Here is a sample, for input&output. Also you can rename the original field based on MIBs in meaningful name for instance: ""SNMPv2-SMI::enterprises.6027.3.1.1.4.1.2" -> chAlarmVarString . You can get MIB database from online.
Also use debug in the output, provide us with more details.
stdout { codec => rubydebug{}}