title: Generate ffmpeg thumbnail from stream in Node.js
body: <p>Im using node.js together with ffmpeg to receive an rtmp-stream and output this into m3u8-format. </p>
  
  <pre><code>[ '-y',
    '-fflags',
    'nobuffer',
    '-analyzeduration',
    '1000000',
    '-i',
    'rtmp://localhost:1935/live/ANMZJ2ZRUiMhKaAoygRXwAfHe',
    '-c:v',
    'copy',
    '-c:a',
    'aac',
    '-f',
    'tee',
    '-map',
    '0:a?',
    '-map',
    '0:v?',
    '-y',
    '-an',
    '[hls_time=10:hls_list_size=0]./media/live/ANMZJ2ZRUiMhKaAoygRXwAfHe/SX3otgDdf6/index.m3u8|' ]
  </code></pre>
  
  <p>Together with this functionality I would also like to output a thumbnail. I tried to do this using the following format but without success.</p>
  
  <pre><code>[ '-y',
    '-fflags',
    'nobuffer',
    '-analyzeduration',
    '1000000',
    '-i',
    'rtmp://localhost:1935/live/ANMZJ2ZRUiMhKaAoygRXwAfHe',
    '-c:v',
    'copy',
    '-c:a',
    'aac',
    '-f',
    'tee',
    '-map',
    '0:a?',
    '-map','0:v?',
    '-y',
    '-an',
    '-vf' ,
    'fps=1',
    'C:/Users/media/out.png'
    '[hls_time=10:hls_list_size=0]./media/live/ANMZJ2ZRUiMhKaAoygRXwAfHe/SX3otgDdf6/index.m3u8|' ]
  </code></pre>
  
  <p>The way I send this information to ffmpeg is by </p>
  
  <pre><code>this.ffmpeg_exec = spawn(ffmpeg_path, args);
  </code></pre>
  
  <p>Im unable to create a thumbnail using this approach. Does anyone know the problem/solution?</p>