Problems with the csc and chroma resample

Hi,

I have a project structure is as follows:

cvi(rgb 24bit)->csc(ycbcr 444)->chroma resample(ycbcr 422)->cvo.

input and output resolution 1920*1080p60 ,now cvo underflowed.

I change cvo fifo to 1920*5 ,cvo remain underflowed.How can I do?

Thanks