Normalization of NGS data to make CNV calls

Question

[QX]

Hi Community,

I have WGS dataset for 4 disease and 4 controls samples. I have computed the coverages for analysis CNV (GATK procedure). However, some samples seem to have more variation than other so I think it is essential to do normalization among samples.

I would like to ask which kind of normalization method should I perform? And any suggestion for package that I could use?

Bests,