my thumbnail creation using ffmpeg is not working on linux server

I am using ffmpeg in linux server...the video conversion is working fine,but thumbnail creation not working...

here is my code

exec($_SERVER['DOCUMENT_ROOT']."/esebd2/ffmpeg/ffmpeg -y -i ".$_SERVER['DOCUMENT_ROOT']."/esebd2/".$target_path." -vframes 1 -ss 00:00开发者_运维技巧:10 -an -vcodec png -f rawvideo -s 320×240 ".$_SERVER['DOCUMENT_ROOT']."/esebd2/".$target_pathImg);

i am using codeigniter framework

when i echo the argument for exec i got this Mr.pekka

/home1/esedirec/public_html/esebd2/ffmpeg/ffmpeg -y -i /home1/esedirec/public_html/esebd2/cxfolder/george/videos/vid9656326.flv -vframes 1 -ss 00:00:10 -an -vcodec png -f rawvideo -s 320×240 /home1/esedirec/public_html/esebd2/cxfolder/george/thumbs/Img9955639.png

but the thumbnail not generated

Not an actual answer but it will help you debug so run this and let us know what output you get :

exec($_SERVER['DOCUMENT_ROOT']."/esebd2/ffmpeg/ffmpeg -y -i ".$_SERVER['DOCUMENT_ROOT']."/esebd2/".$target_path." -vframes 1 -ss 00:00:10 -an -vcodec png -f rawvideo -s 320×240 ".$_SERVER['DOCUMENT_ROOT']."/esebd2/".$target_pathImg, $return, $status);
var_dump($return);
var_dump($status);