The most common formats you can use safely are:
asf - asf/wmv format
avi - avi format
flv - flv format
m4v - raw MPEG4 video format
mov,mp4,m4a,3gp,3g2,mj2 - QuickTime/MPEG4/Motion JPEG 2000 format
Please look at
API docs for the complete list of supported input fortmats.