Error in accessing webcam stream using ffmpeg

i have comnnected a usb webcam into my PC then when i write down

ffmpeg -f video4linux2 -s 720x480 -r 30000/1001 -i /dev/video1 -f avi -vcodec mjpeg -s cif -r 30000/1001 -y silver.avi

on terminal … it gves error ,

[video4linux2 @ 0x99e0420][3]Capabilities: 5000001
[video4linux2 @ 0x99e0420]The V4L2 driver changed the video from 720x480 to 352x288
[video4linux2 @ 0x99e0420]Cannot find a proper format for codec_id 0, pix_fmt -1.
/dev/video1: Input/output error

i knw the /dev/vid1 path is correct… what is this error codec _id=0 cannot find proper format?? plz explain how to fix this?ion

my email is
plzzz help i want a quick solution

m using ubuntu 9.04


Maximum Cash Discount on any plan with MAXCASH

How To Install PHP.INI / ionCube on DreamHost

now its giving this error

/dev/video1: Invalid data found when processing input

plzzzz tell what to do now?