title: python subprocess.call terminates without notice
body: <p>i have a script in python that call subprocess to encode video file below</p>
  
  <pre><code>        args1 = ["ffmpeg", "-i", "my niece.mkv"]
          args2 = MyConfig.DefaultFFMPEGParam + " " + crf + " " + output + ""
          args = args2.split(' ')
          args1.extend(args)
  
          print "EncodeReal : " + uniqueno + " : Try Encode"
          print " ".join(args1)
          subprocess.call(" ".join(args1), shell=True)
  </code></pre>
  
  <p>the print statement successfully prints out below commands</p>
  
  <pre><code>ffmpeg -i "/home/Downloads/my niece.mkv" -tune animation -keyint_min 12 -sc_threshold 45 -bf 8 -b_strategy 2 -refs 10 -qmin 10 -qmax 51 -qcomp 0.6 -direct-pred auto -me_range 24 -me_method umh -subq 9 -trellis 2 -vcodec libx264 -crf 28.0 /home/Downloads/output.mkv
  </code></pre>
  
  <p>which if running this command in script it works well, however if it runs by subprocess.call, it encounter </p>
  
  <pre><code>ffmpeg version git-2013-12-30-61d43a2 Copyright (c) 2000-2013 the FFmpeg developers
    built on Dec 30 2013 11:02:28 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-4)
    configuration: --prefix=/root/ffmpeg_build --extra-cflags=-I/root/ffmpeg_build/include --extra-ldflags=-L/root/ffmpeg_build/lib --bindir=/root/bin --extra-libs=-ldl --enable-gpl --enable-nonfree --enable-libfdk_aac --enable-libx264
    libavutil      52. 59.100 / 52. 59.100
    libavcodec     55. 47.100 / 55. 47.100
    libavformat    55. 22.101 / 55. 22.101
    libavdevice    55.  5.102 / 55.  5.102
    libavfilter     4.  0.103 /  4.  0.103
    libswscale      2.  5.101 /  2.  5.101
    libswresample   0. 17.104 /  0. 17.104
    libpostproc    52.  3.100 / 52.  3.100
  
  
  [1]+  Stopped                 python MonitorService.py
  </code></pre>
  
  <p>It stops by itself! any reason?</p>