Firstly this would be better seen with his shirt off and a pair of shorts. It looks like this person does not have or is not using their hip stabilizers. He is shifting his weight for balance on each leg and perhaps the left side is worse than the right.
The hip flexors and adductors doe not appear to be involved correctly and therefore there is slight circumduction in his gait. Really we need to view a much longer walking in either direction rather than 2-3 steps of this small room. Please take some more video and please do provide more information of what his injuries were. The ankle and knee joint movement does not look to bad from a later view although there is a noticable varus deformity or movement about his left knee during the swing phase of walking possibly indicating past injury? Possible weakness of the right peroneal muscles? Did this person have lumbar nerve damage or a higher level neurological injury?
Also he has a problem turning towards the right. If I were to really compare his gait to other altered gait patterns this looks as though he had right or possibly bilateral above knee amputations and is wearing prosthetic legs with really good ankle and knee joints. It appears more at the pelvis/hip/trunk that the issues might be, or very weak as he is overworking the ipsilateral side to compensate during swing for weakness lower down on the swing leg.
Can we see him in shorts and standing front in front and behind on one leg whilst trying the flex the opposite hip to bring the knee towards the ceiling.
Can he balance on one leg or not?