HOW TO USE A FILE WITH VHDL?

hi everybody, i was havng the problem of how to enter a video by the
vhdl that i will use it to test a my project of compression.
i found that it will be introduced using a video file.
The problem is now how to use files by VHDL???
please if someone have any documents for using files with VHDL send
it to me .
thinks.

FPGA