mean position of the variant within the variant supporting reads

[alg]

Hi,

I am trying to call SNPs using SAMtools mpileup. I am interesting in determining the mean position of the variant within the variant supporting reads. I know there is the -O command which gives: output base positions on reads

Firstly I am not 100% positive what 'mean position' refers to and secondly, while the -O command gives output base positions on reads, how would I determine the mean position within the variant supporting reads?

Any help would be much appreciated.

Thank you.