do you mean 23.976 into a 29.97 fps? 24.97 never heard of that. 23 might be variable framerate(which causes audio issues) which would require handbrake transcoded to quicktime png first. then take the new 23fps and drop into 24.97(if that really is what you want) and it should speed it up. or use clip-pixel motion to convert with optical conversion so there's no speed change.