A video has emerged of a violent altercation in Pittsburgh allegedly involving NFL star Darrelle Revis.

The video shows two men unconscious on the sidewalk while a man boasts in the background about having knocked the pair out.

"Hey I knocked both of these mother f***ers out, both of them," the man is heard saying in the eight-second video obtained by American celebrity website TMZ.

"They both asleep."

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The New York Post reported that the bragging isn't seen on the video and it is not certain whether the voice is that of Revis. But he is the only person charged in the case, cited on four felony counts and one misdemeanour.

The Pittsburgh Police Department allegedly confirmed to TMZ that the video was from a February 12 incident involving the New York Jets star.

Revis is accused of punching Dallas Cousins and Zacheriah Jarvis after the pair followed him down the street at around 2.30am and took video of him with a cellphone.

Revis, according to a complaint, is also accused of threatening a man filming the aftermath, Nathan Watt, with, "Do you want to be next?"

Revis was charged with two counts of aggravated assault, and one count each of robbery and conspiracy to commit aggravated assault, along with a misdemeanour count of terroristic threats.

In the newly released video, you can hear someone off-camera saying, "Shut up before I knock your a** out next."

Revis is adamant he was not the aggressor and said he acted in self-defence. One of Revis' Pittsburgh-based attorneys, Blaine Jones, told reporters Revis "feared for his safety" and sought medical attention. He didn't, however, offer details about the severity of Revis' injuries.

Revis, 31, turned himself in to Pittsburgh police and was released three hours later on a non-monetary bond. A preliminary hearing is set for Friday in the US.

The NFL has said it is "looking into the matter," but his future with the Jets is now more in question than it was before this incident.

Revis was signed to a five-year, $US70 million deal with $US39 million in guaranteed money to return to the Jets in 2015.

The Post reported there is speculation the deal could be voided on the grounds that Revis has violated the league's personal-conduct policy.

If Revis is to remain with the Jets, there is no way he'll do so under his current contract, which calls for him to make $US15.3 million in 2017, which includes a $US2 million roster bonus due March 10.