Process 1:
ffmpeg -re -i <filename>.avi -ac 2 -vcodec libx264 -acodec libmp3lame -ar 44100 -threads 0 -q:v 0 -q:a 0 -f flv -

Piping to process 2:
ffmpeg -re -i - -vcodec copy -acodec copy -threads 0 -f flv rtmp://...