmpeg/bin in to my environment varable， i dont know if fluent-ffmpeg need to know the path of ffmpeg,but i can successfully create a thumbnail with the code below

   exec("C:/ffmpeg/bin/ffmpeg -i Video/" + Name  + " -ss 00:01:00.00 -r 1 -an -vframes 1 -s 300x200 -f mjpeg Video/" + Name  + ".jpg")

please help me!!!