FLV MetaData Injector (FLVMDI) is a Win32 console (command line) application that can add 'onMetaData' AMF data to FLV files. (There's also a GUI frontend FLVMDIGUI). FLVMDI optionally saves an XML version of the injected data, and can add an additional string data or save the onMetaData data to an XML file. FLVMDI has some unique functionality, but it's not as vital now because flashcom 1.5.2+ and Flash Video Exporter 1.2+ adds the required metadata. (Unfortunately there's still a gotcha with Sorenson Squeeze 4, also see Sorenson Squeeze (4.1) FLV Metadata upate...)