Set off cap gains against forwarded short term losses

i earned ltcg on principal protected NCD's inlast A.Y.2014-15.i paid 10.3% tax on them. i also had short term capital losses of previous years<8 years duration which i was carrying forward in my returns.

could i have set off old short term losses against long term capital gains.and not pay tax as i have paid. losses were more than gains.

can i rectify them now by revised returns any claim refund.