Just realized that if I run gst-discoverer on this file:
http://gstreamer.freedesktop.org/media/large/gravity.mpg

It returns nothing as a streamid.

gst-discoverer-1.0 -v ../Videos/gravity.mpg 
Analyzing file:///home/cschalle/Downloads/../Videos/gravity.mpg
Done discovering file:///home/cschalle/Downloads/../Videos/gravity.mpg

Topology:
  container: video/mpeg, systemstream=(boolean)true, mpegversion=(int)1
    audio: audio/mpeg, mpegversion=(int)1, mpegaudioversion=(int)1, layer=(int)2, rate=(int)44100, channels=(int)2, parsed=(boolean)true
      Codec:
        audio/mpeg, mpegversion=(int)1, mpegaudioversion=(int)1, layer=(int)2, rate=(int)44100, channels=(int)2, parsed=(boolean)true
      Additional info:
        None
      Stream ID: (null)
      Language: <unknown>
      Channels: 2
      Sample rate: 44100
      Depth: 32
      Bitrate: 224000
      Max bitrate: 0
      Tags:
        taglist, audio-codec=(string)"MPEG\ 1\ Audio\,\ Layer\ 2", nominal-bitrate=(uint)224000, has-crc=(boolean)false, channel-mode=(string)stereo;
      
    video: video/mpeg, mpegversion=(int)1, systemstream=(boolean)false, parsed=(boolean)false
      Codec:
        video/mpeg, mpegversion=(int)1, systemstream=(boolean)false, parsed=(boolean)false
      Additional info:
        None
      Stream ID: (null)
      Width: 0
      Height: 0
      Depth: 0
      Frame rate: 0/1
      Pixel aspect ratio: 1/1
      Interlaced: false
      Bitrate: 0
      Max bitrate: 0
      Tags:
        None
      
      video: video/mpeg, mpegversion=(int)1, systemstream=(boolean)false, parsed=(boolean)true, width=(int)352, height=(int)240, framerate=(fraction)30000/1001, pixel-aspect-ratio=(fraction)8/9, codec_data=(buffer)000001b31600f0c402cee0a4
        Codec:
          video/mpeg, mpegversion=(int)1, systemstream=(boolean)false, parsed=(boolean)true, width=(int)352, height=(int)240, framerate=(fraction)30000/1001, pixel-aspect-ratio=(fraction)8/9, codec_data=(buffer)000001b31600f0c402cee0a4
        Additional info:
          None
        Stream ID: (null)
        Width: 352
        Height: 240
        Depth: 0
        Frame rate: 30000/1001
        Pixel aspect ratio: 8/9
        Interlaced: false
        Bitrate: 0
        Max bitrate: 0
        Tags:
          taglist, video-codec=(string)"MPEG\ 1\ Video";
        

Properties:
  Duration: 0:03:58.509588888
  Seekable: yes
  Tags: 
      video codec: MPEG 1 Video
      audio codec: MPEG 1 Audio, Layer 2
      nominal bitrate: 224000
      has crc: false
      channel mode: stereo