GPU Bandwidth: As previously explained, people keep upgrading their camera tech while ignoring their computer specifications.This means that Vegas Pro has to do a lot of work to decode the video as it is playing back in real-time. Video Codec: AVCHD H.264 video codec is used by the vast majority which specializes in saving video files after highly compressing them.Thus, the same CPU now needs to work six times more when editing with Vegas, which causes the lag. Standard Definition video is up to six times smaller in file size compared to Full 1080p HD video.