an update...
this is the video_conversion.php im using...

<?php

# For old version of mplayer
# $cmd_mencoder = "$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:l ast_pred=3 -srate 22050 -lavfopts i_certify_that_my_video_stream_does_not_use_b_fram es";
# $cmd_mencoder = "$config[mencoder] '$video_src' -o $video_flv -af resample=22050:0:0 -sws 9 -vf scale=448:-3,expand=448:336 -of lavf -ovc lavc -lavcopts vcodec=flv:vbitrate=500:trell:v4mv:mv0:mbd=2:cbp:a ic:cmp=3:subcmp=3 -oac mp3lame -lameopts abr:br=56:mode=3 harddup";
# For latest version of mplayer
#$cmd_mencoder = "$config[mencoder] '$video_src' -o $video_flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate=$bit_rate:mbd=2:mv0:trell:v4mv :cbp:last_pred=3 -srate 22050 -ofps 24 -vf harddup";

$cmd_ffmpeg = "$config[ffmpeg] -i '$video_src' -acodec libmp3lame -ar 22050 -ab 32 -f flv $video_flv";

//New Mplayer codec
$cmd_mencoder = "$config[mencoder] '$video_src' -o $video_flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate=$bit_rate:mbd=2:mv0:trell:v4mv :cbp:last_pred=3 -srate 22050 -ofps 24 -vf harddup,hqdn3d=2:1:2,scale=640:464";
//Convert mp4 H264
$cmd_mp4_h264 = "$config[ffmpeg] -i '$video_src' -acodec libfaac -ab 96k -vcodec libx264 -vpre hq -crf 22 -threads 0 -b " . $bit_rate . "k $video_flv";

$cmd_all = $cmd_mencoder;

$convert_3gp = $cmd_all;
$convert_mp4 = $cmd_mp4_h264;
$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;

i also tried using this code as the conversion code...
$cmd_mencoder = "$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:l ast_pred=3 -srate 22050 -lavfopts i_certify_that_my_video_stream_does_not_use_b_fram es";