我正试图将一段视频从android手机流到我的笔记本电脑上。我运行了gstreamer，它运行得很好。我的问题在于下面的代码:

   [....]
    pipeline = gst.parse_launch('rtspsrc name=source latency=0 ! decodebin ! autovideosink')
    source = pipeline.get_by_name('source')
    source.props.location =  "rtsp://128.237.119.100:8086/"
    decoder = gst.element_factory_make("decodebin", "decoder")
    sink = gst.element_factory_make("autovideosink", "sink")

    pipeline.add(source, decoder, sink)
    gst.element_link_many(source, decoder, sink)
    [...]

运行它时会出现以下错误:

      (server.py:2893): GStreamer-WARNING **: Name 'source' is not unique in bin 'pipeline0', not adding
       Traceback (most recent call last):
       File "server.py", line 27, in <module>
       py = pyserver()
       File "server.py", line 18, in __init__
       pipeline.add(source, decoder, sink)
       gst.AddError: Could not add element 'source'

我是GStreamer的新手。我已经参考了这个问题来编写代码:用python-gstreamer玩RTSP

谁能指出我做错了什么吗？为什么我会得到Adderror？