When dvddemux adds pads, it exposes pads that have multiple structures. This causes issues when deciding what data is actually going to flow.
Decoders/demuxers should, when adding a pad from a pad template with multiple structures, know what type of data is going to flow through that pad. It should therefore add pads with only one structure.

Ex : This is a pad template:
  SRC template: 'current_audio'
    Availability: Always
    Capabilities:
      audio/mpeg
            mpegversion: 1
      audio/x-lpcm
                  width: { 16, 20, 24 }
                   rate: { 48000, 96000 }
               channels: [ 1, 8 ]
          dynamic_range: [ 0, 255 ]
               emphasis: { false, true }
                   mute: { false, true }
      audio/x-ac3
      audio/x-dts

When the pad is created it's one of those structures, not ALL ! :)

Please fix accordingly.