In my Video Project, I am using Opaque box for subtitles, for better viewing. But, I want to increase the width of Opaque box along the breadth of the video. Means stretching in x-axis.

Also, if i can have one opaque box and in there i can insert my text. Not, like opaque box for each subtitle line.

I am using Ageisub for subtitles, and in there is the option to use opaque box, but opaque box comes with each subtitle line. Like, if for one time code, i have two line in subs, one above and below and correspondingly there are two opaque rectangles for them.

But i want, that if there is one big Rectangle like opaque box along the whole breadth of Video and in there i can insert the whole text.

Is it possible with any software. Any type of help would be appreciated.