why not 640x480

[arunks]

i have 7610 mobile phone and it captures photos in 640x480 resolution

but when i record video in it ...it gives only 176x128 resolution

plz tell me why is it so..

i think video is just a sequence of frames.

so if a single frame i.e. a image is shoted at 640x480 resolution then why cant video be done at same resolution

Yes you are right, a video is actually a sequence of still images captured one after other in a very short span of time. In a still shot a camera takes a picture and saves it. In a video it has to take several pictures in a second (measured in fps:frames per second). Usually mobile phone cameras are capable of 15fps i.e. 15 shots takes in one second. Now a days cell like N93 are capable of 30 fps. But to take so many shots in 640x480 would require tremendous processing power from the phone's processor. Most cell phones (like your 7610) don't have huge graphic processing power. Thats why they either lower the resolution or reduce the frame rate (or both). Now after still shots, videos in mobile phone cameras is improving. All of the N-Series phones support CIF resolution video recording whereas N93 can go upto VGA at 30fps. Soon with the advent of dedicated GPU in cell phones as in computer, videos recorded in cell phone will match that of any handycam.