Flash in version 8 (and even earlier) encode the captured microphone sound propietary and closed Nellymoser codec, it decodes the flash itself of course, but to legally convert it to mp3 wanted to buy the SDK for 30 Grand. Work on decoding it in libavcodec was conducted, I think the Red5 developers even offered 5 thousand those who do opencarry decoder. Wikipedia says
that FFMPEG is now able to decode Nellymoser.
In flash 10 it seems like there is an opportunity to choose the Speex codec, while the default is still the same Nellymoser
With all this, the sending flow is possible only in FMS/Red5/Wowza, etc rtmp media servers. There are still erlyvideo, there is a implementation of rtmp in Python — not sure, however, that they are able to receive streams. In any case, Ntrim POST-request do not potrebuet process, constantly ready to accept connections and write streams