Instaleaza mencoder. E parte a pachetului MPlayer. Cu FFMpeg poti face asa:

ffmpeg -i input.avi -y -acodec mp3 -ab 64k -ar 44100 -ac 1 -vcodec flv -r 15 -s 448x336 -b 500k -vol 500 -flags aic+cbp+mv0+mv4+trell -cmp 3 -subcmp 3 -mbd 2 -partitions +parti4x4+partp8x8 -flags2 +mixed_refs -subq 5 -trellis 1 -refs 5 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -qcomp 0.6 -coder 1 -g 250 -qblur 1.01 output.flv