The FV signal is a GPIF Signal, so you cannot use it as an ordinary GPIO INterrupt. You can stop your sensor temporarily for a while and then change the exposure time and gain.
Thanks for your answer,
However, it still can't fix my problem,
For AE or AWB tuning, you can't just stop sensor temporarily, then set the I2C command,
Because the continuity for video out is very important for some applications. (For example, Surveillance)
If not to set interrupt routine, then if any other method to reach?