You can use mencoder or ffmpeg to do conversion of video to FLV format. You can choose the one that works well on your server. To set this, edit the file include/settings/video_conversion.php

Code:
<?php

$cmd_ffmpeg = "$config[ffmpeg] -i $video_src -acodec mp3 -ar 22050 -ab 32 -f flv $video_flv";
$cmd_mencoder = "$config[mencoder] $video_src -o $video_flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate=500:mbd=2:mv0:trell:v4mv:cbp:last_pred=3 -srate 22050 -lavfopts i_certify_that_my_video_stream_does_not_use_b_frames";

$cmd_all = $cmd_mencoder;


$convert_3gp = $cmd_all;
$convert_mp4 = $cmd_all;
$convert_mov = $cmd_all;
$convert_asf = $cmd_all;
$convert_mpg = $cmd_all;
$convert_avi = $cmd_all;
$convert_mpeg = $cmd_all;
$convert_wmv = $cmd_all;
$convert_rm = $cmd_all;
$convert_dat = $cmd_all;

If you need to use ffmpg for all video convertions, change

Code:
$cmd_all = $cmd_mencoder;
to

Code:
$cmd_all = $cmd_ffmpeg;

If you need to use ffmpge for converting files with extension dat, then use

$convert_dat = $cmd_ffmpeg;
You can also use your own custom convertion command for each of the file extensions.