Feature request: to be able to customize the pre-roll duration

[syldub69]

Hi, The pre-roll is automatically configured to 3 seconds. This is good, but... Sometimes, it could be useful to decrease the value (to 1 or even 0 seconds!) when doing a lots of captures (to save time), sometimes it could be useful to increase the value (for instance when capturing an application which does start very slowly). Could you add the ability to configure a custom pre-roll duration?

[esaruoho]

looks like this is related to #117

[esaruoho]

related to #11