How to show resized frames via opencv wrapper video filter?

[hengchuan]

I want to write an opencv filter that changes the size of frames. I changed p_filter->fmt_out.video.i_height and p_filter->fmt_out.video.i_width in opencv_wrapper.c, and then copied the resized frame data to p_outpic.
The processed frame could display in the vlc window (I draw a circle for it), but it seems to be downscaled to the original window size after my processing. Even if I try to change the window size by the mouse, the frame is resized based on the downscaled one. There are nearly no differences between the nearest and the bicubic interpolation, which should be obvious.
Therefore how can I change the origin window size, or how to display resized frames correctly?