Bulk API - How to get all the contacts that where in a specific campaign

Hi,

i am trying to retrieve all the contacts that where in a specific campaign id.

i looked in the bulk api activities and it seems like i can't filter the results by the activity type :campaign entry.

basically what i tried and succeeded is to get all the contacts that are in a specific activity type like 'EmailOpen' and in a specific campaignid.

but i need to retrieve the results by the campaign entry activity.

is there a way doing this using the bulk API ?

if not can i do it using a different api ? or by creating a segment / list based on the campaign activity entry ?

10x,

Eliram