Paul Walker Death -- Image in Burning Porsche Video is NOT Paul

Paul Walker did NOT make a final desperate attempt to escape the burning wreckage -- and the image seen in video shot right after the crash is definitely NOT Paul ... TMZ has learned.

There had been rampant speculation and buzz on the Internet that a shadowy figure seen around 23 seconds into the video of the burning Porsche Carrera GT ... was Walker trying to get out of the vehicle, but sources connected to the investigation now say it just isn't so ... for several reasons.

First, the sources tell us that, based on photographs of the wreckage ... Paul's body was pinned in an area of the car that makes it clear he couldn't have been flailing outside the vehicle.

Also ...we're told that based on the injuries he suffered, Paul died within a nanosecond of impact, and therefore it's impossible for the image in the video to be him.

It's not clear how long after impact the video starts, but clearly more than a nanosecond.