I420, YUV from webcam

hi!

i have to process images taken by a webcam that supports I420 and YUV. i'm
able to access the data pointer - but - actually do not know exactly how
data is stored in these formats...

the first part of data should be Y in 8bit (W x H) therafter i have no idea
about the order of U and V...

any ideas?

thanks, philipp