vip cores, downscaler and upscaler

Dear,

I'm doing vip cores to realize the downscaler.

Quartus14.0, cycloneV, clocks: nios_cpu_clock- 100MHz, avslon_st_clk- 150MHz, avalon_mm_clock- 100MHz.

1.downscaler

cvi(1920x1080) -- bdil(1920x1080) -- vfb II(1920x1080) -- scl II(720x576) -- itl(720x576) -- cvo(run control)(720x576)

The cvi is overflow somtines and bdil have timing warnning. How to deal with it?