What kind of video-audio converter of the most well-known, it is best to use, take up a minimum of resources?

I would like to download a video and audio formats conversion software:a powerful, practical, take up less of the kind of resources, but also easy to use, high efficiency, who knows which is better?

recommended “format factory”, the latest version is 1.55, video, audio, image format conversion Commission eat.I can go to the download site Nano
/ d / dce4a1917f0f3bcb868ddca1149e6c5804252499e7235601 else I do not know, but I use the “format factory” WINAVI 9.0