He likely means youtube's automatic content filter. I don't know about youtube's system, but video editing is something I'm pretty good at, and if I were to change a video, then I'd add a watermark to advertise my site(two birds and all). Then modify the audio in points of the video that shouldn't be noticeable, such as low volume or bass heavy scenes. As I said, I've never tried to bypass youtube's content blocker, but this should significantly change the video and audio. As for software, I use linux so I don't know what to suggest, but most video editing software should be able to do simple changes.