Facebook on Safari causing a video upload issue (Videos uploaded out of Sync)

I have uploaded a video to Facebook using the Safari browser. The video appears fine in the Facebook app, as well as on Chrome, but when viewed in Safari with the HD option on, it's clearly out of sync. It is not out of sync in standard definition. I feel like I've seen a lot of people talk about this problem, but I haven't seen an explanation. I tried it on my roommates computer as well on Safari, and he had the same issue. We both have recently updated versions of Safari. It would be really great to get a solution on this. Thanks.