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  gst_element_link(source, parser);  gst_element_link_many (parser, decoder, conv, NULL);  if (lpf_on && hpf_on)    gst_element_link_many(conv, low_filter, high_filter, mp3enc, sink, NULL);  else if (lpf_on)    gst_element_link_many(conv, low_filter, mp3enc, sink, NULL);  else if (hpf_on)    gst_element_link_many(conv, high_filter, mp3enc, sink, NULL);  else    gst_element_link_many(conv, mp3enc, sink, NULL);