Hear, see, watch, notice and similar verbs of perception can be followed by object + infinitive (without to) or object + -ing form.

I heard him go down the stairs. (NOT I heard him to go down the stairs.)
OR I heard him going down the stairs. (NOT I heard him went down the stairs.)

Newton saw the apple fall to the ground.
OR Newton saw the apple falling to the ground. (NOT Newton saw the apple fell to the ground.)

I watched him light the lamp.
I watched him lighting the lamp. (NOT I watched him lighted the lamp.)

Note that there is usually a difference of meaning. These verbs are followed by an infinitive when we say that we see or hear the whole of an action or event. An –ing form, on the other hand, suggests that we see or hear an action or event in progress.

I once heard him give a talk on the adverse effects of globalization. (I heard the whole talk.)
As I walked past his room I heard him talking to his wife. (I didn’t hear the whole conversation.)

After can see, can hear etc, only the –ing form is possible.

I could hear him shouting. (NOT I could hear him shout.)
I can smell something burning.

Possessives not used

After these verbs possessives cannot be used with –ing forms.

I heard John giving a speech. (NOT I heard John’s giving a speech.)