Consider the sentence.

The strains on your jacket won't come out.

Here, come out is an active-voice verb. But what is the object and what is the subject for that verb? I'd guess the object here is the strains. Since the object does, but subject recieves the object's action I'd guess that the object (strains) does the action (come out), but it seems completely nonsensical to me. How can the strains do the action ever? Maybe I have wrong understanding about object/subject concepts?

Couldn't you explain?