how to extract i frame from video

i m working with real time digital video encryption on mpeg4 format.

Answer 1

[Image Analyst]

Use the getsnapshot() function to grab a frame from the live video.

[pranali p]

but i want to work with i frame.but to extract i frame??

[Image Analyst]

What is an "i frame"? Like I said, just use getsnapshot():

snappedImage = getsnapshot(videoObject);