I assume you mean Ogg Vorbis audio with AVC/h.264 video in an FLV container? If so, the only problem is that the Flash Player does not support vorbis playback nor is there a codec id for it in the FLV specification. There is however an Alchemy plugin which does decode Ogg but it is not for streaming from FMS and certainly not within FLV. Info on the Flash/Ogg decoder:
http://www.hydrogenaudio.org/forums/lofiversion/index.php/t66269.html
Media types for FLV may be found here, as well as other useful information:
http://en.wikipedia.org/wiki/Flash_Video
Summary:
Supported media types in FLV file format
Video: On2 VP6, Sorenson Spark (Sorenson H.263), Screen video, H.264
Audio: MP3, ADPCM, Linear PCM, Nellymoser, Speex, AAC, G.711 (reserved for internal use)
Supported media types in F4V file format
Video: H.264
Images (still frame of video data): GIF, PNG, JPEG
Audio: AAC, HE-AAC, MP3
By the way, I found your question because I am implementing Ogg/Ogv streaming in Red5 (http://code.google.com/p/red5) for HTML5 and Unity.