Estimating Insert Size From Paired End Data.

Hi,

I have paired end data from illumina. To estimate the insert size in silico ( from scratch ), I have aligned the reads as single end reads to the genome ( mouse ). Now I have the two alignment files ( SAM/BAM). I would like to estimate the insert size ( distribution plot ) from the two SAM/BAM files.

The existing tools will look for the "=" field in the SAM format to consider it as the corresponding mate but not read name. Any one is aware of any tool that estimates the insert size based on reads names from the two sam files ?

Thanks.