The officers who were there probably could, if any could be made to testify. They could even use the video to refresh their recollection.
But this witness certainly can't. The lawyer is asking a retained expert witness for his lay opinion on what he can hear in a video that is already in evidence. If the prosecution objected to that question, I think the judge would have to sustain it: the witness is in no better position and is no more qualified than the jurors to determine what is being said on the video. The video is already in evidence, and the lawyer is certainly free to argue to the jury in closing what he thinks Floyd is saying.
This witness has lost all credibility by saying he couldn’t hear what Floyd was saying.
If a witness lies about one thing, it can be assumed he lied about everything else to which he testified.